# Axle standards explained



## Berkley (May 21, 2007)

I did a quick write up on axle standards so more posters can understand how they work and what they would need if they plan on changing their fork or wheels. There are more standards out there than just the ones I've listed, but this will cover the most common ones. I also didn't cover road bike spacing because that adds unnecessary complexity.

On wheels you can't change the axle type your fork uses without replacing the lowers, or replacing the fork altogether. On rear wheels, you need to make sure your frame and wheels are compatible. Many hubs are convertible to different axle types using various adapters.

Maybe this thread will get stickied so more posters see it.

*FRONT WHEELS*

*20mm Thru Axle:* Unlike traditional hubs, in a 20mm thru axle hub the 20mm diameter axle is actually part of the fork. It typically slides through one fork leg, through the hub and into the other fork leg. Width on a 20mm hub is 110mm. 















*15mm Thru Axle:* A 15mm thru axle hub is almost identical to a 20mm hub except the axle is 15mm diameter and the width is narrower at 100mm. 








*9mm QR:* A traditional front hub uses a 9mm diameter hollow axle with a 5mm diameter quick release skewer. Forks that accept this type of hub are called "open dropout." The axle is part of the hub The axle slots into the fork dropout from the bottom and the quick release is used to clamp it in place. Spacing is 100mm.








*REAR WHEELS*

*142 x 12:* 142 x 12 thru axles are all the rage now. Spacing on these is 142mm wide with an axle diameter of 12mm. They essentially operate the same as front thru axles, on the rear of the bike. Thru axles make the bike stiffer which reduces lateral flex and results in better tracking especially through corners and at speed. 








*135 x 12:* Before 142mm width hubs became the norm, some manufacturers used the 12mm thru axle with a 135mm width. This is not very common on new bikes, as it's been replaced by 142. You can read about the reason for the change here: Syntace

*135 x 10:* The long time standard for rear hubs was 135mm width with a 10mm diameter hollow axle and a 5mm quick release. Again, the axle is part of the hub. This works on frames with open dropouts only. Many bikes sold still use frames with open dropouts.








In order to stiffen open dropout bikes, some hub makers have introduced hubs with 135mm spacing, but with a removable 10mm axle that combines the skewer and axle into one unit. The DT Swiss RWS skewer is a prime example. 








On a similar note, some hub manufacturers offer axle conversion kits that replace the stock axle with one that uses bolts instead of a quick release, like Easton Havoc wheels, or Chris King fun bolts.








*150 x 12, 157x12* Most downhill bikes use wider hub spacing for a stronger wheel build. 150mm width with a 12mm axle is most common. Many newer DH bikes use 157mm spacing with a 12mm axle. The difference is akin to 135 vs. 142.

*Bolt on:* Bolt on axles are found on many department store bikes, but aren't very common on mountain bikes. A bolt on axle replaces the hollow axle in a traditional-style hub with a longer, solid axle and uses nuts on either end to clamp it in the dropouts. Spacing remains 100mm on front hubs and 135mm on rear ones.


----------



## thomllama (Oct 3, 2007)

nice, simple explanations.


----------



## customfab (Jun 8, 2008)

There is only one standard, the open dropout. The rest are fitments.


----------



## DennisF (Nov 4, 2011)

Great info -- thanks!

Could you also post some info on upgrades available to those of us with standard QR frames -- 9mm thru bolt or something like that?


----------



## NazZaR (Jul 1, 2013)

Great thread!

I wonder, if you will allow a nooooob question here .

I have a Fulcrum Red Power 29 XL wheels, the rear one is Syntace 12x142mm standard. Will the shimano 12mm axle/dropouts work with it?


----------



## unrooted (Jul 31, 2007)

Nice!

Can you explain the difference between the following 142x12's:

Shimano
Syntace
Rock Shox Maxle
Banshee
Transition
Etc., Etc.


----------



## dfrink (Nov 6, 2013)

Yes Please! I want to upgrade my front hub to a 9mm thru axle. I would like the new hub to have the ability to go to 20mm in the future (when I replace my front fork). What are my options? Brands? Price is always a strong consiration so are there any brands that are reasobale?

Thanks!



DennisF said:


> Great info -- thanks!
> 
> Could you also post some info on upgrades available to those of us with standard QR frames -- 9mm thru bolt or something like that?


----------



## thomllama (Oct 3, 2007)

dfrink said:


> Yes Please! I want to upgrade my front hub to a 9mm thru axle. I would like the new hub to have the ability to go to 20mm in the future (when I replace my front fork). What are my options? Brands? Price is always a strong consiration so are there any brands that are reasobale?
> 
> Thanks!


hope hubs are all interchangeable .. many others are now too..


----------



## DennisF (Nov 4, 2011)

Thanks Thom. Sorry, it won't let me rep you more 

At SE Bike Expo I demo'd a set of Stan's Crest wheels. The rep seemed very knowledgeable. He said that Stan's hubs can use 9mm/front 10mm/rear thru bolt. 

He also said that I could replace the lowers on my Fox Trek G2 fork to use 15mm thru axle. There is nothing Trek-specific about the lowers. I think the lowers are about $150, and you get new bushings and seals, so by the time I decide to do anything wheel-wise, it may be a worthwhile expenditure. I didn't ask about 20mm. I think that would be overkill for the XC riding I do.


----------



## ozynigma (May 17, 2006)

Mods, can this be made into a sticky?


----------



## thebeast (Apr 8, 2014)

Definitely should be a sticky!! v useful


----------



## meltingfeather (May 3, 2007)

NazZaR said:


> I have a Fulcrum Red Power 29 XL wheels, the rear one is Syntace 12x142mm standard. Will the shimano 12mm axle/dropouts work with it?


Thru axles are frame specific, not hub specific. So yes, you can put the Fulcrum wheels into a frame that has a Shimano axle.



unrooted said:


> Can you explain the difference between the following 142x12's:
> 
> Shimano
> Syntace *X-12*
> ...


Added Spesh's system and deleted the entries that are just bike companies and not different 142x12 fitments. :arf:
I do think it's worth noting that 142x12 is not a standard in that the various axle offerings are not interchangeable between frames.
However, with the exception of the Spesh 142+ the hubs are all interchangeable.
Also, does anyone know of a 142 frame that does not come with an axle? I don't.
Like almost any other part on the bike, you need to know a thing or two before you try swapping parts like axles.


----------



## 274898 (Nov 29, 2005)

The add one more thing to the confusion, on has to remember that there is different thread pitches (ex. coarse, medium, fine threads) for 142X12 thru axles. Each company has their own thread pitch they like to use.


----------



## RobertAxle142 (Mar 19, 2013)

Great, simple explanations of the basics. Agreed this should be a sticky. Lots of info on our website too, to help figure out how to attach racks, trailers and trainers to some of these new axle sizes.


----------



## kyle242gt (Nov 12, 2012)

Great post, love the visuals. Might be good to substitute approximate years instead of "new" and "now".

Funny that one bike is 142x12R/QRF and the other is QRR/15F.


----------



## frdfandc (Sep 5, 2007)

Just to add on the 142+ info. Wheels spec'd for 142+ do not work in a 142 spaced frame, but 142 spec'd wheels work in the 142+ frames.

So a wheel from a Specialized Epic with a 142+ hub will not work in a Cannondale Scalpel, but it will the other way around.


----------



## BJJ Jedi (Jan 2, 2013)

Thanks for the info! Im currently doing a wheel build and this had me confused.

Gracias.


----------



## Mark_BC (Sep 19, 2012)

Is it possible to put a standard 10mm QR Shimano rear cassette hub into the 15X150 dropouts of the Bluto fork? I want to run a regular rear hub in there that will also be used elsewhere, to save having to build up multiple wheels and buy new hubs. Is there an adapter?


----------



## ozynigma (May 17, 2006)

Mark_BC said:


> Is it possible to put a standard 10mm QR Shimano rear cassette hub into the 15X150 dropouts of the Bluto fork? I want to run a regular rear hub in there that will also be used elsewhere, to save having to build up multiple wheels and buy new hubs. Is there an adapter?


Probably not. The rear hub is 135mm wide and the fork is 150mm wide. I know someone who ran a spare rear hub at the front of his fatbike so it would be an interchangable spare. The idea is good but you need a hub of the right width.

Try asking the question in the fat bike section or forums you might get more complete answers there.


----------



## cmc4130 (Jan 30, 2008)

This thread might also mention* mtb 9mm solid bolt-on front axles* under FRONT AXLES,.

In the Dirt Jump world--particularly with the lower/middle range bikes--there are bikes that come with 9mm solid bolt on axle.

They are sometimes mistakenly called 3/8" because in BMX, 3/8" is used. But 3/8" is actually 9.5mm, and the hardware is not compatible.

A rear solid axle is 10mm. So front and rear axle nuts are not cross-compatible.

A 3/8" bolt-on axle front BMX hub: (I couldn't find a good picture of a 9mm bolt on solid axle mtb hub)


----------



## yogiprophet (Jan 9, 2006)

I am looking at a hub (Kore Durox) that has the options of a 135mm x 10mm or QR. I thought these were one in the same. What is the difference?


----------



## b-kul (Sep 20, 2009)

^one (10mm) is bolt on and one is qr i would assume. but looking at their site i only see an option for qr.


----------



## Le Duke (Mar 23, 2009)

One is a thru bolt 10mm in diameter, the other is a QR 5mm in diameter.


----------



## OLx6 (Feb 5, 2011)

Anyone know if it is possible to install a Shimano XT 142x12 mm hub into a bike with 135mm drop outs? Is there an adaptor that can slide into the drop out?

Thanks


----------



## yogiprophet (Jan 9, 2006)

OLx6 said:


> Anyone know if it is possible to install a Shimano XT 142x12 mm hub into a bike with 135mm drop outs? Is there an adaptor that can slide into the drop out?
> 
> Thanks


nope, not unless the bike comes with additional dropouts. My Scott came with about 4 different ones but they are very progressive company.


----------



## OLx6 (Feb 5, 2011)

Thanks for the help


----------



## Tor (Jan 5, 2013)

Anyone know where to find a a axle to fit a 12x157mm rear? Find lots of hubs, but no axles. Any links or info appreciated


----------



## fotooutdoors (Jul 8, 2010)

Tor said:


> Anyone know where to find a a axle to fit a 12x157mm rear? Find lots of hubs, but no axles. Any links or info appreciated


Check with the frame manufacturer.

Typed on my phone. Pardon the autocorrect.


----------



## rwrusso (Apr 12, 2011)

To use something like the DT Swiss RWS, is it correct that the rear hub needs to be able to take a 10mm thru/bot-on axle? It seems the RWS skewer works differently than a 5mm QR skewer that would go through a 10mm axle that's part of the hub.

What are the hub designations for each? 10x135 for everything? Or is 10x135 QR a hub that has the 10mm axle as part of the hub, and a different designation for a hub without the axle and then uses a 10mm RWS or bolt-on?


----------



## White7 (Feb 9, 2015)

10x135 is for a 10mm thru bolt or a DT swiss RWS

QRx135 or 10x135QR is for the typical 5mm skewer,axle is part of the hub


----------



## rwrusso (Apr 12, 2011)

White7 said:


> 10x135 is for a 10mm thru bolt or a DT swiss RWS
> 
> QRx135 or 10x135QR is for the typical 5mm skewer,axle is part of the hub


Thanks White7. That's what I thought, but wanted to be sure. And to use the RWS 10mm skewer or other thru bolt, the hub would need an axle conversion from the QR to 10mm thru, right?


----------



## StumpyXXL (Mar 16, 2015)

Can someone explain OS28 or add it to the list?


----------



## jammer124 (Jul 19, 2008)

*9mm Thru QR*

The OP eluded to this showing a pic of DT swiss axles, but grouped them both as rear axles.
Don't forget the front 9mm thru-axle QR for any standard dropout fork.
These hubs have large knurled interface surfaces - very solid.


----------



## changingleaf (Apr 2, 2010)

I believe OS28 was developed by Specialized a few years ago, but no other hub companies have adopted it. It's fairly simple: It is a a FRONT hub with a 28mm outer diameter end cap, which in the case of Specialized is also combined with 9mm thru skewer. This was designed to work with regular QR forks. Most end caps for 9mm skewers and 15 thur axles only have a 19mm outer diameter end cap. Lateral stiffness testing from specialized showed that the 28mm end cap with a 9mm skewer was stiffer than a 15mm thru axle with a 19mm end cap, thus making the 15mm unnecessary. No other hub companies adopted this so the 15mm thru axle is still around. Also, not all QR forks, but most, had flats large enough to fit the 28mm end caps.

Regardless the 28mm end cap has not completely gone away. It's now an option for some 15mm boost front hubs such as Sram's XO boost front hub. They're called "torque caps". It's also the size of the end caps of the hub used on the "Predictive Steering" RS1 fork.

Note, to use the "torque caps" the fork has to be designed for it. Typical 15mm front forks, even many boost front forks are designed for the 19mm end cap to slide in and will not accept the 28mm torque caps. For example the Trek Stache 29+ bike with the Manitou Magnum 34 boost fork will not accept 28mm torque caps.


----------



## jammer124 (Jul 19, 2008)

*OS28 detailed*

The pics in my previous post are of a OS28 hub.
To clarify the dropouts, here is another pic.
A "non OS28 compatible fork dropout" would be easy to modify for use with a 28mm dia hub.

All these newer front axles in my opinion are marketing hype and redundant.
The 20mm has been around for decades, is lighter, stronger and should be the "new standard"


----------



## Morpheous (Mar 28, 2006)

Need to add 'Boost' spacing now 147 X 12mm rear and 110 X 15mm front. ;-)


----------



## sxotty (Nov 4, 2005)

Is the axle smaller than nominal or hub larger? I tried measuring with a caliper and they seem the same, but I don't have a micrometer. It seems like the axle would need to be a tiny bit smaller than the hub shell to fit through. Maybe I am crazy.


----------

