Disc Brakes on Tri Bikes

Triathlon Forum
1

this is where i’ll discuss any of the stuff i wrote about on the front page. notably disc brakes on tri bikes.

one reply to that article was, “You lost me at disc brakes. Honestly…”

i would have said, and i’m sure did say, the same thing 6 months ago (and a year and 2 years ago). but i realized that i had been thinking about this just based on my perception and intuition, and not by having a fact-based discussion.

in other words, my reaction was this FB commenter’s reaction: you can’t be serious. that’s not a valid basis for an argument.

2

Good article.

But confident descending is affected by a lot more brakes. I might even say that brakes are not as important as body CG, where you grab the handlebars, how you grab the bars, how you grip the brake levers, and how well you can maintain a solid hold those bars and squeeze the brake levers all while riding very fast at a steep downward angle on bad pavement while being rapidly decelerated. With most tri handlebars, much of this is compromised and that is before you even get to the issue of what kind of brake calipers one has.

3

you are so right. that’s why i go a little postal, in the article, on the straight pursuit bar thing. a little wayback deviation, remember when a slowtwitch did this to his ventus? cancellara put some kind of motorcycle grips or something on his. this has to be addressed, in my opinion. there ought to be a product for this. felt’s is the only one out there, at the moment.

4

Yes, that was me. Can’t believe I even need to explain this…

Drag is paramount when it comes to time trialling (and let’s be honest, most triathletes are just TTers with commitment issues). Take a look at the Ventum thread and you’ll see that that there are a lot of people waiting for qualitative data in the hopes that this frame might save 50gms of drag. In fact, pretty much every thread involving bikes espouses the benefit of a lower CdA over things like weight and aesthetics. Speed is what is important, and disc brakes are detrimental to this pursuit. TriRig has built a massive following upon brakes that don’t actually stop (naturally they’ve gotten much better, but still aren’t a patch on DA) because they reduce drag. It’s hardly a surprising trend as fiddly, spongy, and downright diabolical brakes are now a staple on TT/Tri bikes. Clearly in terms of drag disc brakes will always lose (Culprit data below), so what else to they offer?

http://road.cc/sites/default/files/imagecache/node-gallery-display/images/News/Culprit%20table.jpg
http://road.cc/…-which-are-more-aero

**Disc brakes allow you to stop faster thus saving time on technical courses - **Obvious triathlete bike-handling jokes aside, this is an obvious red herring. The number of courses in the world where any semi-competent cyclist would see the benefit over the drop in CdA is minute. If you’re talking about Johnny Chopper with more dollars than sense and the skills that match Froome’s composure, then maybe there are a couple more.

**Discs would allow for more a aero design - **Errr… no. There’s still a giant disc and caliper in the way. Triathletes don’t have to deal with UCI restrictions and yet the top tri bikes are only faster than the top UCI legal bikes at greater yaw where the bolted on bits (greater than 3:1) give an advantage. If you want properly innovative design then look at what Rafael have done with single sided forks and drum brakes (http://vonrafael.com/rafael-r-023-2/).

**Discs are the future - **Not really. They’re just fashionable at the moment as manufacturers are always looking to increase their profits (by selling us crap we don’t need). Pros and their teams are not excited for disc brakes. Quite the opposite in fact. Will you see discs on a TT bike? No. This isn’t a clincher vs. tub debate, this is aero vs. let’s add a Pep Boys spoiler to a Civic debate. If ever TT/Tri frames become a thing, you still have the problem of wheels. A disc with a disc? Really? I wonder who will be the first to develop that…

So yeah, like I said. Honestly…

5

For 1x - have to weigh aero advantage of missing stuff vs increased chain tension (more friction) and smaller chainring. I am looking at trying it for flat courses (so still a big ring) that aren’t bumpy enough to need a clutch dérailleur.

6

you are so right. that’s why i go a little postal, in the article, on the straight pursuit bar thing. a little wayback deviation, remember when a slowtwitch did this to his ventus? cancellara put some kind of motorcycle grips or something on his. this has to be addressed, in my opinion. there ought to be a product for this. felt’s is the only one out there, at the moment.

I’ll take “unnecessary modifications that make me slower for $300 Alex”. Maybe I was a hasty in assuming the terrible bike handling thing was isolated…

7

quoting myself from an interview for 220triathlon.com a few months ago:

“The dedicated triathlon bike appeals to athletes who, for the most part, are looking for every speed advantage or power saving they can find. something extra hanging out in the wind costing them watts when it’s not being used has a hard time justifying itself.
“On that basis alone it wouldn’t surprise me to see highly-integrated rim brakes survive a disc brake revolution as a performance advantage.”

but that’s just me…

8

The only thing is it’ll lead to confusing conversations like this…

“Dan, should I run a disc on that hilly course at next week’s tri or not?”.

“sure Bob, run all three”.

9

On the topic of flat versus upturned bullhorns, in a discussion about the then-new Kestrel 4000, Mark Cote discussed testing by Specialized for the Shiv TT and the difference between flat and upturned bullhorns. The aero difference between flat and upturned bullhorns was “almost immeasurable.” This was several years ago, so maybe better testing has led to different conclusions, but here is the post - Post #101 of 235.

10

do you think this issue is (or would be/could be) exacerbated by a minimum-stack-in-line-with-TT-level-stem-pedestal-the-pads-and-nothing-else scenario?

IME, not everyone wants to be a hunchback every time they’re on the bullhorns…upturns or not.

11

“can’t believe i need to explain this” and “most triathletes are just TTers with commitment issues”

you have a natural tendency toward troll-type speech, but i’ll ignore that for the purposes of the discussion.

yeah, the culprit tests make discs look pretty bad. but i’d like to see what others, who are invested in the process of making very good aero road bikes, and equally good disc brake road bikes, have to say. i wrote all the usual suspects about this. i wrote them because it seems to me that you can’t be heavily invested in road disc bike manufacture (as specialized and others are) without addressing the aero detriment of these bikes. you have to find a way to speed them back up.

what i’m hearing from these engineers, notwithstanding bikerumor’s article, is that the detriment isn’t as great as i thought it was. and this is before you do anything available to you as a bike designer when you don’t have to engineer the bike and the wheels around rim braking.

you might, in the end, be right. but the culprit test was a bike that could accept anything: bolt on rim or disc brakes. shim this, space that, it goes from 135mm to 130mm. this might or might not be a valid way to test a bike designed, from the get-go, as a disc brake bike.

12

“Maybe I was a hasty in assuming the terrible bike handling thing was isolated…”

i can only assume that you only ride flat TTs. for flat TTS, no problem. no need. but triathletes (who are, what did you say, TTers with commitment problems?) are often riding timed races on road race courses. it is not at all uncommon for a triathlete to face a 45mph or 50mph descent, with turns.

no one who rides courses like this downplay the quality of a bike’s handling or braking. but if you don’t ride courses like this, then, you aren’t a target of these sorts of handling imperatives.

13

“do you think this issue is (or would be/could be) exacerbated by a minimum-stack-in-line-with-TT-level-stem-pedestal-the-pads-and-nothing-else scenario?”

first, it’s not just the SC, but the SC is a specific issue because it’s 2 things at the same time: flat pursuit, and no ability to tilt the pursuit. this means that flat pursuit remains flat and there’s nothing you can do about it.

i don’t think this is a design flaw. but i do think it’s a design oversight, for these reasons:

  1. it’s very hard to control the spatial relationship between pursuit hand position and pads, both in height and for/aft, because of the immense adjustability and modularity of the SC.
  2. this is exacerbated by inability to wrestle down where the pursuit position is above/below and in front of the rider’s center of mass, and in front of the steering axis.
  3. when you race outside of madison you might find yourself on courses not contemplated by those who’ll test the bikes mostly in madision.
  4. your customers include those of every ability and morphology.
  5. your dealers will includes those who are experts and… ahem… less so when it comes to preparing these bikes for their owners.
  6. it’s not just the 5 points above, but the combinations of more than 1 point above expressed in a discrete person on a discrete course.

accordingly, i think an aftermarket solution that creates the ability to step back from the double-diamond, super-varsity horizontal pursuit set-up would be a nice alternative for some riders.

14

I’ll take “unnecessary modifications that make me slower for $300 Alex”. Maybe I was a hasty in assuming the terrible bike handling thing was isolated…

Troll factor 5.

15

“can’t believe i need to explain this” and “most triathletes are just TTers with commitment issues”

you have a natural tendency toward troll-type speech, but i’ll ignore that for the purposes of the discussion.

yeah, the culprit tests make discs look pretty bad. but i’d like to see what others, who are invested in the process of making very good aero road bikes, and equally good disc brake road bikes, have to say. i wrote all the usual suspects about this. i wrote them because it seems to me that you can’t be heavily invested in road disc bike manufacture (as specialized and others are) without addressing the aero detriment of these bikes. you have to find a way to speed them back up.

what i’m hearing from these engineers, notwithstanding bikerumor’s article, is that the detriment isn’t as great as i thought it was. and this is before you do anything available to you as a bike designer when you don’t have to engineer the bike and the wheels around rim braking.

you might, in the end, be right. but the culprit test was a bike that could accept anything: bolt on rim or disc brakes. shim this, space that, it goes from 135mm to 130mm. this might or might not be a valid way to test a bike designed, from the get-go, as a disc brake bike.

I thought that was a compliment, after all, y’all’s talk about bikes more than anything else on this forum.

You say that industry experts are saying it’s not that bad, yet they haven’t even tested it. Until last year everyone thought shaving your legs had zero aero benefit, and then boom! So yeah, conjecture isn’t the way to go on this.

Sure, the spacing could have been an issue, but are any wheel manufacturers really going to go with a new standard when so many have already been tried just to appease a niche market?

“Maybe I was a hasty in assuming the terrible bike handling thing was isolated…”

i can only assume that you only ride flat TTs. for flat TTS, no problem. no need. but triathletes (who are, what did you say, TTers with commitment problems?) are often riding timed races on road race courses. it is not at all uncommon for a triathlete to face a 45mph or 50mph descent, with turns.

no one who rides courses like this downplay the quality of a bike’s handling or braking. but if you don’t ride courses like this, then, you aren’t a target of these sorts of handling imperatives.

I ride everything from 10 mile to 12 hour TT’s on all types of roads. Hitting 50+ happens depending on the course, and quite often on training rides, and it’s not really a big deal. I wouldn’t even classify myself as a great bike handler. Truth be told I’m about as mediocre as it gets.

The aero hit on upturned base bars is real. Less than 5 degrees of tilt cost me 5.5w on flat extensions…

16

Just my $0.02, I think hydraulics over cable has a bigger impact on stopping power than disc over rim. Also, regarding your comment on modifications to the fork crown area, I’m looking at my SC and I really don’t see much (if any) low hanging fruit. Sure, without the brakes maybe it could have been shaped differently but what are we talking about here? 10 grams of drag? 30 max? Carl is here, I’m sure he could chime in.

Like another poster mentioned, a much bigger change would be along the lines of what Rafael did with their single sided fork. I was eyeing a Cannondale with a lefty fork the other day and thought “if they could make that fork aero that would be sweet.” IMO, that’s about the only legitimate application for disc brakes in tri as there’s something to be said for comfort.

With regards to good shape, I kind of wish someone could figure out how to make a more ergonomic version of the USE 1 Tula.

17

**Discs are the future - **Not really. They’re just fashionable at the moment as manufacturers are always looking to increase their profits (by selling us crap we don’t need).

Please stop this canard. There is no secret cabal in the bike industry, scheming to take advantage of unsuspecting consumers.

Road bikes w/ discs are selling for one reason - there is a consumer demand for them.

18

I thought that was a compliment, after all, y’all’s talk about bikes more than anything else on this forum.

You say that industry experts are saying it’s not that bad, yet they haven’t even tested it. Until last year everyone thought shaving your legs had zero aero benefit, and then boom! So yeah, conjecture isn’t the way to go on this.

Oh really? Specialized has https://www.youtube.com/watch?v=HXQuSnKkS-I

19

The only reason people think they need them is because they are running carbon braking surfaces. The industry has created this problem, but instead of tilting back to aluminum braking tracks which work very well they are going to try and huck disc brakes to make more money. Until they can overcome the additional weight and aero penalty it is going to be a hard sell for performance minded riders.

Such is this fashion industry. The industry wants you to have a different bike for any environment; TT, non-uci tri, road, fixie, gravel, cyclo cross, cross country, hard tail, full suspension, trail, downhill, freeride, jump, cruiser… What could be better than to make all of your current wheels obsolete.

…

20

You say that industry experts are saying it’s not that bad, ***yet they haven’t even tested it. ***

I don’t think you could know that they haven’t. And Slowman is far more likely than you do know if they have. Specialized certainly has, and I doubt they’re the only ones.

The aero hit on upturned base bars is real. Less than 5 degrees of tilt cost me 5.5w on flat extensions…

I don’t think you’ve understood that issue. It’s not talking about taking a basebar designed to be flat, and then tilting it. That’d be dumb. It’s talking about designing a basebar designed to be flat, but with an upturned bit at the end so your hand can’t slide off as easily under shock. The aero profile of that bit need not present any larger profile to the wind than your hand itself.