Was flicking through some online articles, and came across this one on testing e bike brakes…

Ignore the e bike bit for now, but just found Hope’s setup really interesting!

Would be quite fun to be there when they get teeny little MTB calipers red hot!!

That’s all!

Carry on…

DrP

There is a rabbit Warren of brake testing on YouTube. This one is not very dramatic but is an A380 overweight landing 🙂

After a red run in the alps, at the bottom my brakes are very much like those of that A380 test video! I think I weigh about the same as an overweight A380 too

Interesting they recommended organic pads front and sintered rear, on motorbikes it’s common to use sintered front for more power, and organic rear for better feel/modulation.

And beyond the press do their own version. The Giant Lathe isn’t a new DH bike…

My girlfriend used to have a branding mark on her calf from one of her disc brakes. A perfect semi circle, you could even see the little vent holes and a bit of the spider.

She screamed at the time but it’s mostly gone now. About 8 years later.

I think Enduro mag used that rig for a big brake group test a while ago. Can’t find the article now!

Edit: I’m a moron

Interesting they recommended organic pads front and sintered rear, on motorbikes it’s common to use sintered front for more power, and organic rear for better feel/modulation.

I don’t know that I go along with their theory but they do explain the difference as rear wheel engine braking on a motorcycle being replaced by a load of rear brake dragging on an MTB

I don’t know that I go along with their theory but they do explain the difference as rear wheel engine braking on a motorcycle being replaced by a load of rear brake dragging on an MTB

For me, organic pads in the rear on a motorbike is because the rear brake is mostly used for slow speed control, like riding at walking-running pace, filtering through traffic where a dab of front brake would have you over – so feel over power, and of course it would never get enough heat into it that sintered pads need for the ‘bite’.

Strangely, I have felt my Hope V4 rear lacking some bite when wanting some really light braking, which is probably because I’m using sintered front and rear – they also say that organic fade much, much more than organic, and so that just says to me sintered up front as they’ll have the most heat (doing the most braking), fade less when you need them the most, and then organic rear for better control and cold bite.

Why you’d put the pad which fades the most up front, on a 20+kg bike, baffles me. Yeah, give me a pad that is going to give 20% less power halfway down a hill when I’m trying to stop 25kg of bike doing 20mph.

They even show the organic pads are slightly better from 30-15kph (0.2 seconds faster to stop), but are waaaay worse from 45kph to 0kph (1.8 seconds slower!). Their recommendation makes zero sense.

My girlfriend used to have a branding mark on her calf from one of her disc brakes. A perfect semi circle, you could even see the little vent holes and a bit of the spider.
She screamed at the time but it’s mostly gone now. About 8 years later.

Did you heat it up over the stove or with a gas torch?

Why you’d put the pad which fades the most up front, on a 20+kg bike, baffles me.

many folk even those who you would think would know better seem to fail to appreciate that most braking effort should come from the front brake

In the article they explain it is because the front gets used hard for a short period when the rider wants to brake and therefore doesn’t suffer a huge heat build up and has time to cool before being used again.  They suggest the extra bite of the organic pads is useful here.

On the rear they suggest many riders drag the rear brake to control speed for the duration of a descent leading to much greater heat build up with less cooling.  This is why they suggest sintered on the rear where the bite isn’t needed but fade resistance is.

Again I’m not saying they are right or wrong but I thought their explanation was clear unless I’m misunderstanding.  In another article they suggest running a larger rear disc for the same reasons

Switch pads to circumvent the problem rather than learn to use the brakes properly. 🤦🏼‍♀️

Onzadog
Switch pads to circumvent the problem rather than learn to use the brakes properly.

I agree with your sentiment, but if it’s possible for a brake to fade in extreme use, then it’s an inadequate brake. It’s when things get really extreme that you need your brakes most.

Maybe our pursuit of lightness has led to us under specifying our brakes.

Did you heat it up over the stove or with a gas torch?

It was at the bottom of a descent on one of our first trips to Les Gets. I didn’t see exactly how she did it but I heard her howls. At first it was a perfect purple impression of a disc like it had been painted on. It stayed that visible for at least 6 months.

Anyway…brake pads.

All these conflicting theories and indecision might explain why DH riders use two different compounds in the same caliper. Greg Minnaar definitely runs organic and sintered in the same caliper and it’s something that’s popped up in Pinkbike WC coverage a few times.

Maybe it’s better to always have one pad always at optimum temperature rather than committing your full caliper to a certain range.

In another article they suggest running a larger rear disc for the same reasons

This piece of dumbassery?
https://enduro-mtb.com/en/rotor-size-myth/

So a bunch of unskilled clowns drag their rear brakes down the Alps and overheat them, so everyone should set their bikes up accordingly. Better to just learn to use the brakes properly, surely?

Yes, that one.  I hope I stressed enough that I don’t necessarily go along with their theories and even wonder if the author is trying to win a bet on ‘the most ridiculous thing you can get readers to do’

However

Better to just learn to use the brakes properly, surely?

Yes, but ideally you don’t want to run our of brakes while you are learning do you?  All academic for me, I live in SE England with nowhere near enough elevation to trouble your average brake

Yes, but ideally you don’t want to run our of brakes while you are learning do you?

Then run 8″ rotors front and rear while you’re learning that your bike has two brakes. When you really do need to stop in a hurry, that big brake up front is nice to have.

Do the lathe tests really tell you anything? Power, sure. But what really provides the power isn’t the brake, it’s the finger, and pretty much every mountain bike brake provides more power than you need. So what matters is reliability and feel- not the amount of power but how it delivers it and how easily you can use it. But this test only exposes bad reliability if the brake is completely rubbish, and if it does show something in the synthetic test that doesn’t present in the real world, then it’s irrelevant anyway. And feel is completely a matter of personal opinion. And fade, once you get out of the territory of the completely rubbish brakes, is another finger effect

In conclusion; buy the brake you like the look of then delude yourself it’s the best ever.

So a bunch of unskilled clowns drag their rear brakes down the Alps and overheat them, so everyone should set their bikes up accordingly. Better to just learn to use the brakes properly, surely?

No…it’s not compulsory. You set your brakes up how you like. And learning how to use the brakes properly…well yes. Of course. That’s the idea. But we’re not all born pro level down hillers and it takes time and experience to acquire skills and confidence, so until then improper use of the brakes is highly likely. And wether you’re a pro or a weekend warrior if you are going down a steep descent and need to scrub some speed off and regulate your speed I’m not sure how else you’re going to do that with out using your brakes. That is kind of what they’re there for. Even the pro’s boil their brakes from time to time.

A few things.

First, the third full size photo down of the force being applied at the lever blade. It isn’t being applied at the hook of the blade, changing the leverage and brake power, making the results near worthless.

Second, those above slating Enduro Mag writers for brake dragging are probably relatively unskilled riders and/or don’t ride long, consistently steep trails. If it’s properly steep, releasing the rear brake between corners will make you gain speed so quickly that you’ll blow the next corner. Having ridden with some of the writers and the trails they ride, their opinions are valid. The argument about a bigger rear rotor makes sense, but personally 200mm front and rear would be my preference. I’ve got a rear rotor brand on my left calf from stepping off the back.

Third, organic front and sintered rear also makes good sense. Mountain bikes are ridden very differently to motorbikes.

Think that’s me done.

The argument about a bigger rear rotor makes sense

Sure, if you’re riding steep, fast descents, an 8″ rotor on the back makes sense, just like DH racers have been running for 20 years or more. That doesn’t explain why you would then put a small rotor on the front. That makes no sense.

The argument about a bigger rear rotor makes sense

Sure, if you’re riding steep, fast descents, an 8″ rotor on the back makes sense, just like DH racers have been running for 20 years or more. That doesn’t explain why you would then put a small rotor on the front. That makes no sense.

Pretty obvious, you’ve got enough power with a 203mm front but you’re overheating the rear. Not for everyone and probably only makes sense for extremes of situation IMO (assuming you’re riding well and not dragging brakes on all trails, rather than just steep, tight stuff).

But surely if you cannot release the brakes because of the steepness you ride both brakes not just the rear? I am a big scardy cat and not that good a rider but when in that sort of situation I drag both!

the only time I use rear brake only is if I want to tighten the line round a corner

Maybe a motorbike thing? I had ridden motorbikes for decades before MTBs

But surely if you cannot release the brakes because of the steepness you ride both brakes not just the rear?

It seems there is a large group of riders who:
i) Routinely ride very long, fast descents
ii) Do not realize their bike has front brakes

I do really think this is an issue right across MTBing – riders even good ones who seem unable to use the front brake.

Coming from a motorcycling background the front brake is the one I use most.

But surely if you cannot release the brakes because of the steepness you ride both brakes not just the rear? I am a big scardy cat and not that good a rider but when in that sort of situation I drag both!

I don’t think anyone is claiming nobody uses any front brake on very steep trails, just that more often than not the rear will overheat first.

The Enduro mag article was also calling for people to upsize their rear rotors, not downsize the front. Comparing to Moto brake setups is silly IMO, completely different braking needs and conditions.

It seems there is a large group of riders who:
i) Routinely ride very long, fast descents

The only time I’ve noticed my current brakes (203/203) fading is indeed on long and steep descents in the Alps (although I wouldn’t claim to have ridden them very fast). It’s the rear that fades first in that situation, I’ve not had that setup fade on long, flatter descents.

If you use the front brake properly then it will overheat first IMO as 75%+ of braking should be front wheel

Actually its very similar to motorbikes in that your limiting factor is front wheel grip both for cornering and braking and weight transfer has the same effects.

Actually its very similar to motorbikes

Totally isn’t.  Every time you shut the throttle without pulling the clutch you get engine braking at the rear wheel especially on a single or twin.  Slipper clutches were even developed to reduce this effect.

They aren’t talking about hard as possible braking, they are talking about all braking in a long downhill run.  Hard braking, controlling speed and controlling the bike.  It all uses your brakes

If you use the front brake properly then it will overheat first IMO as 75%+ of braking should be front wheel

Yes, but you don’t drag the front as much, that is the whole point. Everyone else is just saying that the rear overheats more on steep trails because it is used differently (e.g. prolonged dragging in and between steep corners), this does not mean that it’s being used to stop you for a corner – as you seem determined to point out the front is essential for this. Go take your rear brake off, try and ride a proper steep trail and report back 🙂

I’m not arguing with idiots that don’t have experience.

Using the front brake in the wrong place will make you lose traction, slide down the hill so you can’t get on the high line and possibly crash. WC DH and EWS racers also overheat rear brakes, not fronts. Are they wrong too?

I’m out.

Its just showing how little many of you understand the dynamics of braking

One more –

Slipper clutches were even developed to reduce this effect.

Actually they are for hamfisted downshifts – they do NOT slip when you roll off the throttle

I have only ever had brakes totally fail on me twice. And by fail, I mean both levers pull straight to the bar, no braking effect, instant terror. Although they happened on different occasions, they both happened at the same place, almost to the metre. The second time I was just thinking “Ah, this is place my brakes fai… Oh sh!t!”

Pila, descending from the top (top of Couis 1) to the bottom. Both times the brakes failed totally about 100m from where you finally emerge from the trail onto tarmac at the bottom, and hang right onto the road. There is a wee stream on the right. Both times, same place, same bike (Scott Gambler), same brakes (Shimano XT).

I have had brakes pump up, howl, fade, go that weird purple colour, but never total failure of front and rear brakes at the same time, and it happened twice, at exactly the same place. Both times, I put the bike in the stream, and splashed water onto the brakes (caliper and disc) and there was lots of hissing and steam, and they came back instantly. Never happened anywhere else, or on any other brakes, or on those brakes again.

Years ago, and I mean last century, my brother overtook me heading down the Super Morzine shouting “I can’t stop!”. Without a word of a lie, he was leaving a trail of smoke, like a downed Spitfire, and I chuckled as I followed him, wanting to witness the crash. This was pre-Go-Pro, or there could have been money in it.

It turned our his Hope Mini caliper had got so hot that the hose had melted at the point that it entered the compression fitting attaching it to the caliper. His attempts at braking were sending DOT fluid onto the already super-hot rotor and caliper, and it was actually smoking.

He stacked it into a bunch of leaves and stuff, and I pulled the bike out pronto as I was worried it would start a fire. My brother was fine, and it remains one of the funniest things I have seen.

That’s right about slipper clutches, they’re to stop you locking up the back wheel when not matching revs when downshifting. When you back off the throttle, you get full engine braking. As a 1000cc vtwin rider, with a slipper clutch, engine braking is huge. In 1st gear it feels like you’ve chucked an anchor out the back!

But, that rock roll isn’t a normal trail. on a regular, dirt trail, on anything steep, to much front brake will make it lock, so some degree of rear brake is also needed.

For me, I use my rear brake on the mtb as speed control – through a corner, or down a steep section of trail. But on normal trails only bad constant dragging of the rear brake will make it overheat – I find myself with a cold rear brake much more regularly than I do with an overheated rear brake. I have done it at BPW with a 160mm rotor and a 2 pot Deore brake with resin pads, but I don’t often have days when I’m doing 5500ft of descending…

On a motorbike, the rear brake is also used as speed control, not for the main braking – so they are used in quite similar ways. You don’t really use a rear brake on a motorbike over 10mph, it’s used as slow speed control.

So if you’re regularly doing massive descents, then yeah sintered pads and a bigger rotor might help, but for normal trails when the rear brake is used sparingly for speed control, I see the benefit of better cold bite with organic pads.

Go take your rear brake off, try and ride a proper steep trail and report back

I’ve tried riding a steep trail with only a back brake after ripping out the front brake hose in a crash- you just can’t do it because the wheel just skids. It’s possible with only a front brake, although having both is obviously better. The last time I did an XC race, a lot of people were still running rim brakes. It was horrendously muddy and we had to stop several times per lap to dig the mud off the bike. The good riders with rim brakes just unhooked the rear brake cables to stop them collecting mud and rode with only a front brake. I had disks, but they still demolished me on the descents. I tried keeping up for a bit, but just kept falling on my face in the mud so gave up and accepted that I’m never going to go pro.

I think there are two different failure modes with overheating brakes. One is true brake fade, where the pad material overheats. The other is boiling the fluid, which I think is what happened to Troutwrestler. The surface of brake pads have to become extremely hot to generate friction, but if you release them briefly every few seconds, air can flow through and help to dissipate heat. So rather than dragging them lightly all the way down a hill, apply them a bit more firmly then release them momentarily.

If you don’t do this, the pads and rotor are constantly in contact and the heat will be conducted through the pads into the caliper. DOT fluid has a very high boiling point and isn’t affected as badly by water as mineral oil. Mineral oil has a lower boiling point and doesn’t absorb water, so any water in the system will tend to pool at the caliper end. If you drag your brakes down a long hill, the caliper will get hot enough to boil the fluid, with the symptoms that Troutwrestler describes.

So, if you want to bleed off serious speed, apply your front brake firmly, then release it as you enter a turn. Use your back brake to balance the bike, but don’t just drag it all the way down a hill. If you are doing huge alpine descents, then run the biggest rotors you can fit. If you need a bigger rotor on the back, you also need one on the front because that’s the brake that you will need to stop in a hurry. Putting a bigger one on the back than the front really doesn’t make any sense.

I remember years ago (10+) looking at one of the factory Kona riders’ DH bike. It was running a larger rear rotor. I was told at the time that the rider (can’t remember who it was now, Fabien Barel maybe?) used the rear to gradually scrub off speed, which meant it got hotter than the front which was used mostly for hard, intermittent braking.

Aye, what would Fabian Barel know eh? He’s got nothing on the riding Gods of singletrack. 😆

But, that rock roll isn’t a normal trail. on a regular, dirt trail, on anything steep, to much front brake will make it lock, so some degree of rear brake is also needed.

It illustrates exactly why you need to use the front brake as on steep downhills you have virtually no weight on the rear wheel

Of course too much front brake will make it lock – but you get 3 – 4 times as much grip with the front wheel as the rear on any surface

Just on ~thursday I was riding down a steep wet grassy slope. any touch on the rear caused it tostart to slide but the extra grip at the front meant I could control my speed easily with the front. If I had tried to drag my rear brake I would have been sliding down the slope with the rear locked