Tech Breakdown: How 135mm Rear Hub Spacing Affects Road Bike Chainline & Shifting

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

There’s no doubt disc brakes are well on their way to the road bike market. A few major brands like Colnago and Specialized recently introduced production models, Volagi built their brand with them from the outset, and disc brake cyclocross bikes are pouring in.

But what does all this mean for the other side of the wheel? We’ve covered (here and here) some of the technical challenges and concerns of using disc brakes on road bikes and the changes required for wheels. But the conversation’s been missing one critical element of the shift. Virtually everyone that’s making or planning a disc brake road or cyclocross bike has 135mm rear hub spacing on the drawing board.

That’s 5mm wider than what road bike frames have been designed for. 5mm wider than what decades of drivetrains have been designed around. Sure, that’s only 2.5mm per side, which doesn’t sound like much. Until you consider that Shimano only needed 1.8mm to add an 11th cog.

We spoke with the engineers and product managers at FSA, SRAM, Shimano, Specialized, Parlee and Volagi to see how this will affect chain line, shifting performance and heel clearance on what could very well be your next road bike…

CHAIN LINE & SHIFTING

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

One of the biggest concerns we heard initially was how the chain line would be impacted at the extremes, particularly when cross chaining from the little ring to the smallest cog. Granted, most of us know better than to ride like this for very long, but it happens. And when it does, the chain could snag on the big ring, causing a mis-shift, jammed chain or worse if you’re really cranking.

Above is a standard 53/39 Ultegra crankset and cassette on my Moots cyclocross bike. It has 135mm rear spacing and disc brakes. I put the camera’s focus at the chainrings (left) and cassette (right), click to enlarge.

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

What I found in this gear combo was that my chain was dangerously close to the big ring’s teeth (highlighted in yellow). Click to enlarge and you’ll see it better. You can also see how close the chain is to the front derailleur’s cage. It’s not rubbing, thankfully, but -and this is a big but- my ‘cross bike has relatively long 423mm chainstays.

Where this becomes a real issue is with race-oriented road bikes with very short chainstays. The Specialized Tarmac has 405mm stays for most frame sizes, for example. It’s such a potential issue that FSA has created and issued a technical advisory bulletin with the following guidelines to help ensure proper shifting and clearance:

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

At top, the chart shows OK’d chainring and chainstay combinations for standard 130mm hubs. Below it, the same thing for 135mm hubs. The increased limitations become pretty obvious with all that red.

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

And it’s not just the big ring’s teeth that could catch the chain. Shift pins are generally used to help guide the chain up during an intentional shift. But, get the chain too close and it could help out on its own.

While Shimano wouldn’t get into much detail with regards to product designs and research regarding this matter, they did send over their standard statement with regards to compatibility. Dave Lawrence, Shimano road product manager, had this to say:

“Shimano has always been a leader in bicycling component engineering. Part of that success is due to Shimano’s ongoing communication with frame manufacturers. With Shimano’s CX75 and R515 mechanical disc brakes for cyclocross and road bikes, Shimano is well aware of the industry-wide move to wider rear spacing for road and cyclocross bikes. While this does affect chainline, currently Shimano is not changing its 430mm chainstay length guideline for ideal Shimano component performance. Rest assured though that Shimano will continue to speak with frame manufacturers.”

So, what does everyone else have to say? I asked a few standard questions, answers from each brand follow. What’s interesting is that some of them don’t see this as much of a challenge, and others mentioned things we hadn’t even thought of.

For example, most of us assume road and ‘cross bikes are only switching to 135mm hub spacing to make room for the rotors. Maybe. Maybe not. As with many things in life, it depends on who you ask. Thankfully, we ask a lot of people a lot of questions. And equally thankfully, they don’t get tired of it! Here we go…

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

The Volagi Viaje with FSA 46/36 chainrings and XT cassette. Note the increased clearance between chain and big ring. This bike has 418mm chainstays.

THE QUESTIONS & ANSWERS

We spoke with Omar Sisson (head mechanic) and Robert Choi (Co-owner) of Volagi and Tom Rodi (Product Manager) at Parlee before putting together our formal question list. Our conversations with them are transcribed further down. For these questions, we reached out to the companies mentioned and Colnago, but didn’t hear back from them. For the others, the replies are from Jason Miles (FSA, Engineer), Scott McLaughlin (SRAM, lead drivetrain engineer), Charles Becker (SRAM, road product manager) and Ty Buckenberger (Specialized, carbon road bike project manager).

BIKERUMOR: How was chain line and drivetrain function (ie. shifting, cross chaining, etc) affected by increasing the rear hub width to 135mm? What measures did you take to ensure proper performance?

FSA: One problem we’ve seen is when you have really short chainstays and a large difference in chainrings, like, say, a 53-39. If you hit a bump, the large ring can grab the chain and cause a bit of ghost shifting if the derailleur is trimmed in such a way that its cage isn’t rubbing the chain when you’re on the smaller cogs, too. It may also cause the chain to drop to a smaller gear a bit slower than you’d expect.

We’re working on solutions, and our chainrings will have to change. The chain rub you may experience right now won’t be there forever. In the meantime, we make the RD460 wheelset that’s a 130mm road disc brake wheelset. MSRP is $499.99 and comes in at 1830g. It’s been spec’d on one of the Redline Conquest bikes in the past, we’ve been making it since 2006.

SRAM: First, it’s worth mentioning that Road/CX bike rear hub spacing did not change from 130 to 135 to accommodate disc brakes. Bike frame and wheel manufacturers decided that they could make stiffer frames and stiffer wheels with 135 rear spacing. And since they needed to design new road/CX wheels and road/CX frames to accommodate disc brakes they decided to use the occasion to also change to 135OLD. That said, front and rear shifting are effected because the drivetrain is optimized for 130OLD. We have proposed a solution that we hope to implement soon.

SPECIALIZED: We’ve done considerable testing to insure that the shifting wasn’t compromised on our current disc bikes (Roubaix and CruX). The chainstay length on those two models helps. The small/small gear combination on the Roubaix with 135mm dropout spacing isn’t any worse than a shorter chainstay bike with 130 spacing.

BIKERUMOR: Are there certain gear combos that don’t work as well or don’t work at all in this set up?

FSA: See charts above.

SRAM: It depends on the bike frame dimensions but cross chaining while in the small chainring is affected most.

SPECIALIZED: All the gear combinations are available, although not necessarily recommended. Like most bikes the small/small gear isn’t ideal. It functions, you may get some chain/front derailleur contact in that combination. The same contact occurs on most performance road bikes with 130 spacing and short chainstays.

BIKERUMOR: How did that affect heel clearance, particularly for people with bigger feet? What measures did you take to ensure proper clearance?

FSA: It’s not really our department, but if the frame manufacturers don’t account for the narrower Q factor of road cranks, then it could be an issue. In talking with frame manufacturers, we’ve actually been warning them about this for years. If you look at DH bikes that have really wide bottom brackets, it can feel like riding a horse. That’s a no-go on road bikes where you need to maximize power output, ergonomics and aerodynamics.

From an engineering standpoint, we understand why some people want to add the extra 5mm to make up for the non-driveside space taken up by the brake rotor. But, when you ‘re talking about 700c (also 29er) wheels, that extra little bit of bracing angle given to the spokes is so minimal that you’re not seeing a huge gain. At least not enough to offset the potential problems with moving to a 135mm rear spacing on road bikes. You can’t have wildly different spoke angles from one side to the other because the tensions would be too different, so the closer you can get to equal angles and tension, the better wheel you’re going to have. With a 130mm hub, you’ll start out with enough space to add a disc and still have a plenty strong, stiff wheel for road and cyclocross use. I’m not saying a 135mm hub can’t be stronger, but I don’t think it’s necessary for these disciplines.

SRAM: (Scott) Heel clearance isn’t effected with respect to drivetrain. This is definitely a question for frame makers.

SRAM: (Charles) I think heel clearance is not really the question, as nothing changed. Heels usually touch the chain stays. The real question should be about the cranks (near the pedals) running into the chain because the 11t is further outboard. And yes this is a concern on frames with short chain stays and 135 OLD.

SPECIALIZED: Again, the longer chainstay lengths on these models really helps with problems like this.

BIKERUMOR: What other technical, performance or engineering challenges had to be overcome or considered due to the extra 5mm hub width?

FSA: There’s always the chance your derailleur won’t adjust outboard enough to accommodate the extra 2.5mm on the drivetrain side, which could lead to chain rubbing even on the big chainring/small cog combo if your front derailleur won’t move out far enough.

We could very easily add 5mm to our crank spindles and supply them with spacers, but that’s not what people want. They don’t want wider Q factors. We can’t release any info on what we’re working on now. Our new D10 chainrings have offset chainrings for mountain bikes that let you use a double front derailleur on triple cranksets (Editor’s note: you might do this when you replace the big ring with a bash ring or something, effectively making your bike a 2×10). This may not be the best direction for road, but we’re looking into it.

SPECIALIZED: The main challenges are shifting performance and heel clearance along with everything that goes into getting a new model into production.

A CONVERSATION WITH VOLAGI

There were road and ‘cross bikes with disc brakes before Volagi broke onto the scene, but they did quite a bit to cement the concept into mainstream riders heads. Their original Liscio started out with 130mm hubs, but the second generation and the new Viaje steel road bike both have 135mm hubs. They also provide their own wheels, and shown above are their new 11-speed freehub bodies (right). Their splines are exactly 2mm longer than the 10-speed version, thanks to a slightly longer body and deeper machining at the back plate.

In ensure the cassette cleared the spokes, a 1mm taller spacer was required (right) to push the freehub body out from the hub shell slightly. It might seem like we’re getting off track here, but this illustrates that the new crop of 11-speed drivetrains are going to push the smallest cog even slightly further out on some bikes and wheels. So, in some cases, the change might be equivalent to another .25 millimeter or more on the drive side. Here’s what Omar and Robert had to say on the whole thing:

The chain line hasn’t really been an issue. It may have more to do with idiosyncrasies on the frame. In a perfect world, you’d make the adjustments to the design so that you’re only making 2.5mm movements on either side of the hub. So you’re only moving the chain line 2.5mm out, but the frame center line has to be perfect and that’s not always the case.

We’ve looked at a broad representation of derailleur and chainring combinations. That includes the FSA BB386 cranksets with compact and cyclocross chainrings, and the usual range of cassettes from SRAM and Shimano, particularly the ones we build bikes with.

We started to talk with FSA about it, but as we started building bikes and testing things, we didn’t have any issues. It hasn’t been a problem for us. We use KMC chains, if that matters, and so far we’ve only built up bikes with 10 speed drivetrains.

Sometimes it’s more of an issue just switching bottom brackets, but we haven’t noticed any issue even at the extremes of cross chaining. Or at least any more than you’d expect. (Editor’s note: Volagi’s bikes tend to have longer chainstays since they’re aimed at the endurance crowd).

We haven’t tested it with Shimano’s 11 speed Dura-Ace yet, but with our own hubs, we’re redesigning our freehub bodies and taking up that space.

We did have to make some adjustments to the brake mounts to improve heel strike clearance, mainly by moving the hose to the inside of the chainstay. And, for the hydraulic brakes, TRP got rid of the banjo and ran the hose directly into the caliper. For mechanical disc brakes, folks with larger feet (size 11 or 12 and up) could rub the dial on the Avid BB7 mechanical brakes a bit, but models from Hayes and others seem to alleviate this, even the BB5 Road calipers have better clearance because they don’t have that outside cap.

OTHER THINGS TO NOODLE ON

WHY NOT CHANGE THE BOTTOM BRACKET WIDTH?

Road bikes have used 68mm bottom bracket shells for ages, and even the newer BB30 standard uses that shell width. Modern crankset/BB standards like PF86 and BB386 have a wider shell, but the bearings are all internal, allowing for a generally similar Q-factor as bikes from thirty years ago.

When mountain bikes gained steam, many manufacturers settled on a 73mm bottom bracket shell while still using the outboard bottom brackets. Conveniently, this was 5mm wider, matching up nicely with the 5mm wider hubs, which worked out really peachy when disc brakes came on the scene.

So, why not just stretch the BB a bit on road bikes? Well, as Jason at FSA mentioned, roadies don’t want to feel like they’re straddling a horse. A wider stance just wouldn’t feel right on a road bike, physical performance could likely suffer and aerodynamics would definitely suffer. Maybe only a little, but heck, if we’re spending thousands on wheels and frames that promise a few watts or seconds over 40km, keeping things narrow is like free speed.

HOW MUCH DOES 2.5mm REALLY AFFECT HEEL CLEARANCE AT THE CHAINSTAYS?

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

As someone who’s personally worn through too much of his carbon fiber chainstays to feel comfortable, any amount is too much. But, if you want to put it into perspective and see if you’d be affected, tape two dimes to your chainstay where your heel passes it and see if they’re still there after a long ride. Or just look at your chainstay. If you see wear marks and scrapes that align with your heels, you’ll want to really pay attention to how this shakes out.

COULDN’T I JUST COMMISSION A CUSTOM BIKE AND HAVE THE CHAINSTAYS TUCKED IN?

Parlee Z-Zero custom carbon fiber road bike with disc brakes or standard rim brakes

Maybe, but let’s see what Parlee has to say. After all, they just introduced their new top-of-the-line Z-Zero with a disc brake option that’ll have (yep, you guessed it!) 135mm rear spacing. Here’s our conversation with Tom Rodi from the Massachusetts based custom builder:

Our feeling is that there’s nothing that’s really going to be a nightmare. It’s only 2.5mm per side, it doesn’t seem like it’s going to affect chain line too much. But, we do think with new 11 speed drivetrains, people are going to have to pay more attention to minimum chainstay lengths…but that’s not going to affect us too much since we don’t believe in super short chainstays.

There’s a little more of a kink in the chainstays on the new Z-Zero chainstays to accommodate heel clearance. And, on the Zero, we’re also trying to accommodate for wider rims.

We’re fortunate in that many of our customers will send their bikes back in after five to eight years to be repainted, so we can see wear patterns.

If you came straight back with the chainstays then made a severe bend out toward the dropout, it wouldn’t really solve the heel strike issue. Most of the wear we see is at the back 3/4 of the stay. One thing we did have to tweak over the years was moving the cable stop for mechanical groups closer to 6 o’clock.

In testing, it hasn’t been an issue, but like everything else, once we get more real world data, we’ll adjust as necessary.

WHAT DO YOU THINK?

Do you have heel rub issues on your current bike? Do you have a disc brake road or cyclocross bike? If so, how’s it shifting?

Comments

jason - 11/28/12 - 4:57pm

I have a 2009 Salsa La Cruz, with Avid BB5 brakes and the full 10 speed Shimano 105 groupo.
No issues with chain rub or the big ring catching the chain, but as mentioned in the post I try my best to avoid severe gear combos.

Whatever - 11/28/12 - 5:11pm

Total crap article. Typical of BR not understanding how to go indepth when BR actually do something unusual around here: not just reprint a press release.

The rear spacing doesn’t matter, the RDs doesn’t care. Nothing has changed from the RD mount inward. It doesn’t know the distance between dropouts, nor does it care as it moves inward and outward from the position, on which, it has always been mounted. If you really think it is different, run all MTB stuff. Oh, BTW, that MTB works on 130 too! Go figure.

Keep up the good work.

Topmounter - 11/28/12 - 5:13pm

I recommend using a drum brake in the rear, a setup that is still working great on the Ford Pinto.

Steve M - 11/28/12 - 5:48pm

@Whatever- when you are done hyperventilating start considering anyone with a larger foot and the fact the frame is going to be 2.5mm wider where their heel sweeps by 90 times a minute. Perhaps Q factors should grow a bit.

Ajax - 11/28/12 - 6:07pm

Dear bikerumor writer,
Please check your facts before posting false statements. Volagi never did 135mm rear spacing until this year.

Thank you.

Derek - 11/28/12 - 6:10pm

@Whatever Did you even read the article? It’s mostly about front shifting. No one is arguing that it will mess with rear shifting.

BMark - 11/28/12 - 6:13pm

What a stud… running 53/39 on his CX bike. Hot dog!

MB - 11/28/12 - 6:17pm

I agree with Steve M. I had issues wearing through the seatstays on my last steel 29er so now I really pay attention to how my heels strike any bike I ride.

I agree that 5mm wider Q factor is a simple fix. And give me break if it you think that slows you down significantly.

Rick - 11/28/12 - 6:17pm

What BMark said. How many cross bikes come with a standard road double? Someone building a bike from the frame up should choose an appropriate crankset.

James S - 11/28/12 - 6:32pm

It seems to me the obvious solution is to offset the chainrings by 2.5mm and optimize the front derailleur to match. Shimano and SRAM could offer the crankset and front derailleur as part of a disc brake road/CX group.

As far as using a standard road double… Aren’t any of you guys paying attention? They are starting to build disc brake road bikes now, not just cyclocross bikes. In fact, cyclocross bikes generally have longer chainstays which (as mentioned above) don’t really have much of a problem using 135mm spacing.

htimS hnoJ - 11/28/12 - 6:55pm

You’re all arguing about chain line.

What a bunch of sad (deleted).

Ripnshread - 11/28/12 - 7:07pm

This is a good article. Well done. Imop this is one of the main reason we have seen SRAM and Shimano hold off on their hydraulic disc brakes that would be slotted into their main groups. I’m hopping they come out with new drive train systems to fully take advantages of what disc brakes have to offer. I also can’t see what they are going to come up with to combat the issue of overheating due to prolonged steady breaking and the resulting fade or loss of braking that ensues…maybe reverse air brakes like a big rig? lol

JimW - 11/28/12 - 7:37pm

I have a custom Igleheart CX Disc and have had no issues with the 135 spacing.
The longer chainstay @425mm helps obviously. No heel rub on the stays at all with PF30 Red crank,172.5, but they are narrow and my size 8′s contribute. Shifting is fine with a 46/44-38 & 12-26 or 11-28. The 11 feels like crap but 11′s always do.
I’m surprised you BR folks are concerned about little little. That combo has been hit or miss since 9speed. I can’t count the amount of road bikes I’ve had go through my stand where the little little would pick away at the big ring tinging and chiming or grabbing a little bit. 10speed gets worse especially when the chainstays are tiny short like on most of the current boutique stuff.
I am glad to see little little become truly off limits.

Customer: JRA and WTF my bike keeps shifting itself and making this rubbing noise. This sux.
Me: UR doin it RONG!!! See FSA no fly zone.
Customer: lalalala not listening….
Me: FFFFFFFFFFUUUUUUUUUUU!!!!!!!!!!!!!!!!!!!!

Justin - 11/28/12 - 7:43pm

Worst case scenario (and this may not even happen), you lose one cog cross-chaining that you MIGHT have been able to use with less noise on a 130mm spaced rear axle. Get over it; learn how to use your gears!

Mitch - 11/28/12 - 7:47pm

I have recently set up two 135mm rear spaced mechanical disc cross bikes. One with full Sram Force and a 11/28 Shimano cassette, the other with Sram Apex wi-fli cassette/rear derailleur with rival fd and Force CX crank. Neither have had any issues what so ever. We had the usual cable stretch/break-in adjustments performed within weeks of the build, and thats it. I am very meticulous in setting the front derailleur properly, and when this is done, you get amazing FRONT shifting.

Furthermore, if you set the FD properly, and unconsciously cross chain while in the small front ring, the chain will hit/rub the fd cage long before you shift into the outter-most rear cog, meaning the FD will keep your chain off the large ring. This should happen around the 7th cog, and definately by the 9th cog if in the small ring, regardless of chainstay length.

NOW THIS CHAIN LINE BUSINESS HAS BECOME A MOOT POINT.

Summary:

SET YOUR FD PROPERLY!!!

BE CONSCIOUS OF CROSS CHAINING WHICH DESTROYS CASSETTES, CHAINS AND CONSEQUENTLY YOUR WALLET!!!

Justin - 11/28/12 - 7:51pm

Though I should note I’ve never had problems with heal strike on chainstays. There are pedal shims and washers available if you’re really having issues with this.

Mech T.L. - 11/28/12 - 7:54pm

Well, as one who are trained in engineering. My gut feeling is that we do not really need 135mm. There is enough room on a 130mm rear end to accommodate the disc and the frame , if design proper and build right can do the job just as well. Though , with that being stated, I do think 135mm offer some advantage, namely the possibility of more clearance, not just for the disc brake, but for gears, and wheels. A wider wheel with more up to date aero profile together with technology like tubeless tires with a X25 size, with the disc, can dramatically alter how a RB behave especially in cornering, braking, and in the wet.

So far I am not seeing major issue with this , but perhaps I do not have a bike with those extra short Chainstay nor do I use extremely widely spaced front pair of chainrings

Werkin - 11/28/12 - 8:04pm

I have a cyclocross/commuter frame with disc brakes used as a road bike. Rear hub is 130mm, bracing angle is a non-issue, in fact the rear spokes are the same length. No heel strike, shifts fine out back with both road & MTB cassettes and rear derailleurs. Shifts good up front with SRAM/Truvative, Campagnolo, and Specialties TA chainrings. However, Stronglight’s Zicral outer chainring shifts very badly, and I’m sure it would perform badly regardless of axle width, cog count, disc brakes, or front derailleur type.

No mention in this article of variables like an individuals foot length, rotational style, and cleat placement in relation to heel strike. Also, the fact heel strike was/is sometimes an issue with 126mm rear axle spacing, and a chainring size difference greater than 13T can cause chain rub against the big ring in the small small combo even with 126mm axle spacing, are a few perspectives omitted.

Mindless - 11/28/12 - 8:49pm

Why not just go 142×12? It is actually faster to change a wheel than a 135mm QR, oodles stiffer, and same chainline.

Moby - 11/28/12 - 8:51pm

I have a TiCycles ultralight road frame (custom) with Ultegra Di2, bb7 road calipers and 135 spacing. I can make my rear heel hit the caliper arm (outboard adjustment dial) with the amount of float that my Speedplay Zero’s allow, but in practice it isn’t really a problem. Shifting has never been an issue due to spacing but I do not know if the chainstay length qualifies as “long” or “short”. Even if there were minor problems such as mentioned in this article they would be nothing compared to the advantages that discs give me for the amount of wet weather that I ride in.

pete - 11/28/12 - 11:31pm

this conversation is why you don’t ride road bikes ;)

MTB’S FTMFW!!!!!!11!1!

Nullifyer - 11/28/12 - 11:33pm

All of these changes seem like a good reason to move towards internally geared hubs like the Rohloff. With more volume on these hubs prices would come down and engineering cycles would increase. Chain line would not even be a consideration with this set-up.

Your English teacher - 11/29/12 - 12:06am

@Mech T.L.

No offense but…

You may have been paying attention in math class, you sure must have been asleep in English. I counted 12 grammer, syntax errors & mis-statements in 1 1/2 paragraphs.

Even engineers need to communicate with the written word to express themselves. I was distracted by the bad grammer & poor sentence structure to the point of writting this dickish response.

Fixiedweeb - 11/29/12 - 1:34am

You folks don’t get it do you – 135mm is not for increasing stiffness, room for discs, etc… IT’S TO MAKE ROOM FOR 12 SPEED ROAD BIKES NEXT YEAR WHAHAHA.

Sam - 11/29/12 - 2:21am

The only real issue here is heel clearance. As Justin said, you may have one less small small combo available – so you can’t use 39-13 or 39-14 any more, which is really not a concern. To be honest, FSA are right, road disc spacing should be 130. It is only the hub manufacturers’ desire to limit variants they need to produce and stock which is pushing 135.

Mindless - 11/29/12 - 3:34am

@Your English teacher: up yours.

PaulM - 11/29/12 - 4:27am

In the good-old days of square taper BBs, you could just replace your BB with a longer axle. Ok, you’d also have to find a crank with a smaller Q-factor to compensate.

I’d like to see alternative BB designs, either 3-piece with different axle lengths, or maybe a floating chainring-spider that can be shimmed one way or the other. It’d make SS buids a lot easier too.

gear - 11/29/12 - 6:11am

I own one of the original Volagis’ with 130 rear spacing. I have size 12 feet. I have no issues with heel strike. Why change to 135 (spacing) if you don’t need to? It just creates more problems.

mark ifi - 11/29/12 - 8:15am

excellent article, really. good point about hitting the chain stays. i’ve been using 68 bottom bracket, and narrow q factor cross country mountain bike, no issues there. i could hit the chain says but it was never an issue.

Rod - 11/29/12 - 10:27am

Tyler,

Why have you neglected from the article’s inception to fail to mention the Intelligence with which Campy had the vision decades ago, and adopted a 135mm platform??? Also, the entire debacle with the Dura-Ace 9000 Totally Alienating current Shimano Fanatic’s due to their failure to accept the superior engineering of Campy and to pay a royalty to them, instead of trying to re-engineer (A Long Standing Japanese Tradition-Total Failure and ability to Innovate)?

Gino - 11/29/12 - 10:43am

I think they should develop a 2×8 (or 2×9) with 130mm rear hub spacing for disc brake road bikes… but then we would still need triples…. which isn’t a bad thing

Adam - 11/29/12 - 11:06am

I ride small frames, and therefore have short chainstays.
Currently I have a Felt F1 with VERY short chainstays, and the 11T and 12T cogs on my cassette are not useable while in the little ring (39T). At all. The 13T and 14T cogs rub the big ring as well, but are useable.

Heel clearance is not an issue, but chain line certainly would be if the rear spacing were to jump to 135 on this particular bike.
This just begs the question of who disc brakes on road bikes are for. Above, folks with touring and commuting bikes and CX bikes have no issues. Same with Specialized TriCross and Volagi bikes, simply because of their longer chain stays (I assume).

So in practice, with the current technology that we know about, disc brakes on road bikes, intended for high-end road racing are not going to work well. Especially for individuals on smaller frames, 52cm, etc.

According to the Felt website, the chain stay length on this bike is about 403mm (that’s for the new ones, mine is a couple years old). 403mm is a FAR cry from Shimano’s recommended 430mm! I think we’re still a few solid seasons away from cracking this nut.

Psi Squared - 11/29/12 - 1:17pm

Good article. The point of articles like this and the discussion and study by the manufacturers is to determine whether there is or will be functional issues. This is engineering S.O.P. If you don’t think of all the possibilities of things that might go wrong, then one of those things you didn’t think of or didn’t consider adequately might bite you in the proverbial ass. Engineering history is replete with stories of such failures and problems, problems and failures about which the typical poster here would kvetch. It’s a good thing that so many people here aren’t engineers or bike designers.

It may turn out that 135mm spacing on road bikes won’t be a big issue, but it’s damn well good that people are asking questions about it now.

Will - 11/29/12 - 2:55pm

@fixiedweeb: huh. . .i thought the reason for new spacing and new brake technology was to get everybody to fork down yet another $3,000-$7,000 to replace awesome bikes that everybody just bought a year or two ago.

Just a few years ago, bottom brackets, brakes, headsets, etc. were all fairly standard sized parts. I hope that the dust might settle on a few of these issues sometime soon.

trip - 11/29/12 - 3:24pm

@fixiedweeb
But seriously. Kcnc has one in their online catalog. The future, now…..

Jeff - 11/29/12 - 7:44pm

Disc brakes for CX and touring OK, but for a race bike? I can lock the brakes up to easily with rim brakes, with that small contact patch. And wet rims means wet pavement, still too easy to lock up the brakes!

Disc brakes are heavier, need more bracing (read heavier) at the frame, need more, stonger spokes and thicker materials at the nipple area of the rim, because that is where all that braking force is transmitted with a disc brake, all adding weight and rotating weight to boot.

But I could use a wider Q and some interchangability between my MTBs though. Oh yeah I like to keep my chocolate out of my peanutbutter Ha

Jeff - 11/29/12 - 7:46pm

Uhm, I am not an engineer and was terrible in English class :-)

Scott - 11/29/12 - 9:06pm

I better start hoarding Non Disc road frames…You will never see me on a disc road bike. Ever

Psi Squared - 11/29/12 - 10:17pm

Jeff, locking up brakes is not the goal. Avoiding lock-up while maximizing braking is the goal. Disc brakes will provide better modulation, and better modulation means being able to better know when you are approaching wheel lock-up, or on dry pavement, rotation about the front wheel (i.e. max possible braking). Better braking also means later braking points for corners which translates to faster average speeds.

The issues in this article are not insurmountable.

Grant - 11/29/12 - 11:19pm

Interesting article. For what it’s worth, I am riding a Moots PsychloX with sliders, 135mm spacing for disc brakes and sliding rear dropouts set in nearly their forward-most position. Running 2012 model 46×36 SRAM Red Cranks, SRAM Red WiFli rear der, 32 x 11 cassette. (The shifting is as near perfect as I’ve ever experienced BTW, and I am a long time Shimano user.)

I am a terrible cross chaining fool, but have experienced absolutely zero issues with chain line, no heel rub, and in fact, less chain rub than on my short chain-stayed road bike with Shimano groupo and 53×39. I have not measured the chain stays, but as I mentioned, I am running the sliders nearly all the way forward. No issues here with a size 11 shoe.

Spandrew - 11/29/12 - 11:40pm

Heel rub is a personal issue- everybody is different!

Also, I don’t see the the need to mess with q factors. Leave the spindle and crank arms alone, and adjust the location of the spider. BOOM! problem solved.

Moove - 11/30/12 - 3:56am

Most of this alarming data is comming from FSA. My personal experience is that chain rub/ghost shifting is a bigger problem on their chaiwheels in general, than on Shimano chainwheels. So of course they are quick to warn you about this problem to cover their back.

But they(FSA) have a decent solution to the problem. Just increase the chainline to 46 mm.

Ol' Shel' - 11/30/12 - 7:05pm

If your stays are designed as poorly as the carbon bike in the pictures, you will have heel rub issues.

It’s sad that someone gets paid good money to design stays that bow out toward the rider’s heels.

Aaron - 12/01/12 - 9:48am

My solution to this who disc brake mess: keep riding rim brakes on my road bikes. The set-up is lighter, it’s more aero, I can run 12-spokes wheels if anyone would buy me a set of Rolfs (Christmas is coming, people), and they work damn well. I rarely ride in the rain, and I have no mountains nearby, so I really don’t need discs.

Mindless - 12/01/12 - 8:20pm

@Jeff: the fact that you can “lock your brakes” easily is exactly the reason for the disk brakes. They are MUCH easier to MODULATE. Locked up brakes are bad. It is not about power, it is about control – predictable performance in all conditions..

Bnystrom - 12/01/12 - 9:26pm

@Your English Teacher: While I applaud your willingness to take someone to task for absolutely horrible writing, it’s pretty sad that you couldn’t set a better example. “Grammer”? “Writting”? Call me crazy, but I expect that an English teacher should be able to spell words describing what they teach.

As for the whole 135mm chainline issue:

I guess if you only ride road bikes, increasing the Q-factor might seem objectionable, though the variation between different models of cranks and pedals is more than the 2.5 – 5mm increase we’re debating. If you ride a MTB or road bike with a triple, it becomes quite obvious that differences of a few millimeters in Q-factor are inconsequential. When switching between my various bikes, I may notice a Q-factor difference for a few moments initially, then I forget about it and it feels normal after a few minutes. Heel strikes on the chainstays are much more of a distraction, to say the least!

dislivello - 12/27/12 - 1:29pm

solution is: drawing position of caasete exacly same of 130mm hub,and 2:1 lacing on wheel or asimetric rim.on tt
hat condition all work good but attentio dropao
ut max 9 mm or move it 2mm to center wheel ..

barefoot - 01/15/13 - 8:55pm

I had a custom Chitanium disc brake road frame built, and this is about the only thing I didn’t pay enough attention to.

I went with 135mm spacing, so I could use a standard off-the-shelf MTB disc brake hub. My frame builder (XACD) seems to have just copy-pasted the chainstays and dropouts from a MTB design (but shortened the chainstays to my requested 415mm). That looked great to me because the design gives loads of clearance for big tyres and/or fenders if I ever want to use them.

I’m running a 6750 Ultegra compact crank. My first problem was chainring clearance. I’ve had to do a dodgy and use a 2mm spacer behind the RH BB bearing cup, to push the chainline out far enough for my 34T small ring to clear the chainstay. That means my LH crank has slightly less spline engagement on the spindle than it should, but I’m able to get the lock pin in the hole so I’m confident it’s firm and secure. But it is asymmetric, which could potentially cause problems.

At the back, I’m still running 6600 9-speed, 12-25. In small-small gear, the chain skips a little bit on the big ring shifting pins. No big deal – it just serves as a reminder to not use that gear.

I’m close to heel-striking, depending on shoes. My neutral pedaling stance seems to be with feet more parallel than my coasting stance, because I often find my heel hitting (or standing on top of!) the chainstay when coasting, but it doesn’t trouble me when pedaling.

In all, though, I’d be happier all ’round if I could just move my entire crankset out slightly. On both sides. Chainline is pretty flexible really (small-small and big-big are always going to be ugly) and I don’t mind a wider Q-factor.

In the old days, moving my cranks out would be easy; I’d just get a BB with a longer spindle. With the current generation of outboard bearing cranksets, it’s impossible. Ironically, this move to cranksets with strictly locked-in chainlines and Q-factors came just ahead of another change, to 135mm rear dropout spacing on road (and road-like) bikes.

One option that I’m still considering is to change to a MTB crankset. MTB cranks have wider Q-factor (to help with heel strike), and a wider chainline (to help with my chainring clearance). XT “Touring” sets can now be had with 26-36-48 tooth rings. I only have double shifters, so I’d lose the 26 and run it as a double (with the chainline even further out). If 50:12 top gear is high enough (and it is for most people who aren’t Cav), 48:11 is even higher. It’s kind of silly that this is now the only way to solve the problem of, essentially, my BB spindle being a bit too short.

Thom Meyers - 04/23/13 - 11:35pm

Just installed a Shimano 11 speed…today during a group “Computraine”r ride… I heard a load noise…..scary load! Yes, my new skinny 11 speed chain hit the lifting pins on my 50T….Note: that during the setup; I did move my rear wheel back by about 1/2 inch….(thanks to Cervelo’s horizontal (track bike type rear hanger setup)….in other words; you pull the wheel out the back…vs…the more common drop-down and out style hangers.

Do I still have other setup options(?) maybe one option would be; to set rear wheel back an additional 1/4 inch….I’m very lucky I have that option….but would lose some seat stay aero effect….a second option: would be to off set crank to chain side….man I would hate to do that….More…there is some newer science that revels that wide peddles allow for more power!…..(I’m testing 1/4 longer axles via “SpeedPlay” now….and yes, I agree….(An engineer at Interbike last year…..claims to have tested the extra wide peddle axles…..so far only after a few days…..I agree! (Yeah…I could use shorter axles on the drive side…thus allowing me to off set my crank to the chairing side!! not fun options or one’s that I what to do….
thom

Simon Paterson - 11/25/14 - 11:53pm

What is the main issue with extending chainstay length on disc brake road frames? What if the frame manufacturers simply followed Shimano’s guidelines of 430mm; what would be the main issues?

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