need suspension help

_Will_ · Post by **_Will_** » Thu Oct 06, 2011 5:55 pm

Near the end of a decent length curvy ride I began to get a chatter from the front during lefts, right handers were perfectly smooth. This was a distinct rhythmic feedback but only on lefts and on more than one corner and only later in the day (at least that's when I noticed it). By later in the day I mean after around 50 miles or so of corners. Fork fluid was replaced just a few months ago with no apparent leaks, they're stock forks with stock springs. I did upgrade to 20w oil because I like the extra damping but don't see why that would only affect the left handers. It's a 94 US model 600, roughly 60k miles give or take.

Does this sound like tire or fork issues ? If it was tire I'd expect the right to go out first since I favor them mostly. Any idea's from our knowledge bank?

fzrbrandon · Post by **fzrbrandon** » Thu Oct 06, 2011 7:29 pm

Tough to say. If you don't think it's the tire and it was toward the end of a long day, do you suppose fatigue may have been setting in? It's possible that, when you're tired, your technique on the lefties is different enough to make a noticeable change with how you go through the turn. I can't really imagine it being the fork settings alone (oil, etc.) since I believe it would effect both sides (assuming your technique is the same and the tire is not a factor). You say you favor rights also so maybe you just need to work on the lefts a bit more (eventually leading to fatigue not being an issue).

_Will_ · Post by **_Will_** » Thu Oct 06, 2011 8:08 pm

I'd thought about it but the problem was too consistent and didn't really fit what I'd think of as a fatigued technique where you go into a corner half heartedly and jerk some on the way down. This was a perfectly spaced chatter from the front, or think of it like a pulsing. Just a uniform repeated feedback, like there were ridges on the road.

fzrbrandon · Post by **fzrbrandon** » Thu Oct 06, 2011 9:46 pm

Hmmm... I can't imagine that it would be a warped rotor or an issue with a caliper piston because I would think that it would affect both sides. I suppose it's possible that there's enough flex in the front end (which we know there is on the forks) that there could be some abnormal stress on the braking system which is causing the pulsing. Not really sure though so I'm just surmising. I'm assuming you're off the brakes and rolling on the throttle once you've entered the turn, right? If it were me, I might be inclined to pull the rotors to check them for warpage and maybe even overhaul the calipers. That's just me though. <insert paranoid icon>

Hopefully, some of the more suspension savvy folks can put in their two cents.

_Will_ · Post by **_Will_** » Fri Oct 07, 2011 6:56 pm

Definitely off the brakes mid corner, on these roads giving away traction just isn't advisable. The more I think of it the more my mind goes to the bearings. My aren't all that old (less than two years) but it's something that could be affected by excess heat and one more than the other is a possibility. I'm sure there's some uneven forces mid corner depending on lean direction. Now just how to test them?

cowboi · Post by **cowboi** » Sat Oct 08, 2011 5:47 am

Yes. Check the bearings. I had the same issue awhile back and checked everything else first and come to find out it was the bearings that I checked last. So check them. I'd almost bet that is your problem. Good luck. Let us know.

_Will_ · Post by **_Will_** » Wed Oct 12, 2011 5:20 pm

think I found the problem and it's tire wear related to damping. I remember seeing a Dave Moss video on tire wear that I can't find now but damping issues can cause a difference between the levels of the leading and trailing edges of a tire groove. My leading edge has worn so much greater than the trailing edge it's peeling the trailing edge back some. The right side has it too but not to the same degree, makes sense considering my comfort with rights so I do more work with the left side not moving myself off the bike as much. Oddly the exact same thing happened on my friends zx10 , but only on blood mountain. I'm running 20w oil because I like the extra damping but short of emulators or a set of different forks does anybody have ideas?

Here's two pictures, you can somewhat see the height difference and the small chunks at the end of the groove which were all the way around

reelrazor · Post by **reelrazor** » Wed Oct 12, 2011 8:39 pm

i'd seriously consider checking/verifying/correcting for any misalignment in the chassis/wheels/forks.

I've seen and dealt with tire wear that you indicate that was corrected by aligning the triple clamps. Any misalignment there causes unequal trail and caster from left to right.

My preferred method of alignning the triples/forks is to make sure the fork legs are equally 'deep' in the lower triple then loosen everything except the lowermost pinch bolts on the lower triple...

I mean EVERYTHING, crown nut/crown pinch bolt, upper tree pinch bolts, axle, fender/brace bolts.

Then compress the forks as far as possible a few times and tighten teh axle.

Do it(compress forks as fully as possible) a few times more and tighten the fender/brace bolts.

Then a few more times and the lower triple pinch bolts,

then a few more times and the upper pinch bolts.

and finally, the crown nut.

This forces the forks/triples/axle into the same plane.

There's other ways to do it, but that is the one I was trained to use as accurate and fairly quick.

Not a bad idea to spin the fork legs in the lower triple at the very start of this procedure....preferably with the fender and wheel OFF. Any bend will be shown as 'wobble' at the lower end of the fork.

Another thing..once a tire has that kind of wear, it pretty much will ALWAYS have it

_Will_ · Post by **_Will_** » Wed Oct 12, 2011 9:17 pm

Thanks RR, that sound easy enough with the help of my roomie. It wouldn't surprise me if something was off considering when I bought it this poor thing looked like it'd seen the ground so many times Simoncelli might have owned it. I'll work through those

And this sounds like a routine that would be useful in the wiki, would be a great companion to fork seal changes when reassembling

nortstudio · Post by **nortstudio** » Mon Oct 24, 2011 1:15 pm

_Will_ wrote:It wouldn't surprise me if something was off considering when I bought it this poor thing looked like it'd seen the ground so many times Simoncelli might have owned it.

Wow. How ironic, and sad. Weird timing. Just joined this forum, and one of the first threads I read mentions the rider who died yesterday.

Great tip with the triple/fork alignment, buy the way.

_Will_ · Post by **_Will_** » Mon Oct 24, 2011 6:35 pm

nortstudio wrote:
_Will_ wrote:It wouldn't surprise me if something was off considering when I bought it this poor thing looked like it'd seen the ground so many times Simoncelli might have owned it.
Wow. How ironic, and sad. Weird timing. Just joined this forum, and one of the first threads I read mentions the rider who died yesterday.

Great tip with the triple/fork alignment, buy the way.

I'd completely forgotten about the crack but yes very prophetic in light of Sunday's wreck

nortstudio · Post by **nortstudio** » Tue Oct 25, 2011 8:11 am

Wasn't implying it was a bad crack - I completely understood. But yes, very prophetic. I had the odd experience of having read the news online as I was watching the beginning of the race (recorded on the DVR), and listened as the announcers waited for the news to come through, after the crash happened. Weird to know the outcome when the "live" TV didn't yet. Sad. But as they keep saying in coverage of it, unavoidable in a sport such as this.

I read something interesting - by a guy who was involved in a similar accident (put a guy in a coma after hitting him on the track, but the injured rider recovered), about how Colin Edwards and Rossi will be replaying it over and over in their minds, asking themselves whether they could have somehow done something slightly differently to avoid the tragedy. This guys opinion too, was that there was no way at that speed and tightness to the pack in only lap 2.

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