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[2001ex500]

This weekend I took a shot at cutting my front springs as an inexpensive route to stiffening up the very soft front suspension. I set up a test rig with a digital bathroom scale to make sure I wasn't too far off on my calculations. The racetech.com site is very helpful because it will tell you a suggested target spring rate. It told me I needed a .90kg/mm spring for my weight on the street. I decided to shoot a little lower and test ride for a while, and then cut more off later if really needed. Once you cut it you can't put it back.

The stock spring is linear. This is an older design than the progressive spring more commonly used today, but it makes it much easier to accurately calculate the cut needed to get a desired spring rate. Both ends of the spring are also identical, which is just one less thing to get confused. This is as good as it gets for cutting springs. In stock form it is 17 inches long. The racetech site listed the stock spring rate to be .585 kg/mm and I measured a similar value on my test rig.

From another post the formula to calculate the spring rate is:

 the original spring length/ new spring length  X Original spring rate = New spring rate

I ended up with a new spring length of 12 inches, that is cutting off 5 inches of spring. That kind of scared me at first (sounded pretty drastic). That should give me about a .83 kg/mm new spring rate which was about where I wanted for starters. I verified it on the test rig after cutting and it was about what it should be.

Couple more things. Fog's tip about using a 2 claw puller to take out the fork plug is super! I can see struggling with that thing trying to get that little snap ring out. It just takes 30 secs and it's out.

16mm washers fit just right in the fork tube. I replaced the stock washer with one of these because it was much thicker and stronger for distributing the loads from the smaller surface area of the cut end of the spring to the spacer. They also make an easy way to increase the preload or length of the spacer if you need a little fine tuning. About a 1/16 inch per washer.

I used 3/4" black pipe (used for gas piping - metal, not ABS plastic) for my spacer. It has a thick enough wall so is plenty strong for the long spacer I needed. I combined all spacers into one (and preload) so ended up being 8 13/16 inches long! The outside diameter was a little smaller than I ideally would have liked but that is what fit and was readily available. $2.50 per spacer from HD or Lowes. Type K  1" copper pipe has a better outside diameter and a pretty thick wall but would cost much more. I found an old piece I may use for any adjustments I finally make.

I set my oil level at 5 3/4" to start with and will add if needed. I used 10W oil (actually Mobil 1 Synthetic ATF). The local cycle shop didn't have any good stuff, and I had this on hand. It is very temperature stable (as seen in big improvements in my vehicles cold weather shifting) and was better than the stuff at the cycle shop(also basically ATF). I expect I may be changing it out eventually as I tune but has worked very well so far.

I preloaded the spring 3/4" which I realize now is probably too low. dad had reccommended a preload between 3/4" to 7/8" for a .90 kg/mm spring and I realize now I should  have gone for 7/8", maybe an 1" with my lighter .83 kg/mm (dad can correct me here) but it was late and I was tired. Fortunately, a couple 16 mm washers can fix that easy, so it will be OK.

I have not measured the sag yet so I really have no results to report technically. I managed to sneak in a quick ride yesterday and it was MUCH improved. The fork used to dive just coming off the centerstand before, now it's nice and stable. I didn't try any panic stops, but even the overall feel is so much improved. Like I noticed when I changed the rear spring, ironically, large bumps or drops were more comfortable than stock because the suspension travel was so much reduced. I did tend to feel small road imperfections more but not at all harsh. Another nice improvement was in stability in turbulence on the interstate. Now I can feel the air buffeting me from all sides but the bike stayed nice and stable. It used to get a squirmy feel in that situation as I increased my speed and I'd have to slow back down to feel safe.

Anyways, more tuning is needed but even so far the road feel of the bike is greatly improved between the proper rear spring, the cut fronts and 1 5/8" rise from dogbones. I'm hoping to go on my first "road trip" so to speak next week and I am much more confident with the improved feel.

Many Thanks to dad, Rich and Fog and everyone else who helped so much along the way! This forum rocks!

Thanks 

[FOG]

As long as we have such a ambitious soul listening here's an old racer trick to getting a very sophisticated fork. that very tunable.

Cutting the spring to get the best rate for most of the track , but those troublesome compressions that bottom the fork out are hard to deal with with a single rate spring.
Find a smaller set of springs that will drop down inside of the main spring. (I used the internal valve springs from the EX). the rate of this spring doesn't matter too much.  Then cut a piece of tube of a length that will just engage the secondary springs an inch or two from full bottom. Now you can have a fully tunable dual rate fork by just fiddling with the legnth of the secondary tube.

FOG

[MrSciTrek]

I wasn't planning on messing w/ my '05s suspension for a long time.  But yesterday I went for a ride including some 30 mph crosswind gusts... it was not relaxing.

I was thinking that the long front fairing on the bike was like a sideways sail & causing the grief... just live with it.  Your comments below include that the squishy stock suspension is largely to blame for the crosswind dancing.

I need to go reread the suspension forums.

[2001ex500]

  Your comments below include that the squishy stock suspension is largely to blame for the crosswind dancing.

Maybe not in every case. I think that my weight (230 w/full gear) is a factor too as the stock setup is just out of it's league at that point. Someone weighing 120 may not have the same effect even in the cross winds. I'm asking my stock bike to deal with something it wasn't really setup to do and the crosswinds are just compounding the problem further.

[MrSciTrek]

  Your comments below include that the squishy stock suspension is largely to blame for the crosswind dancing.

Maybe not in every case. I think that my weight (230 w/full gear) is a factor too as the stock setup is just out of it's league at that point. Someone weighing 120 may not have the same effect even in the cross winds. I'm asking my stock bike to deal with something it wasn't really setup to do and the crosswinds are just compounding the problem further.

Thanks for the clarification.  I'm maybe 205 in gear, & have a little taller windscreen than stock. Maybe nothing is too stable in 30 mph cross-gusts.  Still... I want improvement w/o ending up w/ something too stiff for the pot-holes of Omaha streets.

[Jkrup47]

I played around with the idea of cutting my front fork springs... or buying new ones from race tech. isn't cutting the springs going to weaken the structure of the spring? cuz aren't they flat on both ends?

[2001ex500]

Still... I want improvement w/o ending up w/ something too stiff for the pot-holes of Omaha streets.

That's a lot what I had in mind as well, as commuting and touring are still two top goals I have for the bike. As I mentioned, so far the bike feels much better on potholes than it did before. I think the suspension can handle the sudden load much better. Just take it a step at a time and allow some time for tuning too.

[2001ex500]

I played around with the idea of cutting my front fork springs... or buying new ones from race tech. isn't cutting the springs going to weaken the structure of the spring? cuz aren't they flat on both ends?

Certainly, new springs from racetech is the way to go, and I may end up there eventually (after I've upgraded some other things... tires, emulators, EBC pads...) However I think cutting the springs is a viable option too, if the cost is a big factor. I'm not aware of any way that cutting the springs really weakens the system. I cut my ends to be flat perpendicular to the direction of the springs travel. True, the cut end is smaller than the factory end, but as long as it has a good surface (the bigger washer)to transfer the load in to the rest of the system it should not be a problem (and you don't heat it red hot and try to bend it flat which could change the temper of the metal). Cutting springs is a pretty common approach to stiffening. There is another post on this subject, too that you could search and find and would give you some more info.

Thanks

[2001ex500]

This is the other post I was thinking about:

http://www.ex-500.com/index.php/topic,134.0.html

[cstem]

When you thinking of buying the Racetechs- let me know- I have some .95's installed right now (came with bike) and am doing some testing this weekend after toying with preload and oil ht/wt.  I roadrace and if it does not work I will be in the market for some .85's (if anyone has some pm me) so I will let you know and will probably let them go real cheap!

This is the other post I was thinking about:

http://www.ex-500.com/index.php/topic,134.0.html

[Lucky#13]

When you thinking of buying the Racetechs- let me know- I have some .95's installed right now (came with bike) and am doing some testing this weekend after toying with preload and oil ht/wt.  I roadrace and if it does not work I will be in the market for some .85's (if anyone has some pm me) so I will let you know and will probably let them go real cheap!

This is the other post I was thinking about:

http://www.ex-500.com/index.php/topic,134.0.html

If you do let me know .i'm at around 220-230 lbs.. IIRC those would be just rifgt for me ..... dad

[dad]

That sounds about right. Match it up with a 500# rear spring and you might have something there.

[ydant]

I did this today.  Drained out maybe 50ml of oil - which explains why I was bottoming out under moderate braking.  There's definite a difference (and, I think, an improvement).  At the very least, I can lock up the front at 30mph without bottoming out - a huge improvement!  The roads were too dark when I went for a test ride, so it was hard to really test the change out.

For other people who can't really visualize things, I took some pictures.  Hopefully these help!


What you need:

• fork oil - about 800ml, so get the liter bottle
• gear puller - I got this one (link)
• a couple of feet of 3/4" PVC pipe (you won't use it all, but it's best to have extra)
• something to cut the springs - I used a dremmel and a cutting wheel
• 6mm allen wrench to remove the handle bars
• 10mm socket/wrench to remove the drain plug (1st gen only)
  

Remove handlebars

Get rid of the two bolts below.  Pull the caps off first, of course.



Remove the cap on the shock

This is where the gear puller comes in handy.  You could do this with a screw driver, but the gear puller is SO much easier.  Thanks, FOG.




You're pushing it down to get to the metal ring that holds the cap from popping out.  Once the cap's out of the way, remove the clip:




Remove the cap

Now that the clip's out of the way, unscrew the puller.  The spring will push the cap out:




Extract the spring

There's a lot of it - 20.1875" worth on my '93.




Drain the oil/suck it out

If you're lucky enough to have a drain hole, use it.  If not, follow FOG's instructions (search) on putting your own drain plug in.  Or suck the fluid out.



Cut the springs

Use the calculations above to figure out how much to cut.  It's easy enough to do again, so be conservative.

Cut the spacer

Again, read the rest of this thread (and the cutting spacers thread as well).

Oil

Pour in the proper amount of oil.  Read the rest of this thread and your service manual for amounts.

Reassemble

Spring, washers, spacer, plug, and push it all back together.  Put the clip back in.



[edit: pictures fixed and mirrored here: http://ydant.com/projects/cutting_ex500_springs.html]

[bobthebiker]

thanks for the writeup with pics. I finally understand how the heck the thing comes out of the fork.    we need a copy of this writeup in the how to section if it isnt already done.

[FazerDude]

This needs to be a sticky.  If I had seen it a couple of weeks ago, I could have saved some money...

[FOG]

It is done. it's been there all along. but these are good pictures. for those reading challenged.

FOG

[mugwump]

Tried searching for "drain plug" and some other variations. No luck. What phrase did you use to find the "Installing your own drain plug" thread.

[ydant]

Here's the thread FOG was referring to.  It's where he mentions drilling your own drain plug.

http://www.ex-500.com/index.php/topic,407.msg3361.html

[mugwump]

Thanks

[nlitend1]

Excellent topic and i'm looking forward to stiffening up the weak front end. However, I'm wondering if it's a good idea to heat off the cut off end and bend it flat so there is more surface area on the spacer. In the following forum http://www.ex-500.com/index.php/topic,134.msg1530.html#msg1530 hotrod says it's a good idea, but here people seems to disagree because it will weaken the metal. Any opinions on the matter? I'd rather just leave it without bending it, if i'll be ok. Also, i'm wondering how to determine the length of the spacer needed. There are many calculations for spring length but not for the spacer. Is that where the preload comes in? Should i cut them so that they stick out of the forks 3/4 to 1inch, and thus provide that much preload when the forks are capped?
Thanks,
Ken

[FazerDude]

I would not heat the spring. 

You want 3/4" of preload, assuming the rate is correct, so you have to figure out how far the cap will push the spacer/spring down.  IIRC, the spacer is not even flush with the top to get that or in other words; the cap will push the spring down further than 3/4" from the top of the fork tubes.  Of course, you may want to start with a bit more than an inch and cut off the too-long spacer until the sag is correct, but for me, with a .9 rate spring, 3/4" was spot-on.

[FOG]

It's perfectly OK to heat the last portion of a cut coil to flatten it. But it's not necessary. as the spring runs in a tube and cannot deflect sideways.  The preload is set when you set the SAG and differs for everybody.  You can take a guess at it, but you may have to make several adjustments. That why I recommend bending that C clip end in a bit.

FOG

[2001ex500]

I was the one who said don't heat the end and it didn't come from me because I'm on the electrical side of engineering. My dad is an aeronautical engineer for 40 some years for the military(now retired) who has done alot of metalurgy (usually when inspecting and diagnosing failures for redesign). We've always done all our own work on cars and performance mods. When I mentioned I was cutting my front springs, he told me he had read not to do it in one of his suspension books (for cars) and he agreed with it (using a bunch of metalurgy terms I can't remember).

From what I've seen in my own research I agree too. I was thinking of heat treating some mild steel to make it stronger and thought it would be simple (when I made my dogbones actually). I asked my dad and he said don't do it. I still thought it would be simple (yeah, even when you get old you still don't want to listen to your folks sometimes ) so I researched on the internet. From what I found, it is too easy to make it worse. You have to heat the metal to a specific temperature and then quench it at a specific rate(in oil usually) to get your desired effect. If done wrong it can become brittle and can fail much easier. And it will fail when it get's a big load on it which is usually a really bad time for it to go.

Beyond all that, I agree with FOG that there is no real reason to do it. As long as you don't put the end of the spring directly onto the PVC spacer (you have a washer between them) the washer will spread out the load more than sufficiently to take any load. I prefer metal spacers myself.

So bottom line, I (and my dad) don't reccommend heating up springs and bending them. You may end up all right but you may not. Why risk a failure (possibly catastrophic) when it is not necessary?

[FOG]

Well , Fog"s a Toolmaker and Has been heat treating steel for 50 years and I can recite you chapter and verse about heat treating and the molecular changes that take place thereby.  Suffice to say a minimum of .04 Carbon is required to allow steel to harden, If the proper temperature is obtained and the cooling done quickly enough.
   Springs are made from .05 carbon steel and are heat treated to a spring temper of 50 RC and can be hardened further, or drawn softer with Heat.  The temp necessary to close the end of a cut spring is on the order of 1300-1500 degrees F and is certainly above the draw temp and close to the conversion point. So you can both harden and soften the end of the spring depending on how you cool it.  If you were to quench it from the 1500 temp immediately in water or oil it would harden to a point of brittleness and would require subsequent tempering to draw it back down to the 50 RC spring temper.  If left to slow cool it would remain soft.

   As I stated the end of the spring has no function except to provide a square platform from which the spring can work more squarely from. inside the fork tubes this would lessen the rubbing on the insides of the tube as the spring works.  In dry conditions this would quickly wear the spring in two. Running in an oil bath (in the fork) much less a concern.

  So Yes by all means close the end of the spring with heat. Just confine that heating to the part you want to bend.  Prevent the remainder of the spring from attaining a temp greater that 400 degrees and you'll be fine. Don't quench it from red hot. Wait till it darkens for a few minutes then it's perfectly OK to cool it in water.

FOG  Toolmake, Mechanical Engineer, Metallurgist.

[2001ex500]

FOG, I have no doubt you could do it well, but I think you just proved my point. It is not a simple process. "Heat it red hot wid a torch, wack it flat wid a hammer and yer dun".  95% of the people who will try it don't have the background you have and won't know to follow the very specific instructions or without a way to measure temp either.  Why risk that when it is not necessary?