steering wobble..

[TheDrunknmonky]

i'm noticing more and more that at speeds above 40 mph my steering has a bit of a shimmy to it.. i'm guessing this is due to the substandard stock forks and wondering what the best way to fix this was.. maybe a gsxr fe upgrade or steering dampers.. advice please.

i have about a month left in my riding season here in detroit and am planning on tearing down the bike for mods over the winter now that i have a new, very large garage to work in since i got into a house and out of the apartment.

[DoD#i]

Not likely. The stock fork springs are soft. They are not "prone to shimmy". Shimmy means something is wrong - long list of possibles - wrong air pressure, badly worn tire, steering head bearings, loose front axle, missing spacer, missing or loose fork brace...

[gregvhen]

it may not even be in the forks. i would guess in the stem if its lthe kind of shimmy like, you push the handlebars foward the they move foward a little then drop back when you let off. (of course i mean more than what the rubber allows.) check to see if the forks can move out of parralell with the stearing stem.

On my bike (bicycle when i was younger not motorcycle) i could push my bars foward and they would pull the front wheel backwards slightly. and when i realesed i could hear the matel clank. thats an exagerated case of what could be wrong with your stearing.

[gregvhen]

and if its not a shimmy, like the way i think of shimmy, and your talking about a woble, check the fork brace ( the metal bracket that your front fender is attached to) you may have to take it off to see because sometimes the holes can stretch but the bolt hides them.
http://www.gstwin.com/racers_corner.htm#fail

scroll down to where it says fork braces.

[noiseguy]

What about checking the balance of the front wheel? Did a weight fall off?

[The Buddha]

Weight falling off will make it bounce more than wobble.

I would definetly look at tire wear, tire pressures, fork brace and stem bearings and its classified in the order of difficulty, not probability.
Rear tire pressure and wear as well as alignment also count ...
Cool.
Buddha.

[TheDrunknmonky]

Wobble sounds more like my problem. It's a light jiggle like riding over a slightly rough road. Kinda like the steering wheel in a car gets when the wheels are out of balance.

[ohgood]

Wobble sounds more like my problem. It's a light jiggle like riding over a slightly rough road. Kinda like the steering wheel in a car gets when the wheels are out of balance.

wheel weight and/or tire inflation along with worn front tire. don't ride like that. 

[lamoun]

Also measure and set right the rider SAG. (~25mm front - ~35mm rear)
if this is not possible, try at least to balance the front and rear of the bike.. (ex. ~35mm front - ~45mm rear)

[TheDrunknmonky]

both tires are at recommended psi and are new.. less than 5k miles on them.  if they are out of balance they came that way from the dealer.. it's done this since i got it and i thought it was normal til i rode a friends katana the other day and didn't feel it.

[Gary856]

both tires are at recommended psi and are new.. less than 5k miles on them.  

What kind of tires you got? You call almost 5k miles "new"?

Whenever I change lane and hit those seams between lanes, my GS wobbles a bit. It's a little disconcerting, but now I just ignore it. My GS has Maxxix Promaxx tires (cheap) with about 4.7k miles. I always thought the wobble is mostly from the tires, and a little from the suspension.

My YZF600R with Bridgestone BT021 tires don't get the same kind of wobble.

[TheDrunknmonky]

they're new enough that i can't tell any tread is gone.. they are the stock tires.. do you think new, higher quality tires would help?

[ohgood]

they're new enough that i can't tell any tread is gone.. they are the stock tires.. do you think new, higher quality tires would help?

ok, so you bike is how old, and the tires - they have a date code on them. if it sat on a dealer's floor for 1-2 years, ya, they might be crappy. you shouldn't feel any type of wobble, wiggle, hop, or anything that increases with speed, or happens at just one speed. nothing. it should be smooth (aside bumps) as glass and no vibration noticable at all. any vibration that increases or decreases with road speed is the sign of something bad to come.

[Gary856]

they're new enough that i can't tell any tread is gone.. they are the stock tires.. do you think new, higher quality tires would help?

I don't know if your "wobble" is the same as my "wobble", so I'll describe mine a little more. The "wobble" I'm describing is tied to road surface imperfections. In one particular stretch of freeway, with concrete pavement and rain grooves (cut in the same direction as path of travel but a little wavy), my GS wobbles continuously, similar to the wobble I get when hitting road seams when changing lane. Even my car wobbles noticeable there, bad enough for me to stop and check if the wheel nuts are loose. My SV650 w/ stock Dunlop tires wobbles there and when hitting road seams, but a bit less than the GS. My YZF600R w/ Bridgestone BT021 does NOT wobble there, nor wobble when hitting seams when changing lane; of course, the YZF has much better suspension than both the GS and the SV.

Assuming there are no other mechanical issues, my unscientific theory is that the tire's road hugging characteristics (how it deforms and conforms to the road surface) is the biggest contributor, followed by suspension and steering geometry. Certain brand/model tires "tracks" freeway rain grooves more than others.  

edit: by "wobble", I mean a sensation that road is slippery and the tires are sliding sideways just a little bit (like 1/2" to 1"), and that the front and rear are out of phase so the bike wiggles, wobbles, shimmy, whatever it's called.

[noiseguy]

What part of Detroit are you riding in? I spent 10 years in the suburbs there. Say what you will about Arkansas; the roads here are great for riding. Lots of curves and hills, and mostly deserted.

Let's get our definitions straight. A wobble is an oscillatory behavior, like plucking a guitar string. It starts up and dies down. Bhudda already gave you the fixes; here's a definition. Is this what you've got?

High speed wobble

Speed wobbles can occur whenever something starts a vibration that matches a resonant frequency of the wheels. A resonant frequency is one at which your motorcycle will vibrate very easily; a particular motorcycle may have multiple resonant frequencies. The starting point may be a bump in the road, a rough patch in the road, or some combination of these factors. Other potential contributing factors include the small torques resulting from wheel rotation and the tiny lateral oscillations that spinning wheels make if they're not aligned with absolute perfection.

http://wiki.answers.com/Q/Why_do_you_get_Motorcycle_speed_wobbles

Essentially loose parts and/or bad suspension setups cause it. Worn steering bearings, front shocks, rear swingarm bearings, etc, in addition to tires.

More here. Bottom line is that a wobble is nothing to ignore.

http://w6rec.com/duane/bmw/wobbles.htm

[lamoun]

Also check the wheels for dents.