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Old 10-29-05, 11:29 PM   #1
soni_guin
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Wobbly bike - known cures?

A guy I was riding with this morning said that my bike seemed kinda wobbly... It will sway from side to side when pedaling, but will pretty much go straight when I'm not pedaling... he said it might be something off-centered... Also, one the 23 miles i ride this morning, it seemed like the bike was fighting me the whole way, like there was something creating resistance somewhere...

Also, my derailler (sp?) won't stay on the largest cog when it's under 70 outside...

here's what all i have done to the bike.

1) '83 Trek 400, 27x1.25" wheels, Suntour group, shifters on the down tube

2 weeks ago, I repacked the bearings. The front ones were noisy, the back one I did because I was doing the front.

While the rear wheel's hub was apart, I took the opportunity to replace the 14/30 6 speed freewheel with a 13/22 7 speed freewheel. When I first put the rear hub back together, one of the cone nuts kept wanting to tighten itself against the bearings... It may have stopped that, it may not have, and might be the problem.


I decided that I'm not too excited about the 13/22 freewheel (I can't climb at all with the 13/22 on there), so I want to put the 14/30 back on...

i need to repack the crank, since it's starting to make a little noise...

Anyway, the guy I was riding with said that something seems to be off-centered... What should i check when redoing everything?


Or, could it be my riding technique... my left leg is much stronger than my right... that comes from driving a car with a stick shift.
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Old 10-30-05, 01:00 AM   #2
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As far as the wobbling problem, is your seat possibly too high? Other problems could be your headset adjustment or technique; or, maybe the guy who told you about your wobbling is full of it. Good luck.
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Old 10-30-05, 01:01 AM   #3
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Check the back wheel. If you have dodgy spoke tension or a broken spoke, the back wheel will do weird things as you pedal hard, and can rub against the brakes. A broken spoke may not be immediately obvious - pull on each spoke.
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Old 10-30-05, 03:12 AM   #4
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Did you true and dish the rear wheel after switching to the wider freewheel?
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Old 10-30-05, 05:02 AM   #5
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You can check fork-alignment, frame-alignment, wheel-dishing all in one step by coasting no hands. Can you ride a straight line? Is the bike perfectly centered and vertical beneath you? That is, if you look down, the top-tube is centered over the downtube an hides the front-tyre when you're going in a straight line?

A misalignment of any and/or all of these factors would cause a pull to one side and you'll end up having to tilt the bike to one side in order to coast in a straight line.

However, in your case, it wobbles back and forth in a pattern. And it only wobbles when you pedal and coasts fine when you don't. What's the variable that changed between these two cases?
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Old 10-30-05, 07:11 AM   #6
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Quote:
Originally Posted by soni_guin
2 weeks ago, I repacked the bearings. The front ones were noisy, the back one I did because I was doing the front.

When I first put the rear hub back together, one of the cone nuts kept wanting to tighten itself against the bearings... It may have stopped that, it may not have, and might be the problem.

Also, my derailler (sp?) won't stay on the largest cog when it's under 70 outside...
what comes to mind is that your hub(s) are loose and the wheels are moving side to side under load... did you use two wrenches to lock down the cone and locknut?

the derailuer one's a bit odd, but sounds like lube is getting gummy in the der or cable and housing when the temperature drops. clean and relube lightly, see what happens.
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Old 10-30-05, 09:13 AM   #7
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Also check for frame cracks, including drop-outs.
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Old 10-30-05, 09:21 AM   #8
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Quote:
Originally Posted by MMACH 5
Did you true and dish the rear wheel after switching to the wider freewheel?
A 7-speed freewheel shouldn't be any wider than a "normal" 6-speed. They both require 126 mm dropout spacing and the 7-speed freewheels were the first "narrow" spaced freewheels so they were the same width as standard 6-speeds.

BTW, I'm aware of the narrow "Ultra 6" freewheels that fit into 120 mm dropouts but they were a short lived idea and shifted rather poorly.
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Old 10-30-05, 04:54 PM   #9
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the freewheels are the same width... It did the same thing before I swapped freewheels, anyway.

I checked front spokes, they're all nice and tight... Some of the rear spokes could stand to be tightened- that may be the problem.

All the front parts are in alignment...

Riding no-handed on this bike is almost suicidal- it's not nearly as stable as the Free Spirit i had as a kid
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Old 10-30-05, 08:57 PM   #10
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The cone locknuts are called locknuts for a reason. One of yours wasnt locked against the cone. If it only wobbles when pedalling you have a low/uneven spoke tension problem.
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Old 10-31-05, 01:51 AM   #11
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Quote:
Originally Posted by HillRider
A 7-speed freewheel shouldn't be any wider than a "normal" 6-speed. They both require 126 mm dropout spacing and the 7-speed freewheels were the first "narrow" spaced freewheels so they were the same width as standard 6-speeds.
Good information.

Thanks.
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Old 10-31-05, 04:14 AM   #12
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i'd say true both wheels
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Old 10-31-05, 07:23 PM   #13
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i'm sending the wheels in for a tuneup as soon as I get some money from a client who is past due...

effin deadbeats!
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Old 11-25-05, 05:04 PM   #14
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A-HA! I know why the bike is wobbly!

I put the stock 6-speed freewheel back on, and watched it as i lubed it. It will rock side to side when the wheel is spinning and the pedals are stationary! It wobbles maybe 1/8" either direction as the wheel spins... So, when I pedal, it pulls the bike to one side, I overcompensate, the bike pulls back to that same side, I overcompensate, repeat forever (or until I get in my miles, whichever comes first )

So... that means i have a bad hub.

BOOOOOO!


(the replacement 7 speed freewheel was hopeless... It wouldn't take any lube, it had a spot where it would lock up on every rotation, so I had the lbs pull it and I put the old one back on...)
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Old 11-25-05, 08:14 PM   #15
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Jeez, this is an easy one... knock off the four shots of Cuervo Gold before you hit the trail!
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Today, I believe my jurisdiction ends here...
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Old 11-25-05, 10:23 PM   #16
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goldschlager... hehe
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Old 11-25-05, 10:43 PM   #17
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Check for a broken axle in your rear hub.
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Old 11-27-05, 04:30 PM   #18
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some freewheel wobble is normal -- don't jump to any conclusions. Even if it is extreme, I don't see how it accounts for your problem.
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Old 11-27-05, 05:57 PM   #19
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Uh... I don't see how a wobbly freewheel can exert lateral forces on the front-wheel. That's the only way you can make a bike carve a non-straight line. All steering is initiated by the front-wheel angle not being in-line with the rear-wheel.


Quote:
Originally Posted by soni_guin
A guy I was riding with this morning said that my bike seemed kinda wobbly... It will sway from side to side when pedaling, but will pretty much go straight when I'm not pedaling...
...
Or, could it be my riding technique... my left leg is much stronger than my right... that comes from driving a car with a stick shift.
I think you've identified the problem right here. The bike goes straight when you're not pedaling. So it's the pedaling forces that causes you the wobble and I bet the weaving is the same frequency as the pedal revolutions. Also have your buddy watch your upper-body in relation the bike's center as well. Can you ride one-legged evenly with each leg in a straight line?

Last edited by DannoXYZ; 11-28-05 at 11:27 AM.
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Old 11-28-05, 11:21 AM   #20
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how do u mean the bike can't coast hands-free? it should be able to. is your headset nice and tight? grab the front brake and rock the bike back and forth; if you hear or feel clicking, the headset is loose.

otherwise it sounds like technique. lower your saddle and pedal smoothly.
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