People usually have this one sorted out before their conversation with us about wheels, but we get asked for our opinion on thru axle versus quick release all the time. Here are a few thoughts.
The two compelling things about thru axle are security of wheel to bike connection, and repeatability of rotor placement. With quick release disc builds, we've always supplied bolt on skewers rather than actual quick releases. This is because the brake force in a disc wheel pushes the wheel forward and down - out of the dropouts. On a rim brake wheel, that force goes in the opposite direction - up and back, into the dropouts. There's also the issue of the quick release lever potentially being next to a hot rotor. With a thru axle system, the entire axle goes - you guessed it - straight through the fork or frame, and the axle would have to come out before the wheel to bike connection was lost. It's harder to screw it up.
Mark's bike always look great. Thru axles both ends here
You might say "yeah, but only an idiot doesn't know how to use quick releases!" Guilty as charged, but my first time out with a new suspension fork several years ago nearly cost me my beautiful face, as the movement of the fork legs kept working the quick release loose. A bolt-on skewer stopped that issue cold, but from now on it's only thru axle suspension forks for me.
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On a quick release hub, the knurls on the end cap faces bite into the frame or fork to make a secure connection with the hub. That works well, but the knurls never quite line themselves up perfectly each time you install the wheel. On your rim brake bikes, you might have noticed this once or twice, and fixed it by loosening and then re-closing the qr. With discs, the rotor's clearance between the pads is much less than a rim's clearance between rim brake pads, and that fit becomes more exacting. A thru axle set up is more precisely repeatable.
I love this photo, and it shows the end cap knurls
While my current road disc bike has quick release front and back, and they work just grand, if I was getting a new disc bike - road, cross, or mountain - it would definitely be a thru axle front. The decision on the rear gets a bit murkier.
The quick release standard for disc rears is to have the dropouts 135mm apart, with 10mm diameter dropouts. Already on road bikes, which often have chain stays about 405mm long, the 135mm spacing causes some friction. First, it's hard to keep your heels clear of hitting the wider-spread chainstays (especially when you're a duck-footed freak like me). Second, the chain line gets more tortured as you shift to the outer cogs. Shimano says you need a 420mm chainstay for their drive trains to work correctly on 135mm rears. Specialized goes so far as to move the drive side flanges inboard on many of their disc hubs so that you can use the full gear range even with a 405mm chainstay. The problems with that are that you're somewhat limited to their hubs with their bikes, and moving the inboard flange in is precisely what you don't want to do from the wheel's perspective. For what it's worth, you can totally use a normal hub in these Specialized bikes, you just don't want to do any small-to-small cross-chaining - even if you are Andy Schleck.
Thru axle rears generally have 142mm dropout spacing, with a 12mm axle rather than 10mm. With long chainstays, hey no problem. On road bikes, it's complex. The overall width of the hub is the same on a 135mm QR hub as it is on a 142mm TA hub. On the QR hub, the outboard-most 3.5mm on either side ride in the dropouts, where on the TA hub the outboard ends of the hub nestle into a pocket/face on the inside of the dropouts. The 142-based frame will have a tiny bit more overall width. The hub shells are exactly the same, it's only the axle that will be different between a 135mm and a 142mm hub. The repeatability and security of attachment favor the thru axle rear just like it does on the front, so that's what we'd personally choose, all else being equal.
So the rear is a little bit more complicated than the front, but I expect that I'll see a new 135mm thru axle "standard" for road bikes when I go to Interbike in September. We'll need to give White Industries a little time to make the kit, but our CLD would be able to handle that format. And I thought this blog would be shorter than it was. Sorry.
13 comments
Hey Dave—Yes, the carbon Specialized Diverge bikes (and perhaps their Disc Tarmac, not sure) utilize a derailleur hanger that is inset 2.5mm, which some owners found is not compatible with a host of 'normal' rear 135mm thru-axle hubs…there have been several owners venting about this issue. Milling the derailleur hanger a bit has allowed enough clearance, as several owners have reported. By any means necessary, I guess….
So I'm thinking I will get a set of White CLD "alloy customs" from you in QR for my current QR CX bike (CAADx), let the market sort itself out in a year or two, then convert my QR CLD hubs to whate QR becomes the standard when I'm ready to get an affordable CX frame (Trek Crocket or maybe a Rock Lobster). Does that sound reasonable and cost effective for a bicycle which I'll ride twice per week, three months out of the year?
Trey – Well, I missed the comment and then we covered it all yesterday but for anyone who might read, yes, I think your plan is completely sound and sane. A bike that gets ridden 2x/wk 3 months/year is still ridden more than many people who even self-identify as bike riders can imagine riding. I love Rock Lobsters, you should get one. Other cx bikes for which I currently have the lust are Squid, Honey, and Geekhouse. I'd stain my shorts to see what Squid could do with graphics around our colors and logo.
Quick question here: 142X12 uses the same effective flange to flange spacing as 135 hubs correct? The extra 7 mm is accounted for in axle length that slots into dropout cuts on each side that are 3.5 mm in frames designs to accommodate 142X12 TA's. The comment in the blog post about 142X12 not happening on road bikes with short chainstays was more about heel clearance right? because the spacing issue isn't any worse than a 135 hub. Not to mention tons of manufacturers are going to 142X12 for disc road in 2016. I do believe 142X12 by nature of having to have enough threads do tend to be a little wider because of that. Just verifying.Great post BTW as for what it's worth, I also heel strike from time to time on a road bike with 130 spacing and 412 stays, so I guess I'd be really screwed on a super short stay bike with 135 / 142X12 dropouts. UghI was thinking about getting a disc road bike, but honestly I'm not quite sure – for me it has everything to do with other factors like chainstay length etc than actual braking performance.
Yeah, it's heel clearance – the hubs are the same overall width, but in a 135 it fits into the dropout, where with 142 it butts against the inside of the dropouts. Hence, wider outside dim of the frame.