08-07-2004, 10:52 PM
08-08-2004, 12:46 AM
i dont know the actual physics of it (and would like to find out), but they are typically caused by an abnormal weight bias on the rear of a bike. this causes the front to become "unloaded", overly sensitive to lateral inputs, and therefore unstable. if the front wheel encounters rough pavement in this condition, it can lead to a wobble.
the root cause here is an unstable steering geometry. bikes are typically designed to be stable and any deviance from this occurs either due to chassis modifications, riding style, or (usually) both. you are most likely to encounter wobbles when coming out of a turn or when accelerating hard. its best to let a bike sort out wobbles by itself and not fight it or apply additional throttle. wobbles during cornering are typically accompanied with understeer, so if your bike is unstable in corners, be ready for an involuntary "wide line". of course the best cure is prevention and if you havent made any mods to your chassis, adjusting rear preload can solve most wobble issues. a forward biased centre of gravity also helps.
i believe there is another kind of wobble that is related to braking, maybe someone can shed more light on it.
my 2 cents...
the root cause here is an unstable steering geometry. bikes are typically designed to be stable and any deviance from this occurs either due to chassis modifications, riding style, or (usually) both. you are most likely to encounter wobbles when coming out of a turn or when accelerating hard. its best to let a bike sort out wobbles by itself and not fight it or apply additional throttle. wobbles during cornering are typically accompanied with understeer, so if your bike is unstable in corners, be ready for an involuntary "wide line". of course the best cure is prevention and if you havent made any mods to your chassis, adjusting rear preload can solve most wobble issues. a forward biased centre of gravity also helps.
i believe there is another kind of wobble that is related to braking, maybe someone can shed more light on it.
my 2 cents...
08-08-2004, 09:18 AM
For me, I get wobbles when I didn't do a smooth corning transition. (Ie. Bad timing acceleration timing and not shifting by weight smooth from one side to the other)
I don't think you can fight the wobbles even if you try so like ez said let the bike sort it out itself.
I don't think you can fight the wobbles even if you try so like ez said let the bike sort it out itself.
08-09-2004, 08:45 AM
When I first picked up my bike, it came with a brand new tire...on one of the corners I took, the bike started to wobble, luckly I was able to ride thru it. Scary sh*t.
08-10-2004, 09:31 AM
They can also be caused by incorrect tire pressures.
08-10-2004, 11:24 AM
Bad tire balance...
rear shocks not adjusted the same....
bent frame parts (swingarms, ...)
rear shocks not adjusted the same....
bent frame parts (swingarms, ...)
08-10-2004, 12:02 PM
also, really bad front shocks (pogo-like)
10-05-2004, 03:02 PM
I had one coming over a hill...yeah, it is scary!!!
05-09-2005, 02:11 PM
i read somewhere recently that acceleration wobbles are caused when the front tyre becomes unweighted enough to cause it to either leave the ground completely or lose traction. when it comes back down or regains grip along a different line than the rear, a wobble is caused.
i did have a braking wobble recently and it felt like a corss between the rear tyre "hunting" and super-sensitive steering due to a sharp rake angle caused by heavy braking
i did have a braking wobble recently and it felt like a corss between the rear tyre "hunting" and super-sensitive steering due to a sharp rake angle caused by heavy braking
05-27-2006, 11:47 PM
http://w6rec.com/duane/bmw/wobbles.htm
Here are some things to check.
1. Correct tires and air pressure. Twenty five years ago this meant Conti or Metzler at about 30-34 lbs. Today it is higher.
2. Tires balanced correctly. Are you sure you have really balanced them? Can your repair shop really do it? Read about balancing a BMW motorcycle wheel.
3. Tires in very good condition, especially the front? We found that when the tread is down to 1/2, replace it, balance it and many wobbles will disappear.
4. Tight wheel, swing arm and steering bearings?
5. Good shocks and mounting bushings?
6. Saddle bags? Remove them.
7. A top box is just about the worst thing on a bike. The problem is both aerodynamic and weight. Even empty they can cause a wobble. Remove it for the tests.
8. A BMW /5 (and others too) must be neutral steering. To test this I prefer to go through a 50-60 mile sweeping curve. Let go of the bars and it should stay in the same curve. If it wants to turn tighter (fall down) it is too low in front or too high in the rear. Is the bike high enough? Does it have sagged out springs or a front tire with a low profile? It can also have forks bent straight back towards the engine. It may track straight but not turn properly. If it wants to stand up and go straight in the curve, maybe the front tire is too big, the rear too small or the rake too great. When the dealer got the BMW it was neutral steering. You may not care about neutral steering, but you better be concerned to find out what has changed.
9. The /5 and later with the telescopic forks have a reputation for wobbling. It is only partly true. If the forks are properly aligned they won't have stiction. This can be a very important factor in wobbles, especially high speed wobbles. The forks may need to go through the alignment procedure to work correctly.
Here are some things to check.
1. Correct tires and air pressure. Twenty five years ago this meant Conti or Metzler at about 30-34 lbs. Today it is higher.
2. Tires balanced correctly. Are you sure you have really balanced them? Can your repair shop really do it? Read about balancing a BMW motorcycle wheel.
3. Tires in very good condition, especially the front? We found that when the tread is down to 1/2, replace it, balance it and many wobbles will disappear.
4. Tight wheel, swing arm and steering bearings?
5. Good shocks and mounting bushings?
6. Saddle bags? Remove them.
7. A top box is just about the worst thing on a bike. The problem is both aerodynamic and weight. Even empty they can cause a wobble. Remove it for the tests.
8. A BMW /5 (and others too) must be neutral steering. To test this I prefer to go through a 50-60 mile sweeping curve. Let go of the bars and it should stay in the same curve. If it wants to turn tighter (fall down) it is too low in front or too high in the rear. Is the bike high enough? Does it have sagged out springs or a front tire with a low profile? It can also have forks bent straight back towards the engine. It may track straight but not turn properly. If it wants to stand up and go straight in the curve, maybe the front tire is too big, the rear too small or the rake too great. When the dealer got the BMW it was neutral steering. You may not care about neutral steering, but you better be concerned to find out what has changed.
9. The /5 and later with the telescopic forks have a reputation for wobbling. It is only partly true. If the forks are properly aligned they won't have stiction. This can be a very important factor in wobbles, especially high speed wobbles. The forks may need to go through the alignment procedure to work correctly.