[Closed] How big are your rotors then?

IMO in the alps you want as big as you can get to stop then overheating...
Those who say otherwise probably haven't been there...

160/140 on my hardtail 🙂

Full sus has 185/165 and it did fine in the alps on fresh fluid, though I'm not really a downhiller 🙂

When i lived in the alps i had vbrakes 🙂 morgins/chatel border so it was hilly. Would have liked disks but i was poor lol

I run 185 rear and 205 up front with sintered pads. I have no issue with over heating, my pads don't glaze and they still bed in properly. The weight difference between this and the 165/185 standard option was about 40 grms. I can't think of any reason not to have big rotors. Then again, my brakes modulate very well, if they were grabby, I guess i wouldn't want big rotors. Don't know if it's size related but my pads last for ages.

I rode in the alps in 2007 with 200mm rotors front and rear, and still cooked them ! I'm not light mind. If you are big, you need BIG brakes !

Felt - 203mm front 185mm back

Giant - 160mm front and back

203mm front and 185 rear on the Nomad, 160 both ends on my Hitman, V-brake on my commuter

never had anything more than a 160mm on any of my trips to the Alps. Any bigger and you just lock the wheel. Bleed brakes before you go, you won't get fade

203 & 185 on the Hustler. Put them on for the Mega and can't be a55ed to changed them back. Weigh a few grams more now - am i bovverred

185 front and rear, would like to go a bit bigger tbh

203 front and back, I've killed saints and strokers in the alps. I only way 11 stone, and don't drag them.... perhaps I should just man up and brake less....

203 means more mass for the heat to be transferred to...

180F and 160R, never had a problem in the Alps/Pyrenees (or anywhere else for that matter).
XC race bike has 160 F&R, more than enough power and modulation there.

I've know a guide in the Alps who rides on 160/140 with no problems. It just depends on how good a rider you are and how good your brake set-up is. In fact for a while he was running V-brakes on a hardtail and he still thrashed all the guests on their 6" travel, 203mm rotored full sussers.

160 front and 140 rear , i dont need anything more my HT.

203 f/r on my 5 Spot, 160s on everything else.

160s burn your skin more quickly when they brand you on a alpine downhill crash!

160/140 here too, I'd go 180/160 on a bike for the Alps though.

203 front, 180 rear. There is no real benifit of smaller rotors in the Alps etc, but it depends on what you are riding and how fast you are doing so.

The size of the rotors has little to do with whether they'll lock up - that's more to do with your grabby hand and fine motor control.

I've found that with bigger rotors I don't have to squeeze quite so hard, and they generally have better modulation, but they're certainly not grabby. There's such a little difference between weights, and because that weight is around the centre of the wheels, I'd fit as big as you've got.

One thing worth mentioning is the brake design/manufacturer. I have a couple of sets of Juicy's with 185mm rear and they work perfect in the big mountains. However, i have just bought a bike with Hope Moto's fitted as standard and they're absolutely crap in comparison to the Juicy's. Possibly pad compound but I certainly have to pull on the lever hell of a lot harder.

What are your brakes?

I had 203's front and back in the alps, now runing 203 front, 160 rear on my HT. Never had any probs with that. IMO 203 front and back on an HT is overkill, but for riding DH go as big as you need to stop you and stop them over heating

I've got 203mm on the front of my Pitch and 185mm on the back.

On the Handjob I've got 185mm on the front and 160mm on the rear.

nice 😆

180 front and rear for the mid wales mountains (on my superlight)

Any bigger and you just lock the wheel.

As Mildred says, if you lock the wheel, you are doing something wrong.

I run 200/203/205?mm Hope M4's front and rear and they are, by far, the best brakes I've used. Changed one set of pads up front (to Reds after 4 months) in nearly 3 years, riding in Alps, Fort Bill, Inners, Wales. Original pads rear. And I drag the brakes like a complete wuss. 🙄

That said, I used to have (g)Hayes with 8in rotors and they were the worst brakes ever. Ate pads on a monthly basis and still didn't work.

Bleed brakes before you go, you won't get fade

I thought brake fade was due to pad material overheating and lowering its coefficient of friction. Bleeding the brakes shouldn't have any effect.

i am in the alps and have been riding here twice a week or so over the last year.

203 up front with 160 on back.

no i don't need more at the back. 80% or so of braking force goes through the front wheel. lay off the brakes. don't hang on the the rear, better off pumping the brake on long decents, not dragging it.

J

Bleed brakes before you go, you won't get fade

What Dibbs said. Bleeding has nothing to do with fade. That's all about heat in the pads, and the compound changing its friction coefficient as the temp rises.

With un-bled brakes you just get a spongy feel as you are compressing the gas (air) in the lines - you can't compress a liquid, which is why these hyd brakes work in the first place.

However:
What you can get with air in the lines, if it is near to the caliper is the air expanding due to the heat build-up (the high altitude / low outside pressure making this worse). You then get into the realm of the brakes binding due to the residual pressure on the pads once you have let go of the levers (vapour lock). Pads rub, heat up more, brakes fade, you squeeze harder against the bubbles, compress them more, apply little more pressure to the pads, you don't stop.

Also a good idea to make sure your brakes are bled before you stick the bike in the hold of an aircraft, or you may end up with the low pressure expanding the bubbles in the lines and forcing the fluid out - probably onto your pads.

Lots of people who don't understand how brakes work on this thread

203FR 185RR on the Demno 7
160 FR and RR on the BLT.

i have 180mm/160mm on the ht & 203mm/160mm on the full sus.the only reason i have an big front rotor is down to the wotan,s .

I don't think I brake much then as a set of sintered pads lasted me the 3 days DH'ing lats year.

Had 203 and 203 then but seem to remember the back being overkill?

Mini pinks, 160 front n rear.

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203 & 180 on the DH bike, 160x2 on the everything else.

I can't imagine running a 203 set up on anything but a pure DH bike. Its just not needed. Set the brakes up properly & learn to ride off the brakes properly. It makes such a difference.

"never had anything more than a 160mm ... Any bigger and you just lock the wheel"
"I've know a guide in the Alps who rides on 160/140 with no problems. It just depends on how good a rider you are and how good your brake set-up is"

... and how heavy you are

Grippier tyres will let you put down more braking force before locking up

Currently got 185/185 on the FS after cooking 185/160mm in the lakes, 160/160 on the HT just because the 140mm doesn't put any power down.
I ran 203/185mm in the alps just because I could get a Shimano 203mm much cheaper than an avid 185mm. I still managed to cook the rear 185mm once

On the flip side I know a couple of light riders insisting on 8" rotors F&R really struggling to get their pads to bed in, having the pad fall off the rotor. Theres not many places most people ride regularly enough to bed in new pads with excessively sized rotors.

"160 FR and RR on the BLT"
You fitted brakes to a sandwich? I'd like to see that

In the mid 90's I rode chamonix, morxine etc, on hardtails, with 60mm suspension and v brakes.

We did a big, fast descent in cham and some of our tubes blew up because the rims got so hot!!!

Old fluid has a lower boiling point than fresh.

Having said that, i think a lot of people bleed brakes far too often.

Never boiled the oros 180 f/r on my heckler, or juicys 203/185 or ones 200/180 and they have all been dragged down big hills.

Old Minis however didn't seem to cope well with heat.

Lots of people who don't understand how brakes work on this thread

Like those suggesting that you'll just lock up your wheel with bigger discs? 😆

As others have said, the point of bigger discs is better heat dissipation. Not ridden in the Alps, but done 3000ft descents in Utah where you're going pretty much straight down with nothing really technical - you need to control your speed though, so end up dragging your brakes at fairly high speed most of the way down. My 160/140 were making all sorts of horrible smells and noises by the bottom of that - they still worked, but had very definitely faded. A lot of fading on bikes is down to the pads outgassing as they heat up. If I was doing that sort of thing all the time I'd definitely go for bigger discs, even given that we were racing and had to drag the weight to the top of the hill first.

I have eight inches front and rear.

Oh no.

That sounds very wrong.

500

203 front, 180 rear on my full sus. 180 front, 160 rear on my hardtail.

Congratulations to all those who ride in the alps on small disc braked bikes, or have done it with V brakes etc. Medals deserved by you all obviously 😉

In seriousness, having now ridden for about 7 weeks in the Alps in total over the last few years, and seen so many people lose so much time riding due to problems with their brakes, I say unless you want to tempt fate, or particularly like having your hands pump up too much cos you're squeezing the levers so hard, go with a 203mm rotor on the front and at least a 180 on the back for certain. If you're a heavy guy, it's worth investigating bigger rotors still. And stay away from the sintered pads in the Alps, these will only help you boil your brake fluid very quickly! One guy I rode with my first time in the Alps had almost his entire holiday ruined because of his brakes. He'd saught advice off people on a mountain bike forum (dunno which one) and they had told him his 165/145 Hope Minis would be fine for riding in France. Still, he made sure they were properly bled and had new pads fitted before going.

Well, each day his brakes had to be re-bled. He'd boil them on every descent, and some descents were so bad he'd have to get off and walk down whilst the rest of us were riding! Personally I think it's better to be over prepared than under prepared, and I can't think of anything worse than not being able to ride something because your equipment isn't up to it (as opposed to the rider, which in my case is all too often, but at least my bikes aren't stopping me). Especially if you've paid a lot of money to be riding abroad!

Did people used to ride in the Alps with rigid bikes and cantilever brakes?

I have heard tales of people doing that, Rich. Don't believe it though - I mean how could that be possible?

Modern disc brakes aren't that heavy, I think I'll carry an extra set around with me when I go to the Alps this summer.

Can't be too careful.

I heard tell of some French riders, who...and you're not going to believe this: come down the sides of mountains on hardtail racing bikes, with as little as 80mm travel forks, sometimes wearing only the protection that a pair of Lycra shorts afford...Sometimes, and this is the really unbelievable part, they don't (I know, amazing) go straight to the bar, get shit-faced, and tell their mates how Rad they are for getting down a dirt track with 8 inches of suspension travel, and huge brakes to compensate for their lack of co-ordination...

how big? 4 foot big enough?

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ah, sorry, wrong kind of rotor 😉

Ive got 203s f+r on the sus bike and 180f 160r on the ht. Went for 203s because ive hit too many trees to risk it further and they cost no more than smaller ones. Also I really am no bothered about the less than 100g extra weight! The ht has second hand brakes so I didnt choose the size and tbh im probably not going to be taking it anywhere that i will get up to speeds that will exceed the capacity of those brakes slowing down about 17-18st of rider kit and bike.

If you can have them for no extra cost and minimal extra weight why not have them? Seems stupid not to.

I've got 180 front and 160 back, no plans to upgrade to 203/180 as i weigh about as much as a gnat, so have plenty of stopping power for my needs

nickc

Yes indeed, I've seen a few riders on similar bikes riding in the Alps. All making it down the hill in one piece etc.

I view it a bit like singlespeeding though, making things harder than you need to just cos you want to. Not my thing if you get me.

Not seen anyone ride a proper DH track on lightweight HT yet though, certainly even a good rider would really struggle over braking bumps that are 8 inches deep, large drops, big doubles etc. It's all doable of course, but to me the fun isn't simply the achievement of still being alive at the bottom. It's in being able to ride as hard/fast as you can down something and not being held back by your equipment.

185/185 on my heckler. all the stop i need plus a litle bit more. nice to be able to lock the back wheel easily to get round tight bends. tried the 160 on the back and no comparison really, plus i like having a more balanced lever feel and even pad wear??

used sintered pads last year with no boiling fluid issues and didn't even say goodbye to any pads either. In fact, they are still in the calipers and going next time!