mid-high speed wobble!!!

Ok, on my way to work today, I was running through some sweeping turns on my 1000ST and noticed a pretty bad wobble from the rear of the bike. I was at neutural throttle, (not speeding up or slowing down) as soon as I began to accelerate out of the apex of the turn it seemed to fade away. I was doing about 70mph (give or take a few). It has a new front tire and a 75%rear. And I wasnt even turning that aggresively. It has a 1 inch lowering kit in the front forks, and aftermarket shocks on the rear. The rear shocks seem to be of decent quality, and dampen very well. They are, however, on their stiffest spring setting. I can't feel any slack in the swingarm or any of the other bearings on the wheels or steering head. I also feel the wobble ever so slightly right after I let of the throttle to decelerate.
Any suggestions on how to chase this down?

What immediately jumps out at me is the 'new' front tire...balance problems?

Mcdroid wrote:

What immediately jumps out at me is the 'new' front tire...balance problems?

It's smooth as silk running straight... No bounce from the front end at all. And I know those bearings are tight.

Just had a thought though. Could it be caused by the windshield creating turbulence and slightly shaking the handlebars in a turn? It equals out to be about 2-3 wobbles per second so it's not fast like a shudder, still controllable in turns. But I feel like I need to take it very easy in the turns just in case somthing happens.

The feeling just takes away from my confidence un turns.

Post edited by: hat0791, at: 2005/10/26 15:02

So, it comes and goes? If that is the case, have you been over this road before on this bike under the same conditions? Is this section of Hwy grooved?...the reason I ask, is that the first time you hit grooved pavement and don't expect it, the bike will wobble and scare the tar out of you.

i have the same problem with my bike, somebody said it may be the rear spokes, how are yours?

How heavy are you? Maybe the preload is too high in the back, and you're just bouncing a little. Does it do it at all while swerving from side to side in your lane to check for it? Is the rear tire overinflated? I've done that one before...especially after getting a tire mounted at a shop. What about the rear tire...is it flat in the middle with a square edge for you to tip on and off of as the bike leans? When I bought my bike, it was like that, and mine felt pretty bad in mildly agressive cornering until I put a new rear tire on. You get on that rounded "point" between the center and the edge, and wander around on it. Very uncomfortable, but probably not too dangerous at most speeds... if you don't freak out. :blink:

75% of it was tire pressure! I've got the cast wheels so no spokes to worry about. I was running 24-26 psi, and dropped it to about 20. The wobble is all but gone!I still get just a tad of wobble in sharper turns now, but I weigh 155 so I think I need to drop the preload at least one notch. It is much better though and I'm much more confident in it now...
Thanks for y'alls help! Now all I have to di is fix that busted clutch cable... lol!

Hey Hat,
Have you checked the steering stem your last comment gives it away "I also feel the wobble ever so slightly right after I let of the throttle to decelerate."

When you let off the throttle your front suspension collapses a bit which makes your effective rake steeper. I'll bet your steering stem bearing is either loose or is worn. Try this:

Let go of the bars at 30 MPH but keep your hands gripped as if the handles were three inches in diameter. Now smack the right handle. Does the bike start wobbling out of control or does it wobble and straighten up by itself.

Condition one: adjust or replace the steering stem bearing.

Condition two: Steering stem is fine, keep looking for the source of the problem.

KZCSI

Post edited by: kzcsi, at: 2005/10/27 21:10

Nathan, I'm glad you experienced this with no harm. You now know the term speed wobble. Unfortunately it was an inhernit problem with these bikes. Frame flex, roads and poor tires enhance this. These bikes are not like todays modern sport bike and can't be ridden as such. Knowing when and how it feels is a big plus. Ride as normal but be prepared for the sudden lane change. I have at speed experienced a lane change. It can scare the crap out of you, but respect it and know it can happen will make you respond to it. Be careful.

I'll check the steering head as soon as I get a clutch cable. (Broke yesterday a stoplight..)
I went over the bike and made sure EVERYTHING was nice a and snug last night and couldn't find anything loose. I grabbed the front wheel and tried to see if there was any slack in the head but didn't notice any. Did the same to the rear swingarm. I'm going to go ahead a pull the tripple down and grease the bearings anyway so I'll double check them at that point. I dropped the rear suspension's spring rate down a notch as well.

So far though, it's much better. We're making progress! lol

I'd also like to know what grade of fork oil to use in these bikes, and how much should I use to get a solid, fairly high dampening rate?

Think about getting new bearings. Your bike is old and so are the head bearings. Tapered bearings will correct the situation.

Also tire pressures make sure you have enough air in both of your tires. I usually run about 24f and 35 rear but that is open for disscusion.

Post edited by: galaxian, at: 2005/10/28 09:03

Speed wobbles? Know them well. Had a night, doing about Cou80gh mph on the highway here, taking a turn aggressively and crossed over a parallel seam in the concrete bridge. Heart jumped to throat, dump dropped to pants as my brain thinks, "I know where this is going, I've seen footage of this on the internet" Backed off the accellerator and jammed myself between my foot pegs and the handlebars. she eventually leveled out.

Steering head was loose, underwear was lost. Fixed the first of the two.

(not serious about the underwear)