Disc brakes

[kfjatek]

Some may have seen the recent UCI move to suspend use of disc brakes in the pro peloton: http://www.cyclingnews.com/news/safety- ... sc-brakes/

This has made me think if/what impact that might have on triathlon. Not sure use of disc brakes is in any way specified in tri regulations (national or international), and where things aren't mentioned as far as I remember the individual sports' bodies' regulations are in force.

A) Have folks seen disc brakes in the pro ITU peloton this season?
B) Has anyone seen TT/tri frames for disc brakes yet? They're bound to show up at some point - and I think actually have massive impact in my opinion on safety of TT/tri training in particular.

[Jack Hughes]

Think we need a bit more data.

They've been in use on MTB for ages... and lots of mass start MTB events have happened. And I am sure there must have been crashes...

So, do MTB riders get their legs and other dangly bits cut off? if no, why not? What is the difference between a mass start MTB and a road race? [Yes, crashes are a bit different/bigger in road races??]. Are the differences the same in triathlons?

Why are disc brakes more dangerous than chain rings? Is it because you mainly land on a wheel in a crash? Or because they are sharper?

There's also questions about if it really was the disc brakes causing the injuries.


So.. lots of questions to answer first.

I'm far more worried about open roads in tris than I am about disc brakes... and I'm not that worried about open roads.

[kfjatek]

Different speeds on road vs. MTB? Longer distance/duration of events? "Group" riding in races as part of deliberate strategy (drafting etc.)? Bigger peloton a in general? All that potentially means that road cyclists spend more time closer to one another and so the risk of contact with another rider's bike is higher. In MTB you've got mass starts, but the field thins out fairly quickly.

I can see why disc brakes could potentially carry additional risks in the peloton - guess somebody will come up with a clever way at some point (likely in the next 12-24 months) of mitigating or at least minimising that risk - smaller discs? Encased is some protective fairing? Etc.

For TTs and non-drafting tri's I think disc brakes would be an awesome idea though. The risk you see in a peloton is completely gone, the brakes themselves could potentially be more aero and - most of all - braking performance would be improved, which is a biggie in my opinion, especially if you have to emergency-brake from tucked in position.




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[IanM]

For TTs and non-drafting tri's I think disc brakes would be an awesome idea though. The risk you see in a peloton is completely gone, the brakes themselves could potentially be more aero and - most of all - braking performance would be improved, which is a biggie in my opinion, especially if you have to emergency-brake from tucked in position.

No, no and thrice no!

Disc brakes are never going to be as aero as hidden calipers in newer frames.

As for braking performance, unless you're doing mountain TTs/Tris, potentially in the wet, then you should have more than enough braking power for an emergency stop. I have no issues stopping very quickly (in the dry) even with carbon rims. And if you're in a race where you need more braking power, you probably need to be on a road bike rather than a tri bike.

[kfjatek]

Meh, you could hide the brake blocks behind the fork etc. to make them aero too

Disagree on braking performance though - and practicalities of e.g. training situations. Better braking performance of disc vs calliper brakes means they would at least partly compensate for the time it takes to move your hand/s from the sticks to the brake levers. At TT paces that may translate to a couple of metres of braking distance, which could make the difference between swearing the sh*t out of a silly driver and "woodpecking" yourself into their bonnet.




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[IanM]

Which, arguably, is more about awareness of surroundings and being ready to react than any potential extra braking performance. If I'm going along on a training ride (and in a race in fact) approaching a T junction and there's a car approaching the junction or stationary & waiting to pull out, then I'll be up covering the brakes and looking to make eye contact rather than just assuming the driver has seen me and is going to honour my right of way. Disc brakes wouldn't change that. And the performance of my rim brakes, even in a race situation with carbon rims and carbon specific pads, is decent wet or dry, as proven to myself in freezing cold hail/rain at the weekend.

Don't let the bike industry's latest marketing angle brainwash you

[Worrying Will]

Has to be said I find it hard to see how disc can cause issues as they are on the inside of the frame the same as your cassette. If you are that close you can get cut anywhere.

With regards braking I prefer my discs on the cx. But the moment the go you have had it. I found this out at a cx race.

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[Jack Hughes]

What's the difference between disc and rim?

In terms of stopping efficiency, not a lot.

The differences appear when you get hydraulic brakes: it's much easier to brake when your fingers are cold and tired. I can apply much greater pressure via the hydraulics than I can with the wire rim brakes, possibly more smoothly and reliably (although that might be just less effort).

If you are riding through mud, then the rims can get dirty: on the HotW in torrential conditions, the rims were covered in an emulsion of grit from the road, which wore the brake pads out. This wouldn't be a problem with disc brakes.

Possibly disc brakes can dissipate heat better, in a safer way. Braking on the rims causes the rims to wear, so wheels might well last longer with discs. So asking your rims to hold the tyres and be the braking surface increases the possibility of catastrophic failure (also c.f. HotW when one guy's wheel exploded due to possibly wear and tear or manufacturing defects combined with heat from excessive braking and (high) pressure from the tyre.

So, I like the idea of disc brakes in specific circumstances. But these aren't the ones that occur in a "normal" TT or triathlon. They occur a lot on the MTB, 'cross type riding, or long, long days in the mountains.

For me:

Discs:
MTB
Cross
Tandem
Touring bike (having to ride in the rain, cold, hills)/Cobble Crushing bike

Rims:
TT
Triathlon
Conventional road/fairweather road


The big dislike with disc brakes is that they start to move brake servicing towards a specialist, rather than do-it-yourself. Lots of things that require more specialist tools, vs the basic allen key, spanner for rim brakes.

[kfjatek]

If I'm going along on a training ride (and in a race in fact) approaching a T junction and there's a car approaching the junction or stationary & waiting to pull out, then I'll be up covering the brakes and looking to make eye contact rather than just assuming the driver has seen me and is going to honour my right of way.

Behaviour at junctions etc. goes without saying - I'm talking of situations where you can't see the car, e.g. if they pull out of a property on the side. Situations like that do happen and certainly raise one's heart rate pretty quickly. Anything that makes you react with *quicker* effect in situations like this must be a good thing.

Don't let the bike industry's latest marketing angle brainwash you

It's less that and more sheer logic. If we assume braking "proper" from 30kph to 0kph takes 5 secs with rim brakes and 4 secs with disc brakes, and it takes 1 sec to move your hand from the aerobars to the brake lever, disc brakes give you the "overall" performance of a regular road bike on a TT, and that has to be worth something.

The big dislike with disc brakes is that they start to move brake servicing towards a specialist, rather than do-it-yourself. Lots of things that require more specialist tools, vs the basic allen key, spanner for rim brakes.

Haven't thought about that - and it's definitely an important point.

[IanM]

Behaviour at junctions etc. goes without saying - I'm talking of situations where you can't see the car, e.g. if they pull out of a property on the side. Situations like that do happen and certainly raise one's heart rate pretty quickly. Anything that makes you react with *quicker* effect in situations like this must be a good thing.

Maybe I'm looking at this from the position of being lucky enough to have to ride about 1/5 of a mile from my front door and then I'm in countryside, so the typical things I usually have to worry about are entrances to fields and farms etc, and have good visibility on those so can assume a defensive position in the road on approach and stay in aero position. If I'm riding through a built up area where there is scope for something pulling out that I've not seen, then I'm unlikely to be in position.

It's less that and more sheer logic. If we assume braking "proper" from 30kph to 0kph takes 5 secs with rim brakes and 4 secs with disc brakes, and it takes 1 sec to move your hand from the aerobars to the brake lever, disc brakes give you the "overall" performance of a regular road bike on a TT, and that has to be worth something.

A significant number of pros on Twitter are saying there's little to no difference between the braking forces of rim and disc, because you'll reach the end of the tyre grip before you reach the end of the braking power of rim brakes. I'd imagine the biggest benefit of them is the improved modulation in the wet, but I then go back to my earlier point - you shouldn't be committed to riding fast in bad conditions in a position that compromises your ability to brake if there is the chance of needing to do an emergency manoeuvre. If that is the case, and you want the best possible braking, get on a road bike with disc brakes.