Buckled wheels?

[CB San-Remo2006]

I heard that its possible to reduce the buckle in a wheel by adjusting spoke tension. If so how is it done? Does this reduce a wheels strength or deform it in any way?

 

[Retro Grouch]

I heard that its possible to reduce the buckle in a wheel by adjusting spoke tension. If so how is it done? Does this reduce a wheels strength or deform it in any way?

Depends.

If you are talking about a wheel that looks like a taco, often it's possible to push it back into line by reversing the forces that pushed it out of line. If it will pop back into line on it's own like that, a little minor fiddling with the spokes may make it rideable again.

If you are talking about a rim that resists all efforts to go into line on it's own, that means the rim itself has been bent past it's yield point. If that's the case, no spoke tension adjustment will ever make a good wheel out of it.

 

[ScienceIsCool]

I heard that its possible to reduce the buckle in a wheel by adjusting spoke tension. If so how is it done? Does this reduce a wheels strength or deform it in any way?

Buckling a wheel by playing with spoke tension is not something I would expect. When I think of buckling, I think of the wheel coming out of plane and becoming a "taco" or "saddle" shape. This is only caused by excessive lateral strain on the rim. I doubt you could do that by spoke tension alone and here's why:

If you increase spoke tension, you introduce stress in the hub flange, spoke, and rim. The question is, what fails first? Almost always the aluminum rim fails and the spoke pulls out of the spoke hole. It won't buckle though...

John Swanson
www.bikephysics.com

 

[Aussie Steve]

How about a wheel that is not buckled but is out of round, i.e. when holding rear wheel off ground, and you spin it, you can spot an up-and-down movement of the rim as it passes the brakes. Only about 4 or 5 mm, but on the road, you can bloody feel it and your groin gets chafed. any ideas on how to spot the culprit and also how to fix it?

 

[Phill P]

If you don't know how to do something like this....ask your LBS and get somebody who does know what they're doing to fix the problem for you.

If you screw it up, your slightly out of shape wheel may become a very out of shape wheel, and as a result you may become seriously out of shape, or if your lucky just stuck a long way from home with an unrideable bike.

 

[daveornee]

How about a wheel that is not buckled but is out of round, i.e. when holding rear wheel off ground, and you spin it, you can spot an up-and-down movement of the rim as it passes the brakes. Only about 4 or 5 mm, but on the road, you can bloody feel it and your groin gets chafed. any ideas on how to spot the culprit and also how to fix it?

Sounds like the rim is bent.
If so, replace the rim, dish, true, stress relieve, check spoke tension balance, and adjust as required.
Did you hit a pot hole or curb?... or was the wheel like this from new?

 

[daveornee]

I heard that its possible to reduce the buckle in a wheel by adjusting spoke tension. If so how is it done? Does this reduce a wheels strength or deform it in any way?

Spoke tension should be even (per side if dealing with rear wheel) and adjusted at the suggested tension per the manufacturer of the rim.

 

[CB San-Remo2006]

Spoke tension should be even (per side if dealing with rear wheel) and adjusted at the suggested tension per the manufacturer of the rim.

I have no idea about anything like that but I adjusted random spokes and got lucky. However I have had my bike long enough to get its moneys worth and if all else fails I can get a new wheel for it.

 

[rcrampton]

You could read Sheldon Brown's article on wheel building. It explains the fundamentals of how a good wheel is built. After reading it you should be able to pluck the spokes to make sure you have reasonably even spoke tensions with the wheel true. If you're mechanically inclined you might be able to tweak anything out of whack to where it should be. If things don't go well your LBS can fix it for you for probably $20 if you don't hose it up too bad.

I'm no wheel expert but I've been able to tweak wheels back into true and they seem to last. I think choosing components and building a wheel from scratch takes training but maintaining them is well within the ability of most bike owners.

 

[dabac]

How about a wheel that is not buckled but is out of round, i.e. .. on the road, you can bloody feel it and your groin gets chafed. any ideas on how to spot the culprit and also how to fix it?

1) remove tire
2) Get a whiteboard pen or anything fast drying that'll write on the rim but still wipe off easily
3) Spin wheel, bring pen closer and closer to the rim radially from the outside until brief contact is made.

You have now identified your high spot

4) Spin wheel, bring pen closer and closer to the rim radially from the inside until brief contact is made.

You have now identified your low spot

Assuming you've held the same approach speed with the pen the length of the stripes ought to give you a good indication whether the wheel buckles out(which can happen if spokes were tensioned sloppily, or if the wheel buckles in, which can happen if you run over/into something hard.

A wheel that buckles out can be adressed by slacking all spokes maybe 1/4 turn and then taking in the spokes at the high spot 1-2 turns.

I don't know if a wheel that buckles in is salvageable by any means, it might require that the rim is untied and shaped by itself first.

Wipe off stripes, spin wheel and repeat marking process. Continue until high/low spot are no longer easily identifiable. (long,weak stripes.)