Braking on hills: scrub off speed vs riding the brakes?

[fooferdoggie]

Sorry, I would need to differ. There are several hills locally that have me paying attention. One is only maybe a couple hundred yards long, ending at a stop sign....

I bet not like this 90 degree turn about 100 feet. We walk this one on the tandem

 

[fooferdoggie]

My wife was using rear brake most of time as I discovered hard way. She said had poor braking, rear pads were totally gone (metal on metal) while front had hardly been used. I've asked her to use both brakes together, think she is now based on wear.

Ya it’s easy to use the back too much. I do on the tandem as off road the front wheel will slide out on a turn if you use the front and I got into the habit of using the back too much

 

[EMGX]

You guys crack me up. Whatever someone's (limited) experience dictates translates into the "right" or "wrong" way for everyone to think or do things, often with specious arguments for "proof" devolving into insults and offence taken.

I live on a mountain (OK, not a very big one but an actual mountain) and all of my rides from home involve both long and short steep grades down to ~sea level (the river in the upper left of the image). I've ridden bikes with hydraulic discs, mechanical discs and rim brakes (and even a coaster brake and a roller brake bike) in both dry and wet conditions. I've done intermittent braking and continuous braking. With caveats they have all worked to my satisfaction and relatively comparable effect (except the roller brake). Use and do what you want and feel comfortable with but at least consider that your experiences might not be some universal truth.

 

[Catalyzt]

This is a useful -- if gratuitously contentious -- thread. In particular, the advice about rolling slowly to cool off brakes, is very helpful. I poked around a bit since my first post here, and on the eMTB forums, there was a very similar debate, and those folks aren't stupid, either.

The consensus definitely favored intermittent braking, but with an important caveat for those of us who ride dirt: Sometimes, this is simply not possible. Descending Brand Park Motorway, and intermediate/advanced trail that has many patches of fine, loose, sierra sand, and VERY short stretches of up to 27%, I did notice that the steepest segments were not the problem-- I instinctively dumped speed before I hit them. What was treacherous was the gentler, 10%ish sandy stretches that are somewhat rutted and have modest amounts of rocks that preceded the steep segments, or that happened before other problematic terrain-- sharp or blind curves, deeply rutted trails, or rock gardens.

Instinctively, I gritted my teeth and used continuous braking in these situations, and it seems like there is some broader agreement on this. Your brakes will lock up much sooner on sandy terrain, you have to avoid anything like hard braking or you'll lose traction. The sand builds up under your wheels or something, only very light braking is possible, and intermittent braking won't take off enough speed. (If you're going from a sandy section into an easy section with good traction, it may not be a problem -- you can brake intermittently and let the bike float a bit, that's part of the fun. Same thing if the sandy section is predictable, doesn't have ruts or rocks.)

@Stefan Mikes , I wouldn't say that riding the brakes is wrong. I would agree that it is best avoided when possible.

I use both brakes on fast decents to slow down at my comfort speed.
On dirt or gravel road I only use rear brakes
Riding the brake is not advisable

Front vs. rear is a separate issue, but I do use the front brake even on sandy trails. I start by braking lightly with the front, to burn off some speed, then squeeze a bit harder for the rear. There's almost no danger of going over the bars with light front braking-- but descending a trail, I'd rather lose traction with my rear wheel than my front! If the front tire loses traction, I may not be able to turn properly. Gravel is easier-- only one gravel track that I ride, it's a circular route, and I only ride it going up!

 

[Rexlion]

I've never owned a bike with rotor style brakes yet. Calipers on my Trek Pure. FWIW I'm looking forward to joining the "rotor-y club".

 

[Gionnirocket]

better to learn to modulate your braking. on a regular bike you can use the back brake for a bit then switch to front while the back cools off. thats how I do it on the tandem on really long descents.

I do the same... Not that I have any mountains to descend or exceptionally heavy loads but for some reason I find it enjoyable
Never went over the bars, never warped a disc and never had my brakes fail so see the fun way can actually work too.

 

[AHicks]

Well, you're an exceptionally large person on a bike. You're right though, taking that into consideration.

TT

Thank you for being so gratious! You can say big, or FAT. I'm OK with that! And clearly, I can build momentum very quickly.

 

[AHicks]

I bet not like this 90 degree turn about 100 feet. We walk this one on the tandem

What's REALLY scary about approaching a hill like that is for the potential for wet leaves......

 

[fooferdoggie]

What's REALLY scary about approaching a hill like that is for the potential for wet leaves......

Yep the ground had needles and such so not taking a chance. If it was straight after it would not be so bad.

 

[Stefan Mikes]

@Stefan Mikes , I wouldn't say that riding the brakes is wrong. I would agree that it is best avoided when possible.

You are describing short and steep trail segments. Of course riding the brakes may be necessary there.
I'm talking about road descents when the bike gets at high speed very quickly. Intermittent braking is necessary there, followed by riding the brakes just before you have to stop. (It wouldn't be fine to let the brake fluid boil or fry your brakes).

Front and rear brakes: The front brake offers 70% of the stopping power, and the rest is done by the rear brake. Blocking the front wheel means "over-the-bars" but blocking the rear one often results with sideways slipping of the bike and a crash. Both brakes should be applied, sparingly.

 

[dodgeman]

I’m not sure there is an exact method that is best. I will say it’s best to keep your speed down, even if that means riding the brakes a lot. If you let off the brakes and let your speed build up all the way to say 40mph, it will build up a lot of heat to slow down again.

 

[Stefan Mikes]

I’m not sure there is an exact method that is best. I will say it’s best to keep your speed down, even if that means riding the brakes a lot. If you let off the brakes and let your speed build up all the way to say 40mph, it will build up a lot of heat to slow down again.

Intermittent braking allows you to control the speed at, say, 28 mph. That is the speed I'm familiar with. It is a rare situation I allow myself for any faster downhill ride (my maximum was 67 km/h or 41.6 mph under well controlled conditions). The worst of situations I had to handle was a downhill ride on heavily cracked asphalt. I had to ride rather slowly to maintain traction, so the brakes were being applied more often than not. After the final riding the brakes before an intersection, I stupidly touched the front brake rotor with my fingers... to actually burn them!

A controlled descent at 45 km/h (28 mph). On that specific ride, something went loose in the steering part of my Vado. It could have ended with a bad crash! I stopped there to join my brother and tightened the thing.

 

[Nvreloader]

Ya, But wouldn't it be so nice to have a 3-5 spd manual trans to use for compression going down those steep hills....LOL...........WHEN NEEDED, I am a manual user, my self....

 

[AHicks]

Ya, But wouldn't it be so nice to have a 3-5 spd manual trans to use for compression going down those steep hills....LOL...........WHEN NEEDED, I am a manual user, my self....

I've done hills steep enough where the diesel didn't have enough engine braking available! 38k motor home can be pretty interesting in this situation! Yes, you can hit the top of the descent at 30-40 mph so you can get down into second gear, but what do you do when the rpms STILL start climbing into the red? You're already red lined, so down shifting to 1st isn't a very good plan. The answer is to know how to manage your (very well maintained) brakes....

 

[Nvreloader]

+2

 

[m@Robertson]

Some good points made above. In particular: Nothing works for every situation. I noted the hill down from my home that ends in a T intersection is so steep (its slope increases about halfway down, too) I have to start very slow and lean on both brakes *hard* alllllll the way down to keep my speed from increasing past about 10 mph, which lets me come to a dead stop at the T. Any faster and I won't be able to stop. That short run strains even my super duper brake system. I typically overheat them and they start losing effectiveness - and smelling - about half of the way down (which means I am glazing the pads which is very bad), although I have been practicing lesser clamping to try and get to the bottom without that happening, with mild amounts of partial success so far.

As far as the textbook is concerned, thats all bad. But in the real world, on that particular hill, thats what has to be done. Alternate braking on that hill will result in my zooming out into traffic at the bottom of the hill as one brake, modulated to ANY degree, ain't gonna cut it.

In terms of braking technique, I found it best to rely on a method burned into my head so when I panic, it kicks in automatically. My initial brake grab is always for the rear. That gives me less overall braking performance, but is more controllable. Once weight transfer sets in, I work in the front to achieve whatever result I am going for - keeping in mind the back clamping pressure so I don't induce a skid. I get pretty much even pad wear front vs. back because of this.

And when I panic stop, I panic on the safe side when I suddenly clamp the s**t out of my rear wheel vs. my front. One time, I was cornering hard and poof out of nowhere there's a car in my lane I am turning into. I did the instinctive clamp at the time which was the front brake. This locked the front instantly and, since I was cornering, the rear wheel popped up and to the side, in the air, followed by the front wheel going up after it. Sheer luck saved me as I released the brakes, landed half-sideways and recovered (not so gracefully) without crashing. Just one of those was plenty to get me to rethink how I engage the brakes.

 

[AHicks]

Some good points made above. In particular: Nothing works for every situation. I noted the hill down from my home that ends in a T intersection is so steep (its slope increases about halfway down, too) I have to start very slow and lean on both brakes *hard* alllllll the way down to keep my speed from increasing past about 10 mph, which lets me come to a dead stop at the T. Any faster and I won't be able to stop. That short run strains even my super duper brake system. I typically overheat them and they start losing effectiveness - and smelling - about half of the way down (which means I am glazing the pads which is very bad), although I have been practicing lesser clamping to try and get to the bottom without that happening, with mild amounts of partial success so far.

As far as the textbook is concerned, thats all bad. But in the real world, on that particular hill, thats what has to be done. Alternate braking on that hill will result in my zooming out into traffic at the bottom of the hill as one brake, modulated to ANY degree, ain't gonna cut it.

In terms of braking technique, I found it best to rely on a method burned into my head so when I panic, it kicks in automatically. My initial brake grab is always for the rear. That gives me less overall braking performance, but is more controllable. Once weight transfer sets in, I work in the front to achieve whatever result I am going for - keeping in mind the back clamping pressure so I don't induce a skid. I get pretty much even pad wear front vs. back because of this.

And when I panic stop, I panic on the safe side when I suddenly clamp the s**t out of my rear wheel vs. my front. One time, I was cornering hard and poof out of nowhere there's a car in my lane I am turning into. I did the instinctive clamp at the time which was the front brake. This locked the front instantly and, since I was cornering, the rear wheel popped up and to the side, in the air, followed by the front wheel going up after it. Sheer luck saved me as I released the brakes, landed half-sideways and recovered (not so gracefully) without crashing. Just one of those was plenty to get me to rethink how I engage the brakes.

Which reinforces a point Tom brought up a while back (I think were were talking about motorcycle safety classes?). You need to KNOW how far/long it takes to stop your bike ahead of time!!! Finding out in the middle of a panic stop is NOT the right plan....

 

[justforfun]

I enjoy a steep hill with a stop at the bottom. From about 35mph I apply both brakes and come to a smooth stop. So far, so good.

 

[Jason Knight]

You should be able to figure out just by using your brain. If you have a rotor in open air, it cools one way. If you surround it with something that is highly insulating that is also almost touching it... then duh of course the air will not cool it as evenly.

I really have to question if one square inch -- or less -- of ceramic impregnated resin is "highly insulating" given they seem to get just as hot. To the point I was able to smoke them on a hill. Admittedly steel's s*it heat absorption and dissipation is why it's so prone to heat expansion/contraction issues, again the surface area to mass ratio should reduce that problem.

This is standard training for high performance (i.e. race track) driving and the problem is worse, not better, on a bicycle because the rotors are soooo thin the heat sink that is a brake rotor has far less material to work with.

In a material that has absolute garbage heat absorbing, storage, and dissipation. Irregardless of the material though, the thinner the rotor the more surface area per mass, thus the faster they can cool. Bigger thicker rotors cool slower because of their reduced surface to mass ratio. Just as thicker rotors should be more prone to warping as they cool akin to a bad temper, such as the difference between a nail and a shoe. I was a farrier's apprentice for a bit, so I know a wee bit about metalworking, forging, etc.

Again why I put thermal compound on my front rotor where the aluminum hub meets the steel disc. That contact point should be sucking the heat out of the rotor.

oh hell yes. I've got a front rotor right now I can't fix because of it.

Have you tried torching it to relax the metal?

Thats because you are all worked up and not reading carefully. I said such a technique was used when bedding the rotors. Anyone with any brains is bedding their brakes on a sleepy neighborhood road thats not an alpine descent.

Some of my sleepy neighborhoods ARE "apine descents". Though what you were quoting wasn't referring to "bedding them in" I was referring to during a normal everyday ride.

If you have to stop on a steep downgrade (like at a stoplight), you reach your 'stop' point a few cars back.

You utterly, totally, and completely misunderstood what I was saying. Which seems to go hand in hand with your not seeming to understand much of anything I'm trying to say.
I was not referring to a normal stop, I'm referring to where you're halfway down a hill and HAVE to stop because your brakes are losing grip and/or blowing smoke. How the bloody hell are you supposed to continue going down "gently" to let things cool off when you're halfway down a hill and they're overheating? That's not just directed at you either. This "oh just slow down to let them cool" s*it doesn't mean anything in places where you're choices are stop completely or go 40+.

Aka almost every "normal sleepy neighborhood" to the east of where I live.

I was NOT referring to a normal stop like an intersection.

Brake rotors are heat sinks. More material in the rotors means more heat can be sunk into them.

Which with steel is a dumb idea, as it will retain the heat too long... with the larger thermal mass again having a lower surface to mass ration, basically CREATING warping when/if you bring them up to temperature. Same fallacy as liquid cooling on PC where once you hit the thermal limit of your coolant, you're prolonging heat when the load stops. Depending on the performance regime it can do more harm than good in the long term. Reality not stopping hundreds of so-called "experts" from extolling the virtues whilst sweeping the problems under the rug. Card stacking at its finest and a way to sucker people into wasting money on a bad, high maintenance, situation dependent solution.

I thought that's why a lot of rotors I was looking at had aluminum hubs, lots of holes in them, etc. Increase the surface area and use a secondary metal with better thermal properties.

I'm a little surprised nobody has made a rotor with heat pipes on it.

Thats because you are all worked up and not reading carefully. I said such a technique was used when bedding the rotors.

The statement you quoted wasn't directed at you specifically, and again you didn't understand what was being said. Read the blood thread, nearly everyone is saying to slowly swap between front and rear when going downhill, to alternate betwixt the two.

I don't understand how you do that without going over the bars when applying enough pressure for the fronts to do... anything of value on a real hill. My saying that had / has not one single Joe-blasted thing to do with bedding in brakes.

This is why sports cars and race cars have huge brake rotors.

And why they are often two thin disks with large amounts of porting between them to force more air through and REDUCE the mass / increasing the surface area for better cooling.

Because the material used is a garbage heat sink.

Its also why things like alloy hats on 2-piece rotors decrease the severe-duty effectiveness of a brake rotor because they reduce the mass that can absorb heat (their benefit is reducing rotating mass).

Utter poppycock depending on the material, given that aluminum by mass and surface area outperforms steel anywhere from 8 to 20 : 1 depending on the alloy. Simple thermodynamics.

There's a reason copper and aluminum are preferred for heat sinks in nearly every industry.
Again steel's crappy 16..40 wm/k to aluminum's 160..240 wm/k. Aluminum, copper, and silver are your friend if you want to get rid of heat and/or prevent something from overheating. As is surface area, not mass.

It's akin to radioactivity, where a large radioactive mass emits less radiation than a smaller one due to again "surface to mass". Aka "density". Thus why radioactive dust with a larger surface area to mass ratio makes places like the Pripyat exclusion zone more dangerous on windy days. Or why walking on the surface is far less dangerous than doing something dumbass like digging trenches there. My heart bleeds for the Russian soldiers who weren't even told where they were and are now dying of radiation poisoning. Not bad enough the war crimes against an enemy without committing them against your own troops.

Bicycle rotors will rust. I keep some bikes at the coast and the progression is slow but its there.

ALL ferric metals rust, it depends on the environment. In fact stainless rusts faster in highly corrosive environments than even normal iron. Stainless just rusts slower in low corrosive conditions. Like a rope mill I worked at where the beeswax boilers for the lariat were these giant 80 year old iron tubs that needed to be replaced. The new ones were custom made out of stainless by so-called "experts" and they rusted clear through in six months. Under really nasty conditions iron > high carbon > stainless. Under mild conditions it's the other way around.

I think I mentioned it before in this thread, there's a reason seafaring ships use sacrificial anodes.

 

[fooferdoggie]

this is why Shimano makes ice tech rotors aluminum in the core and fix to help cool them.
this is what we have on our tandem.