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Is this safe?

Old 08-15-08, 02:42 PM
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MadeInItaly
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Is this safe?

I just put 25mm tires on a bike. The front tire is rubbing on the front brake . So when I put the front wheel on, the axel is not flush against the fork. Will this slip or is the quck release strong enough to keep the 1mm of space? I'm 185lbs on 700c wheels. Or just stick w/ 23mm tires?
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Old 08-15-08, 03:35 PM
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Originally Posted by MadeInItaly View Post
I just put 25mm tires on a bike. The front tire is rubbing on the front brake . So when I put the front wheel on, the axel is not flush against the fork. Will this slip or is the quck release strong enough to keep the 1mm of space? I'm 185lbs on 700c wheels. Or just stick w/ 23mm tires?
Theoretically the load isn't carried by the axle, but by the dropouts being pinched between the QR and the locknuts. Still, if the QR were to slip things would get nasty real fast. I'd stick with the narrower tire instead.
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Old 08-15-08, 03:43 PM
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Nope. Not safe. The skewer doesn't handle the load, so it will slip, the wheel will stop, and you will fly over your handlebars.
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Old 08-15-08, 04:02 PM
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It's odd that it clears the fork but not the brake. Well atleast I can run the 25 on the rear and a 23 on front. I should be doing that anyway.

I really love the feel of 25's. Oh well such is live. Not sure the red looks good anyway. Going over the bars doesn't sound like any fun.

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Old 08-15-08, 04:21 PM
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Originally Posted by urbanknight View Post
The skewer doesn't handle the load,
Well, Sheldon Brown wrote that it does, he even described a wheel he'd put together with zero axle protrusion beyond the locknuts, said it worked OK.

I'm inclined to believe him, as wheel axles are threaded all the way, and still can sit for years in steel dropouts w/o suffering any damage to the threads. If the axle was carrying the load I'd expect the threads to suffer some damage fairly quickly at the support points.

Makes sense from a general engineering standpoint as well, as it's quite rare to have a fastener loaded in shear. It's far more common to have the fasteners clamp two bits together, and then have friction between the surfaces carrying the load.
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Old 08-15-08, 04:24 PM
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^ Makes sense, and I don't mind changing my mind to that of Sheldon Brown's.
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Old 08-15-08, 04:35 PM
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Well i'm going for my sunset ride in a few. If I don't report back by 9pm , then I crashed and broke my CB.
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Old 08-15-08, 05:31 PM
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bad idea
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Old 08-15-08, 05:40 PM
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Crazy storm rolled in here in NY. Gonna have to test it out in the AM. Makes sence about the threaded axle not showing any where. It must be true what SB reported. He was always right wasn't he!!!
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Old 08-15-08, 08:31 PM
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Is it just me or is anyone else here puzzled about why a tire touching a brake pad would cause problems at the QR skewer?

If the tire is rubbing on the brake pad then you adjust the pads or calipers to compensate. If part of the axle is sticking out past the outer face of a dropout then that's a whole other issue that has nothing at all to do with the brake pad touching the tire. Or more accurately you've got TWO problems.

Or am I missing something that all the rest of you figured out already and I should just go sit in the dunce corner?
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Old 08-15-08, 08:51 PM
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Originally Posted by BCRider View Post
Is it just me or is anyone else here puzzled about why a tire touching a brake pad would cause problems at the QR skewer?

If the tire is rubbing on the brake pad then you adjust the pads or calipers to compensate. If part of the axle is sticking out past the outer face of a dropout then that's a whole other issue that has nothing at all to do with the brake pad touching the tire. Or more accurately you've got TWO problems.

Or am I missing something that all the rest of you figured out already and I should just go sit in the dunce corner?
Yes, you are missing something. It's rubbing the brake not the pad. The tires are too tall not too wide.

Now go to the corner.....
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Old 08-15-08, 09:32 PM
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I think I missed something too and will sit in the corner with you, so don{t feel too lonely. I thought he replaced the tires with wider 25mm vs 23mm tires, not taller tires? I{m not so good with tires, but does going from 23mm width tires to 25mm width tires increase the height?
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Old 08-15-08, 09:37 PM
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Yes they are wider and taller. They look like lightbulbs on some rims.
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Old 08-15-08, 10:55 PM
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(.... a little voice speaks from the corner....)

So the gap you're talking about is in the top of the U in the dropout? OK, now I see.....

If it was me using these bigger tires I wouldn't just trust the pressure from the skewers. I'd pack a small shim of metal into the gap in the U of the dropouts "just in case". I know everyone is saying that the QR will hold just fine but I'd be worried about bumps from potholes or rocks shocking the axle up and possibly out of alignment. Some little pads of metal in the gap would prevent that. Yeah, maybe it's a "belt and suspenders" answer but in something like this it's better safe than sorry.



... can I come back now? It's lonely over here what with all the whimpering and talking to himself that tafigueroa is doing I'm getting worried that he'll snap and start busting up bikes or something..... He's got that look in his eyes.......
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Old 08-15-08, 11:51 PM
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Granted...
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Old 08-16-08, 12:16 AM
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24mm
http://www.vittoria.com/index.php?op...073&Itemid=116
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Old 08-16-08, 12:20 AM
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But they only come in green.
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Old 08-16-08, 12:22 AM
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green means go!
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Old 08-16-08, 05:02 AM
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Originally Posted by BCRider View Post
...I'd be worried about bumps from potholes or rocks shocking the axle up and possibly out of alignment.
Well, that's the thing with the unexpected. Figuring out how strong something needs to be to stand the planned loads is fairly straight forward, figuring out reasonable margins for the unforeseen is a tad more difficult

Makes me think of that stage in the TdF when LA went offroad and cut through the rough between two legs of a hairpin descent. My guess he felt rather pleased that his bike had some margins of strength beyond what it needed on the road then.

If you hit an obstacle big enough to send you OTB anyhow it really doesn't matter if you shifted the wheel in the dropouts at the same impact or not. But sure, there can be an intermediate level of disaster where the properly seated wheel would have survived while the wheel with the modified mount fails.
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Old 08-16-08, 05:56 AM
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Wheels and tires move around a bit in dynamic situations. Cornering flex, minor changes in the wheel true down the road. Changes in air pressure due to temperature.

IMHO you need a little more margin than that.
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Old 08-16-08, 06:16 AM
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I expect a different make or model "700x25" tire might fit properly. Bike tire actual sizes are highly variable among manufactures even with the same nominal sidewall numbers. Some 700x25's are really 23 and others approach 28.

I once had a pair of Performance's house brand "700x23" tires that were so big they wouldn't clear the front derailleur's operating arm while other makes of 700x23 did fit just fine.
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Old 08-16-08, 10:37 PM
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Why 25mm?
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