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I have a 100x15 front 142x12 rear cyclocross frame. I'm considering getting mid range wheels with quick releases that come with thru axle adapters. The wheels are lighter and better than most options in this price range that come with native thru axles.

Question is, are there any negatives for using qr->TA adapter besides weight?

The wheels in question from crc http://www.chainreactioncycles.com/prime-race-disc-road-wheelset-2017/rp-prod142942

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    For reference those appear to be (I would almost say "are" but life is full of surprises) Novatec XD611SB (front) and XD612SB-11S (rear) hubs. You can look at their catalog (imb2b.com/ebook/catalog/bicycle/novatec-hubs_2017/#50/z) to get a little more info on how their convertible system works, hubs on page 14 and adapters on page 46-47. – Nathan Knutson Jan 25 '17 at 0:19
  • @NathanKnutson does that mean the store page is simply inaccurate? From the catalogue it was not entirely clear to me. But it seemed that there are adaptors to change the hub to each standard, rather than an adaptor that fits a typical QR hub and TR forks. – gschenk Jan 25 '17 at 23:10
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    @gschenk Nope, there's nothing wrong with the description on crc. – Nathan Knutson Jan 26 '17 at 8:37
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    this website has some decent photos of the end caps/axles in action for novatec hubs: fatfisher.com/item/… looks like they thread on which is interesting, many companies just pop in such as the SRAM roam/rise: bikerumor.com/wp-content/uploads/2011/10/… – Paul Jan 26 '17 at 15:21
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This is a deceptively complex question because it touches on many aspects of hub design, and answering it properly would also require taking some kind of survey of what design choices have wound up getting made for the various convertible vs. dedicated size through axle hubs, particularly in terms of what bearing sizes are used. Furthermore, for practical purposes the story is quite different for convertible road vs. mountain front hubs, because within mountain many of those hubs use bearings with a 20mm ID so they cover 20mm all the way down to QR, whereas the size variance involved with a 15mm/12mm/QR hub is much less.

But, broadly speaking, the main potential downside to convertible hubs of this style is that even if you're fine with it being as big and heavy as it needs to be to have good bearing durability, the person who designed it might not see things that way. They'll probably see it instead at some level as a trade-off that has to be made. And while usually in practice that may only make a marginal difference (I don't think I've met any convertible hubs with extraordinarily teensy bearings), the bike industry is quite good at occasionally turning out products that shave grams in unfortunate ways, on things like bearings and spokes where a little weight spent goes a long way towards durability.

Again, this applies more to fronts than rears, because the variance in axle size is so much greater. I doubt it applies to rears much at all, but determining that is where the aforementioned survey of bearing choices used across hubs would come in handy.

Some companies (I'm thinking of White with their Venti front hub, but there are others) have wisely taken the pressure off to make compromises here by making the 20mm in their lineup a dedicated design, and the others convertible. That makes even more sense now that 20 is firmly DH/FR, where there are going to be other aspects of the design you want more usage-specific, but for a while it wouldn't have been as easy a choice because before 15 came out, 20 was seeing use on trail and even XC bikes.

Another aspect is cost, particularly when there's a rear hub like the one in question involved. The endcaps and axles cumulatively make a pretty big pile of precision machined parts you're paying for but maybe only using some of. Not a huge deal, especially if you're going to actually use the convertibility, but for example with Novatec hubs like these being high quality Taiwanese stuff, you are paying something for the extra parts, and what's really going on is if you're buying a wheelset/hubset that just comes with all the conversion parts, you're paying for a manufacturer's decision to simplify things by just giving everyone everything and letting the costs tick up accordingly. (When a bike brand or wheel manufacturer orders hubs from hub manufacturers, it's entirely up to the buyer whether to get the extra conversion hardware. Hub makers most commonly wouldn't be sending all that stuff out since most of their hubs wind up OEM on bikes.)

In cases where a hub is convertible across axle standards where one reason for the new standard was to change hub geometry to create a strength increase, such as hubs that can work on both 12x142 and Boost 148, you get none of the advantages of the new standard.

Finally, it only gets harder to create effective sealing when you're designing around multiple different axle adapters that might be used. That doesn't necessarily mean sealing will be deficient, but it is at some level a downside.

To be clear, there are no major categorical downsides to hubs like this. A lot of them are out in the world performing very well. But there are subtle downsides that get incurred as a result of adding more factors to the design criteria.

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    with front or rear it can be nice to have an old wheelset that now is able to fit a boost frame or vice versa (135x9/142x12 to 148x12 and 100x9/100x15 to 110x15). Not to mention fatbike dimensions, being able to put your 29er wheelset on your 26er fatbike. The problem is, you gain none of the advantages of the wider spacing.. the hub flanges still have to be where they would for the narrower spacing and you often have to redish the wheel between bikes. – Paul Jan 26 '17 at 15:18
  • That's true. I'll edit later. – Nathan Knutson Jan 26 '17 at 15:45
  • So without knowing how the hubs are designed, if the wheel was designed for the purpose you were using it the only downside would be cost of machining adapters? – ELion Jan 26 '17 at 21:00
  • TL;DR, upvoted anyway was looks clever. – Drew Jan 27 '17 at 13:41
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I suspect those wheels will have all the normal benefits of a QR but with the adapters will not have any of the benefits of a through axle.

So the adapters will allow you to use a QR wheel on a through-axle frame, but will not give you the same level of stiffness that a single thread-in through axle would give.

In the end, this wheel still has a QR skewer through the middle, regardless of what adapters are on it. That might be fine - QRs work great on many bikes. But its not a TA wheel hub and never will be.

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    Are you sure about that? The Prime wheels appear to change out the whole axle for the different formats (e.g., 12mm x 142mm). The limit may a lowest common denominator hub flange width, but the axle looks reasonably well executed. – Rider_X Jan 24 '17 at 23:50
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    There is no QR skewer involved when they're in TA mode. – Nathan Knutson Jan 25 '17 at 0:20
  • @NathanKnutson thats interesting - the description states its a QR hub with TA adapters. If it can take either, using adapters for both types of axle, then that's really cool, And surprisingly forwards-thinking for bike component makers. – Criggie Jan 25 '17 at 0:42
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    wait, what? @nathan, this seems like this allows the hubs to have many different axles used, as many companies do. with end cap conversion kits. I don't see how this allows you to use a quick release hub in a 142x12 frame.. – Paul Jan 25 '17 at 4:00
  • nevermind. brain fart. you should post an answer explaining the end caps or I can. – Paul Jan 25 '17 at 4:02
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+250

After looking more closely at the photos, it looks like the specific hubs/wheels in question are the Prime Comp Alloy Clincher Disc Road Wheelset seen here. These have Prime RD020 Disc Hubs - front and rear. Looking closely, it doesn't seem as though these are rebranded novatec hubs, but they do seem to utilize a very similar end cap design.

Front

For the front, it looks as though the end caps pop in:

enter image description here

for thru axles, the axle is separate and should be included with your frame, the end caps simply provide the mating surface to the frame/axle.

enter image description here 15mm thru - upper surface mates to fork

enter image description here 12mm thru - I believe the top part shown here is the interior portion of the cap

These caps are something that simply 'fills the gap' between an oversize bearing inside the hub and the desired axle.

Rear

On these particular hubs, the rear seems to operate somewhat differently. The drive side end cap appears to thread onto an oversize axle (to set preload?). I believe that the axle itself functions as the mating surface for the non drive side of the hub.

enter image description here Hub in QR 130x10 configuration with all included parts

enter image description here 142x12 axle and drive side end cap

Excuse the question marks, but Prime is pretty sparse on details. It appears to be very similar to Novatec's configuration, which is shown in full here and is where I drew some inferences:

enter image description here

refer to the lower half for the rear hub, although Prime never pictures any non drive side end caps. I do not believe this particular front hub works as pictured here.

Other Systems

Many companies are doing something similar now, all with their own little spin of course. They make a hub with oversized bearings that create some physical limit as to the maximum axle size, and then use caps to effectively shim the interior diameter and determine the final spacing of the hub.

SRAM

SRAM recently introduced their roam/rise/rail wheels which utilize end caps that pop in. SRAM also has some proprietary end caps for the front called torque caps that increase surface contact for increased stiffness (they claim).

enter image description here clockwise: 9mm drive side, 15mm drive side, 9mm non drive, 15mm non drive

Hope

A nice blog post here that describes the process of changing the hub to a different axle standard. A few photos from the post:

before
before

enter image description here
add pliers..

enter image description here after

I'm having a very hard time finding more useful images, but some more brands that I know employ end caps (feel free to edit):

  • DT Swiss
  • e13/The Hive
  • Salsa (made by Formula)
  • Industry 9 (i9)
  • Spank
  • So, thing is, this is very well done and worthy of the bounty that was posted, but it's not dealing primarily with answering the question. – Nathan Knutson Jan 27 '17 at 6:38
  • @nathan yes I agree. I believe you answered the question properly. this is in response to criggies request for a detailed explanation of how the end caps work. perhaps should be moved to its own q/a – Paul Jan 27 '17 at 6:43
  • That's great! As @NathanKnutson says, expand a wee bit to mention adv and disadv (I know that wasn't in the bounty suggestions, sorry) – Criggie Jan 27 '17 at 6:44
  • Also, they're some kind of Novatec hub because the 'ABG' freehub splines are a Novatec thing, unless someone else licensed it, which seems unlikely. Looking closer at the front shell it's true that the scallopy cut out bits distinguish it from the exact one I thought it was. I bet the internals are all the same though. – Nathan Knutson Jan 27 '17 at 16:11

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