Viewing 40 posts - 1 through 40 (of 54 total)
  • Road Bike Braking On Steep Hills. Fast and Hard or Long and Slow?
  • andysredmini
    Free Member

    I did a road descent last night which was around half a mile long, perfectly straight, a constant 30% plus gradient and had a drainage gully every 100m or so. I started off quickly and within seconds was nearing 40mph. I soon realised this was a stupid idea and slowed right down. I could smell the rubber of the campag brakes and the rims were boiling hot. I let them cool down and set off again tried going slower which again led to cooking smelly brakes. I stopped again for them to cool and set off again at crawling pace dragging the brakes and stopping every 100m or so for things to cool. I also tried picking up speed and braking hard to scrub back down again at medium speed and slow speed but this felt harder on the brakes than dragging them.

    After trying the above options I can’t say which was the most effective. Fastest was obviously the most fun but I think I would of easily got to 50 plus mph and the gate at the bottom means there is no run off if it goes wrong.

    Any thoughts on what is the best way? I have done plenty of long steep descents before but nothing like this. They normally have corners you need to slow for or plenty of run off after the steep bit. I would of probably took the mick if someone had asked me this before last night.

    I spent part of the descent and ride afterwards wondering how discs would fare compared to rim brakes on a hill like that.

    joshvegas
    Free Member

    Edit: that didn’t go well

    Edit Edit: hard braking then coast. You need to gain confidence in exactly how quickly you can stop

    cloudnine
    Free Member

    You haven’t experienced proper road biking until you’ve got a wobble going on at around 50mph.. Stay off the brakes and just grip the top tube with your knees or check recent footage of froome for additional downhill mph..

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    andysredmini
    Free Member

    Getting up to 50 is pretty normal on a couple of hills round here but thankfully I have never had to worry about stopping or had much wobble. This was so much different to anything I have ridden up or down before though.
    I cant wait to do it again.

    mrblobby
    Free Member

    Stay off the brakes, stay loose, and bunny hop the drainage gullys 🙂

    Oh and don’t crash, it’ll really hurt.

    teamhurtmore
    Free Member

    Was just under 50mph coming down Duncton Hill this week. I was trying to keep braking steadily though but still found the corner at the bottom bloody scary with traffic coming quickly the other way!

    I would suggest that steady braking is the better method of control?

    adsh
    Free Member

    Discs not an issue.

    I regularly pedal against my disc brakes on long steep hills to maintain my power zone on training rides. With a modicum of common sense it’s absolutely fine.

    FuzzyWuzzy
    Full Member

    If I know the descent well I’ll brake when I need to (and only as hard as I need to), if I don’t know it well (and don’t have good visibility of what’s coming) I’ll drag a bit to keep speed in check then brake more as needed. In your situation if I knew it well I’d probably not be braking (and hopping the gullies) until near the bottom then brake as much as I needed to stop in good time for the gate. If bunny-hopping wasn’t an option I’d probably just coast and brake hard before each one.

    JAG
    Full Member

    Brake hard and occasionally; gets the rim to a higher temperature than slow and steady. The greater temp’ differential between the rim and air, when you release the brake, will mean it cools quicker during the off-brake periods.

    Brake soft and constant; rim will not get as hot but the heat input will be constant. The cooling rate and heat input rate will equalise at some point and then your brakes will maintain a constant temp’ until you release the brakes.

    The truth is that it doesn’t actually matter as you have the same amount of Kinetic Energy and Potential Energy to convert into heat. What matters is the volume of material in the braking surfaces; the rim and the pads. This plus the airflow and the rate of cooling afforded by the individual design of your brakes/bike will determine how hot it gets and how long it stays hot.

    In other words; brake as you see fit – the only decisions that influence how hot everything gets have already been made by the brake and bike manufacturers*

    * this assumes they do any analysis at all – which I doubt 🙂

    JAG
    Full Member

    One more thing; disc brakes contain less metal and hence will get hotter – however they will cool quicker.

    You’d need to do the maths to figure it out 🙂

    BUT it still comes down to;

    the same amount of Kinetic Energy and Potential Energy to convert into heat

    and

    the volume of material in the braking surfaces; the rim disc and the pads. This plus the airflow and the rate of cooling afforded by the individual design of your brakes/bike

    TomB
    Full Member

    Where is this hill? Sounds a great climb……

    In the lakes only hardknott has sections >30%, and they are very brief. Managed to blow a tube descending Honister on Tuesday in the heat, should have lowered pressures and been more aware of rim heat, but just about avoided the wall of doom.

    jambalaya
    Free Member

    I regularly pedal against my disc brakes on long steep hills to maintain my power zone on training rides. With a modicum of common sense it’s absolutely fine.

    Roadies really are a breed apart. Pedalling uphill against your brakes !

    As someone who is not comfortable at high speeds on a bike this braking / hills issue is another item on the list in the “against” column for road riding. As I have said before hitting a tree is no bargain at 30 mph but it certainly beats going under a car/lorry at a closing speed of 100mph

    mattsccm
    Free Member

    If you are worried why not go at a pace where one brake controls you. The other can be cooling. It does work.

    burchill
    Free Member

    jambalaya – Member
    Roadies really are a breed apart. Pedalling uphill against your brakes !

    Downhill.

    andysredmini
    Free Member

    I wasn’t worried. I Just curious if there was an accepted best way to not cook the brakes.
    Some of the above pretty much confirms what I thought that there is no right way only what you are comfortable with.

    The road has no name (that i saw) its a service road over towards clee hill.

    Next time I’m going flat out and see what happens. Nice knowing you all!

    adsh
    Free Member

    Roadies really are a breed apart. Pedalling uphill against your brakes

    Downhill and I’m not a roadie!

    puddings
    Free Member

    David Arthur and Richard Hallett, back in the days when RCUK was reasonable rather than a pure press release site, did some basic research on a range of rims (alu, top end carbon and no name carbon) following David having a blowout while descending on a set of carbon rims (admittedly on an alpine mountain road of several kilometres). I can’t find the article at the moment but they found that the risk with dragging on your brakes, especially if you have carbon rims, is the rim over heating leading to a blowout (less common on alu rims because they cool a lot quicker). The advice IIRC to brake hard and release just before coming to a complete halt with the final movement helping in the cooling.

    andysredmini
    Free Member

    Hard and late is my preferred normal method. Much more fun than dragging for the whole descent. Sometimes feels a bit out of control but all adds to the fun.

    jambalaya
    Free Member

    Downhill and I’m not a roadie!

    Now I really am totally confused.

    fifeandy
    Free Member

    Short and hard, don’t drag for any significant amount of time.
    Once you get up >30mph you can get pretty good air braking by sitting up and sticking your knees and elbows out.

    Also,
    A) Eat less cakes – shouldn’t be cooking your brakes to that extent on such a short descent unless you weigh as much as an HGV
    B) Half a mile @ 30%+ didn’t happen unless its on Strava

    pdw
    Free Member

    The truth is that it doesn’t actually matter as you have the same amount of Kinetic Energy and Potential Energy to convert into heat.

    Yes, but you have a choice of how you generate that heat: with friction in the brake or through air resistance.
    By descending at higher speeds, you can lose more to air resistance, and less through braking. Of course, you’ll get down quicker giving your brakes/rims less time to cool.

    onehundredthidiot
    Full Member

    Just finished my road ride for today the last downhill is a good 3km of 8% so easily get to 70kph. I keep off the brakes until I need them then it’s hard to scrub speed and off them as soon as possible for the corners. Saying that I definitely need to sort the back one as even on full pull the bike doesn’t stop. Think the blocks are glazed.

    thecaptain
    Free Member

    Try riding a tandem for a few years, then you’ll learn about rims overheating.

    Two solutions are (1) to ride down slowly, all the potential energy goes into the brakes, but the power dissipation is low enough that it doesn’t get too hot, or (2) go close to terminal velocity while sitting up in the wind, most of the potential energy goes into the air (wind resistance) though if you have to brake, the power dissipation may be very high. Obviously this approach is only viable when you have decent sight lines and no sharp bends.

    Somewhere in the middle, where you are going reasonably fast but not enough for wind resistance to take over, you maximise your problems.

    It doesn’t really matter all that much whether you brake steadily or pulse on and off, the main issue is how fast you’re descending overall.

    adsh
    Free Member

    Now I really am totally confused.

    As part of training for XC I ride my mountain bike on the road to get longer periods of training at a specific power/HR intensity.

    Freewheeling downhill is below that intensity so in order no to waste that time I pedal against my brakes.

    Clear?

    benp1
    Full Member

    I went down a hill on my little clown bike brompton the other day. Strava says it peaked at 41.6mph, however accurate it is. It felt quite quick, certainly span out in 3rd gear

    There’s a 90 degree right part way down, thankfully I was given the heads up. I nailed the brakes and I have to say that it really wasn’t keen on slowing down! Made it round the corner fine in the end, but the lack of power was a bit of a surprise – they’re fine for normal pootling obviously

    jakd95
    Free Member

    I think the road you’re talking about is the old incline plane that comes off the back of Brown Clee hill. It’s where the railway that brought down stone from the quarry at the top of the hill used to run. It’s not a classified road but has a right of way and is paved. And I can vouch for it being that steep and long (and dead straight too). I’ve only ridden it on the mtb with disks though, wouldn’t fancy it on a road bike.

    andysredmini
    Free Member

    @jakd95

    That’s the one. I was told by a mate that it would be unrideable so I had to go and find out.
    Looking on strava this afternoon it the hill averages 20% but hits over 30% on the steep bit. So my initial comment about it averaging 30% was a bit out. Still steep as though!

    Dibbs
    Free Member

    This is the fastest descent near me Crowcombe Descent, nowhere near as steep as the OP’s but fast all the same. I tend to stay off the brakes as long as possible and brake at the last minute but I feel much more confidant with disk brakes over rim brakes.

    fifeandy
    Free Member

    As part of training for XC I ride my mountain bike on the road to get longer periods of training at a specific power/HR intensity.

    Freewheeling downhill is below that intensity so in order no to waste that time I pedal against my brakes.

    Clear?

    Made sense the first time for those of us into the whole training zone thing. Probably makes us seem like complete nutters to the other 95% 😆

    twisty
    Full Member

    Slow and steady keeps the rims cooler because you are spreading the dissapation of energy over a greater time.
    There is also stuff to do with kinetic energy being half mv^2 and friction created on rims being proportiinal to their angular velocity which means when you are scrubbing off high speeds you are dumping heat into rim at a much higher rate than at lower speeds.

    jam-bo
    Full Member

    i guess you can always run out into the gravel pit…

    Dibbs
    Free Member

    i guess you can always run out into the gravel pit…

    ouch!!! 😉 What tyres for an escape road?

    twisty
    Full Member

    Had nightmares about what I wrote above as it is a gross over simplification.

    There are so many variables to factor in it is rather complicated.

    Go really slow and steady will keep brakes cool (as speed ->0 temperature increase ->0), but on a steep slope going at a steady 30mph might be worse than modulating between 45mph->30mph by stabbing on the brakes because this in the latter you are using more air resistance to slow you down and stuff.

    Standing up to increase air resistance will help, or getting a bit silly but large plastic carrier with handles over shoulders could make a handy parachute.

    FunkyDunc
    Free Member

    I really hadn’t thought about braking, I’ve always just done it when I’ve needed to.

    Never failed to work for me… Well apart from once when I didn’t brake enough 😆

    wilburt
    Free Member

    I wonder how the hundreds of thousands of folk riding mountains passes every month with 30km descents, switchbacks and 100m drop offs survive.

    How do you know the brakes were outside safe operating temprature?

    njee20
    Free Member

    Mountain passes are rarely that steep.

    twisty
    Full Member

    How do you know the brakes were outside safe operating temprature?

    Because as the pads started turning to goo your braking power faded and you had a serious brown trouser moment pulling the levers as hard as you can while trying to maintain control of the bike.
    Plus the burning smell.

    gofasterstripes
    Free Member

    I think this is a really interesting topic, one I pondered on the last tour.

    Breaking on NZ roads on a fully over loaded tourer was always a bit interesting*, I wondered the same thing.

    Increased air resistance sounds like a reasonable analysis – if you drop a weight over a height you liberate “an energy”. The more air resistance you thrown into the equation the less KE the brakes will have to dump. Assuming that in the braking period your rims don’t overheat or your tyres blow, then dumping the KE into thermal suddenly at a point will be a smaller total.

    I’m going with this approach in the future.

    *XTR M970s on ceramic rims will stop you VERY fast…but how much heat can the wheel handle…?

    wilburt
    Free Member

    Sorry thats BS, show me some evidence of brake failure, if brakes failed under that sort of use the manaufacturers would be out of business and getting taken to court.

    Sounds more like a nervous rider with social media tourettes.

    Mountain descents can be that steep, perhaps not the ones you’ll see on the tour but even their combination of repeated corners and overall length will put as much strain on brakes and a hill in the UK.

    andysredmini
    Free Member

    Sounds more like a nervous rider with social media tourettes.

    Who said anything about being nervous? Curious to know what is considered best practice yes. Nervous no. And we all have social media tourettes or we wouldn’t be posting on here.

    I suppose ultimately I want to go down this hill as fast as possible and want to know which way is less likely to kill me.

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