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The Almost Complete Lowdown on Road Disc Brakes

Colnago Mapei C59 image

The Almost Complete Lowdown on Road Disc Brakes: cycling has a proud history of innovation and technical advancement: mountain bike disc brakes, power meters and electronic shifting are good examples.

Some advancements are quite substantial—disc brakes on mountain bikes for example—and some are incremental, but still worthy, improvements (shifting, brake calipers etc).

At their core though, bikes are essentially still bicycles. Short of material and parts improvements (performance, weight, construction), we are mostly left with what end up being small advancements* or adaptation from other platforms.

(*This is very true relative to, for example, phones over the last few years.)

The latest advancement would appear to be road disc brakes. There’s no doubt disc brakes were a massive improvement for mountain bikes and it’s perhaps surprising it took so long to see them on the road.
As road disc brakes become more prevalent, the obvious question becomes “should I get road disc brakes”.

Is there a problem?

I love me a good marketing campaign and like many things, cycling is no different in its striving to sell stuff to us (there’s nothing wrong with companies making money).

However, I view a lot of stuff in cycling with skepticism as to its efficacy or value. Now, that’s not to denigrate anyone buying new tech or gimmickry: that doesn’t worry me in the slightest.

What I like to ask is: “is this really necessary? Will it make my cycling more enjoyable?”

Basically you’re asking yourself “is there a problem here that needs fixing”.

The answer is subject to bias because our answer will be influenced by the cost of acquisition (amongst other factors. Probably. Cost is the main consideration though, don’t deny it. If you had endless money you’d buy almost everything like this). Example: I see value in a power meter but it’s expensive to the point where I can’t justify it (yet).

This question is important because it makes sure you’re informed and not waylaid by marketing guff (note: I am a content and information marketer and try and steer clear of guff. If you see me writing guff, call me out!)

Initial thoughts

On their surface, road discs kinda make sense, right? Look at mountain bikes: incredible stopping power without loss of stopping capability (depending on the brake), assuming the brakes have good modulation. (Modulation is effectively the ability to fully control the amount of stopping power via the level. Poor modulation basically means no brakes or locked wheel. Good modulation gives you the ability to feather the brakes, stop firmly or lock it up.)

But think a little deeper. Bent discs (squeak squeak). Bleeding. UPGRADE COSTS.

So initially, I thought, “flamin’ hell, what a lot of cobblers. My SRAM rim brakes and Yokozunas cables are epic.”

Bottom line? Not needed for 95% of cyclists.

(Let’s not confuse disc brakes on the road (RDBs) with Mountain Bike Disc Brakes (MDBs). In mountain biking there is a clear need for them.)

So let’s dive in and take a subjective look at things and get the complete lowcown .

Benefits of Road Disc Brakes

Road disc brakes offer definite performance benefits.

  • Better braking: more power (assuming good modulation)
  • Better braking in the rain
  • If you bust a spoke you have a better chance of getting home (depending on the wheel)
  • Later breaking: better descending, better in races (?)
  • Lighter wheels (how much lighter is debatable), market moves en masse to carbon
  • Less toll on arms on descents: less brake pump
  • Possible cheaper Total Cost of Ownership (TCO) as (hopefully) pads and discs are cheaper than rims

As for maintenance: my mate Tim reckons these will eventually mean lower maintenance, citing well-tuned Shimano XT hydraulic MTB brakes as an example.

And lighter wheels? Much has been made of the fact we’ll end up with lighter wheels and to an extent that’s true, as braking tracks are removed.

More mass can be moved to the center of the wheel, reducing outer weight and helping you climb faster. Additionally we can move en-masse to carbon wheels.

However, wheels will still need decent spoke counts and construction to withstand the braking force.

Frames will be stiffer in the rear end to match the wider 135mm rear wheel spacing (current spacing is 130mm) and forks will need strengthening.

Downsides of Road Disc Brakes

Remember that these downsides are on what is essentially first generation technology. As the technology becomes more mature expect many of these issues to disappear

  • Chainline and shifting issues, particularly on bikes with shorter chainstays (Bike Rumour has an EXCELLENT write up of these issues right here), bikes like the Roubaix are allegedly ok
  • More weight! An extra 340grams (until low weight wheels become available)
  • Not widely supported by frame manufacturers (Specialized, Colnago and Volagi are exceptions with Parlee catching up): expect this point to be out of date by early 2015
  • On Shimano you have to go Electronic (Ultegra and Durace) for shifters
  • SRAM hydraulic recall
  • Not many disc specific wheels (yet)
  • Mechanical servicing = pain in the bottom for some (I hate servicing my MTB discs)
  • Extra costs for compatible wheels
  • 135mm rear spacing (called 135OLD); discussed below
  • Disc specific frame with stronger forks needed
  • Potential disc drag, unless you’re set up properly (made a bit easier with dual piston brakes)
  • Unclear support by frame manufacturers of SRAM, Shimano and Formula
  • Travelling: quick release in cable lines (Formula support this) until we have internal hydraulic lines, unless you have quick release in cables, make sure you can travel with the bike (VeloNomad bike bag reviews: you’ll probably need a Scicon Aero Comfort Plus 2.0 TSA (check out my Scicon Aero Comfort 2 TSA review.)

Current road spacing is 130mm (130O.L.D. or 130OLD), disc is 135mm (manufacturers actually started moving to 135mm so they could make stiffer frames and wheels, according to SRAM at least) so your 130mm wheels won’t fit (you need a disc hub too).

You could rebuild your wheels with 135mm hubs, but really, it makes more sense to just buy disc specific wheels. I asked my mate Tim, who works at one of the biggest Specialized dealers in Oz, and is mechanic-extraordinaire about rebuilding: “waste of money”.

Let’s cover the elephant in the room: how ’bout those GIANT FREAKING HOODS.

Just look at these suckers!

SRAM hydraulic brakes hoods

SRAM hydro hoods (image courtesy of Volagi Bikes)

I personally much prefer Shimano Road hood ergonomics than SRAM, so the Shimano ones (just as big) might be ok.

They’re bloody big though aren’t they?

The Future of Road Disc Brakes

The sky’s the limit: there are some very cool possibilities though.

  • Quick release through axle similar to mountain bike (more stiffness). There are rumours this might appear next year.
  • What about a rim with no internal structure that usually supports braking surfaces.
  • Discs could shrink to 135mm or 120mm for road bike OR they will stay mountain bike size, but use materials that we can’t rely on in the dirt such as oversized carbon rotor carriers, carbon/alloy/composite, or titanium.
  • Hydro lines will be integrated into the frames better: perhaps complete internals? Might make servicing hard/impossible.
  • How about integrated brake lights in the now vacated (perhaps co-located with rear HD surveillance hoon-cam camera) caliper spot.
  • Twin front rotors for more power from smaller rotors (This apparently is already patented by Rock Shox).
  • Larger tyres.
  • Frames could get SUPER light: Specialized reckon they can get disc specific frames lighter than rim frames.

Should I Get Road Disc Brakes

Looking at the issues, what you’re really looking at, is a complete new bike.

I actually looked at a Specialized Roubaix Expert SL4 Expert (below) for my bike before settling on an SL3 Tarmac SWorks (rims) due to budgetary reasons.

Specialized Roubaix SL4 Expert Disc

Image courtesy of Bike Rumour

Obviously, the selection is quite limited for now, with Specialized, Colnago and Volagi having disc specific models and Parlee and others (Cannondale) not far behind.

So for those thinking about disc brakes on their road bike now, or for those reading this well after publishing, here’s who I think should get a road disc brakes bike.

Obviously if/when road disc brakes take off, it might become a no brainer, but initially, here’s who I think road disc brakes and disc specific bikes make sense for:

  • If you’re in the market for a new bike and who can afford it, and like the models on offer
  • If you are able to service hydro discs (or can be bothered learning) or can pay someone to do so
  • Those who need the latest tech because they will look like a pauper beside their mates at the coffee shop otherwise
  • Those who live in areas with incredibly sh$tty roads (Northern NSW folks this means you) where you could bust a spoke and need to Phone a Friend to mount a rescue (thanks Wes) or catch a taxi
  • Those who live in areas with big mountains or lots of hills generally

Here’s who don’t really need road disc brakes (especially initially). This changes if disc brakes become super ubiquitous, well supported and are cost comparative. (Good hedging bets there, right?)

  • Those who always ride on flat, smooth road for coffee shop runs (Beach Rd) – keep in mind points 1 and 2 above
  • Recreational riders
  • Most lower level racers (I can see a benefit in crit racing)

If you’re the type of person who can spare some cash, and likes to live on the bleeding edge of new tech, along with any bugs that come along with it, then go for it.

The SWorks Roubaix above and this Colnago C59 look kinda hot. Ok the ‘Nago is VERY hot.

Colnago C59 disc road bike image

Colnago C59 Disc (image courtesy of Two Hubs

For the rest of us, I think we can wait for road disc brakes to become more commoditised and any kinks to be worn out.

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by Tim Marsh

Tim is an ex Melbournite now living near Byron Bay on 10 acres, happily growing mangos, avocados and lots of other stuff, with his wife Kate, son Arthur and adorable Golden Retriever, Whiskey (RIP our 1YO G/R Poppins :( ).

2 comments… add one

  1. Any suggestions on packing the S-Works Roubaix Disc in the Aerocomfort 2.0 TSA bag with the 135mm rear frame width? Do you add some washers or something to make up the extra 5mm of width?

    1. I just added two 2mm washers, one on each side, and it seems to work fine.


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