interesting article on discs in the pro peloton

mrmo wrote:Jimmy Ray Will

mrmo wrote:

Jimmy Ray Will wrote:

How hot will a disk get from that single heavy application? Not sure.

not sure, but there are documented cases of the aluminium cores of Shimano Ice-tech rotors melting, so it must be possible to get the rotors HOT.

Yes it’s staggeringly easy to get them bloody hot, especially giving it beans – or in my case Off-road Death Grip Of Fear – downhill. That said the newer rotors in particular (e.g. Freeza) are supposed to shed heat very quickly.

Jimmy Ray Will

Jimmy Ray Will wrote:

rogermerriman wrote:

the riders being burnt by disks in a crash doesn’t sound likely.

brakes get hot, on steep twisty descents, and so on. this watching the pro races isn’t where you get pile up’s which tend to be, either at or the build up to a sprint finish, or rolling along and some one touches a wheel.

in both cases the disk should be frankly cold.

Again, from the pro races I have ridden, I have never come down in a sprint finish… crashes tend to be in and around corners or as mentioned, ‘just riding along’, but will always, always include some desperate and heavy hauling of the brakes before impact!

How hot will a disk get from that single heavy application? Not sure.

not very or it would overheat rapidly when descending, rolling down the Blorange after the TOB had come though, even after lots of speed up, slow down drag the brakes etc, following vans/bikes etc down. barely warm at the bottom.

TheHound wrote:Braking

TheHound wrote:

Braking disparity.

Formula 1 Valencia 2010 – Mark Webber Huge Crash: http://youtu.be/nyMLLnQIWho%5B/quote%5D
In fairness that’s nothing to do with the brakes. Webber didn’t appreciate how much faster his car was in the slipstream of the Lotus (and perhaps Kovalainen lifted off realising he was going to get overtaken anyway). Neither were near the braking zone, which for an F1 car is only about 100m even at that speed.

[quote=Jimmy Ray Will]How hot will a disk get from that single heavy application? Not sure.

Not too difficult to calculate – specific heat capacity of steel is about 0.5 kJ per Kg per deg C. So to raise 100g of disc by 1 deg C takes 0.05 kJ, to raise it from 20 deg C to 100 deg C takes 0.05 * 80 = 4 kJ. Now, bear in mind that the pad takes half the friction heat generated, you need a retardation of 8kJ to get 4kJ into the disc. So you need to work out what speed equates to an 8kJ total retardation for an ~80kg rider/bike combination (assuming no heat lost to the air, aero drag discounted, tyre grip and ability of the rider to pull the brake lever assumed to be infinite).

crazy-legs wrote:Quote:If

crazy-legs wrote:

If discs were so good for the pro riders, explain the poor take-up with elite CX racers?

Cost and availability.
Pro CXers have about 6 bikes each (at World Cup level) and each bike will have a couple of sets of wheels at least.

There’s also the tendency of the drop barred end of the sport to cling to tradition. I was riding a fat tubed aluminium mountain bike with an inch and an eighth steerer and an aheadset while the majority of the pro peleton were happily tooling around on ferrous frames with quill stems and inch steerer tubes.

CX is catching up, mostly via the kids. Wout Van Aert was on disc equipped superprestige at Hasselt on Saturday (although I think he was swapping between cantis and discs during the race and he is quoted on Cyclingnews as saying the “new” discs slowed him down through corners, which is a bit mysterious and off message for a SRAM sponsored rider) and MvdP at Overijse yesterday (like Lars VdH, MvdP appears to ride discs all the time). Even Nys spent some of yesterday’s Druivencross on discs (although didn’t help him make up for what appeared to be tyre problems in first lap).

hampstead_bandit, that maybe
hampstead_bandit, that maybe the case, i will agree it doesn’t happen that often been riding MTBs for 20ish years as well, it does happen. would it happen more in a close peleton maybe???

And yes one was a standing around and disc rested on calf moment.

I don’t really think it is a reason to ban them as it is rare, just one of those things to consider.

As for cuts, bladed spokes on modern wheels are probably as dangerous.

Quote:If discs were so good

If discs were so good for the pro riders, explain the poor take-up with elite CX racers?

Cost and availability.
Pro CXers have about 6 bikes each (at World Cup level) and each bike will have a couple of sets of wheels at least.
There simply isn’t the mass market availability yet to supply that level of support. And they’re pros anyway, if their brakes clog up they simply swap bikes and leave it to the mechanic to sort it all out! As with road discs, it’s going to be an innovation that is more aimed at the privateer racer rather than the elites.

Seen a few mtbers with disc rotor brands. It can happen.

More usually at the bottom of a long Alpine descent when the brake-dragger dismounts to boast about the gnar shredded and the lines pinned on the way down and inadvertently stands against the rotor. =))

monty dog wrote:If discs were

monty dog wrote:

If discs were so good for the pro riders, explain the poor take-up with elite CX racers?

The take up in the US is not so poor – but regardless of where in the world you are, they are expensive to fit to a team especially as there are times and conditions when people prefer rim brakes.. so you’re suddenly dealing with a lot more combinations of equipment if you just double up. Even in the US there was quite a bit of (quite valid) criticism of them when they first came in – as single sided, cable pull brakes were pretty much all anyone had.. and they could seriously suck as races went on. Things seem to be improving significantly with the widespread availability of twin-sided, hydraulic setups – so it will be interesting to see what happens now in Europe.

There is also an element of cross being seen as still a sport of traditions – which discs rather go against – although how much that might actually effect a pro team I don’t know… probably not a massive amount.

What few comments from professional riders actually using discs i’ve heard or read have more or less been positive across the board regarding performance – but that doesn’t mean they necessarily want to use them. That’s people for you… thankfully.