2016 Specialized SCS 135mm disc brake thru axle design explanation & development story

2016 Specialized Crux cyclocross bike with SCS thru axles

The decision to build a bike a certain way is typically made more than a year in advance. Sometimes two or more years. Sometimes there are competing standards or solutions that haven’t been developed yet that need buy in. And sometimes folks are willing to gamble on something they believe in.

In this instance, we’re talking about 12×135 thru axles versus the much more common 12×142.

Think back to HD DVD and Blu-Ray. Both had major brands behind them, and both ended up on the market to let consumers decide. It’s an apt analogy, except in the case of digital movie formats, there was a clear technological winner. Here, after talking to The Big Red S, it’s possible both axle standards could end up playing in garages around the world.

We spoke with Specialized’s Road Brand Manager, Mark Cote, to get the story behind the SCS (Short Chain Stay) disc brake thru axle design. Here’s what he had to say…

“The only two options that existed for thru axles going into this two seasons ago, 135mm and 142mm, and it was looking like 142mm was going to be too wide and cause heel clearance issues. The major reason we went with 135mm is that it worked with all SCS parts in development. It allows us to keep the chainline where it needs to be with chainstays under 420mm. We also didn’t want to change Q-factor on the cranks.”

Specialized first encountered this challenge with the MY2013 Roubaix Disc, which was their first road-going bike with hydraulic disc brakes. It has chainstays that were too short to meet guidelines from SRAM, so they spec’d a wider crankset to get the chainline where it needed to be. And then Cote says they got flak from fitters who complained the Q-factor was too wide. And, it limited the use of other aftermarket cranks already on the market.

The Crux Disc debuted in MY2012 in alloy, and for MY2013 in carbon, both of which used standard 135mm QR dropouts, which was the normal mountain bike standard. These bikes had chainstays longer than 425mm, which technically put them in the allowable spec range, but the chainline wasn’t optimal.

How will 135mm rear hub widths affect road bike chainline and shifting performance

And chainline is a major concern. When road bikes first started getting disc brakes just a few short years ago, we had a long technical discussion with frame and wheel makers about the impact of going from 130mm to 135mm hub spacing. SRAM and Shimano look at a frame’s chainstay length and mandate which cranksets and chainring offsets can be sold to the brand as OEM equipment…they won’t sell them something that doesn’t meet their chainline specifications.

“We had to make the commitment to a thru axle standard about 18 months ago,” says Cote. “Frames were starting to get made in January in order to ship by April, which meant the decision was made around July 2014. At that time, we believed 135mm SCS would be the prevailing standard. We sent drawings of this standard to many frame, wheel and component manufacturers for them to use, royalty free.

“The whole industry is figuring out how to best serve road cyclists. For us, we feel this is the best solution for short chainstay bikes. It wasn’t a solution made just to lock anyone into our wheels.”

In fact, Cote says Fulcrum also makes wheels for SCS, and there’s an open patent out there, which they did so that anyone could use it but no one else could patent it and make it proprietary. Cote says Specialized also has some handshake agreements with other wheel manufacturers that they were hoping would be on the market in time for cyclocross season, but that’s out of their hands.

Specialized-SCS-dropout-versus-non-SCS-dropout

But, there’s a light at the end of this tunnel. Cotes says a non-SCS thru axle derailleur hanger is coming in November that’ll allow you to run normal 12x135mm thru axle hubs as opposed to 135mm SCS. The part will be free to all riders who purchased a 2016 Crux bike or frameset. And, it’ll allow other wheel manufacturers to easily adapt their wheels to this system by simply creating unique end caps utilizing their existing 135mm hub shells.

Zipp disc brake 202 303 clincher tubular (17)

Zipp’s ready. Their latest Firecrest carbon 202 and 303 and alloy 30 Course disc brake wheels offer end caps that’ll let their 135mm QR hubs switch to 135mm thru axles. And who doesn’t like Zipp wheels?

For fans of Specialized’s SCS wheels, Cote adds: “We offer five wheelsets ranging from a $250 Axis 4.0 alloy wheelset up to the $2,200 Roval CLX 40 carbon tubulars. And starting in November, we’ll also be offering an Axis hubset with Centerlock and an 11-speed freehub body so you can build your own wheels from it.”

Other options include upcoming wheels from Hope Tech, using a variant of their hubs laced to carbon tubular and clincher rims. Or Next Devo’s adapter kit for DT Swiss hubs.

“At the end of the day, we created a standard that we thought was the right thing for road bikes and decided to use it for our ‘cross bikes, too,” says Cote. “As the entire industry is working towards a standard, we knew we’d learn a lot eventually leading to a committed standard for disc brakes in the industry. All riders committing to new thru axle cross bikes are experiencing compatibility challenges with their older wheels going into this season. This isn’t unique to the 2016 CruX – But you know what? (The Crux) rides amazing, there’s no brake or heel rub issues and the people racing it are really enjoying it.

“Where’s it going in the future? That’s not anything I can speak to right now, but obviously we’re taking all of this feedback into consideration.”

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Francois
Francois
6 years ago

So basically the main reason for 135 spacing is because they started the process a long time ago and couldn’t adapt? Is this supposed to be a valid reason?

Also it seems that all their issues stem from an obsession with short chainstays. And here, I’ll have to agree with the guys from Rivendell: make them longer! (http://www.rivbike.com/kb_results.asp?ID=112)

dead
dead
6 years ago

When can I get a 12×126 rear end for my 1986 Nishiki Olympic.

CXisFun
CXisFun
6 years ago

“who doesn’t like Zipp wheels?”

Me.

CBontheEVO
CBontheEVO
6 years ago

From Google Translate:

“As the entire industry is working toward a standard, we knew we’d learn a lot by going to a proprietary design and having customers foot the bill. Once a true standard is decided upon, we’ll adopt that and force consumers to upgrade again. We didn’t believe we could pull it off, but the fact that consumers are just this stupid really surprised us. Haha Suckers”

Mike
Mike
6 years ago

“And who doesn’t like Zipp wheels?”

*raises hand*

Hogdog
Hogdog
6 years ago

“We’re taking taking all of this feedback into consideration”… I really hope so because this is an almighty cock-up.

Ernst
Ernst
6 years ago

Thinking from a consumer perspective… so hard for companies apparently these days…

cheffdog
cheffdog
6 years ago

To Francois: I see the argument for longer stays to create stability, but the writer even states that the sacrifice is turning radius and nimble handling. Since we are talking about a CX bike, quick turns and nimble handling are at the top of the “yes please” list. So I have to agree with the short chainstay choice by Specialized here. Woah, that is the first time I ever did that. I hope they won’t sue me.

Birdman
Birdman
6 years ago

SCS was the ONLY reason I didn’t give $3500 of my hard earned money to Specialized for the Diverge… That’s that.

goridebikes
goridebikes
6 years ago

Tyler, this is an excellent apology on your part for writing a less-than-positive review of the system in your previous article. I especially enjoy the part where Specialized was allowed to proofread this article before publishing – seems much better. I feel that this article strikes a much better balance between offering re-worded press releases versus editorial commentary on a questionable move from an industry-leading brand (who remains the only brand embracing the SCS system).

Also related to the discussion – I find it INSANELY frustrating that specialized would spec an extremely thin ROUND spoke for use with a straight pull hub at high tension. Holy windup batman… What ever happened to Aerolites?!

JBikes
JBikes
6 years ago

I don’t see the issue here. Somebody needs to hash out a TA standard for road/cross bikes. 12×142 seems too wide for Q-factor desires. Not sure why 10×135 wasn’t tried out to minimize dropout bulk (rigid rear triangles probably don’t benefit from the bigger axles), but not sure that part really matters.
12×142 seems to be a way of using existing wheels or using MTB stuff, that’s it. Its a new bike though and Specialized is using this on road frame too. Maybe I’m missing something that others are overlooking.

DISC MY BREAKS !!!
DISC MY BREAKS !!!
6 years ago

Anyone have a clue about the Q-factor on a MTN bike and heal clearance on a MTN Bike that has been using 12×142?

My thought is this shit has already been worked out…

come on Specialized, don’t release half baked rebuttals… it doesn’t help the brand!

I would have bought the Diverge or CRUX if it wasn’t for the SCS wheels!

Jaxs
Jaxs
6 years ago

Completely agree with @goridebikes.

More Cowbell
More Cowbell
6 years ago

its a valid reason about how they got there, but also a valid reason for a consumer to reject the product

Cyclingengr
Cyclingengr
6 years ago

Maybe they should have used Boost instead?

Evan
Evan
6 years ago

CBontheEVO
The article says specifically it’s not a proprietary axle design “there’s an open patent out there, which they did so that anyone could use it”

Jon
Jon
6 years ago

3.5 mm outward movement at the end of each chainstay? At the heal it somewhere around 2mm. It seems like a forming the chain stays would do a lot more to facilitation heal clearance than bucking the trend of 142 TA.

JBikes
JBikes
6 years ago

@DISC – I can’t say for sure, but MTB cranks have q-factors typically around 10mm larger than road cranks, which may or may not be an issue. As such they can adopt the “135mm” hub (includes 12×142) more readily.
This seems more a new standard for road bike TA , applied to CX bikes (right or wrong). I actually think it is a good idea for road vs the current 130 when discs are involved. The market can speak with regards to CX. You can buy a number of 12×142 CX frames that I don’t think have heel clearance or chainline issues (TCX being one)

JBikes
JBikes
6 years ago

I knew I saw that picture before. This is a good article regarding the current subject matter.
http://bikerumor.com/2012/11/28/tech-breakdown-how-135mm-rear-hub-spacing-affects-road-bike-chainline-shifting/

Pablo
Pablo
6 years ago

Didn’t Peter Denk confirm in the F-Si article that there was zero gain going from 9×135 QR to 12×142 TA, on any hardtail bike? And on this website nonetheless.

Sounds like BS from the kings of marketing BS to squeeze even more dollars out of consumers.

Fred
Fred
6 years ago

Um, since 12 x 142 has the same spacing as 10 x 135 qr, chain line should not be affected. The 142 measurement is not equivalent to the Over Lock Nut dimension of a 135 hub. The 142 measurment includes the bits of the hub which protrude into the frame. 12 x 142 has the same bracing angle, chain line, brake location, frame spacing, etc as 10 x 135 qr. This is why Boost 148 was created, to provide a better bracing angle. Bikerumor covered this a few months back but here’s an@other source:

http://www.pinkbike.com/news/12×142-explained.html

I guess my point is Specialized made an error and are trying to put a spin on it.
I personally have had 0 issues with QR disk bikes, and feel that the whole thru axle thing is silly. But if the best new bikes have thru axles that’s what I’ll buy when my current rides wear out. I am definetelty not buying a bike with 12 x 142, since boost is on the horizon…
And I would really rather not buy a specialized as I don’t like the way they do business, but if they have the right bike at the right price, well…

Lennart
Lennart
6 years ago

If chainline was such a concern why not use a different chrankset with a 3 mm offset simular to boost . I mean specialized makes and specs their own cranks and id much rather have a propriatary cranck than hub. Also the heel clearance issue, just adjust the shape of the seatstays inward a bit. So it cant be a straight line but we are talking only a couple mm here, I dont see how that cannot be accomodated for

Fred
Fred
6 years ago

Oops, got it, Specilized managed to keep 130 spacing with a thru axle.. So shorter chain-stays but with a worse bracing angle.. Hmmm … Still silly … I am holding out for boost ..

R4ND4L
R4ND4L
6 years ago

Biking is the new golf. Company’s are changing stuff so fast hoping everyone will buy new. Just wait 6 months and buy on sale. Oh yeah the golf industry imploded maybe its not such a good idea to screw your customers over specialized and trek. Just take their word for it, it’s guaranteed for 6 months or until they run out of parts because last years design is obsolete.

Keagan
Keagan
6 years ago

Mechanical Engineer here. They had to make the commitment 18 months ago because it takes time to design everything, get molds made, get vendors lined up to machine components. There’s no “oops we picked the wrong thing, lets change it 3 months before release”. That just doesn’t happen. I agree with their design decision. I don’t want a wider Q factor on my cross bike. I also don’t want to hit my chain stays with my heel. I have a 2014 Crux with 135 mm QR Disc and the chain line is sub-optimal – shifting is not as good as it should be. I also hate having to re-align calipers every time I swap wheels (and yes I do have a procedure for installing wheels s the QR bottoms out and is in the “same” position every time). I want thru axles for their repeatability, safety, and stiffness (I would have liked to see the Focus RAT system, but that’s not as big of a deal). It sounds like the biggest error wasn’t in design decisions, but in presentation of what happened, why they chose the design they did, clearly indicating that they were giving away the design, and that other wheel manufacturers are going to offer SCS hubs but that timing prevented them being offered at launch of the bikes. To me this is a lot like the rim brake to disc brake transition, I sold all my rim brake wheels with the rim brake bike and used that money to buy disc brake wheels and bikes. You either commit, stop complaining, or go buy someone else’s bike. Standards take time to develop and all start somewhere as “proprietary this or that”.

PK
PK
6 years ago

Specialized takes their motto ‘Innovate or Die’ quite literally. because Specialized is admitting to have run out of solutions.

anonymous
anonymous
6 years ago

I wouldn’t have minded if they came out with this last year instead of the half assed QR with special hubs they came out with last year, but now everyone has gone 142. It’s not a question anymore.

badbikemechanicx
badbikemechanicx
6 years ago

Bright colors are in. It’s the 80’s.

SO ANGRY AT HUB SPACING
SO ANGRY AT HUB SPACING
6 years ago

On behalf of everyone whose life was ruined by The Big S trying to make chains last longer and whatnot, I am angry and am going to write my emotions on BikeRumor.com.

Seriously though. Hubs keep moving outwards and you expect the Q factors to remain the same? Something’s gotta give.

CRUNN
CRUNN
6 years ago

I hope Specialized is reading these comments, because I’ve been waiting for them to make a thru axle cyclocross bike I can swap my MTB thru axle carbon wheels with for two years now. It would be so nice to just be able to swap thru axle wheels between bikes, especially when the carbon ones cost so much. I thought 2016 would be the year Specialized would come around and think about the consumer. Nope, not this year. Maybe Specialized should get out of their offices and talk to the consumer who can’t afford to buy a new bike with new standards every year. Their philosophy is very short sighted…On their way to finding a standard, all their doing is pissing everyone off.

P.S.The Q factor doesn’t bother me at all on my 2014 S works Stumpjumper hardtail with 12X142+, and my heel doesn’t hit the chainstay either, so I think the “official” explanation from Specialized is B.S.

sd
sd
6 years ago

I for one am glad that BR doesnt have to have the manufacturer proof read all the stuff they post. I don’t wanna read a marketing website and the specialized article was a breath of fresh air for once (heck, look at bike radar scripted interview videos for example!).
That’s generally instant-no-longer-go-there-unless-linked-by-ppl for me.

Then again having specialized official reply is great as well. I suspect BR should have made the disclaimer that specialized did proof read though 😉

Now then again, i think zipp, roval wheels are great but they’re also expensive and i’d rather have my hand built carbon wheels at 600-1k USD (for both wheels) even thus they might be just a tad worse. For that reason I’m still aiming to a 12×142 bike. Not exactly hoping to get such a wheel with custom hanger + custom caps at the same price or/and any time soon.

I’m sure specialized reasons are pretty close to how it happened, but its still not the choice i’d have liked they would have done.

Walt
6 years ago

Chainline and Q-factor/etc are the same for 135×10/QR or 142×12. The cassette and hub flanges are in exactly the same places, the dropout just captures a wider hub shoulder on the 142 setups. Many high end hubs can be converted back and forth by simply swapping endcaps.

They are literally identical in terms of rider ergonomics and chainline, so I’m baffled by this article. If we were talking about 148×12 or another wider standard that would be another story but AFAIK that’s not the case here.

-Walt

Keagan
Keagan
6 years ago

Chain line is not the same because they use a 68 mm BB not an 83 mm BB. Even though a 135 mm hub has the same chain line position as a 142×12 mm hub (since all that is really different is the length of the thru axle and the end caps), the frame is based on road bike cranks, not mountain bike cranks. To add the slots for a 142 mm TA they have to make the chain stays wider, hence the heel rub issues.

If indeed they are offering a non-SCS derailleur hanger soon (and giving it to customers for free) then this really is a complete non-issue.

greg
greg
6 years ago

As Walt said, standard (non-SCS) 135×12 and 142×12 have the same dimensions practically everywhere. Dropouts are thicker and have 3.5mm channels to guide the axle in. That’s it. We’re talking a thicker dropout. Chainstays can be where they are.
As I said in the previous article’s comments, all that’s needed is a non-SCS hanger, and dude says they’re coming in Novemeber. Now the only issue is for people wanting double cranks (yes, they’re out there). Can’t run a wider-chainline crank because the front derailleur braze on is too far inboard (possibly).

Mathme
Mathme
6 years ago

@Walt– that’s exactly what I was thinking. There are tons of frames out there that can be easily converted to accept 142 and 135qr. This is a strange rationalization for a 4th standard that the industry wasn’t demanding.

John
John
6 years ago

In case anyone in Morgan Hill is reading these comments…

It wasn’t so much the incompatibility of the new Diverge hubs/wheels (though that does bother me), it’s that it felt like it was done so underhandedly. I couldn’t get a straight answer from my Specialized LBS, I couldn’t get a straight answer when I called the Big S directly (and no, despite what I was told, my existing wheels would not work with the alternate derailleur hangar). Thankfully, someone on RBR was already researching this at that time helped me to ask the right questions. The whole experience has soured me on both Specialized and that LBS; I felt like I was a rube, getting duped, the only one in the transaction not “in on it”.

Then you only “come clean” (let’s be honest, there is still a ton of spin in the above article) after the BR article that explicitly calls you out on it.

Trust is so hard to earn and so easy to lose.

Adam
Adam
6 years ago

This is progress..but cross season started September 14and will dang near be over by the time this new hanger hits my lbs. Axis wheels are not in stock and it was just yesterday their $1800 roval control sl became available.

logandj
logandj
6 years ago

I have three 12×142 bikes, two CX (Focus and Giant) and one Giant MTB. I have size 13us feet. I have no chainline or shifting issues and zero heel rub. Oddly enough I do get heel rub on my road bike with standard road hubs.

If my feet don’t have issues it’s hard to imagine someone who does.

Kernel Flickitov
Kernel Flickitov
6 years ago

In a few years we’ll have lightweight internally geared wireless drivetrains, with perfect chain line and zero dish rear wheels. What you’re seeing now is all the mistakes we need to go through to get to that point.

Doug
Doug
6 years ago

It looks like bicycle manufacturers can’t decide on hub standards right now. I decided to buy a KTM motorcycle instead of a bicycle. Maybe some day when bicycle standards gell I will buy another bicycle. In the meantime, I will buy a vehicle that offers much more value, and won’t be obsolete in a few weeks. And I will ride one of my fleet of obsolete bicycles when I get the urge to go motorless.

PTymn Wolfe
PTymn Wolfe
6 years ago

Thankfully, a Mechanical Engineer has spoken. All other opinions are now meaningless.

MnMDan
MnMDan
6 years ago

Wait..wait…wait…

So what am I missing here?
MTB…started with 135mm QR before moving to 142mm TA. Same chain-line. Cranks did not change. My feet sit on the pedals.

Road/cross…started with 130mm QR and have moved to the 135mm QR/142mm TA. My feet sit on the pedals.

On neither bike do my heels clip anything. I either don’t notice/don’t care that the Road/Cross has a slightly different Q-factor than the MTB, or its a non-issue.

5k/year on road/cross, 2k/year on MTB. No biomechanical issues.

Oh, and if it is/was such an issue, why is 142+ still being used on MTB’s? Surely that would negatively affect chainline (it moves the cogset 2mm outboard) similar to what Specialized says it is trying to correct via this new hub dimension by moving the corset inward . Are they making it worse in one area, making it worse in both areas, or just assume the consumer will buy their proprietary $#&!.

So, which one is it?

MnMDan
MnMDan
6 years ago

*cogset…not corset…autocorrect fail.

Gillis
Gillis
6 years ago

It’s about maintaining Q-factor which is less than on a road bike than on a standard mountain bike.
(130mm QA ~ 135mm scs) : (135mm QA ~ 142mm TA

greg
greg
6 years ago

Gillis,
That is incorrect. The road cranks available right now with +2.5mm chainlines maintain their original Q-factors.

Andrew
Andrew
6 years ago

@logandj Not sure about the Mares CX, but the Mares AX has straight chain stays and I definitely get a little heel rub.

R4ND4L
R4ND4L
6 years ago

As far as the engineering goes for bikes, in the infamous words of Grandpa Dean bike mechanic for around 30 years, if you want to know how to build a bike just ask a bike mechanic. You can engineer poo in a box and it will still be poo in a box.

sideburnz
sideburnz
6 years ago

Anybody else find it funny that that chainline photo actually makes it look like the cassette needs to move outward to be better?

timbo
timbo
6 years ago

I have been waiting over a year to get spare through axles from Specialized for my Diverge. Nothing off the shelf fits, and they have no spares. I ordered them when I bought my bike.

Unique things are fine, but they need to keep spares.

raphael
raphael
6 years ago

Guys. If you dont like what they are doing. Dont buy it. There happen to be many other bikes available.

…if specialized wants to make bikes with SCS let them.