SCS FAQ - READ THIS FIRST (then just email me I guess)

Posted by Jerry Chabot on

Hi Specialized bike owners! I have generated a lot of blog content on the SCS situation over the past year. So much so that it seems to have generated more questions than answers. Since I still get 10 emails a day on SCS questions from people looking to get wheels on their Specialized Diverge or Crux (gosh I wish I sold ten sets of wheels a day...), I think it is time for an FAQ post that I can point people to, or hopefully avoid some email traffic. << You can still email me, I don't mind! We are small and personal and helpful and respond to all emails in minutes. Go ahead, try me! (and then maybe buy some wheels from us, ok?)

Where to start? Ok, lets hit the basics. What is SCS? It is 130mm spacing road disc through axle. Say it with me "130mm Road Disc Through Axle". It is NOT, I repeat, NOT, 135mm spacing disc. It just so happens to MEASURE 135mm end cap to end cap, and that is a horrible coincidence that I blame Specialized for. Why couldn't they have gone to 136mm or 134mm and avoided the number one confusion around SCS? Sigh.

135mm spacing is what any regular old disc quick release hub is. 130mm spacing is what any regular old road rim brake quick release hub is (nowadays). When bikes went to through axle, they needed some way to keep the wheel centered and "retained" in the drop outs while you fished your axle through, unlike QR where the little skinny nubs stick into the drop out (and actually EXCEED 135mm if you were to measure, 135mm is face to face of the interior of the drop outs). So, bike companies created a 3.5mm recess in the inside face of the drop out, and extended the end caps 3.5mm per side. Net net is 135mm inside clear space (OLD - over locknut dimension) just like on a quick release bike, but now your hub measures 142mm. Voila, 12x142mm spacing is what any regular old disc through axle hub is. 

OK, ignoring boost and other MTB and fat bike specific axle standards for a long minute, lets move forward on SCS specifics.

There are two flavors of SCS bikes out there - Through Axle Bikes and Quick Release Bikes. Now, pay attention cause this is where the rubber meets the road on SCS, ok? Ready? Maybe take a sip of coffee now so you don't have to take your eyes off the screen later and miss something. I'll wait. 


Act 1: SCS Bikes Identified and Defined

Through axle SCS bikes are 130mm road bikes with disc brakes. Its a 130mm hub, people. OK, yes, your axle is labelled "12x135", I know. But refer above to what happens to a 135mm quick release MTB hub when you turn it into a through axle: it becomes 142mm!! Subtract the length of those extensions that allow the hub to stay put in the frame while you fiddle with the through axle and what do you get? 135mm. If you measure the inside of the rear triangle, what do you get? 135mm. Analogously, SCS is 12x135 THROUGH AXLE! 130mm spacing with 2.5mm extra added on each side to center the wheel in the frame. If you measure your rear triangle, it is 130mm. Why Specialized did not add the now standard 3.5mm per side and make SCS 12x137 so that no one would be confused is beyond me. But here we are. In terms of Specialized models, they are CARBON THROUGH AXLE frames only. Carbon Crux (2016 only), Carbon Diverge (2015, 2016, 2017 I believe). Carbon Roubaix (205, 2016, 2017 I think). 

Quick release SCS bikes are 135mm disc bikes. Plain and simple. Basically just a quick release mountain bike. 135mm spacing to make room for the disc brake. Quick release so the wheel centers fine. They are regular old bikes, NOT SCS AT ALL!!!! That is the "ah hah!" moment here, if there is one, that I hope you take away. These quick release (rear) bikes are SCS only in that Specialized put a 130mm disc road hub on them, with a funky SCS hanger to make it all work! All SPECIALIZED ALUMINUM ALLOY FRAMES are QUICK RELEASE and therefore NOT REALLY SCS. They just have some SCS bits bolted to them (hanger, wheels).

That is right, the only thing SCS about a quick release bike is the SCS road disc wheel that they put on these things, with a special SCS derailleur hanger to essentially convert the frame from "regular old bike" to SCS to make it shift with the SCS wheel in there. All you need to do is to purchase a regular old derailleur hanger for your bike, either from Specialized or the Wheels Manufacturing #146, or other third party replacement hangers. Once that is installed, you have a regular bike.

BUT WAIT, you still have SCS WHEELS!!! No, I can not make a kit or build you wheels that let you have it both ways.  It is impossible for us to build an SCS quick release wheel. We would need a 130mm road disc quick release hub, and those do not exist, other than the Axis wheels that came on your bike. No one makes one. All the quick release DISC hubs you can purchase are 135mm hubs, and you can not end cap your way outa that. If you want to upgrade your wheels on your alloy frame you need to replace the hanger with a regular hanger, buy regular quick release axled disc wheels, and put your Axis or other SCS quick release wheels, with the SCS hanger zip tied to them, on a peg until you sell the bike. If you want to run both wheels, you will have to change your derailleur high and low stops, and thus your shift cable length, by 2.5mm every time you swap wheels. It simply isn't a reasonable solution. The good news is, you have a regular old bike, so the world is your oyster for wheel selection. We sure hope you buy ours in return for all this work we have done helping you get this far. Seems fair ;) 



(please remember to wash your hands)


Act 2: SCS Through Axle Wheels

Why yes, we do love to build wheels for carbon, through axle, SCS bikes. The Diverge and the Crux are great bikes, and deserve great wheels. We especially appreciate the bright colors that Specialized continues to go with. We love colors and we "specialize" in custom colored builds that will make your bike look RIDICULOUSLY GOOD. Lean in, I will tell you a little secret... blacked out bikes and wheels are boring because everybody has one and the market is slowly swinging away from them because people want to express themselves.

It's true. Not black is the new black. And we are leading the charge. No one has the depth of color options available that we do. And no one builds factory wheels as customizable as we do. 

So you want upgraded wheels for your SCS carbon through axle bike. OK, what can we do for you? Two avenues: 

End Cap Solution: We mix and match end caps (long story short) and build your wheels on that specific SCS end cap set up so that it is dished correctly. You leave your SCS hanger on your bike (the through axle one that came on it) and we build you wheels on standard 12x142 hubshells with end caps that make it fit and work just like it did from the factory with the SCS hubs.

  • Will your through axle engage a few threads less than before? Yes.
  • Is this a problem, or any different than when you install the factory approved non SCS hanger? No.
  • Can you run a 12x142 axle if this bother you? Yes.
  • Will your wheels work on any other bike down the road with a simple end cap swap? Yes.
  • Will this "correct" your chainline for short chainstays like those found on the Tarmac Disc? No
  • Does your chainline need correcting on a long chainstay bike like the Diverge or Crux? No. 
  • Have we tested the living crap out of this assertion on a couple hundred wheel builds and with our cyclocross and gravel racing team of 40 people? Yes.
  • If the shifting is not to your liking, will we take them back? Yes.
  • Future proof investment. You're welcome, we think we are pretty great too, thanks for noticing. 

SCS Hubs: We build your wheels on 12x130 through axle SCS specific hubs from Hope. They are the only vendor making such a hub (for now). They are hard to get. They are long lead. We keep them in stock just for you. This set up replicates the factory build. You retain the full chainline correction Specialized intended. 

  • Do you have a Tarmac Disc? If so you should buy wheels built on SCS hubshells.
  • Do you have nice carbon Roval wheels for your Crux, or several, and you just want another set for your quiver? If so you should buy wheels built on SCS hubshells.
  • Can we do these in colors? Yes.

Congratulations! You made it through the important stuff! You now know what you need to know to make an informed purchasing decision. Please take a moment to browse our store on your way out. Please and thank you. Please check for any items you may have left in your seat, and return your 3D glasses to the bins in the foyer. If you enjoyed any spirits this evening, please consider taking an Uber.

Act 3: Specialized Reference Information and Explanations

Do you ever wonder if you just left too soon after the awkward pause after the standing ovation? Did you miss the encore? Was there ANOTHER encore? Did you blow it? If you are still here then the answer is no! You have in fact stayed for the encore! You sir, are a dry sponge still trying to soak up all the SCS information available! Here are a couple supporting bits of information to round out your knowlege:

Quick Release Bike SCS Hanger Identification:

This diagram shows the difference between SCS and non SCS quick release hangers. If your bike has the "dogleg" or offset hanger, it is the SCS hanger, and the lockring on a non SCS wheel will hit and prevent you from installing the wheel or shifting. 

SCS Tech Specs


Carbon Through Axle Non SCS Hangers:

This next image shows you the difference between the stock SCS through axle hanger, which has a nice recess in it to self center the wheel, and the Non SCS hanger Specialized now sells to ostensibly allow you to run "any 12x135 through axle wheel" on your carbon SCS through axle bike. Couple issues with this. 

  • You can't find any 12x135 through axle wheels. Ok, DT makes end caps, not much else out there. And the end caps are unobtanium (we buy them all and keep them in stock for you)
  • If you do get a 12x135 wheel, and use the conversion hanger, your dish is going to be off. Big deal? No not really, but sort of, on a cross bike with big tires and mud clearance.
  • The wheel does not self center, and putting your through axle in and finding the hole on the derailleur side and engaging the threads is an absolute PITA. I could not live like that. 
  • The non SCS hanger is often unobtanium. 

SCS and Non-SCS Hangers

SCS and Non-SCS Hangers

Well, that's it. You made it to the end, well done. Now go buy some wheels please! 

_takes one last bow to roaring applause, collects roses thrown by adoring fans_