Disk brakes and big steep hills

[smifffymoto]

Are disks still not recommended for alpine type road descents?

[NorthDave]

Why wouldn't they be? I'd rather be on my disc bike all day long in that environment.

[smifffymoto]

Overheating and brake fade are cited as the reason used to be the reason for not using them.
Is it still a valid argument against using them?

[battered]

No it's not valid, and imo never was.

Discs are resistant to fade long after any rim brakes have melted and been destroyed.

[JustinF]

just did 9 days in the alps on a fully loaded (23kg*) bike equipped with shimano 675 hydrauliccs, they got a bit hot occasionally, never faded and I died only twice.

• drop barred gravel bike loaded with tent, mat, bag, clothes etc

Edited by JustinF on Sunday 25th September 09:18

[moleamol]

DH bikes generally have bigger discs, that doesn't give more power, it's so they can cool and not get too hot/fade.

[SixPotBelly]

My road bike has 140mm Freeza rotors, and I spent three weeks in the mountains this year. I like to think descending is my thing, well more so than climbing is anyway, and despite getting carried away on every descent they never faded nor showed any signs of overheating. I don't like dragging brakes though. My preferred style is to brake hard for a hairpin, release and keep released until the next hairpin.

My 'adventure bike' (or whatever they're called this week) has more common 160mm rotors. Like Justin I just got back from the Torino-Nice Rally, bikepacking through the Alps. Biggest difference to my road bike mountain trips, aside from hauling 10kg of luggage, was half the route was unsurfaced, so much speed checking was required in between the corners on the looser, rockier descents. Again no fading at all, but the rotors did get a little warm on the longest, worst surfaced bits. But I would stop halfway down to take a few pics anyway, and let them cool off. If I hadn't, I think my hands would have got too tired too carry on long before the brakes faded.

In short, I wouldn't worry. In fact, I believe you'd be at more risk from overheating rims on a conventional braked bike than from disc brake fade. As evidenced by those I saw walking down the Colombiere on l'Etape this year...

Edited by SixPotBelly on Sunday 25th September 11:07

[wobert]

moleamol said:

DH bikes generally have bigger discs, that doesn't give more power, it's so they can cool and not get too hot/fade.

The diameter of the disc (or rather the radius) has a direct influence on the torque that can be reacted during braking.

With everything else being equal, a larger diameter disc will give greater stopping force than a smaller disc.

[Thorpy]

Who's ever said disc's aren't suitable for big (alpine) descents? Must have been one of those "stuck in their ways types" that is scared of "new" technology. Discs are vastly superior to conventional calipers in every way (apart from weight).

[battered]

wobert said:

The diameter of the disc (or rather the radius) has a direct influence on the torque that can be reacted during braking.

With everything else being equal, a larger diameter disc will give greater stopping force than a smaller disc.

It will, for any given brake caliper effort. Given however that any hydraulic disc brake can lock either or both wheels under any conditions with a modest squeeze, it's academic. Once you can easily lock either wheel, "better" brakes just mean that you can lock the wheel with less brake lever effort. If the effort required is already very small, then it's no benefit.

[smack]

Just use pads designed for high temperature - organic pads don't cut it for downhill work. No different when you take your car to the track, you use pads designed to be more resilient to heat/fade.

[SixPotBelly]

smack said:

Just use pads designed for high temperature - organic pads don't cut it for downhill work. No different when you take your car to the track, you use pads designed to be more resilient to heat/fade.

Really? I used organic pads for all the trips in my post 4 above. They cut it just fine.

[Alicat]

No problems with disks on steep hills. Did a tour of Switzerland on the road bike. Yes, they get hot, but no fade issues.

[Alicat]

No problems with disks on steep hills. Did a tour of Switzerland on the road bike. Yes, they get hot, but no fade issues.

[RGambo]

disk brake son alpine descent are far better than rim brakes in my experience. i'm a lardy 85kgs and NO fade issues at all on my shimano hydraulics. I used the standard pads that shimano provide.

[Your Dad]

If you're constantly dragging the brakes then they'll heat up and fade, disc or calipers. Learning to modulate braking and descend efficiently will help.

[battered]

Your Dad said:

If you're constantly dragging the brakes then they'll heat up and fade, disc or calipers. Learning to modulate braking and descend efficiently will help.

Certainly, but only a fool does this, surely? In situations where I have to brake constantly, say on a steep descent with poor visibility, I alternate F & R to let them cool down. Not had a problem yet, other than wearing out a set of brake shoes coming off Ventoux in streaming wet and fog. Not that anything was going to overheat that day, icing up was more likely. I had to stop and run about halfway down to avoid hypothermia.

[ecs]

I've done huge descents on my DH bike before in the past - the disks got so hot they were glowing and the mud on the disk side of the frame was caked on dry. No fade though.

[Fluffsri]

Disc LOL.

[HughG]

SixPotBelly said:

My road bike has 140mm Freeza rotors, and I spent three weeks in the mountains this year. I like to think descending is my thing, well more so than climbing is anyway, and despite getting carried away on every descent they never faded nor showed any signs of overheating. I don't like dragging brakes though. My preferred style is to brake hard for a hairpin, release and keep released until the next hairpin.

My 'adventure bike' (or whatever they're called this week) has more common 160mm rotors. Like Justin I just got back from the Torino-Nice Rally, bikepacking through the Alps. Biggest difference to my road bike mountain trips, aside from hauling 10kg of luggage, was half the route was unsurfaced, so much speed checking was required in between the corners on the looser, rockier descents. Again no fading at all, but the rotors did get a little warm on the longest, worst surfaced bits. But I would stop halfway down to take a few pics anyway, and let them cool off. If I hadn't, I think my hands would have got too tired too carry on long before the brakes faded.

In short, I wouldn't worry. In fact, I believe you'd be at more risk from overheating rims on a conventional braked bike than from disc brake fade. As evidenced by those I saw walking down the Colombiere on l'Etape this year...

Edited by SixPotBelly on Sunday 25th September 11:07

Just out of curiousity are you a powerfully built company director or a lithe whippet of a cyclist? Or put another way, if I were doing similar on my Shimano 675s with 160 discs trying to stop my lardy near 100kg do you think I'd have a problem!