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Front End Wobble

  • Thread starter Thread starter huntb
  • Start date Start date
H

huntb

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I have recently developed a front end wobble that starts at speeds around 40-50mph. The wobble happens every 5 seconds or so. I've read that it could be several different things including swing arm bearings, front wheel bearings, fork bearings, unbalanced forks, loose forks or abnormal tread wear.

Is there anything else I should be checking for? Any advice on how to go about checking the items I've already listed? The tires are new as of a month ago and they were balanced at the shop that mounted them. This problem just started happening (became noticeable) last week.
 
huntb said:
I have recently developed a front end wobble that starts at speeds around 40-50mph. The wobble happens every 5 seconds or so. I've read that it could be several different things including swing arm bearings, front wheel bearings, fork bearings, unbalanced forks, loose forks or abnormal tread wear.

Is there anything else I should be checking for? Any advice on how to go about checking the items I've already listed? The tires are new as of a month ago and they were balanced at the shop that mounted them. This problem just started happening (became noticeable) last week.
Click to expand...

Did the shop mount the wheel on the bike too? Check that the bolts for the forks and axle are put back and tightened properly. Also, when I mount the wheel back on the bike I bounce the front end a few times while on the centerstand with bolts loosened to align the front wheel and then tighten things down after. Check too see if your front brake is dragging by putting on centerstand and have someone weight the rear end to lift the front wheel clear and it should spin easily. Abnormal tread wear won't really show on a new tire for at least hundreds of miles. Did you double check tire pressure too? Are the front fender's 4 bolts tightened? Those should be loosened before the "alignment" process to true up. Are they air forks and have equal air pressure? You might as well check the rear shocks to see if the preload setting is the same for both sides. When troublshooting there is a difference between a wobble and a weave and what causes each.
 
Last edited:
lurch12_2000 said:
Did the shop mount the wheel on the bike too? No. Check that the bolts for the forks and axle are put back and tightened properly. Also, when I mount the wheel back on the bike I bounce the front end a few times while on the centerstand with bolts loosened to align the front wheel and then tighten things down after. I'll try this. Check too see if your front brake is dragging by putting on centerstand and have someone weight the rear end to lift the front wheel clear and it should spin easily. I did this and at least one of them was dragging. How should I fix this? Abnormal tread wear won't really show on a new tire for at least hundreds of miles. Did you double check tire pressure too? I did and it was good for what the spec on the tire was but I put a little extra in it. Don't know if that will help much but I've read generally people over-inflate tires. Are the front fender's 4 bolts tightened? Good question, I'll check. Those should be loosened before the "alignment" process to true up. Are they air forks and have equal air pressure? I'm not sure, I assume oil. You might as well check the rear shocks to see if the preload setting is the same for both sides. My shocks are non-adjustable ('81 model) When troublshooting there is a difference between a wobble and a weave and what causes each.
Click to expand...

See my comments in blue above
 
huntb said:
See my comments in blue above
Click to expand...

The front forks do use fork oil and should have the same amount (8oz) each and you do have to take the caps off to check levels (or better yet if it's been a few seasons take apart forks, drain out and clean), but my '82 650E also has air valves on top that you fill to about 10psi. This acts as a preload in addition to a spacer if used on each fork spring. If one is 0 lbs and the other has pressure then the air in the tube is uneven and each fork may respond to road surface differently at speed.
Even '81 rear shocks should have a preload adjuster down at the bottom using a spanner type wrench or a philips head screwdriver to rotate. Normally there will be 5 settings and be sure they are the same. The later '82 models also had a dampening adjustment dial up top (setting 1-4).
36 lbs air pressure for both front and rear is usually a safe starting point for tires, but normally that's not going to cause a wobble. Extremely low pressure may cause more of a weave especially if it's the rear tire low or if the rear tire is squared off considerably.
One of the brakes will definitely cause a wobble at speed since the rotor is heating up and probably dragging more. You should consider overhauling the front brake system if it's old and grungy brake fluid and was sitting for awhile. You will have an "exciting" moment on the highway if one brake really seizes up if neglected!!
 
This is some good info, I'll definitely be checking into some of these things tonight. And you're right, I definitely need to overhaul the front brakes. I'll try to get that done this week too. I was waiting on steel brake lines to change out the fluid though.

Speaking of overhauling the brakes, how much could I turn down the rotors? All three have nasty grooves in them
 
huntb said:
This is some good info, I'll definitely be checking into some of these things tonight. And you're right, I definitely need to overhaul the front brakes. I'll try to get that done this week too. I was waiting on steel brake lines to change out the fluid though.

Speaking of overhauling the brakes, how much could I turn down the rotors? All three have nasty grooves in them
Click to expand...

I've never turned down a motorcycle rotor. Not sure if anyone would do or even safe to. Better to source a good used rotor or buy after market replacements if you can find for an older GS. There might be other GS models that use the same rotors, but I don't have any specifics. If they are really scored then even if someone would turn I doubt you can safely get down to a smooth surface without getting too thin. Then they would probably warp under hard brake use and heat.
 
huntb said:
Speaking of overhauling the brakes, how much could I turn down the rotors? All three have nasty grooves in them
Click to expand...

The minimum thickness spec is embossed into the rotor hub. On your model the front should be 5.5mm and the rear 4.5mm. Take a look and make certain before you have them surfaced at a clutch surfacing joint.
While you are at it, remove and inspect your steering head bearings.
 
GSX1000E said:
The minimum thickness spec is embossed into the rotor hub. On your model the front should be 5.5mm and the rear 4.5mm. Take a look and make certain before you have them surfaced at a clutch surfacing joint.
While you are at it, remove and inspect your steering head bearings.
Click to expand...

Won't removing the bearings degrade their integrity? Is there a safe way to do so without damaging them?
 
huntb said:
Won't removing the bearings degrade their integrity? Is there a safe way to do so without damaging them?
Click to expand...

You may check the steering bearings by unweighting the front end while on the centerstand and slowly pivot the fork all the way in either direction stop to stop. If it flops too easily you may want to tighten a little. If it's hard to move then the bearings could be suspect. If you have notchiness then the bearings need grease or on their way out. Still no substitute for removing and checking but may narrow your troubleshooting. It's usually something that hardly gets done with routine maintenance.
 
lurch12_2000 said:
You may check the steering bearings by unweighting the front end while on the centerstand and slowly pivot the fork all the way in either direction stop to stop. If it flops too easily you may want to tighten a little. If it's hard to move then the bearings could be suspect. If you have notchiness then the bearings need grease or on their way out. Still no substitute for removing and checking but may narrow your troubleshooting. It's usually something that hardly gets done with routine maintenance.
Click to expand...

When I had the front end up yesterday I recall the side to side "flopping" as you described. So the next question is, how do I tighten this?
 
Don't forget to check and service the swing arm bearings while you are at it. Another spot that isn't to well maintained.
 
huntb said:
Is there a way to test the bearings without taking the whole thing apart?
Click to expand...
No special tools except perhaps a fish scale. If the bearings are dry, rusted, pitted then you are probably in trouble and in need of replacement. You need to pull it apparat far enough to get new grease into the upper and lower bearings. If there is any notchiness the replace. You need the bearing tight enough so the wheel will not flop. The GSXR manuals use the fish scale to measure about 5 lbs pull on the clip on to turn the wheel so that gives and idea.
a low speed wobble at about 30-40 mph when hands are removed is most likely a loose head set bearing.
 
didn't the "WOBBLE" start only after the tire replacement? if so I i'll question the balance of the tires. easy to check. tear off wheels, put axles into them and place on jackstand... if one or both wheels seems to be in need of balance,OR HAS RUN OUT?? RUN back to where you got the tires and make them re-do the balances to see if there is a heavy spot.
 
barnbiketom said:
didn't the "WOBBLE" start only after the tire replacement? if so I i'll question the balance of the tires. easy to check. tear off wheels, put axles into them and place on jackstand... if one or both wheels seems to be in need of balance,OR HAS RUN OUT?? RUN back to where you got the tires and make them re-do the balances to see if there is a heavy spot.
Click to expand...

The wobble actually started a few weeks after the new tires were installed. The weights are still there too, but good call on the jack stands idea, I'll have to give that a try
 
huntb said:
Is there a way to test the bearings without taking the whole thing apart?
Click to expand...
Yeah, try side to side and forward and back, though I would just take them apart and inspect the races as well. I checked some swing arm bearings that way once and it felt fine, no movement. We decided to go ahead and pull it all down, what a surprise we got. It was junk inside, no grease, water damage, rust, races were marred to the point it was about to freeze up, that explained why we didn't get any movement. Do it the right way the first time.
 
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