Unstable bike

maximark

maximark

Joined
Aug 24, 2012
Messages
418
Location
Park Ridge, NJ
Bike
1994 ST1100
I've recently changed rear tire from Bridgestone to Dunlop due to a bad flat and had to ride on it (flat) about a mile on and on grass shoulder of highway. I didn't balance the wheel and now my bike is really unstable. It began to wobble side to side once I've reached 80 m/h and also I had to break rapidly due to traffic jamm (separate occasion). Now I wonder if it's due to wheel imbalance or forks or steering bearings? It's scary sometimes.
 
It could be way out of balance but my only experience with one that far out is more of a bouncing effect, not wobble. Maybe someone else will chime in.
 
A couple things- How is the air pressure? Don't trust a dealer to set the pressure correctly. A low tire can squirm all over. Have you checked the beads of the tire compared to the rim to make sure they seated all the way? Some tires can be a bear to seat the bead, and will hop and bounce because its somewhat out of round from not seating. How about the axle? Is it tight to specs (or at least reasonably close)? A loose axle will allow the wheel to move. And a real shot in the dark, but always a possibility- is the tire clean? Someone could have gotten tire lube on the outside of the tire and that would make it very unstable. Or grease, or anything else in the shop. Make sure the tire is clean (including in the tread). If it looks like oil or anything else might be on there clean it really good with dish soap and water (won't dry the rubber like harsh cleaners or degreasers) and rinse well. It wouldn't hurt to wash it anyway, you could just have a lot of mold release on the tire from the mfg process.
 
maximark said:
I've recently changed rear tire from Bridgestone to Dunlop due to a bad flat and had to ride on it (flat) about a mile on and on grass shoulder of highway. I didn't balance the wheel and now my bike is really unstable. It began to wobble side to side once I've reached 80 m/h and also I had to break rapidly due to traffic jamm (separate occasion). Now I wonder if it's due to wheel imbalance or forks or steering bearings? It's scary sometimes.
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Actually, your issue is due to mismatched brand wise tires. Cord configuration is totally different between the two brands and they don't play well together on these bikes, and that ill handleing rears its ugly head even worse if using mis-matched radials,BTDT. Flip-side of that is my 31+yr.old Yammy XS11 Venturer doesn't care, as long as both ends of bike are on good rubber. IMO , some of that has to do with frame design and geoetry, so the even older scoot doesn't mind.
 
Check and make sure the bead is set all the way around both tires. It can be close but not quite in place and will cause a very unstable ride. Ask me how I know...
 
It's possibel Brant is correct in his assessment but I've mixed brands and bias/radial (doing both now on lipSTick) with no ill effects. That being said, if the bike was stable before the change and now isn't stable, it's likely caused by the rear tar. I no longer use Dunlop, they are down near the bottom with Avon at The CattGarage.
 
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Agree with George-I used to run Dunlops on both of our ST1100's but now run nothing but the GeorgeCatt Specials-Bridgestones!!!! And mileage has really improved-even pulling my Aspen Sentry camping trailer.
 
Could also be an issue with axle/spacers/bearings. I would get the bike up on the center stand, check the bead, round and bearings.

Keep us posted.
 
So what you're guys saying that I should buy a new Bridgestone and not to look into forks and steering, what I was thinking that could gone wrong when I drove on grass shoulder of the highway.
 
Are you ok with putting your bike on the centre stand, chocking the front wheel and going though the gears. You might see the problem right away if you can watch your back tire while it is spinning around. Just sitting on your bike and going though the gears might indicate a high unbalance.
Some have attached their bikes to the ceiling with chain hoists and slings as an added safety measure.
 
maximark said:
So what you're guys saying that I should buy a new Bridgestone and not to look into forks and steering, what I was thinking that could gone wrong when I drove on grass shoulder of the highway.
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Don't buy anything until you have checked the cheap/free stuff first, like we have listed off. And unless you crashed in that grass and hit a tree or boulder, its doubtful you did anything just by running on grass. Care to post pics of some of your rides George? LOL.
 
Didn't crash or hit the tree, it was rough- some branches after Sandy ( the storm) but no, no hard impact. Just considering the age of the bike and who knows when the bearings and forks were done last time...
thats a good idea to try to run "dry" thru gears. Thanks, keep you updated.
 
We need to clarify if it is a "wobble" or "vibration".

I'm assuming high speed wobble not vibration.

I assume this is for your ST1100? It is a bias ply but I'm not buying into that being the cause of a wobble. Pressure is a good starting point. Other than that, I'd be looking for a different brand.
 
If the bike needs maintenance due to age, miles, or neglect, go ahead and do it regardless of the tars. I had to do rear wheel bearings while in BC last summer, started the trip no problem but the instability increased dramatically over just a couple hunnert miles. So, yes, the tar flat tar and other problems could happen coincidentally.

Keep us poSTed.
 
I ran all gears on stand and yes, she was shaking like old washing machine on spin cycle. So I'll get new bearings, make sure that tire sits properly on the rim and take her to service to check the balance.
will let you know.
thanks guys!
 
maximark said:
I ran all gears on stand and yes, she was shaking like old washing machine on spin cycle. So I'll get new bearings, make sure that tire sits properly on the rim and take her to service to check the balance.
will let you know.
thanks guys!
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Seems like just changing a tire would not cause such shaking. Check that all spacers and your axle installation is correct and there is no play. Could be out of balance but It would take a pretty bad tire to cause such problems. Make sure your direction of rotation for the tire is correct also. May not be setting on the bead but I would think if it is not you would be loosing air(assuming it is a tubless tire.).
 
Iffin you have bad bearings you should be able to feel that by turning the wheel by hand and pushing side to side looking for any play. As mentioned earlier, the bead may not have seated correctly and that should be evident by slowly turning the wheel by hand while looking where the tar meets the rim.
 
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