Brakes rub when I stand and pedal – Help please

[hozn]

Can you move your wheel side to side by grabbing it and pulling/pushing it laterally? It could be play in the hub aggravating the issue.

It could be a not-stiff rear wheel or it could just be the frame. If it started happening recently, is it possible you have a crack in your frame (probably rear triangle).

[creadinger]

Excellent questions. I’ll check all of that, but I fear the results. I did get a new rear wheel relatively recently. A Velocity Chukker. I can’t recall if this problem was coincidental, but would make sense if the wheel is just not stiff enough. That would be preferable to a frame crack!

[sam_aye_am]

Check your quick release first. Then see if there is bearing play in the hub as hozn described. Finally check the spokes for obvious tension differences…simply grab pairs of spokes and squeeze together to get a feel.

My 2013 Roubaix came with a crap wheel set. No matter what I did, I had brake rub when I stood up to accelerate up a hill. Built my own wheels with quality stuff and not an issue. Also shaved a full pound off.

[hozn]

Yeah, good point on checking the QR too — at least rule out the really easy stuff.

Very possibly the rear wheel, yeah. And good suggestions to check for any obvious issues in spokes there. If you can, maybe borrow another wheel? @GB, might have a 700c rear wheel you can borrow for testing

If it is the wheel, obviously getting a new one would make sense. I don’t know much about that rim, but thought I remember it being wide (I am too lazy on my phone to google it) which should yield a stiff wheel — with the right spokes, lacing, etc. Maybe a good opportunity to try building a wheel yourself too!

[creadinger]

The wheel is probably wider than average. It’s wide enough I can put on 35mm tires for touring and stuff. I typically ride on 28s. It’s a beefier rim for greater strength too because I’m a clydesdale+. I have the 32 spoke version.

So last night I pulled on stuff and squeezed spokes and generally tried to make stuff move that shouldn’t. I couldn’t find any movement other than the spokes may be looser than the spokes on my other bike. Hard to tell, bu it’s definitely not out of true at all. It’s supposed to be a good wheel. At least that’s what the guy who built it said. I wonder if I should go back to the shop and insist they investigate the issue?

[hozn]

Well, if you run your brakes super close, you might want to just open them up a bit? Or change the offset of the pads to give you more clearance on whichever side is rubbing. I’ve definitely had to futz with brakes back when I used to use rim brakes (this is an advantage to disc brakes) since it’s probably not realistic to expect your wheel not to move *at all* when you’re putting significant forces into the system. If you have another wheel you can swap in and show that it does not rub, with the pads adjust just as close to the rim, then I would bring it back and ask them for their opinion. Of course it is possible that if the wheel is correctly built, there may be nothing that could be done short of choosing a different hub/spoke/rim combination. If the other wheel rubs now too, then maybe turn your attention to the frame.

[hozn]

Also, I found this to be great read: http://www.slowtwitch.com/Tech/Debunking_Wheel_Stiffness_3449.html — though I don’t remember exactly what it said, so I should probably read it again

[creadinger]

@hozn 108892 wrote:

Well, if you run your brakes super close, you might want to just open them up a bit? Or change the offset of the pads to give you more clearance on whichever side is rubbing.

Adjusting brakes – that has been my go to so far by fixing the symptom, and not the actual problem unfortunately.

I’ll try swapping the wheel with my other one to see what happens. It’s the exact same wheel as the problem wheel though, so it could be interesting. Heh.

Interesting article! I don’t understand most of it, but parts definitely did make sense. For me, the bottom line I feel is that I’m using a rim/spoke combination that should be ok. I have plenty of spokes on a heavy duty rim, so I just don’t think it should be occurring.

[Vicegrip]

Why not? Excluding something being loose some flex is something to be expected. Everything flexes even when working right. If you set one part to a to a tolerance that is tighter than another part you get unintended results. Can you open the brake and still get good stroke and stopping power? I am but a standard fred and I found that I can stand and bend my bikes. I can see/feel it. If the bike were built such that I could not cause flex at the top end of what I can produce it would be over built for 99% of its use.

[hozn]

Vicegrip has a good point. You should expect some flex. And it could be, per that article, that the rim is too stiff (compared to spokes) and that you would actually get less rub from a rim that was more compliant.

In the end, if you can’t find a brake configuration that minimizes or eliminates the rub, then I would agree that you probably want to change something up. Switch to disc. Of course discs can rub too (usually front), though switching to thru-axle has all but eliminated that.

But if the rear end is feeling especially flexy, check your frame for cracks. E.g. I cracked a frame on DS chainstay near BB and that explained a lot about how the rear end had felt in its final months.

[Harry Meatmotor]

One easy way to check what’s flexing if you hear rubbing (either tires rubbing chainstays or rim rubbing brakes) is to manually flex the rim towards the seatstay or the chainstay. While the bike is hanging in a stand, or just sitting up against a wall, grab the chainstay and spoke and squeeze the spoke towards the chainstay and watch what moves. Most bikes are fairly flexy – some definitely more than others.

quick anecdote: one night while we were running a computrainer competition, one participant hooked up his old 12-speed commuter bike to the computrainer. once things got spirited during the “race”, the rear triangle of the frame was flexing so much it nearly popped out of the trainer. We had the axle firmly tightened in the trainer, but because there was so much flex in the bike frame and rear wheel, the tire was smacking the sides of the roller. we ended up having two folks grab the seatstays from behind the bike to try and limit the amount of movement on the trainer, but it was really a lesson in just how much a crummy bike wiggles around underneath you when you’re putting out some power.

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