Alpine Brakes

Morning all. After an Alps trip this summer where I was repeatedly cooking my brakes, I need to make sure the same doesn’t happen next time (zero back brake into steep “back-country” corners at Alpine speeds wasn’t much fun)!

So what do I do? Current setup are XTR 4-pots front and back with a 200mm rotor up front and 180mm rotor out back. No problems with the front brake but the rear was pulling to the bar halfway down a run. Had it bled after day 1 but it was still pretty temperamental for the next few days.

Options are:

– give my current brakes a total service and upgrade the rear rotor to a 200mm. The rears were absolutely cooking – will a bigger rotor cure that? What about pads? What should I be using for long alpine descents to keep the heat down?

– change them for something else? Just read a grouptest which reckoned Hayes Dominions are great but the same test also raved about the XTs/XTRs.

What I don’t want is to head out to the Alps with dodgy brakes again!

A bigger rotor will help, a thicker rotor will also help. There’s also things like the finned pads and ice Tec rotors

If you’re cooking 200mm 4 pot XTRs then I’d spend the next year working on not dragging your rear brake all the time. You could try 220mm rotors on them or different pads. You could run a 220mm on the back maybe? I know a few people have for places like the Alps.

The Mavens are supposed to be very good and powerful brakes, but I would have thought that even they’d get too hot if constantly dragged down alpine descents.

Bigger rear rotor first thing I’d try. and better pads, like Galfer green

 No problems with the front brake but the rear was pulling to the bar halfway down a run. Had it bled after day 1 but it was still pretty temperamental for the next few days.

This is a feature with Shimano.

Someone will be a long to tell you you’re an idiot who doesn’t know how to bleed brakes properly. You need to do them by lamplight at the crossroads at midnight or something.

Similar issue here.My brake set up – Zees with 203/180 2.0mm Magura rotors, Uberbike Race Matrix pads – worked great in normal/UK use, but inadequate when I rode Les Arcs this summer. I suspect I’m a serial brake dragger which doesn’t help things.

Since returning this summer I’ve:
– swapped to TRP Slate EVOs
– fitted 220/203 2.3mm thick rotors

I’d been using the Slate EVOs with 203/180 2.3mm rotors on my trail bike and they’d been a big improvement, hence me sticking another set on my Geometron where they’ve been ideal. Whether they’re up to Alps use or not though, I’m unsure.

Further plans:
– pads: Galfer pads once I’ve used up my current spares (but definitely before next Alps trip)
– possible change brakes again to TRP DH-R EVOs, or go all-in on V4 Tech 4s if the Slate EVOs aren’t up to the job.

+1 on adapt your braking style.
+1 on bigger rotor.
Can you get finned XTR pads?
Get a full service and fresh oil the week before you go?

Bigger = more ability to absorb and dissipate heat, the cheapest place to start is 220mm rotors, Merlin have Shimano 220mm rotors for a little over a  tenner I think these are 1.8mm or spend a little more for Uberbike/Alien rotors which are 2mm. Bigger calipers help too I went for Codes but the first thing I’d change is rotor.

200mm rear rotor, finned metal pads, a fresh bleed and you’ll be fine.

I’ve the SLX 4 pots and done hundreds of runs down the pleney steeps on them without issue. They get hot but everything does out there. I also like how well bled shimano brakes just loose power when overheating but keep the same bite point, whereas SRAM codes go back to the lever the hotter they get. But Shimano 4 pots with finned pads are more resilient than codes ime.

How heavy are you is the other question?

I splurged on some new Hope Tech4 E4s for this summer’s trip (swap from Tech3 e4), but also upsized my default 200/180 rotors to thicker 220/200 Magura e-bike rotors. Hilariously overpowered for UK riding, but gave me zero performance issues and (more importantly) zero arm/hand fatigue issues. Not a surprise as I’m only 145lb…

As others have said – technique also helps, brake less, but brake harder when you do. Sometimes difficult to put into practice on tricky natural trails, but have it in your mind to let go of the things whenever you can to give everything a chance to cool down.

“Just read a grouptest which reckoned Hayes Dominions are great but the same test also raved about the XTs/XTRs.”

I’ve got SLX on one bike and Dominions on the other. The Dominions are in a completely different league.

then I’d spend the next year working on not dragging your rear brake all the time.

In some places this isn’t an option though, It’s an easy out to say “Oh, your technique needs work” when on much of Alpine tech, if you’re not checking your acceleration,  you’re doing warp speed into the tees, or worse. XTR two pots should be capable of bringing you to a dead stop on most terrain, but if you’re struggling with a 180mm out back than the obvious swap will be a larger rotor. Brake pads are a trickier choice IMO. In theory both resin and sintered offer their own advantages and have their own disadvantages, but aftermarket options are so varied, it’s a bit of a lottery, but well bedded in fresh pads are a must. Plus if you’ve not bled the brakes in a while, fresh oil is gong to help.

when on much of Alpine tech, if you’re not checking your acceleration, you’re doing warp speed into the tees, or worse

Yes, but your front brake is the one that does most of the hard work. If you’re cooking the rear brake but the front is fine, it means you are dragging the rear. As suggested above, brake harder using both brakes, then release them briefly to cool them. This allows airflow between the pads and rotor so the pads have a chance to cool. If you continuously drag the brake, the pad is constantly being heated and never has any airflow to cool the surface.

I don’t think I need to adjust my braking style – this was on stuff that was generally where you let go of the brakes for a few seconds you were straight to terminal velocity through the trees on off-pistey type walking trails and we weren’t exactly hanging around either. Weight wise, 11stone’ish + riding gear.

I’d start by bleeding them.

Fitting a larger 2mm thick rotor on the rear.

Using Shimano finned organic pads.

Have done multiple years worth of Alpine holidays riding backcountry walking paths on Shimano brakes with a similar setup.

Never had a problem.

It’s much easier to adapt your braking style if you have reliable brakes IMO.

I run Codes with 220mm front, 200mm rear HS2 rotors for the Alps. They’re bomb proof.

I’d start by bleeding them.

Fitting a larger 2mm thick rotor on the rear.

Using Shimano finned organic pads.

Have done multiple years worth of Alpine holidays riding backcountry walking paths on Shimano brakes with a similar setup.

Never had a problem.

Thats where my head is at currently…

What pads are you using?

I was using Uber Bike Race Matrix which were fine usually but last summer I vowed never to use them again after cooking them a couple of times. I’ve gone back to OEM pads (SRAM for me) and I’ve not had an issue again.

New MAGURA GUSTAV PRO mtb brakes on test – Consistency over power

2.5mm rotors but only available up to 205mm.

If not that, then 246mm rotors front and rear https://www.pinkbike.com/news/dh-bike-tech-super-sized-brake-rotors.html

As others have said. The biggest rotors you can fit in your frame is the answer.

Big rotors and finned pads are awesome, try them… but now your Shimano brake is doing the wondering bite point thing I’d replace the whole unit as well… my experience is that once they’re unreliable a service or bleed only restores them for short periods.

I’ve heard good things about Lewis brakes. /shoulder shrug emoji/

I’ve not tried this fix, but may be of interest:

https://nsmb.com/articles/shimano-brake-bleed-and-bladder-repair/

…but yeah:

Braking technique -> Bigger discs -> Fancy fins

but now your Shimano brake is doing the wondering bite point thing I’d replace the whole unit as well

My son has just moved from XT 4-pots with what felt like a ridiculous initial bite, but wandering bite point, to Magura MT5 Pro’s. He’s loving the consistency and modulation, and is noticeably a tad faster on his Strava times….His XT’s with Uber bike Race Matrix has issue in the Alps, but a swap to Galfer or EBC pads solved the pad glazing and reducing power through a run.

may be of interest:

Ta.

there is one massive mistake you can make while trying to swap out worn Shimano brake pads; not cracking open the bleed port on the lever while pushing the pistons back into their seats

Well that explains a lot. And who knew?

Shimano brakes are well documented to be unreliable on long descents. I happily use them on a trail bike, but never in the alps.

Personally I get on really well with Sram Code RSC brakes (if you can still get them). A fresh bleed with Motorsport 320 degree dot fluid, Uber bike race matrix pads and 200mm discs let’s me drag as much as I’d like on upto 30 minute descents with zero issues, I’ve even used them on a 60lb ebike (plus 14 stone me) in the alps with zero fade or pump up. If you added 220mm rotors, you’re guaranteed no issues.

Why cooling fins don’t work on disc-brake pads – Kogel Bearings

Kogel’s perspective is that it’s not the pads that need to be kept cool, but the fluid.

They make ceramic backed brake pads to try and reduce the heat transfer.

I’m @ 100kg plus and had exactly the same issue as the OP. I was a back brake dragger and had a few boiled brake issues that were quite frankly really scary. I went from 2 pot 185s to 4 pot 200s in an attempt to cure things. It was the change in braking technique that sorted it for me.

After a couple of Alps and Spain trips, and finding the same issues as OP my recommends/what worked for me:

Biggest rotor out back you can, The dreadfully named Freeza Rotors (Shimano Ice tech) work great if sticking to Shimano brakes (as I have) but are spendy – worth it IMO.

Decent bedded-in pads – Tried Shimano but find they glaze easily so ended up with Trickstuff Power.

With those two changes not had any issues and reduced arm pump!

Funny about the few comments about re. Uber Bike pads… thats what I was using this summer…

Did a bit more research last night and am going to try the RT86 rotors (may as well chuck one on the front at the same time) with the triple layer thing to aid heat dispersion vs a solid rotor as well as full proper service and some decent, bedded in pads. Give me an excuse to make a pre-Alps trip to Golfie or something 🙂

I’d not recommend  the RT86 rotor.

They don’t last very long at all and not sure they keep things any cooler.

Better off going for a 2mm solid rotor.

I’d also disregard anyone that recommends race matrix pads.

Some of the worst pads i’ve ever tried .

I took Zees and 4 pot Deores out to the Alps last year (2 bikes).

The Deores were troublesome, probably leaking a touch at the calipers in hindsight. The Zees were brilliant with 180/203 standard rotors like yours. And this included some pretty steep stuff in Verbier.

I think there are things you can do to improve your chances of better braking, but with Shimano it’s always a bit of luck as well.

Better off going for a 2mm solid rotor.

+1, Magura Storm HC 2.0mm are inexpensive and work better with Shimano brakes than any Shimano rotor I’ve used.

Re the multiple comments about UberBike pads… I’ve had mixed results. I’d no longer recommend. Race Matrix been my go-to pad for years for MTBing, but I’m likely to go elsewhere once my current stash is finished.

His XT’s with Uber bike Race Matrix has issue in the Alps

Funny about the few comments about re. Uber Bike pads… thats what I was using this summer…

I’d also disregard anyone that recommends race matrix pads.

Previously I’ve recommended Uberbike Race Matrix but no longer would. They’ve been my go-to for years but I’ll be trying something different once my current stash is finished. Good for normal/UK use inc steeps at Golfie, Dunkeld, Pitlochry etc. My issues have all been Alps* riding. Each time I think I’ve addressed the issue here in the UK (via thicker/bigger rotors etc) and it’s only when I ride again in the Alps I discover I’ve not.

For that reason I’ll try Galfer next time – probably green front and red rear.

* ‘Alps’ for me isn’t park trails – it’s the steep off-piste, natural trails around Les Arcs and La Plagne. Glazing and subsequent squealing under hard use with a scary lever-to-bar moment on a sustained descent.

the RT86 rotors

I run these. They’re great. But I also have some solid thicker (Galfer) rotors on t’other bike, and better still… assuming weight is irrelevant to you.

But if your Shimano brake is now mullered… bin it and replace at the same time as changing rotors.

https://www.onyerbike.com/components/brakes/sram-disc-brake-maven-ultimate-stealth__19517