Author Topic: Front wheel wobble  (Read 1644 times)

Offline roadrocket

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Front wheel wobble
« on: 30.12. 2007 19:11 »
I have not been riding much on the A10 the past season, and had some bother with my monobloc. However for next season I think I'll have some tasks ready, and one should be sorting out the front wheel. I have the 1969 tls brake, stainless spokes, and a steel rim of some description (not original, but same size). The forks were totally rebuilt a few years back, and I installed tapered head bearings from SRM. I have tried to true the wheel as much as I could, given my humble tools (wheel in forks, makeshift pointers), and have something like 2 mm play sideways, and probably also out of round. I get some wobble at low speeds, but can't notice any from 30 mph and above. I would like to get rid of the wobble, and asks the following: is the amount of play way more than should be tolerated? Could the wobble be due to balancing (have tried to check this, seems ok). Would loosening all spokes and starting all over be a solution? I'm not happy about taking all the spokes out, I replaced the old ones one by one... I have built a number of bicycle wheels for my race bike, they came out fine, but starting from scratch with one for a motorcycle scares me a bit.

Otto in Denmark
Otto in Denmark

Offline LJ.

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Re: Front wheel wobble
« Reply #1 on: 30.12. 2007 20:49 »

Might be worth considering the fact that your wheel spindle could be worn.... I too experienced a 'wheel wobble' sometime ago and replaced the spindle. I measured the two with a vernier and although there was not much difference in the two spindles measurements.... It was enough to cause a noticable wobble. Problem cured when new spindle fitted!
Ride Safely Lads! LJ.
1940 BSA M20 500cc Girder/Rigid- (SOLD)
1947 BSA M21 600cc Girder/Rigid-Green
1949 BSA A7   500cc Girder/Plunger Star Twin-(SOLD)
1953 BSA B33  500cc Teles/Plunger-Maroon
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Online groily

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Re: Front wheel wobble
« Reply #2 on: 30.12. 2007 21:25 »
Hi roadrocket, Yes, any of the things you mention might be responsible for the wobble, as well as LJ's spindle thought. 2mm - nearly a 10th of an inch - is quite a lot to be out of true on the rim, and if it isn't round that won't help. (Better to try to get to about a quarter of that, by seeing with your pointy device where the biggest gap is, and adjusting the tension of the spokes opposite by either slackening or tightening same as for your race bike. . . ). Then check by ear that all the spokes 'ring' about the same note when you ping them as the wheel goes round, etc etc bore bore blah blah. Putting wheels together is far easier than the mystics who do it for a living would have us all believe . . . but a dial gauge does help and you do have to have measured the offset of the rim from the hub if there is any - which on a front wheel there usually isn't.

Now, that's all well and good, but may have absolutely nothing to do with your problem. I'd actually start from a different and easier angle - called TYRES. If either the front or the rear is not centred properly in the well of its rim, you'll get wobble. Best remedy (to start with anyway and it's free) is to pump them up far too hard - say 3 to 3.5 bar, 45+ psi - then let them down - and then pump them up to usual pressure. If the wheels are out of the frame, bounce them around on the floor vigorously when they are pumped up to the high pressure. (I always do exactly this when fitting a tyre, whether for a car or a bike or even a wheelbarrow or lawnmower, for this very reason). You can see from the lines on the sides of the tyres when the things aren't on right. It is amazing how badly steering is affected by old, hard, out of true - and probably dangerous - tyres. And amazing how many of us try to pretend they're fine, me included because I'm too mean to buy new ones if I can still see the faint outline of the tread pattern. . . .
I had exactly your symptoms a few months ago (bad wobble up to about 30 mph, nothing above that speed) -and  it was the rear tyre that was guilty. Replaced it (have fun reading that thread here in Tech Topics!), and the steering was perfect. In the meantime I'd wrongly diagnosed all faults known to man from steering head bearings, fork bushes, wheel bearings, bent rims, misaligned frame, you name it - and they were all OK all along. I envy you your proper front brake! Groily