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Discussion Starter #1
I have a 2001 EX500 that I just bought not too long ago as my first bike. I've noticed that when I turn into a corner quickly or am leaned over somewhat far (not near the bike's limits, I'm sure) that the rear wheel will often lose traction and skid a bit, until regaining traction. Needless to say this has made me a bit hesitant to ride my bike hard, which is a bummer.

The bike's had 2 previous owners, so is it possible that the suspension has been tweaked? I'm a light guy (around 130lbs), so maybe the suspension needs to be softened a bit or something? Is it adjustable?

The tires have a decent amount of tread left. I'm not sure how good they are, though. They're Bridgestone Spitfires, 110/90 front and 130/90 rear. Both have about 30psi in them. What is the larger-than-stock tire size doing to the handing?

Does anyone have any suggestions?

Thanks.
 

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that 130/90 sidewall is probably flexing too much during lean. change the rear to the stock size, 130/70R17 to correct.

i'm surprised that you're not complaining about the front... that should be a 110/70R17.
 

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What of the front tire? Can an oversized front hurt steering?
 

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When you stand the bike up on its own, no rider, does the rear suspension compress at all? Lift the rear and gently let it settle to observe this. It should compress, just the smallest amount, like up to 1/4" max when measured from the wheel to the body. If it's zero but will start to move with just the slightest of effort, like a fingertip force, that's about the max you should have. This is indicating proper rear spring pre-load which is adjustable. If it's topped hard it may be causing the problem, not letting the suspension do its thing. This measurement is referred to as "free sag".

That said, the springs on these are notoriously soft and can often benefit from a change, even at your relatively light weight.

You could further check the "static sag". That is the suspension travel as measured with your weight aboard. You'll need a few friends to hold the bike, lift to top the suspension, and settle to compress, measuring the travel with you aboard in riding position. That's the Reader's Digest version for measuring sag. More detailed info is available at one of the suspension web sites like Traxxion Dynamics or Racetech. BTW, that measurement for "static sag" should ideally be in the range of as little as 3/4" for the track and up to 1 1/4" on the street. The difference in the "free sag" number to the "static sag" number is indicative of the proper spring rate for the applied weight.

IMO, you shouldn't chase "static sag" any more than what you can accomplish maintaining at least zero "free sag". The problems created by having it topped out hard on "free sag" is worse than the benefit of a more appropriate "static sag". BTW, an excessive "static sag" with a good "free sag" is indicative of too soft of a spring. Think it through, it will become clear. Hope that helps.
 

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Knightslugger said:
Do you mean one with a taller than stock profile? or wider than stock?
I guess we were looking into taller tires? What kind of results should you expect from either?
 

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Discussion Starter #7
Thanks for the replies.

Knightslugger:
The front seems to do it too, but it is less noticeable than the rear. Could increasing tire pressure help with this problem until I get new tires?

Dad:
Thanks, that's some good information. I tested for free sag and the bike's suspension doesn't move at all until I apply a good amount of force on it with my palm. From what you said, that sounds like a good thing, right? I'll have to test for static sag when I have a few people around to help me out.

How hard is it to adjust the stiffness of the rear suspension? Is it adjustable, or does it require an entirely new spring (or modification of the existing one)?
 

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SuprSonik said:
I tested for free sag and the bike's suspension doesn't move at all until I apply a good amount of force on it with my palm. From what you said, that sounds like a good thing, right?
I fear you may not have understood what was said. Please confirm this so we can be sure we had a meeting of the minds. ;) I just want to be sure as you made no specific mention of lifting to be sure it was topped out before to observe the downward travel.

Did you lift on the rear to be sure to top it out, then let it settle? It is that motion that you're looking for and should be in the range of 0" to 1/4". If there is NO motion of the suspension between lifting on it and letting just the bike's own weight settle on the suspension, and then, to get any downward motion at all it takes a fairly large downward force, then the spring is cranked up too hard and doesn't let the suspension function properly. If that is the case it is a strong candidate as the source of your complaint and NO, it's NOT a good thing.
 

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SuprSonik said:
Thanks for the replies.

Knightslugger:
The front seems to do it too, but it is less noticeable than the rear. Could increasing tire pressure help with this problem until I get new tires?
I don't honestly know if it would help or not... i've never run taller profile tires on a bike before. I've done it on quad tires and it made the whole bike sloppy just from the sidewall flex. i guess it would help keep the sidewalls shapely, but running high pressures have other side effects to other portions of the tire. Honestly, i wouldn't ride it any further than i would have to in that condition. find yourself some decent tires and slap them on. If you want to stick with the stock sizes, Pirelli makes great tires according to those who have them. otherwise you can put a 110/70 or a 120/65 up front and a 140/70 or 150/60 in the rear. that will open up some newer technology for you, such as the Michelin Pilot Power in the 110/70~150/60 combination. the pilot power tires are PHENOMINAL. You wont be disappointed with those at all. if you are, there's something wrong with you.
 

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Your 30 psi front and rear is not enough, I don't know what Kawi suggests with stock tires for your bike but here is a good general guide from Metz I use:

http://img.photobucket.com/albums/v443/jcp8832/MetzPSI.jpg

It shows 34-36 front and 36-38 rear so being on the light side you might want to try 34 front and 36 rear. I'm about 100# heavier than you and 36 front and 38 rear works well for me.

There is generally more flex in the taller sidewalls but the preferred wheel size for a 130/90 is a 3.0" wide wheel so your 3.5" wide rear wheel would stiffen it up a bit. I've put about 120k miles on a couple GS500s and tried a couple 130/90 rears with long life touring rubber. A K491 Dunlop in that size broke loose constantly but a 130/90 Metz ME88 handled as good as the 110/70 and 130/70 OE size BT45 Bridgestones did in my opinion.
Type of tire and tread compounds make much more difference than size.

The bias ply Pirelli Demons or Metz Lasertecs would grip a lot better in OE sizes for your next set of tires or the supersport radials like the Pilot Powers in the 110/70 and 150/60 sizes like Knightslugger suggests for the best grip with less tire life.

I'm currently running a Lasertec front with a Conti Road Attack rear that sticks like glue and has yet to budge from it's intended line. :)

Tires I've tried on the GS's, they come with the same size OEM tires and wheels as the 94 and later EX500s do.

http://img.photobucket.com/albums/v443/jcp8832/GS500tirelog.jpg
 

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Discussion Starter #11
Dad:
Sorry I wasn't clear, but yes, that's exactly what I did. I'm going to do it again later when I have more time, more help and a tape measure, but there was absolutely zero movement from what I could notice. The suspension doesn't seem to flinch under its own weight or light pressure, until I push down on it with a fair amount of force, and then there is a noticeable amount of movement.

Knightslugger:
Will putting a wider tire on the rear have adverse affects on the bikes handling? I know it will turn in quicker, but aside from that I'm a bike handing newbie. There are no problems running a radial on the EX500?

gsJack:
Thanks, I'll try adding a bit more air. That's a useful chart to have.
 

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SuprSonik said:
I've noticed that when I turn into a corner quickly or am leaned over somewhat far (not near the bike's limits, I'm sure) that the rear wheel will often lose traction and skid a bit, until regaining traction.
Well, based on that original complaint and your discovery of a topped out hard rear suspension, I think you have your primary answer and immediate problem. Backing the spring pre-load off to get the kinds of sag numbers mentioned will make a big improvement.

I've taken some liberties to fill in the blanks on your original post, assuming you might better describe the problem as a "skipping" action when you hit a bump in a corner, bouncing the rear, unloading it, and re-gripping when it comes back down. Almost as if it "skips" or "steps out" a small amount. If that's grossly wrong, please say so.

I looked back through some notes I made a time ago when working out the rear suspension on my 500 and found my ratio and static load numbers. I also found an error in a post in another thread. :eek: The mentioned (soon to be edited) 3.5:1 ratio is correct for linkage length changes, adjusting ride height by modifying the swing arm link lengths, but is a different thing altogether and not correct for shock adjustments. That ratio should read 2.85:1. I'll edit them after making this post in case somebody would use them in the future. The ratio really just helps to not have to keep taking the shock in and out, adjusting purely by trial and error.

For a starting point, remove the shock and back the spring off all of the way to loose. Bring the nut down to just take the play out and measure the spring's free length. Then continue to tighten the nut, compressing the spring 7/8" from its free length. This should be a very close starting point, if not perfect (1/8" to 1/4" free sag). Install it and check your results. If final minor adjustment is needed use a 2.85:1 ratio for the required change. Wheel change divided by 2.85 is the change required at the spring, due to linkage ratios.

The tire items mentioned are not without merit but I don't feel they are the cause of the exact issue you've brought up here. The lower pressures shouldn't cause what you described. They effect wear but should only help grip, not hurt it, as long as they were at at least 30psi. Much lower than 28 front and 30 rear, I'd say you might feel something if you were more experienced but not at the experience level we're talking here, if I understand it properly. As your experience grows, tires will prove to be very important to you but let that be its own search or new thread.

Access to the top shock bolt requires removing the tail section and using two sockets and extensions, one from each side, to grip the bolt and nut. The lower should be evident looking at it from the bottom. It drops out the bottom.

While it's apart, slide the linkage bearing sleeves and seals out, clean, grease, and re-assemble. Good maintenance item done. Also, lift the rear wheel or set the bike on the ground before to final tighten all of the bolts. That will take all of the play out of them in the normally loaded direction. Good luck.
 

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SuprSonik said:
I have a 2001 EX500......................the tires have a decent amount of tread left. I'm not sure how good they are, though. They're Bridgestone Spitfires, 110/90 front and 130/90 rear.
It just occured to me that the Spitfires don't come in a 17" front, must be something else on the front? If a 150/70/17 won't fit on a EX500, I don't see how the 130/90/17 Spitfire could fit the rear? It's a big, wide 130/90.

http://www.motorcycle-karttires.com/glamourindex.aspx?productID=4&LookupID=8
 

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Can't think of anything off hand that comes in a 110/90/17 size front tire, there are many 110/80/17 fronts available though.

I'm almost sure the Spitfires never came in 17" fronts.

A too stiff rear end can cause the skipping out described, but the worst skipping out I ever experienced was when the rear shock leaked out almost all of it's fluid like my 02 did at about 5k miles. Very difficult to ride home without a rear shock. :(
 

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gsJack said:
A too stiff rear end can cause the skipping out described, but the worst skipping out I ever experienced was when the rear shock leaked out almost all of it's fluid like my 02 did at about 5k miles. Very difficult to ride home without a rear shock. :(
That is very true. An extra step while the shock is out can prove out the shock's condition.

After backing the spring pre-load off, continue to remove the spring from the shock. Inspect the shaft for score marks and for oil leaks. The shock is nitrogen charged so it will have a spring effect extending it. With reasonable effort compressing it should travel smoothly over its full stroke, exhibiting a smooth hydraulic resistance both ways.

To verify the nitrogen charge, use a bathroom scale. Weigh the shock by itself. Then stand it on end and push the shock on the scale until it travels about 1/2", noting the scale reading. Then, ease off the pressure until the shock just starts to travel in return direction. Note the scale reading at the point where it just starts to move. Subtract the original dead weight of the shock from both readings, average the remaining compressing and extending numbers and that result should be 54#. If so, that's perfect. I'd consider anything reasonably close to that number to be OK based on the crudeness of the inspection rig but I've used this method and did get very exact numbers as described.

That's a calculated result of the nitrogen charge pressure, 284 PSI, and its piston effect on the shock shaft. The reason to read the force both directions is to cancel the stiction effect of the seals. It will be higher in the compressing direction and lower in the releasing direction by the amount of friction in the seals. If it passes that inspection, it can be considered serviceable.
 

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Discussion Starter #17
Dad:
"Almost as if it "skips" or "steps out" a small amount" is a perfect way of describing how it feels. It doesn't necessarily happen ONLY when the road is a bit rough, though - sometimes if I make a real sharp turn the rear will skip out a bit too. But generally, yes, that's an accurate description. I'm going to adjust the spring and do everything else hopefully this weekend. I'll let you know of the results. It doesn't sound like it will be too difficult.

I'll inspect the shock while I'm at it. That's an interesting method there, with the bathroom scale and all...but whatever works.

gsJack:
I feel like a dope now...I just double checked and the front wheel is indeed 110/70, not 110/90 (I guess I overlooked it since my thread was mainly about the rear end.) But it is indeed a Bridgestone Spitfire, and it's most definitely 17". The rear is 130/90/17.
 

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Just another Check it: I have seen several bikes where the top shock mount holes were elongated. Obviously from the shock moving the bolt that wasn't tightened securely. Even a 1mm amount of movement here will allow the tail at the grab handle to move almost 3/4". This is uncontrolled and can be felt as a clunk or a bit of vagueness.

FOG
 
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