Disc brakes and quick releases – what's the deal?
 

Hello all. Long time reader, first time caller, etc. I have a 2019 Rockhopper 29, which has quick releases and disc brakes. Recently came across the discussions about the safety issues with disc brakes and quick releases. The physics makes sense to me, but most of the bikes I'm seeing on the market (I've been looking at upgrading) still have disc brakes and QRs, so I'm a bit confused. (Also wondering about the safety of my Rockhopper.). Are manufacturers just ignoring the issue, or has the disc brake/QR issue been eliminated somehow? Cheers all.

I have 1 15 year old mountain bike with disc brakes and quick releases. The only modification I have made was to buy a pair of Shimano closed cam skewers which are much more secure than the open cam ones that came with the bike. Nowadays the majority of disc brake equipped bikes use thru axles that may look like quick releases, but are more secure

Most bikes that are on the market now have thru-axles. They might superficially resemble quick release levers if they have handles on them.

If the dropouts on the fork face forward rather than backward or straight down, it is a bit safer.

The advice to use closed-cam levers is good advice. DT Swiss also makes a quick release that essentially emulates what a thru-axle does, and it has a screw-in mechanism rather than a clamp. It is arguably the best.

In any case, it is a good idea also to get steel rather than titanium.

My experience has been that as long as the tightness of the QR is tightened properly and checked occasionally (every couple of rides) then it won't be a problem.

But, as mentioned above, most new bikes don't have the same QR system with a 5mm skewer as were common BITD

Not arguing with anyone, but when I was looking at the specs on a lot of common bikes (Rockhopper, Sirrus, most of the Trek models), they're mostly listed as quick-release. Am I misreading the specs? I'm not a bike expert by any stretch of the imagination.

All of those bikes have thru-axles.

You can have "quick release" levers on thru axles that allow you to remove the axle without a tool. Maybe that is what you are seeing?

I don't think Trek or Specialized make any disc bikes with actual quick release skewers anymore.

Edit: Looks like I'm wrong about this. I see some Sirrus models on the lower end of the price range with what appear to be 9mm quick release skewers. No idea why they would sell these.

Unless I'm misunderstanding, there are Marlin models that are the same. Can't post links (not enough posts yet), but the Gen 2 Marlins seem to have QRs. The Rockhopper Elite and Expert models do too (that's what a hub description like "Formula DC-22, 6-Bolt freehub, disc, 135x9mm spacing, quick-release" means, right?). Skimmed the Surly site earlier and they seem to have QRs and disc brakes too. If I'm misunderstanding, I'd be grateful if someone cleared it up for me, because my bike shortlist is awfully short.

The Rockhopper is their lowest end and most basic trail bike, as they classify it. The Stumpjumper is their next level up and it has Thru-axles. Don't know why the difference. But it is what it is.

Moving from QR's to a thru-axle wasn't the big deal for me that I thought it was going to be. So I really could care less what the bike has. If the manufacturer feels it's good enough, then I'll assume it's good enough for the intended use. If you are somehow using it in a manner it wasn't meant for, then you might have some worry.

Welcome to BF

The potential danger is if the front quick release skewer lever opens all the way, wider than 180 degrees, and gets caught in the disc brake rotor.

After reports of three skewers somehow getting caught in the brake rotor, Trek recalled more than a million skewers and replaced them with skewers whose levers only open 90 degrees.

If you keep your quick release skewer closed tight, there is no danger. Also, if you install the front skewer so that the lever is on the driveside of the bike, away from the rotor, there is doubly no danger.

I read about the Trek recall, but I thought the main issue with QRs/discs was that hitting the front brakes hard enough can put a ton of force onto the skewer, pushing it out of the dropouts (the work that James Annan did).

Correct - there's more potential for user-error on quick release not being installed correctly. I suppose theoretically this is more dangerous with disc brakes than rim brakes, but I thought manufacturers were moving away from QR in general just to avoid the "oops I didn't tighten it down" situations.

On a more practical level, disc brake setups are very sensitive to any minor misalignment, and TA's largely solve this problem. I had a MTB with disc/QR's many years ago and had to often faff around with aligning the calipers to avoid rubbing rotors. I don't have those problems with disc/TA.

Honestly I can't think of any reason to avoid TA's nor do I understand why manufactuers would even continue to make QR frames. I assume QR/Disc hubs are not that common anymore, yet you correctly note that a fair number of them are still being sold. Future wheel upgrades on those bikes will be limited.

Thru axles keep the wheel in alignment better and this is important with disc brakes where the tolerances are much tighter than with rim brakes. The Boost hubs and axles are much stronger and so used with e-bikes and mountain bikes where the support for the fork is important. The thru axle also allows for a lighter fork to be used as the thru axle connection is a much stronger one and better at dealing with lateral stress on the wheels.

And this is why I'm confused. If there's a genuine safety issue here, why is the QR/disc combo still so common? I'm hoping my next bike purchase will be my last, and I'd like to have something that I can rely on for quite some time, as well as now being a little concerned about the safety of my Rockhopper.

As others have pointed out, it's only common on low level new bikes. If I had to guess, I'd say they are using up frames that are contracted for or otherwise in the pipeline. I wouldn't be concerned about using your existing bike but there's no reason to buy another one w/o thru axles. You'll also get what has become the new standard spacing.

That's not the only problem. If the dropouts do not face forward, the braking force tends to eject the wheel. Although I have never had that happen, I did have the front wheel move slightly with respect to the (forward-facing) dropouts in my Gen 1 Enve fork when I used external cam skewers. I noticed because the brake pads would rub after a ride with hard braking until I would re-seat the wheel. The internal cam ones, or DT Swiss ones, have eliminated that problem. A lesser fork could have been more problematic.

Some people have had problems with the back wheel moving with respect to QR dropouts under heavy load. (I have not.)

They are cheaper, and a bit easier to work with. If you have good internal cam levers, or DT Swiss bolts, they can be safe. I have two mountain bikes with QR and external cam (inferior) levers and they have been fine, too. But if you are worried about it, get the DT Swiss bolts.

As far as I know, QRs are less popular on disc bikes because they wheel has to be centered carefully, whereas with through-axles the wheel always goes back in exactly the same orientation.

My Fuji Sportiv has QRs and discs, and I have to play with the wheel a little every time I take it off or the brakes will drag a little. On top of that a through-axle is stronger (though less convenient.) Now I guess some through axles have built-in handles so no extra tool is needed.

As for the QR handle hitting the disc ... if your QR is that loose the wheel could fall out anyway. Most riders I have met are smart enough to use a QR properly. I suppose if one could forget to tighten a QR, s/he could likewise forget to tighten a through-axle. In any case ... Darwin.

I think the safety concern is more lawyer based than reality based. If you're properly installing the QR skewers I don't think there's anything to worry about.
I personally wouldn't buy a QR disc brake bike, not due to safety concerns, but for the other reasons stated (alignment issues and potential future compatibility issues).

I never had issues with alignment using QR levers. As long as I was the one setting up the brakes and wheels, it was easy for me to repeat wheel removal without alignment problems. It was when someone else set things up that it all went south.

Three complaints with thru axles, 1. it is a PIA to use most of the time on the rear wheel, 2. thru axle loosens when riding, 3. stripped threads on the frame or the axle, which happens frequently enough due to user error. Outside of that they are ok.

I still race cross on a 10 year old QR disc brake bike...am I gonna die???

As long as you're using quality quick release such as Shimano for example and as long as that quick release is tightened properly there is no way that your wheel will ever come out of the drop outs. Most forks also have safety tabs called lawyer lips which make the wheel even less likely to come out....Wheels coming out of drop outs only happens to idiots who fail to properly secure the quick release and who also grind off the lawyer tabs from the fork drop outs. Ignore all the fear mongering and don't worry about it.

You will according to all the thru-axle fan boyz

Never had an issue with centering the wheel. and once tightened it's impossible for the wheel to move in the drop outs

The DT Swiss RWS QRs are also really nice and can get a little bit tighter than cam QRs imo

It's amazing that quick release used to be standard on very high end bikes many years ago and now it's only found on low end bikes. Damn marketing.:rolleyes: