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In brief: between a standard quick-release skewer and a bolt-on skewer, which will provide greater clamping force?

More detail:

Modern bicycle wheels are held in place by clamping skewers that run through hollow axles. The typical "quick release" design has a built-in lever on a cam that you close with you hand to secure the wheel, like this:

QR skewer

If you prefer not to have the quick-release mechanism on your hub for whatever reason, it's possible to retrofit your axles with "bolt-on" skewers which forego the cam and lever for simpler hex heads: Bolted skewer

The torque spec for bolt-on skewers is generally 7 N-m, while Shimano recommends 5.0 - 7.5 N-m tightening torque on their quick-release skewers.

My question: How would these torque values applied through their respective systems (7.5 N-m through a cam versus 7 N-m through a threaded fastener) compare? Which would likely result in a higher clamping force (if we're assuming proper lubrication with no contamination, etc.)?

Generally, people seem to believe the bolt-on design clamps down better, but I've seen some people insist the opposite is true. Conventional wisdom in the bicycle world is notoriously dodgy, so I was hoping to get some expert insight.

Carl
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  • Additionally since this question was asked, through axles have become more common on both MTBs and Road bikes. Often associated with disk brakes. – Criggie Dec 16 '17 at 08:23

1 Answers1

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My question: between these two designs, which could I expect to offer stronger clamping force?

The only truly measurable quantity here is the torque of the bolt-on skewer, which you have stated is 7 N-m. Using this, it's possible to determine the clamping force of the skewer, but it's not really relevant right now (and we'd need to know a lot more about the skewer's properties).

You're correct that the whole "leave a bit of a dent in the palm of your hand." thing is dodgy. As far as I know, there is no ASTM standard test for hand denting (though this is tongue-in-cheek, I really hope someone can prove me wrong, just because of how ridiculous that would be). Personally, I like to torque the quick-release skewers on my bike so that I can barely get them closed, and I like to think I have pretty strong hands. I've never stopped to look at the dent in my hand afterward, and my bike doesn't seem to notice a difference.

Given the variability inherent with this sort of rule-of-thumb approach, I don't think there's a way to truly answer this question.

grfrazee
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  • Yeah, it's one of those "how much does a box weigh" sort of questions, isn't it? Half of the trouble I've had is basically figuring out exactly what questions I should be asking. But, aha! I did find Shimano's official spec for QR torque: 5.0 - 7.5 N-m. I'll update my question to reflect this and restate the question somewhat. – Carl Dec 10 '15 at 16:54
  • @Carl, I understand, it's tough sometimes. Your question is interesting and valid, just not particularly suited to an exact answer. – grfrazee Dec 10 '15 at 16:56