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Discussion Starter · #1 ·
I recently bought a Kona Unit X and it comes with hydraulic disc brakes. When I got it and installed the wheels, I noticed a slight rub on the front and a very small but continuous rub on the back brakes. I took it to a shop, and the shop owner said that he recentered them and the front brakes had a slight bend but he fixed it. I took it home, rode it, everything was great.

Then, I released the front QR to see if I could get a better amount of compression on the wheel bearings, and I seat the wheel fully, set the QR, and it's rubbing again. I released the rear wheel as well, seated it fully, and it has varying amounts of rub everytime I undo the QR and reseat the wheel. Are QR and disc brakes always this fickle? Shoudn't they stay centered as long as the wheel is seated correctly? It just seems like any slight movement I do throws off the extremely fine clearance between the disc pads and the disc, and I don't see how people don't get driven crazy from having disc brakes!:madman: Any advice on how to keep them solid between wheel removal and replacement?
 

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Discussion Starter · #3 ·
Thanks for the reply Dougal. That seems like the most logical thing to do at this point. I don't even know how QR became such a big thing when every amount of pressure slightly adjusts the position of the wheel in the fork and the pressure on the bearings. For perfectionists this seems like a nightmare.

I'm going to take my bike to the shop again and ask him to help me with some basics of this QR stuff. After that I'll be looking into options to switch to Thru Axle.
 

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If anyone has success with QR setups with disc brakes I'd love to hear some of that.
I had reasonable success with bolt-up skewers back in the day (early 2000's) when I had 8" Hayes mag brakes and a QR fork.

Reasonable success because I still had some bolt-up skewers break and strip out. Simply low quality parts back when it was hard to find anything decent.
 

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Right. The key here is you're adjusting things, it's changing stuff. Settle on how tight you want the QR and just ensure that it's that tight every time, that is, as you start to close the handle it starts to make contact at the same point every time. As long as you can do that, I've had reasonable luck with QR and disc brakes. But if you have to adjust something, you'll need to recenter the brakes most of the time to prevent some sort of rubbing. The good news is, with a little practice, you get to a point where when you do have to recenter the brakes, it only takes a few minutes.
 

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If anyone has success with QR setups with disc brakes I'd love to hear some of that.
One of my older bikes has hydro disks and QR's. I have always re-centered its calipers whenever I removed the wheels, in addition to always having the bike on the ground when tightening the QR's for consistent fit.

1) Loosen the caliper bolts
2) Grab and hold the brake handle
3) Tighten the caliper bolts (while holding the brake handle)

Only takes a couple of minutes.
 

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in addition to always having the bike on the ground when tightening the QR's for consistent fit.
^This has always worked for me.

1) Loosen the caliper bolts
2) Grab and hold the brake handle
3) Tighten the caliper bolts (while holding the brake handle)
^This had never worked for me. I always had to re-center the calipers visually. But the first method usually does the job.
 

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As originally posted by fredcook & fmendes....

"in addition to always having the bike on the ground when tightening the QR's for consistent fit."

Install QR with weight on the bike. Adjust brakes. Anytime you remove and replace, just do it with the bike on the ground. Once accomplished, I never had to fool with them unless I replaced pads. It always worked for me before I started using through axles, and even with those, I'm in the habit of doing the same thing, though it's not that critical anymore.
 

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Thanks for the reply Dougal. That seems like the most logical thing to do at this point. I don't even know how QR became such a big thing when every amount of pressure slightly adjusts the position of the wheel in the fork and the pressure on the bearings. For perfectionists this seems like a nightmare.

I'm going to take my bike to the shop again and ask him to help me with some basics of this QR stuff. After that I'll be looking into options to switch to Thru Axle.
Quick releases predate modern bicycle disc brakes by a LONG TIME. QR's have been around since the 1930's or so.

Modern disc brakes didn't start becoming a big thing until 60+yrs later.

And disc brakes are the biggest reason that thru axles took off because it's unavoidable with a QR that differences in clamping force will change the caliper/rotor alignment. The only way to deal with it is to get REALLY practiced with applying the same clamping force any time you replace a wheel. It's also definitely a bigger deal up front than in the back (the back of a hardtail, at least).

Also, for a very long time, the majority of bicycle wheels used cup and cone hubs, and you adjusted bearing preload at the hub. It's relatively recent with cartridge bearings that axle clamping force affected bearing preload at all.
 

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Discussion Starter · #12 ·
Quick releases predate modern bicycle disc brakes by a LONG TIME. QR's have been around since the 1930's or so.

Modern disc brakes didn't start becoming a big thing until 60+yrs later.

And disc brakes are the biggest reason that thru axles took off because it's unavoidable with a QR that differences in clamping force will change the caliper/rotor alignment. The only way to deal with it is to get REALLY practiced with applying the same clamping force any time you replace a wheel. It's also definitely a bigger deal up front than in the back (the back of a hardtail, at least).

Also, for a very long time, the majority of bicycle wheels used cup and cone hubs, and you adjusted bearing preload at the hub. It's relatively recent with cartridge bearings that axle clamping force affected bearing preload at all.
Well, I learned something new today. So are sealed cartridge bearings affected by clamping force?

Thanks for all the replies by the way. This has been very educational.
 

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Well, I learned something new today. So are sealed cartridge bearings affected by clamping force?
To a degree, at least. I think there are limits with the way that the whole system is designed that make it nearly impossible to bind up the hub bearings on decent hubs from clamping force alone.

FWIW, for comparison's sake, consider other bearings on your bike like the headset or the bottom bracket. You absolutely can put so much preload on your headset that you can bind up the bearings. And depending on your crank/bb design, you may or may not be able to bind the bearings by tightening the cranks too much (or by using too many bb or spindle spacers).

You can bind up the bearings in a cup and cone hub, but to do that, you have to tighten the locknuts, and clamping force on the qr or thru axle stops with those nuts and doesn't affect anything between.

One benefit of thru axle systems is that it's much easier to keep clamping force consistent, and that is a real benefit when you're talking about the precision adjustment of disc brake calipers on a bicycle.
 

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It doesn't matter how carefully you align or clamp the QR skewer. A disc brake under hard braking will push the axle down against the safety tabs, cocking the wheel over as it does so.

Bolt up or through axle are the only ways to make this work.
 

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I recently bought a Kona Unit X and it comes with hydraulic disc brakes. When I got it and installed the wheels, I noticed a slight rub on the front and a very small but continuous rub on the back brakes. I took it to a shop, and the shop owner said that he recentered them and the front brakes had a slight bend but he fixed it. I took it home, rode it, everything was great.

Then, I released the front QR to see if I could get a better amount of compression on the wheel bearings, and I seat the wheel fully, set the QR, and it's rubbing again. I released the rear wheel as well, seated it fully, and it has varying amounts of rub everytime I undo the QR and reseat the wheel. Are QR and disc brakes always this fickle? Shoudn't they stay centered as long as the wheel is seated correctly? It just seems like any slight movement I do throws off the extremely fine clearance between the disc pads and the disc, and I don't see how people don't get driven crazy from having disc brakes!:madman: Any advice on how to keep them solid between wheel removal and replacement?
The best way that I've found is to do it with the bike upside down, so that I can be sure that the axle is seated before I tighten the QR. We only have so many hands! This is especially so for the front.
 

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The best way that I've found is to do it with the bike upside down, so that I can be sure that the axle is seated before I tighten the QR. We only have so many hands! This is especially so for the front.
Can be done in a number of ways. When I feel lazy not to remove the bike from the stand, I grab the wheel and the frame around the seat stays and force one against the other. This is a bit more difficult on a plus size bike, of course.
 

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I have two bikes floating around my stable with QRs (touring bike and commuter). They share 3 wheelsets between the two. I swap wheels around between them often and rarely, if ever, have to adjust the brake calipers. I have no problems getting a consistent brake rubbing and setup out of these wheelsets.
 

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I have had pretty good luck maintaining disc brake alignment by putting the bike with wheels down on the ground and putting a decent amount of weight on the stem for the front or saddle in the rear to force the axle nubs into the dropouts, and then flipping the QR lever. There are probably way more disc brake QR hybrids out there now than there are thru axle disk brake bikes.
 

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If anyone has success with QR setups with disc brakes I'd love to hear some of that.
I had this problem on my road bike. The solution was to replace the external cam QR levers with the best internal cam ones I could find: Shimano Dura Ace. (In your case, Shimano XT levers should do the trick.)

The problem is that the external cam skewers just don't clamp down enough, and the wheel moves slightly. If you don't have a fork with dropouts that face forward, this can be a real hazard, not just an annoyance.

Getting the internal cam quick release levers completely solved the problem. But if I ever upgrade my fork, it will be through-axle.
 
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