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I would be surprised if it’s possible to actually boil brake fluid in the UK
I'm sure Geex would set you straight on that if he was still around.
I am not sure I have ever boiled a brake in the UK. I certainly did when I first started going to the Alps.
If the bike is upright (ish) Then even on really steep terrain the front brake is the most powerful brake on the bike. As you lean over you are obviously sharing that traction with cornering so need to reduce the brake pressure.
I had a front brake hose burst at Cmwcarn DH trail one day no way I could get the bike slowed under control without the front brake, I ended up in the salad 🙂
But thing is to ride well you need both brakes, don't understand how anyone can ride just using one or the other. There are two for a reason 🙂
I’m sure Geex would set you straight on that if he was still around.
Tbf, Geex is a good rider, I'd be inclined to take his opinions a lot more serious than some of the Last of the summer wine types on this thread! 🙂
Geex is the biggest skidder I've ever seen. He's the only person I know that can throw up dust from his tyres when it's muddy. Not sure if he's actually aware that he has a front brake tbh
I’m with TJ, having to stop on the steep stuff on Stage 2 at the Naughty Northumbrian last year was a front brake affair, back was skidding instantly but I could easily stop, on damp clay and roots, with proper front use.
I wasn’t aware we had to consider actually stopping
That's not what I was getting at, I was pointing out that for all everyone seems to think that as soon as it gets techy your front brake doesn't work I was still managing it on S2. Plenty of folk fishtailing about the place nearly making a mess of themselves proving me right too.
I'm trying to stick to the actual point of the thread rather than getting into a slagging match; that is you should be using your front brake for control far more than you probably think and "compensating" for dragging with larger rear rotors (to the point of being bigger than the front) is just very bad practice and only serves to reinforce bad habits. We all start somewhere but even in the alps this very much 'back of the pack also ran' never managed to boil his brakes with a 180 rear. You don't need bigger rotors, just better skills, if you're pushing your hardware that hard you're riding beyond your limit.
As ever, the topic has drifted off course, I canny be ****ed any more tbh.
I came across a thread earlier whilst searching, was 9 years old, was a wee reminder of how this place used to be before it became an echo chamber.
you should be using your front brake for control far more than you probably think and “compensating” for dragging with larger rear rotors (to the point of being bigger than the front) is just very bad practice and only serves to reinforce bad habits.
Yes.
Geex is the biggest skidder I’ve ever seen. He’s the only person I know that can throw up dust from his tyres when it’s muddy. Not sure if he’s actually aware that he has a front brake tbh
My lad was the same until I made him start paying for his own tyres... front brake seems to be for switchback endo's only... last time at FOD he deathgripped the whole of Endo... and didn't crash till the very end (but only due to his mates Dad being on the trail)
This is easily put to the test.
Yep it's pretty easy to test and no special equipment needed. All anyone needs to do is get a top 10 in DH or Enduro at international level then they can lecture on "correct technique".
Except (and willing to take advice from Tracey or anyone else with the same race record) your likely to find out that every pro has different technique.... just like some prefer Shimano vs SRAM vs Dirtisimo etc. or if you're Danny H and it's raining you just don't use them (not convinced he uses them much anyway)... I noticed several of the Atherton team are not using Dirtisimo on their bikes either or weren't last time I was at Dyfi.
your likely to find out that every pro has different technique
My money would be on them all running a front brake and a back brake, using both of them, and using a lot more front brake than back when they want to stop in a hurry. If you know different, please enlighten us.
I feel this sleeping bear need poking again....
Lights touch paper..stands back...
Braking force distribution myth – how do you really brake?
You need more braking power at the front than at the back: this is the usual argument many riders make for having a bigger rotor up front compared to the back. It’s true, in principle, If you hit the brakes before going into a corner, you’re guaranteed to have upwards of 70% braking force at the front and a maximum of 30% at the rear. However, the decisive factor that leads to an overheated rotor is not those short, hard braking manoeuvres, but what you do throughout the descent. While engine braking on a motorcycle slows down the rear wheel as you let go of the throttle, the only thing keeping your speed in check while you descend on a mountain bike is the brakes. That means they have to dissipate a lot of energy in the form of heat. Usually, we use the rear brake to maintain our speed, because that way the front wheel remains easy to control and is able to generate the most cornering grip. Unless you want to do a stoppie to lift your rear wheel around a switchback, you wouldn’t normally want to lock up your front wheel. The constant friction at the rear results in significantly higher temperatures, which leads to fade and ultimately to overheated brakes and discoloured rotors.
DrP
Oi!
the only thing keeping your speed in check while you descend on a mountain bike is the brakes.
And aerodynamic drag (plus mechanical friction, but aero is much bigger). On a straight road descent, you will eventually hit a terminal velocity if you are brave enough to not use any brakes. In that case, 100% of your energy is being dissipated through aero drag and mechanical friction. In a more realistic situation, the faster you go, the greater the proportion of energy dissipated through aero drag, so a smaller proportion is dissipated through the brakes. However, because you are going faster, this entails more power (because power = force x speed). This means that the power of the braking (i.e. energy dissipated/time) will not decrease proportionately to the lower proportion of energy dissipated. On top of that, at higher speed, there is much higher airflow around the rotor, so the brakes can dissipate heat more quickly. But, if you drag the brakes for long periods, that heat will be conducted into the brake pads and then into the caliper, whereas if you apply the brakes in short bursts with a brief pause, air can circulate between the pad and rotor and cool the pad surface. So, it's much more complex than that silly clickbait article makes out.
Usually, we use the rear brake to maintain our speed, because that way the front wheel remains easy to control and is able to generate the most cornering grip.
A really clever way to avoid this problem is to do your major braking on straight sections and limit your braking in turns to just balancing the bike rather than bleeding off serious amounts of speed.
Unless you want to do a stoppie to lift your rear wheel around a switchback, you wouldn’t normally want to lock up your front wheel.
I've never seen anyone do a stoppie by locking up the front wheel. The thing with brakes is, you don't have to lock them up for them to slow you down. You can modulate the front brake so that it slows you down without locking up or causing a loss of control. The idea that touching your front brake is going to sent you out of control is just silly.
don't know if you're joining in the trolling/needless continuation, Hols2? Either way, go on then:
the article is specifically about enduro mountainbiking. Aero drag is not going to be worth factoring in as a braking force on steep, tech terrain.
Don't know if you've read the rest of the thread, perhaps not. Not always possible to do all your braking in a straight line if the track you're riding is steep and doesn't have any/many straights. And a lot of them don't.
Don't know if you're getting hung up on the difference between and endo and a stoppie? If you are, imagine the author isn't, or that he wrote endo instead. You do an endo by locking up the front wheel. It's how you do it. The only time when you'd want to do it on a descent is on a tight switchback when you want to pivot around the front wheel. Yo do it when you're upright and when the front tyre has enough grip on the ground to keep it from breaking away. If there isn't, and it's less likely that there is if you're not upright, the front will wash out and you'll almost certainly fall off.
Not always possible to do all your braking in a straight line if the track you’re riding is steep and doesn’t have any/many straights. And a lot of them don’t.
The steeper the trail, the more you need to rely on your front brake because the rear locks very easily and you can't control the bike very effectively on a steep descent with the rear wheel locked (you'd see that was discussed earlier if you read the whole thread). Even very tight, steep trails have short transitions between turns. This is when you can most effectively bleed off speed by using your front brake. The point isn't that you should never use your rear brake, it's that dragging your back brake all the way down a hill because you think you'll crash if you touch the front brake is really bad advice. That article is nonsense.
Don’t know if you’re getting hung up on the difference between and endo and a stoppie? If you are, imagine the author isn’t, or that he wrote endo instead.
I don't have to imagine anything, I can read what he wrote, which is nonsense.
Unless you want to do a stoppie to lift your rear wheel around a switchback, you wouldn’t normally want to lock up your front wheel.
You can read maybe, but there's a comprehension failure, unless you've not quoted some context you have an issue with.
Not a lot wrong that statement at all. You don't want to lock up the front wheel while descending except in about one particular circumstance. What wrong with that?
It's just not very relevant. Locking the wheel (deliberately) doesn't really have much bearing on the rest of the thread.
Not wanting to lock the front is exactly what most of the thread is about. For the sake of completeness, he points out the one circumstance where you do want to.
Advising average riders that they should put a smaller rotor on the front is really, really bad advice.
TBF to the author of the article he does say that the one rider he's talking about has gone from a stock bike with 200/180 front rear to 220/220 both ends, and then settled on 200/220 front rear. So while he has strictly speaking "downsized" his front rotor, he's actually overall just increased the size of his rear rotor.
Personally I'd say that braking on very steep sections has as much to do with ground condition, tyres, body position, and confidence as well as it does on brakes, and that nothing beats practising
TBF to the author of the article he does say that the one rider he’s talking about...
One rider, eh. Excellent basis for a tech article.
You can easily boil dot fluid. I have done it in as little as a couple of hundred yards. Drag one brake dow a steep descent at walking pace. Funnily enough it was the front.
Funnily enough it was the front
Probably would have been ok if you’d used a little more rear with it 😀
I had no rear brake.
You can easily boil dot fluid. I have done it in as little as a couple of hundred yards. Drag one brake dow a steep descent at walking pace. Funnily enough it was the front.
Would be interesting (seriously) to try and replicate that with different grades of fluid, and also with old, contaminated fluid. I've never boiled a brake on a bike (did it in a car once), and don't regularly flush the fluid so I have no idea how close to the limit they are. IIRC, Dot 5.1 fluid has the highest boiling point, followed by DOT4, then DOT 3. Would be interesting to see if the difference is actually observable in the real world, under controlled conditions.
"IIRC, Dot 5.1 fluid has the highest boiling point, followed by DOT4"
Yup, though a good dot 4 can exceed the spec for dot 5.
Thing is though, you don't have to boil fluid to have your brake act up. Pads can cause issues way below boiling point, but people always tend to just assume they've boiled the fluid. To get up to actual boiling points in the fluid, you'll usually see the discs start to discolour first (which happens somewhere close to 300, but not all of that gets to the fluid, and of course heat conducts away through the rest of the fluid) so it's a pretty good rule of thumb that if your discs look good, and your fluid is in decent condition, you didn't actually boil it and you want to look elsewhere for your issue.
(I've had rotors way hotter than this without actually losing any noticable braking, I suspect because those particular brakes had fairly insulating pistons so even though the friction surfaces were way up into the 300s, the fluid never was)
The really important thing is dry vs wet tbh. Like, I use an inexpensive, pretty much base spec 5.1 which boils at 280 dry, but wet it's only 180. 280 is doable but you have to work at it, most quality brakes won't do it except in extremes. But 180's obviously very different. It's not so much "100 degrees less", it's "within easy overheating range" and "not within easy overheating range".
But, dot 4's minimum spec is 230/155 so dry/new dot 4 can easily outperform tired dot 5.1. dot 5.1 seems more wet resistant ime but the bottom line is both types are absolutely fine when fresh and absolutely crap when wetted out, and will spend most of the time somewhere close to absolutely fine.
And then you add in the variable quality of your bleed, the possibility that there's some design issue in the brake seals, reservoir, whatever... And there's a lot of likely suspects out there that don't require such heat.
But on the OTHER other hand, how many bike brakes go years without bleeding? Or even replacement? I have Formulas from 10 years ago that I love but for so many enthusiasts that'll seem incomprehensibly old.
One of the times I boiled the fluid - and it did boil was a set of brakes that had not had new fluid for a while. I had a failure of the rear - seal blew and then went down a steep slope at walking pace on the front brake only - on a loaded tandem
My tandem discs are well blued
so I'm going to chip in here with my views on the topic (that actually has gone WAAAY off the OP!)
I have a 200mm front, 180mm rear. CODES, great brakes...
yes... for technical and trail riding, I agree the front does the mainstay of braking to SLOW DOWN.... but... if you're simply wanting to MAINTAIN speed without speeding up (such as riding flowy berms, or bombing down a very long alpine descent) then the REAR brake is the one to go for...
I reiterate... I'm not wanting to slow to a lesser speed... I'm wanting to MAINTAIN speed. if I drag the front then I risk my steering grip. if I drag the rear then I neither speed up or slow down, nor skid, but simply maintain speed....
I can see the logic in wanting the rear to remain cool throughout this process.
TJ... remind me...is a drag brake on a tandem on the front or rear.... ;D
DrP
Agree with that DrP.
Dr p
Modern tandems don't have drag brakes. They have discs with the big one on the front
The tandem we had was newer than the one you have and came with a drag brake. Though it was removed straight away. (Think drag brakes are more for road riding.)
It also had the same size rotors back and front. 203 Hope vented...
2x tandems here, why you wouldn't fit the largest discs you can front and rear is beyond me. We even have voice activated rear vee brakes fitted incase of any disc brake failure 😀
OK... but I didn't ask "do modern tandems cons with disc brakes" did I!
I asked which wheel the drag brake, if fitted, comes on....
anyway....
I'll let this die down a bit, then chip in with more kindling in a few days 😆😅
DrP
Also... i actually DON'T agree with the need to have a bigger rotor at the rear! I think it's not necessary for me, but I believe the science and logic FOR the argument holds truer that some of the answers given here...
We even have voice activated rear vee brakes
That was how our drag brake was set up.
I think it was faulty though as it kept "self activating" 🤣
I solved that problem by removing it.
Just as an aside to this discussion:
We used to see boiled brakes over here all the time, back in the days of Hayes 9s, Hope Minis and Avid Juicies (actually Hayes were pretty good on that front).
These days, it's very, very rare to see a boiled brake, even with the worst brake draggers. Think the only time I've seen it in the last couple of years has been with really obvious mismatches (heavy rider, cheap brakes, 160 rotors) and even then they have to be a mega brake-dragger.
I can't say I've personally noticed brake fade in years. Mostly running Hope E4s, 203 rotors both ends, organic pads.
We used to see boiled brakes over here all the time, back in the days of Hayes 9s, Hope Minis and Avid Juicies (actually Hayes were pretty good on that front).
I still have some old Hayes 9s on my commuter bike, they must be getting on 20 years old now. Still work, which is a testament to how reliable hydro disk brakes are. Modulation was always horrendous, but they never seemed to overheat, whereas Hopes (based on internet forums) were't as reliable on big descents. My theory on that was that the Hayes calipers looked like they'd been taken off a tractor, so those heavy calipers acted as a heat sink that stopped the fluid from boiling, whereas Hope and Shimano tried to get the weight down to match rim brakes, hence the stories about boiling, fading, etc.
Yeah, the Hayes pistons were phenolic / ceramic or similar too, whereas some other brands were still using metal pistons, which transfer much more heat to the fluid.
I found a set in a drawer the other day when I was cleaning out the garage. I would bet they still work too. Even found a spare piston & seal kit so I could definitely get them working!
It's been a whole week, can you believe it!?
https://www.pinkbike.com/news/bike-check-myriam-nicoles-commencal-supreme-mullet.html
Needs to learn how to brake properly, like on a motorbike. FiSiKs!!!
Needs to learn how to brake properly, like on a motorbike. FiSiKs!!!
But if you read the article, you'll see that big rotor front, small rotor rear is what pros seem to go for.
One interesting spec choices on Myriam's bike for this weekend was the choice to go for a 200mm rotor on the front and then the larger 220mm option out back, which seems to be the reverse of what we have been seeing on other people's race bikes.
Which raises the question of why she went opposite. Turns out, if you look closely at that frame, it's not possible to run a smaller rotor on the rear. So she's actually running the smallest rotors she can on both ends of the bike.
But if you read the article, you’ll see that big rotor front, small rotor rear is what pros seem to go for.
Keen to see some examples of pros running smaller rear rotors on DH bikes. Prior to the new 220mm rotors it would be very strange to see anything but 203/203mm (okay, maybe 200/200). I'm sure there's some manufacturer influence on 220mm rears too as many bikes warranties don't cover use of these.
Nope. Try again.
https://www.commencal-store.co.uk/supreme-dh-27-29-team-c2x31379307
In fact, the bike she's on is yet another new prototype. I highly doubt one of the most dialled teams on the WC DH circuit would make their World Champion a frame with a rear brake mount that doesn't allow her to use the rotor size she prefers.