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So I read all these answers about the bike moving underneath the rider back and forth when standing on the pedals. So how much is actually effective and how much is for "show" (looks cool) I have a friend that ocassionally uses my bike and throws it violently back and forth when getting on the pedals. I don't think he is strong enough to really radically make the bike do this but after the rides the back wheel becomes untrue and the brakes rub because the wheel is that much out of line. I have to take it for the wheel to be trued. What advice should I give him about properly riding on the pedals so that I don't have to have the wheel trued everytime? I am fairly powerful on the pedals but I don't have that much movement.

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    Strange for a wheel to come out of true through normal riding. Is he hitting potholes or going up/down kerbs/curbs ? – Criggie Apr 1 '17 at 10:17
  • Sounds like your friend is sprinting out of the saddle and using his arms to push the bike around, effectively raising the angle of the bottom bracket axle to get the pedal around faster. This also shouldn't be putting your wheels out of true, however the raw tension on the chain can move the rear wheel in the dropouts, more-so if its not fully tight, or if the dropouts aren't parallel to each other. – Criggie Apr 1 '17 at 10:21
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    If you have really lightly-built wheels it's possible to put them out of true by working the bike as you describe. This could maybe be expected of a wheel on a racing bike, but should not occur or a more mundane bike, and especially not on anything resembling a "mountain" bike. What kind of bike do you have? (And how much does your friend weigh?) – Daniel R Hicks Apr 1 '17 at 11:36
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The way he's riding is bad because it damages your bike. That in itself ought to be enough reason to stop. You could point out that all the effort spent pushing the bike from side to side is wasted; he could use he energy more effectively to push the bike forwards using the pedals.

I suspect that if your friend was riding his own bike, he'd be less cavalier about his treatment of it.

I'd be inclined to say one of the following things to him:

  • "Please return my bike in the condition it was in when I lent it to you; either don't damage it, or get it properly repaired before you give it back", or
  • "You're not borrowing my bike any more"

Note that different types of bike are designed for different purposes. You've tagged this as "road"; we generally want road bikes to move forward efficiently, but BMX riding (for example) is very different. It sounds a bit like your friend isn't used to this kind of distinction.

  • I think this is the right advice: if you break my bike, you don't get to ride it. – David Richerby Apr 1 '17 at 20:21
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I learned the hard way that hard pedaling can put my rear wheel out of true if some or all of the spokes are too loose to begin with. At one point I actually thought someone was vandalizing my wheel and loosening the spokes by hand. I finally figured it out though, tightened up all the spokes properly and evenly: end of problem.

  • Good point - hard riding does show up flaws that otherwise would go undetected. Perhaps OP's wheel is not very well tensioned. – Criggie Apr 1 '17 at 23:51
  • And it's not terribly unusual for a wheel to "loosen up" in use. Depends on the spokes, rim, and effort put into building, but there is a fair amount of stretch in certain combinations. – Daniel R Hicks Apr 2 '17 at 2:17
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The main reason for throwing bike around when sprinting is to reduce the leverage from pedals. The pedals are left and right from the contact point between tires and ground, and when standing up one needs to compensate the twisting force from pedaling by twisting the handlebars the opposite way. This wastes strength, but the force can be reduced by moving the pedal closer to contact line by tilting the bike.

Properly built road bikes should survive it, and are often ridden like it.

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