Author Topic: Front end "shimmey"...? (Read 3636 times)

RUSS M8 · « **on:** May 26, 2006, 04:33:00 AM »

Hey guys, my Bandit is a pretty stock 1996 B1200S.
Hey, a question for anybody with experiance &/or expertise. As I cruise along in a straight line on the Bandit, if I take a hand (or both hands) off the bars and watch them as I roll along, they are moving from side to side. They are not moving very far, and the bike never feels like it is gonna launch into a tank slapper or anything, but I dunno if there is something wrong or that is just how it is?
Facts;
- the steering head bearings are not very old.
- there is zero slop in the steering head (checked by pulling forks back and forward)
- the fork bushes are brand new
- the fork springs/oil/gold valves.... are brand new
- the wheel bearings are good

The bike is basically stock at the moment. It has lighter bar end weights. Forks almost flush (have experianced this @ flush/@ 5mm through/@ 10mm). Rear ride height standard.

Maybe the front wheel is dynamically out of balance ????

Maybe there is that much flex in the forks without a brace ????

Maybe the tire is faulty ????

Maybe I am so fat I am sagging the back down too far ......... ????

It seems to need steering head tightened, or a steering damper, but the Bandit has pretty slow geometry, so as standard it shouldn't need a damper.

Just brain storming out loud here people, any help would be good.

txbanditrydr · « **Reply #1 on:** May 26, 2006, 05:52:04 AM »

With everything you mentioned you omitted tire type and mileage..... both can contribute to the shimmies. I have the same thing only much worse right between 42 - 52 mph. I tightened the head bearings which helped but then the bike handled poorly in the turns so I backed off the nut. There is a certain level of tension using a spring scale as described in the factory manual.... I believe there should be 7 - 17 ounces of resistance as measured with the scale attached to the end of the handle bars before the bars begin to move. "Initial resistance" is what they call it.

Tire tread pattern can cause this... the rain grooves that criss-cross (Saaailing...sailing away - oops, sorry) the tire centerline are prone to this behavior and if the tire is "cupped" the effect will be magnified. I would love to get rid of the damn head-shake and the best solution to date is to keep my hands on the bars.

jfudo · « **Reply #2 on:** May 26, 2006, 03:02:28 PM »

compare your situation with this post...

http://forums.banditalley.net/viewtopic.php?t=3819

RUSS M8 · « **Reply #3 on:** May 27, 2006, 01:39:39 AM »

OK, tire type and milage. It is a Michelin Pilot Power 120/70-17. It has only a few thousand K's on it, and still looks pretty new. No squaring off, or feathering or any funny wear at all. I have always had Pilot Powers on the front. (pressure 36psi)
I will try adjusting the steering head bearings, they are not that old, but I will see how the adjustment goes.
At least if others have had the same sorta problem, it makes me happy my bike is OK, and there isn't a real problem

scooter69 · « **Reply #4 on:** May 27, 2006, 09:21:37 AM »

I have the same issue but mine are Avon ST45's on a B12 with around 170km on them. Would my problem be not enough break in time yet???

DaveG · « **Reply #5 on:** May 29, 2006, 10:41:22 AM »

it's the front tire
don't believe what some say about bearings.
when they overtighten them they create a streering damper.

get a front tire without the centre groove and things will be fine.

scooter69 · « **Reply #6 on:** May 29, 2006, 02:10:37 PM »

Quote from: DaveG

it's the front tire
don't believe what some say about bearings.
when they overtighten them they create a streering damper.

get a front tire without the centre groove and things will be fine.

Ok....so I'll live with it for now until the tires get some more wear. Next addition is a steering damper from Holeshot anyways...that should help

Thanks

Bazza · « **Reply #7 on:** June 02, 2006, 03:18:52 AM »

Quote from: DaveG

it's the front tire
don't believe what some say about bearings.
when they overtighten them they create a streering damper.

get a front tire without the centre groove and things will be fine.

I am also now pretty convinced of this. I have Avon's on mine that create a shimmy when I let off the throttle about 40 mph. Does not get worse, does not get better with tire age. It does get more noticeable when I have more weight on the rear. (Sidebags & tailbag)

solman · « **Reply #8 on:** June 02, 2006, 03:26:20 AM »

I've had tire shimmy in the past as well. As soon as I bought a new rear tire, it went away. If you noticed which tire I replaced, it isn't always the front tire that can cause this problem.

scooter69 · « **Reply #9 on:** June 02, 2006, 07:59:03 AM »

Quote from: solman

I've had tire shimmy in the past as well. As soon as I bought a new rear tire, it went away. If you noticed which tire I replaced, it isn't always the front tire that can cause this problem.

Well in my case both tires were bought and installed on the same day. Guess it might just be something I've got to live with for now.