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Author Topic: Rear Shock Options, Including Budget  (Read 44692 times)
dad
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« on: January 19, 2007, 07:00:27 AM »

Hopefully this summary will help to group a bunch of scattered replies on the topic. Obviously, it's all JMO. Smiley

I found just a re-springing of the stock shock to be a very adequate economy answer to the wallowing and general lousy handling experienced on these as you start to push them, ESPECIALLY for just street use. It's NOT a Penske but is still a dramatic improvement. If you're not experiencing those wallowing problems, not pushing it a bit, or just a cruising type rider, ignore this post. Wink

I took the time honored approach that on a budget, the best bang for the buck is get the spring right. These are so soft that that approach made even more sense the more I thought about it. I took the measurements, figured the linkage ratios, drew up some cups, sourced a used spring, and proceeded. I was AMAZED with the improvement and easily recommend it to anyone who wants to improve the suspension but hasn't the money to do it "right" (translation: Penske, translation: $). Wink

I've used this on the track and will again, finding it totally rideable, but the shock absorber's weakness really shows there, cold tearing tires. Inflating a couple of extra pounds over typical track pressures will help, but not totally cure that. If you're a rider who track rides and can push that hard you could probably justify the cost of a Penske just with a season's tire wear savings alone and could realize the benefits of a nice, tuneable shock.

But if you're a street rider, possibly a novice track rider just getting into it, you won't have the tire tearing problem and will LOVE the dramatic improvement in handling if you're riding twisties even a little hard. On the street, even experienced riders won't be able to push so hard as to have the cold tear issues and will find that it's rideable at a pretty good pace, certainly FAR better than a stock set-up. Not a Penske, but not so bad. Smiley

It requires a spring for your weight, a set of special machined spring cups and, not necessary but highly recommended, a set of links (often called dog bones) to raise it.

The spring is a 2" X 6" series from Hypercoil and is the same spring used on Penske's shock. They are available in 50# increments. The range most likely to be used on these is 400, 450, or 500#, and for the really husky ones, maybe a 550#. New cost, about $100.

The spring cups are machined from 6061 aluminum and should cost no more than $100. I can make them for that, shipped. That price may be better depending on material costs.

The links to raise the rear and built with a minor outward step in them to clear the spring's slightly larger diameter should cost no more than $65. If you weren't raising the rear the stock links can be used but a washer should be added to each side to afford just a little more clearance. The addition of the washers then requires a longer set of bolts to maintain the engagement of the locking feature on the stock nuts. The spring will just fit between the links either with this mod or a purchased Penske, but even the slightest shift of it on the spring cups or the smallest variation in diameter will cause it to rub. Not good. The additional 1/16" per side assures clearance.

Summary: The cost for the shock mods alone is about $200.
Add the links for a truly complete package and the total is $265.

Shopping for a used spring from a racer who has had occasion to change his Penske shock's spring could be as little as $25 shipped (that's what mine cost) so you could conceivably complete the whole deal for under $200. If you have access to a machine shop and can figure out the parts, maybe way less than $200.

Next lowest cost package to my awares is a basic Works Performance shock, ordered and sprung for your weight, at about $400. That's an old price and from memory so it may be more, not likely less. It would still need the links if raising the rear was to be done so add the $65 for those to complete the package. That makes a total of about $465.

The ultimate, the Penske, sprung for your weight, is around $875. It has everything including adjustable ride height. (For those not familiar, ride height adjustment is NOT the same as spring adjustment. All of these, including your original, have spring adjustment, but not ride height.) At its lowest setting it already raises the rear 7/8" but can then be adjusted up from there. It should have washers added to the stock links to assure spring clearance and then longer bolts to assure the locking nut engagement. Those longer bolts will not be hardware store stock in that size and length so will have to be ordered from a fastener supplier. Expect between $10 at best and $20 at worst by the time you cover shipping and handling, getting that package up to just under $900.

So, there you go. A good list of the options... for the rear. Grin If you're going to do the rear you should really consider doing the front, too. The best handling is when you keep the front and rear working similar. With a  spring change at the rear that will be at least a one third increase for anybody but the lightest rider (the stock rear is 300#) and it will underscore the front's soft springing.  Sad

At the front expect to spend $150 for parts to do the springs alone. That would include the springs, fork oil, and a little for miscellaneous. Add another $150 for cartridge emulators and you'll have all of the parts for the front, as good as it gets. No high dollar Penske options here, thank goodness. Wink The works for $300, the minimum for $150, or maybe shop the racers again for used.

Additional Notes:
This list is from my experience with my bike over about 10,000 miles riding as modded, riding it on both street and track, about equal amounts of each. (I use it coaching novice sometimes.) The total list of mods is:

1. re-sprung rear.
2. links to raise rear (started at 7/8", now at 1 1/2").
3. re-sprung front.
4. cartridge emulators front.
5. front raised 1/2" by sliding tubes in triple tree clamps.
6. radial tires.
7. lowered stock bars (approx. 2") using old 600 risers.
8. carburetor pilot screws out 2 1/2 turns.
9. EBC front brake pads.
10. EBC floating front rotor. (Just installed, warped two stockers beyond hope.) Sad

That's the TOTAL list. And in that configuration it can be ridden quite fast without doing scary things. Smiley If I were racing it or running against my lap timer at track days, going for the track record, Wink I'd certainly want a Penske. If one comes my way at a steal, I'll buy it and put it in. Other than that, I'm content with the bike as it is.
« Last Edit: January 19, 2007, 10:38:55 AM by dad » Logged
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« Reply #1 on: January 19, 2007, 11:59:44 AM »

 :)Thanks dad! I really appreciate you sharing this. That's a great writeup. I am definitely saving up to do the economy option rear and then front. Even if I never make it to the track, with my heavier weight(I'm working on that too Tongue) the bike will be so much better.

Great Job! Smiley
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« Reply #2 on: January 19, 2007, 03:18:12 PM »

Stupid human question:  What exactly does wallowing feel like?  What is happening with the bike when it "wallows"?
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« Reply #3 on: January 19, 2007, 04:17:34 PM »

Stupid human question:  What exactly does wallowing feel like?  What is happening with the bike when it "wallows"?
Good question.
Here's my stab at an answer. When we say a bike wallows in curves and corners we are describing a sensation that feels like the back end is hinged. It feels like its fish-tailing a bit but the movement is in the frame and shock components, not the tire breaking traction.

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« Reply #4 on: January 19, 2007, 07:40:12 PM »

wow, great post dad, im at work right now and only had a chance to skim over it, i was wondering if second gen rear shocks fit first gen EX500's?

thing is, i have an 89 and might be inclined to pick up a used second gen shock if it would fit my bike.

again im at work and only skimmed over the post and am sorry if this was mentioned in the thread.
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« Reply #5 on: January 19, 2007, 08:59:35 PM »

"i have an 89 and might be inclined to pick up a used second gen shock if it would fit my bike."

It'll fit...but it is the same crap shock...only newer.
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« Reply #6 on: January 20, 2007, 12:32:14 AM »

"i have an 89 and might be inclined to pick up a used second gen shock if it would fit my bike."

It'll fit...but it is the same crap shock...only newer.

hmmm

Quick question , is the ZX6 shock any better than the EX  Huh I know it's adjustable , BUT is it any better ?

okay then same question, would i be able to put a zx6r shock on my 1st gen?would it fit/work better?
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« Reply #7 on: January 20, 2007, 01:06:57 AM »

Quick question , is the ZX6 shock any better than the EX  Huh I know it's adjustable , BUT is it any better ?

More importantly, is it the right spring rate, proper stroke for this linkage ratio, and dimensionally able to drop in. I don't know the answer to that but highly doubt it. It wouldn't be a reach to assume it has better dampening characterisitics. The stockers don't set a very high threshold. Smiley At the same time though, the build quality isn't bad to my awares. They are a Showa shock, decent seals, decent chromed shaft, don't leak... you know, shitty, but retain all of their shitty qualities over a long service life. Shocked I'd call that a quality of sorts. Grin

What I worked out was a low cost alternative to the grossly soft springing and the resultant poor handling, and it's all bolt on. The real answer is very costly. This is an alternative for those who are unable or unwilling to spend what it takes to do it really right. And it's NOT a bad alternative, especially for just street use. I feel that for street riding, on a scale of zero to a hundred, where stock is zero and a custom Penske is 100, a properly sprung stocker will get you about 80. Decent for just street use, WAY better than stock.

I don't know what else to say about this. It's a dramatic improvement over stock and at a fraction of the cost. On the track, the shock's weakness shows in cold tearing tires but that's not an issue on the street. If you're track riding HARD, then you could probably pay for the Penske in tire savings alone and get the additional benefit that a properly tuned shock affords. If this were a powerful sportbike, the same thing that causes the cold tear could result in a propensity to slides but these don't have that kind of power so it's not a problem. You can get away with it.

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dad
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« Reply #8 on: January 20, 2007, 01:24:39 AM »

okay then same question, would i be able to put a zx6r shock on my 1st gen?would it fit/work better?

Absolutely not. I have a ZX-6R (636) for my main track bike and the shock and spring is WAY too big in diameter. It won't physically fit in the space available, much less link up to the attachment points.
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« Reply #9 on: January 20, 2007, 03:15:29 AM »

okay then same question, would i be able to put a zx6r shock on my 1st gen?would it fit/work better?

Absolutely not. I have a ZX-6R (636) for my main track bike and the shock and spring is WAY too big in diameter. It won't physically fit in the space available, much less link up to the attachment points.

ah, thanks for the info.

So is there no point with replacing my existing shock from 89 with a used one from say 2000 up? if i were to find one off a bike with less miles, would i notice a difference?should i not bother and just spend my money on booze n hookers?
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'89 EX-500
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« Reply #10 on: January 20, 2007, 10:12:22 AM »

So is there no point with replacing my existing shock from 89 with a used one from say 2000 up?

It seems they are the same so unless yours is malfunctioning, no point in replacing it. I have no direct experience with the pre-94 models so can only pass on what I've read or heard on those. From Bitzz's post, it seems they are the same so could be used to replace a bad one.

The main purpose of the thread was alternatives to improve handling as you ride these harder and harder. The Penske and Works shocks have long been identified as solutions but are fairly costly. I was just adding another lower cost option and first hand review of the performance, finding it to be a dramatic improvement, and enough details that the change could be completed by mere mortals. Well worth the effort if you're finding the wallowing point or the pegs scraping but a Penske isn't in your budget. Also, a good stepping stone if you're one who is progressing in the learning curve and trying to push a little.

That's exactly what my motivation was in doing this in the first place. My daughter, who had been riding this on the street, was ready to start track riding. I didn't want her to come up against the wallow and think it was part of what she had to learn to deal with. It's not. I used this effort as a learning tool for her to understand the hardware functions as well as the riding of it. As it came together, I found it to be so much of an improvement that I felt it was worth passing along to others who might be in the same position. I have since bought springs for my weight and ride the bike myself at times. It's fun.

Hope that's helpful.
 
« Last Edit: January 20, 2007, 11:34:30 AM by dad » Logged
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« Reply #11 on: January 20, 2007, 02:56:07 PM »

As mentioned earlier the build of the stock EX shock is not bad per se...it just doesn't cut it. If you get a NEW OEM shock it will exhibit the same bad traits.
I think the problem with the OEM is over heating, there isn't enough oil in it...and the oil in it is fish oil.
I have heard of people getting the OEM shock FIXED. Replace the fish oil with something decent, renew the seals, maybe a little tuning in there, AND ADD A RESIVOIR.
If you weigh more than I do, about 135#, your biggest problem is the spring. If you can get the sag set, then ride without bottoming or getting coil bound you're set.
If you can't you need a spring.
A point that doesn't seem to be coming out in these posts that is vitally important to what you are doing here is that the spring and the shock do two VERY DIFFERENT jobs. You HAVE to separate these jobs.
If you have the right spring, but the wrong shock...the thing won't be right...or...if you have the right shock, but the wrong spring...the thing won't ride right...BUT they are two very different problems, with different symptoms AND different soloutions.
Just because on a motorcycle the spring and shock are seen as a unit doesn't mean that they ACT as a unit.
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« Reply #12 on: January 21, 2007, 07:10:44 PM »

As mentioned earlier the build of the stock EX shock is not bad per se...it just doesn't cut it. If you get a NEW OEM shock it will exhibit the same bad traits.

Yes, I agree. That's where I was going with that reply. If you DID have a shock with a damaged shaft, leaking, etc, there are often used ones showing up on E-Bay for a very fair price. I've seen them go for $35. That's what I would do if I had a bad one. They seem to hold up fine, albeit with all of their faults. Smiley

I think the problem with the OEM is over heating, there isn't enough oil in it...and the oil in it is fish oil.

Actually, re-sprung, the shock runs cold while the tire runs hot. I actually took temp readings out of curiousity when I discovered the tire issues running the track. (Shannonville, Ont actually) Smiley The energy is there and is not being contained by the shock so shows up in the tire.

It was the second day I ran the re-sprung shock and noticed that, while riding and handling dramatically better, it was abusing the tire. Shannonville has a rep for being a bit abrasive but this was way out of that explanation range. This was while running Michelin vendor recommended track pressures on a 150 Pilot Race, then Pilot Power. I found tire temps at 175 F. Shocked These don't have THAT kind of power to justify anything NEAR that temp and was underscored by bigger bikes running the same brand tire with similar recommended pressures and similar weights, lapping faster as their power affords, NOT having this problem. After riding with another coach aboard one of the Ducati rental bikes, a bike of similar weight, lapping together for about 10 minutes, we compared tires and temp readings. It was very interesting and displayed a trend I came to expect.

His tire was wearing beautifully, scuffing a little but as expected, reading 135 F, while mine was at 175 F. Shocked Then we shot the shock bodies. His was at 138 F while mine was at 104. Smiley Very interesting.

I attribute that difference to his shock working to contain the energy of the small movements while my shock was allowing the oil to whistle through unrestricted, never absorbing the energy therefore never getting warm. (Note:1) The energy was left for the tire to deal with so the heat appeared there. Adding several pounds to the tire helped this tremendously but was still not a complete cure. The tire still tears a bit, way more than it should. And that's what my qualifier about using this as a track cure is all about. And why I suggest that for the track, even though it will handle OK, your increased tire expense may exceed the cost of purchasing the proper package, the Penske. And the Penske, being a proper package, will afford additional handling benefits. Those are likely to show in better lap times. WIN, WIN! Wink

On the other hand, on the street especially, and as a rider is gaining in skills while his wallet remains stagnant, Wink installing a proper spring will dramatically improve the handling and allow his skills to progress. You won't experience the cold tearing because you can't run that hard on the street even if you're riding stupid fast for the street. Even on the track, unless you're able to push pretty hard, it will STILL afford a benefit. As you start tearing tires, add a couple of pounds and start saving for that new shock. Wink

I have heard of people getting the OEM shock FIXED. Replace the fish oil with something decent, renew the seals, maybe a little tuning in there, AND ADD A RESIVOIR.

I think at that point, I'd save the money and put it towards a Penske. It would take a suspension guy with tools and knowledge to perform that work and, unless he's a buddy giving away his time, I can't imagine that the labor wouldn't get well into the range of a proper shock. And even at his best, he won't be able to give you all of the features designed into the Penske.

If you weigh more than I do, about 135#, your biggest problem is the spring. If you can get the sag set, then ride without bottoming or getting coil bound you're set.
If you can't you need a spring.

And THAT'S what this is all about. Even at 135# you could use a stiffer spring but may not experience the gross wallowing that a heavier rider will... at least not as soon. These things are undersprung worse than ANY bike I've EVER seen that has the word "sport" in its category description. The stock spring is about 300# per inch as I measured mine, a '96, using a load cell and arbor press in my shop. At 160# you could already use a 400# spring on the street, maybe more on the track. That's a full 1/3 increase. And THAT'S why the improvement exists... and is dramatic, moreso the heavier the rider is.

A point that doesn't seem to be coming out in these posts that is vitally important to what you are doing here is that the spring and the shock do two VERY DIFFERENT jobs. You HAVE to separate these jobs.


Yes. The original post contained qualifiers for the claims, but in answering these questions the details behind the claims are hopefully clearer... and educational. Much of this is generic to bike suspensions.

If you have the right spring, but the wrong shock...the thing won't be right...or...if you have the right shock, but the wrong spring...the thing won't ride right...BUT they are two very different problems, with different symptoms AND different soloutions.

That's right. BUT, it's a time honored fact that getting the spring right is first, holding the bike up properly in the travel range, then the shock to help control it smoothly. This fix addresses the most important element, the spring, while ignoring the secondary element, the shock. That's why it is a qualified fix. This fix oversprings the shock. It is a dramatic improvement but not perfection. Hopefully the extensive descriptions that have evolved in the posts have clarified that. It IS a dramatic improvement, it is NOT perfection. If the cost benefit wasn't so dramatic it wouldn't be worth the effort. But it is... so it is. Wink

Just because on a motorcycle the spring and shock are seen as a unit doesn't mean that they ACT as a unit.

Yes. Smiley



Note:1 If the stock spring was installed I would expect these readings to be different. I would still expect a hotter than optimum tire, just not AS hot as I saw, BUT... would expect more shock temperature. In this scenario, the shock is trying to do the spring's job, wallows, travels excessively trying to contain the energy, and becomes warmer. The shock is doing more work therefore exhibits the additional heat.

I never checked this exactly this way but did track ride it with the original spring. The tire was not so overstressed but it wallowed viciously. That was the motivation behind this whole exercise. I also gained four seconds a lap at that same track after re-springing it. And that is within 1.6 seconds of what the fastest local EX racer, riding a full race prepped bike, with proper suspension, is getting on that track. Mine is still streetable, stock geared, taped lights, etc. I let that confirm what my experienced seat of the pants told me. Smiley
« Last Edit: February 14, 2007, 12:58:32 PM by dad » Logged
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« Reply #13 on: January 21, 2007, 07:22:22 PM »

Holey Moley.  These postings oughta come with some fractional college credits. 
Read enough of them, take a quiz, get some credit...

I weigh 185, 5'11":  just a street guy who wants a bike that is predictable & capable for emergencies.
The rear spring change w/ stock shock looks about right, unless I missed something.
Thanks.
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« Reply #14 on: January 22, 2007, 08:00:35 AM »

This thread is exceptional for anyone interested in modding their suspension.  I'm taking the plunge this spring Roll Eyes , and am now saving for a properly weighted rear spring, and new springs for front (maybe from Race Tech, or maybe just cut and shim depending on availability of cash).  I had another thread asking if I could really feel a difference since I'm only street riding at present, and "dad" suggests this is a real possibility with the indicated mods.  As FOG said "if you don't try you'll never know".

Mr. SciTrek I'm your size, and would appreciate hearing about your experiences in upgrading suspension after you begin.

"dad" I'll PM you about the specifics of bones and cups for the new rear spring.
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« Reply #15 on: January 22, 2007, 12:52:40 PM »

I appreciate that this appears to be of interest and is being helpful to some. It's time consuming to make these long posts and even at their length, some subjects aren't in as full detail as I might like. But it's coming out. Don't hesitate to read some of the suspension websites, especially their tech articles or FAQ's.

Let me take a minute now to underscore a long understood riding principle that "It's the rider, not the bike". Don't perform these mods with the idea in mind, thinking or expecting that with these mods you'll suddenly ride like Rossi. That will never happen on this or any other bike. You still have to develop the skills to use what you've got. This takes a long time and a lot of practice. Pushing past your comfort zone, forcing the learning curve, re-sprung or not, will get you crashed.

Well then, why bother with any of this? If this was the ZX-6R board or any other later model sportbike, I'd be agreeing. I'd say leave it alone and get to work on your skills. BUT... this is the EX-500 board, home of the most grossly undersprung sportbike in the world. Wink
Example: I'm planning a spring change on my ZX-6R right now. The stock springs are .85's, progressive wound, and I deliberated between .90's and .95's, both linear wound. I'm tweaking, not making dramatic changes. I ordered the .90's because I'm teaching a lot, running less than my max all of the time, and feel that will be best all around. Now, for comparison, what's in the front of an EX? Stock they are .46's or so, Shocked and hardly a one of you will end up with less than a .80, many will be as high as .90 and some at .95's. THAT is a BIG change. In the range of DOUBLE what they came with, not just a step or two. That's why, even early in the learning curve, it can be helpful to get them closer to right. A step or two on the soft side is still rideable pretty quick. But fully one half of the right spring force is asking a little much of the rider. Wink It helps as you learn, letting the bike remain somewhat planted and letting the rider maintain some confidence as he pushes harder.

Now, with THAT qualifier in mind, Wink what CAN you expect from this. If you're already experiencing peg scraping or wallowing, you'll get some immediate benefit. The bike will be much more planted, a more solid platform. It's also possible, even likely, that if you're having some of those issues that YOU might be contributing to the problem with your riding position, weighting the bars, and such. A combo effect. Wink Never quit working on your skills. Throughout your riding career, look to your skills for better performance, not the bike. THAT'S where the biggest bang for the buck lies.... these bikes being the exception as noted. Smiley

And if you're not experiencing any of those problems? Well, especially with cartridge emulators in the front but also the springs closer to correct, the bike will handle the bumps more appropriately, not dive as bad on hard braking even to the point of bottoming the front suspension hard, and will exhibit a generally more solid feel. That confident feel may have you riding a little faster but only because the firmer feel will help your feeling of comfort with the bike. It will have some benefit but it is really a factor of the harder you're pushing the hardware, the more you'll realize the benefit. For a putt around town cruiser, especially with a light rider, it will be minimal.

Hmmm. Hope this is helping.
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« Reply #16 on: January 22, 2007, 03:55:47 PM »

Well, this has turned into more than I bargained for but....

We've jumped right over a basic tool in setting up your bike, spring change or no. That's checking and setting the sag. Anybody care to spell that one out? Wink

Cover "free sag" and "static sag". Then, with those numbers known, we can use them to tell if our springs are near right, regardless of their rates. The difference between the sag rates tells us that. It's also pretty generic for any sportbike. It can identify something that's grossly wrong or in the hunt, within the range of rider preference, not right or wrong.
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« Reply #17 on: January 22, 2007, 04:07:53 PM »

It's been done look in FYI for this:
Setting your Sag
A freebe to better handling
One of the most often overlooked adjustments to your Ex is the Sag setting This is the amount the bike's springs colapse when you sit on it. Both front and rear are adjustable, Here's how.

Measure first: Put a piece of tape or a mark of some kind on the body near the rear. with the bike on it's wheels held vertically by a friend your going to measure from the ground to this mark like this.
Have your friend:
1 lift the tail as much as he can and let it down slowly, measure

2 push down on the tail and let it rise slowly, measure

3 average those two measurments. thats the top point

4 Have both your friends try to bottom out the travel to get the
bottom measurments.

4 sit on the bike and repeat the process, have a 2nd friend measure for you (you do have 2 friends don't you?)

The diffrence should be about a third of the total rear wheel travel.

If you get too little you spring is too stiff, strong , hard, back off the adjusting collar around the top of the shock. Theres a lock nut you must release first. a long screw driver and a hammer are your tools.

If your sag is too much tighten the spring collars. Same process as above.

Front
The process is the same as the rear, but the adjustment is tougher
to make adjustments you must remove and change the leghtn of the spacer above the springs.

To do this:
Prop the front wheel off the ground, remove the handle bar riser from the top triple clamp leave all the cables connected. With a small 2 legged wheel puller hold down the plug against the spring. fish out the lock ring. Release the wheel puller and the spring will push the plug out for you. (no it won't fly.........far). remove the spacer on top of the spring and fit a longer or shorter one according to wheather you want to stiffen (Longer) or soften the forks.
Reassemble and measure again. NOTE HERE: bend the end of the lock ring up and in for about 1/8 inch to make it easier to fish out the next time.

The next time is now if you didn't get what you want.

General notes: The ex is rather softly sprung and responds well the stiffining both ends. Unless you a 100 Lb. Girl (or ride like one).

Usually a stronger spring is required in front for 150 lb or more riders.

Stronger rears are also aavliable too but fitting one will most always overpower the shock and cancle any gain. General note more spring requires more dampining. In front you can thicken up the oil, in back your screwed (Penske, but still screwed $700+ ).

Have fun Kiddies and ride safe.
FOG
« Last Edit: January 22, 2007, 06:59:47 PM by FOG » Logged

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« Reply #18 on: January 23, 2007, 01:25:38 PM »

...If the number you get is between 90-100 mm your good to go ...

Whoa! That's 3-4 times what it should be. Shocked

I'll try to post some more detailed stuff later. The whole deal in all of its gory detail. Wink Fog's basically right but might be hard to follow if you don't already know what you're doing.
« Last Edit: January 23, 2007, 02:27:33 PM by dad » Logged
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« Reply #19 on: January 23, 2007, 01:38:27 PM »

I guess the head instructor at MMI in Florida doesn't know what he's talking about  Huh

Not if hes recomending 4 inches of sag.

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« Reply #20 on: January 23, 2007, 02:19:59 PM »

Those are dirt bike sags. Sportbikes are much less. They don't even have much more suspension travel than you're talking of using for sag settings.

A sportbike for street use can be as little as 7/8" at the stiffest extreme, but is getting in the realm of troublesome after 1 3/8". They get worse the further out of the specs you go.

And there's not a suspension expert you'll talk to who would agree with those numbers you quoted. If you require the measurements in millimeters it's between 30 and 35mm that you're typically striving for. I'm old and think in inches Wink ... but .03937 gets me the mm's every time... including too many decimal places for this work. Smiley

Please, let's not fight about this. If you're not clear or don't understand something, please ask. It may be tedious at first but in the end, it's pretty straightforward stuff. I'm sure we can get to an understanding. And do you know what? Most DON'T grasp this and don't know how to interpret what the info is telling them. I guess I should get typing. Sad Grin


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« Reply #21 on: January 23, 2007, 02:30:51 PM »

"I guess the head instructor at MMI in Florida doesn't know what he's talking about  ...."

You're right about that!
This write up is about at track setup of a race bike, the question was about buddie's street bike.
Their system would work IF they have done alot of the preliminaries,have a good set of race notes, using the SAME bike, with the SAME rider (who doesn't gain or lose an ounce from weekend to weekend...yeah right), etc etc. On a race bike the variables should be known before hand, only to save time in the pits, from doing set up weekend after weekend.

We don't have that luxury.
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« Reply #22 on: January 23, 2007, 06:44:14 PM »

Since I've opened this can of worms, might as well try to finish it. Sag settings. What should they be, how to measure, and what we can tell about the appropriateness of our spring rate from them. This is also pretty generic for sportbikes in general so it's a good thing to understand.

There are two sag numbers.
One is called "Free Sag". That is the amount that the suspension will compress without the rider on the bike. Just the bike, standing upright, all by itself, on level ground.

The other is called "Static Sag". That is the amount that the suspension will compress with the rider on the bike, standing upright, on level ground.

The sag is adjustable by changing the "pre-load" on the spring. That is accomplished by turning that spanner nut on top of the spring for the rear, or changing the spring spacer lengths in the forks at the front. OR, most newer bikes have adjuster screws on the top of the front fork tubes that allow some pre-load adjustment without requiring modification to the internal spacer length. (Unfortunately, the EX isn't one of those.) Sad When acceptable ranges can't be accomplished, it requires changing the spring. It will become clear as we go. Roll Eyes Grin

GETTING THE MEASUREMENTS

For this segment we'll focus on the rear but the basic principles/theory apply to the front equally. There will be details that vary but the core principles remain the same.

You'll need a tape measure, a friend or two to help with holding the bike and getting the readings, and I recommend some duct tape to attach the measure to the bike. Extend the measure and lock it in the extended position. Tape the free end to the body directly above the rear axle, letting the locked tape measure body hang down, measure tape in line with the axle. (Place a strip of ductape on the body to serve as a paint protector, then tape the measure to this.) It is nice to align a whole number with the reference point you chose on the axle. This would be with the suspension topped out, extended fully against the top stop. Now proceed to getting your measurements.

At the front, measure the fork movement directly. Place a wire tie around one of the fork tubes to use as a sliding reference point. As you compress the suspension it will slide the tie up the leg, holding the travel reference point to be measured.

FREE SAG, NO RIDER

At the rear.
The desired "Free sag" is a pretty well fixed number and should be between 1/4" up to as little as just zero. Any tighter and the bike's suspension can't extend sufficiently after hitting a bump to maintain tire contact with the ground. We'll look at this more, later. It is measured by first lifting up on the bike to be sure the suspension is fully extended, topped out. That can be done by pulling it over on the sidestand or just lifting up on the grab rail. In this position, check that the axle reference you are measuring to aligns with a whole number on the tape measure. It makes it easier to get your measurements if it is aligned with a whole number. Then, gently let just the weight of the bike settle down on the suspension. Make sure the bike's vertical and you're not lifting on it or pushing down on it, just steadying it so it won't fall. Record the change in measurement at the axle, the amount that the suspension compressed from topped out.

Now, to cancel out the stiction of the suspension components from your measurements, bike still vertical, push down on the bike, compressing the suspension slightly, then gently release it. Let the bike come up slowly and when settled, record that dimension. The difference between the two is the stiction of the suspension components and needs to be cancelled out. Take 1/2 of that difference between the two measurements and either add it to the first measurement (compression, the one from letting the bike settle from the fully extended position), or subtract it from the measurement taken by compressing it and letting it rise (rebound). That number is the "free sag", corrected for component stiction.

If you got NO movement from topped out to the weight settled on the suspension, then the spring may be too tight, too much pre-load, and we have no way of knowing how much that is. Of course, it's possible that the suspension is just topped out, not pressing hard against the top stop but just settled against it. To determine if that's the case, with the bike standing upright, apply the lightest of downward force on the bike, just the force of a lightly placed fingertip. If it starts to move right away, that could be considered zero and may be left alone at this time, BUT... only the lightest of downward force, just a fingertip's effort. Otherwise, you have to back the spring pre-load off and measure until you get at least some sag, or at least a number that we can comfortably call zero as we just defined it. (More on this later.)

As long as you have some "free sag" and have recorded that number, corrected for stiction, then proceed to measuring the "static sag". We'll adjust after we get both of these numbers and digest what they tell us.

At the front.
All of the basics remain the same but the methods of getting the measurements will be slightly different. Place a wire tie around one fork leg. Slide it down to engage the fork leg. Now, it will slide with the fork movements, pushed to a position by the travel. As you lift the bike the tie will remain at its highest travel point so the travel can be measured directly from the tie to the top of the fork leg by topping the suspension out and measuring the exposed fork leg directly. For rebound dimensions you'll be bouncing the front down and releasing slowly, therefore will push the wire tie past the point that you're trying to measure. For those dimensions, once the load has settled, hold that position while the person recording the measurements slides the wire tie down to engage the fork. Then unload the bike, top it out, and record the measurement. All of the principles remain the same. Only the method of measuring has changed.

STATIC SAG, RIDER ABOARD

"Static sag" is the measurement of the suspension travel with the rider aboard, feet on the pegs, in riding position. To get this measurement it will take a person or two to hold the bike upright and one to read the tape measure. The rider should assume riding position and try to remain still to assure the accuracy of the measurements. To measure the rear it may help to steady the bike from the front to have the least possible effect on the rear readings, and from the rear for measuring the front.

Proceed in the exact same fashion you did getting the "free sag" numbers, front and rear, except rider aboard this time. The measurement is that from the suspension topped out at full up travel to compressed with the rider aboard, bike held vertical. (This why it's handy to set a whole number on your scale to the topped position at the beginning. No need to recheck it. It doesn't change.) Lift the bike slightly and let it settle gently, recording the number. Then compress it and let it rise gently, recording that number. Take 1/2 of the difference between those two readings and add it to the compressing number or subtract it from the rebounding number, the same as you did getting the "free sag", cancelling out the stiction. Now we've got the "static sag" number, corrected for stiction.

Again, measuring the front repeats the steps described for "free sag", but with the rider aboard. OK?

Checking the measurements a couple of times is good practice to be sure you haven't accidentally pushed on the bike in a fashion that will alter the readings.

NOW, we got 'em, what do we do wit' 'em. Wink

SO... JUST HOW DOES THE SPRING WORK?

Well, first, let's think through what the spring is doing and get rid of an often held but wrong idea. The idea that winding down on the spring makes it stiffer. It DOESN'T!  Shocked Bear with me on this, and don't proceed until you understand it. It is critical in the whole picture and once understood, you'll never refer to "winding down" on the spring as "making it stiffer" ever again... because it doesn't and you'll be part of the select few who understand why. Wink Shocked Grin

EXAMPLE:
We'll pick some nice round numbers out of the air to demonstrate the principle, keeping the math simple, focusing on the principle as it applies to the spring ONLY. The example will focus on the rear but the same principles apply at the front. (BTW,this principle is generic to springs but we're using a suspension example.)

As the need for a specific number arises, we'll use:
1) a 100"# linear spring.
2) a 100# force each end from a 200# rider sitting on the bike.
3) a 200# bike, balanced with 100# at each end.
4) 5" total suspension travel
5) For simplicity, we'll place the spring in straight alignment/compression with the axle so we don't have to adjust for the leverage/ratios of the swing arm or rocker linkages.

Here goes. Smiley Spring, all by itself, not in a bike. It's a 100"# linear spring. That means the spring compresses 1" for each 100# of load applied to it. If we apply a 200# load, it compresses 2"... and so on... (until it's coil bound, of course). Wink Got that? Make sure.

OK. Now, we have this spring in the bike, pre-loaded with the adjustment nut to a number, let's use 1/2". As such, we have the nut wound down 1/2" so have pre-loaded it with 50# of force. Got it so far? Make sure. (Linear spring, 100"#, wound down 1/2" = 50# of force.)

OK. Now, if we were measuring the "free sag", what would we do? We'd lift on the bike to be sure it's topped out. Right? The spring will extend until it comes up against the adjuster nut. The nut that we wound down 1/2", pre-loading the spring with 50# of force. Right? That's our starting point. Now, when we stand the bike up to measure the sag, applying its 100# of force to the spring, it will move down, compress. How far? An additional 1/2", yes? The first 10, 20, right through to 50# never caused any movement. Why? Because we already had a 50# pre-load in the spring. At 51# and beyond we started to get movement. Got it so far? Make sure. We would have a reading of 1/2" "free sag". (With a 50# pre-load on a 100"# spring, placing 100# load on the spring results in 1/2" additional movement.)

OK, if you're still with me, Wink let's look at the rider aboard. We already determined that our example has 1/2" "free sag". Now we're going to place an additional 100# force on the spring by putting the rider on the bike. We were already compressed 1/2" (free sag) due to the settings we had so when the rider gets aboard, we add another 100# so the spring compresses another 1". We now have a "static sag" of 1 1/2". Right? We had a 50# pre-load, applied a 100# force to the spring from the weight of the bike alone, compressing it 1/2" additional, then added 100# more, compressing it another 1", to the present measurement of 1 1/2". Got it? Cool, huh? Smiley

Now, let's play with our adjusting nut, see if we can make this example stiffer.... or do we just move it around, wind it up OR wind it down.
Let's turn the nut down another 1/2", adding another 1/2" pre-load. That has us at 1" pre-load on our 100 pounds per inch spring. So what happens to our sag readings? Our pre-load is at 100# and our bike only weight is 100#, so the "free sag" goes to just zero. Right? Got it? Therefore it follows that our "static sag" goes to 1", right? Our "free sag" is now zero so when we put our rider aboard, his 100# force moves the bike down 1". Hmmm.

Winding the nut down hasn't done anything but move the starting height that all of this occurs. Putting 100# weight on it moved it 1", same as before, even though we wound down 1/2" on the spring. We didn't change the amount the suspension moved. The same load moved it the same amount, just from a different starting point. Got it? Did we "stiffen" anything? No.

Now, just to complete the circle, we'll back the nut off to zero spring pre-load. We stand the bike up with its 100# load and measure our "free sag". It will be 1", right? And then we put our rider aboard with his additional 100# and our "static sag" will go to 2", right? If you're seeing it and agreeing, you've got it... this far.

OK, so all of the screwing we do on that nut has not directly changed the spring's stiffness, the loads, the spring's ability to handle loads, NOTHING... except the ride height, moved it up or down. BTW, we don't want to adjust ride height there. While it effects ride height, we don't want to adjust ride height there. More on that later.

Now, and this is important. All we want to use the adjuster nut for is to move the spring's operating range to optimize the available suspension travel, getting it in the most useable, practical operating range. The best range for both up and down movements, to allow the wheel to follow the road the best it can.

Let's continue to use our ficticious suspension above, one more exercise at the extreme to underscore the point. We wouldn't want to adjust it to have 4" of "free sag" in a suspension that has a max travel of 5", would we? As soon as our rider got aboard, his 100# would move it down another 1" to 5" "static sag", the full operating range of our suspension. The first bump we hit, the suspension could absorb nothing. It's bottomed. Not that it is a likely scenario to see anything this extreme, it's still demonstrative of the principles involved and adding spring tension at this point... or taking it away, we accomplish nothing. The suspension is completely out of its operating range, unable to do a thing for us.

And to complete this circle of extreme examples, what if we pre-loaded the spring 2". It will be pre-loaded with 200# of force. Stand the bike up on its own, applying its 100# force, and the suspension never moves, right? Now put the additional 100# force of the rider aboard. The suspension still doesn't move, right? Make sure you're following this far. Now, the first bump you hit, the suspension moves a bit because it exceeds the 200# load and pre-load, the bike goes up a bit, and then as you clear the bump, IMMEDIATELY the wheel leaves the ground!... because we've got it set topped out hard against the adjuster nut, unable to extend. Shocked Not good. Wink But this is EXACTLY the nature of the problem you create as you try to wind down on too soft of a spring to get an appropriate "static sag", having ignored the "free sag". More on this later. Smiley

CONCEPT SUMMARY

At this point we should have a good grasp on the basic concepts and terminology as it relates to the springs. What we should understand is:

1) The definition of "free sag" and static sag".
2) How to measure them.
3) A given spring has given capacities, and will move a predictable amount for a known load. (A 100"# spring moves 1" for each 100# applied. 200# will move it 2", etc.)
4)The adjuster nut changes the height, the position in the available travel range that the spring moves as its capacity to support the applied load dictates. It does not stiffen the spring. It does move the range in which the spring operates.
5) The travel range is fixed by the shock travel length at the rear, and the fork travel length at the front.

This is continued in another post titled: FINAL EXAMPLE, CONCEPTS APPLIED
This one exceeded the allowable characters. Shocked Grin
« Last Edit: January 25, 2007, 12:20:31 AM by dad » Logged
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« Reply #23 on: January 23, 2007, 09:05:11 PM »

Hang in there...  some/many of us are still reading & thinking.

Keep the emotions in neutral & the brain in gear & analyze, eh?
The group of us will get things squared away, or agree to disagree... no harm done, eh?

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smithmax
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« Reply #24 on: January 23, 2007, 10:34:32 PM »

As far as racing goes, it appears that the consensus is to purchase a Penske (or other brand) set-up.  I was considering this until A) I learned it would cost me ~$700 and B) I learned that this is more for "racing" applications, not really just tooling around town/hills, sometimes with the wife on board.  The alternative I was told about was to purchase replacement parts, and send my set-up to a "Suspension House" (anywhere that has the know-how and the technology to professionally assemble and set up suspension).  I was told that this would only cost $200-$300 for everything, and it would be the best (most cost effective) solution for a guy like me...

Just my two cents
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