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Downhill braking

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  • September 25, 2019 at 10:15 pm #30145
    phototext

    Im lucky enough to have a place in Spain. Im going to buy an orbea gain for my local ride which will be 600m climb in 6km (ceros de Moro near Mijas)  I’m 65 so I don’t intend to plummet back down but will drag the brake a lot. I’m concerned about overheating. I can buy a d50 with mechanical discs or a d40 with hydraulic discs. Which would you choose? Thanks

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  • October 8, 2019 at 6:08 am #950277
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    Mybike

    Robert Hardy wrote:

    Robert Hardy wrote:
    It seems to me that continuous light breaking controlling the speed of descent to a near constant will cause fewer problems than occasional heavy breaking, The energy that is dissipated ultimately as heat will be the same in both cases, but heavy breaking will result in much higher brake component temperatures during the period of braking, whilst continuous breaking will result in a lower equilibrium brake component temperature to be established.

    That will actually create more heat. Hard short braking will work much better and produce less heat. It give the rotor fluids time to cool

    October 7, 2019 at 10:48 pm #950275
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    Robert Hardy

    It seems to me that
    It seems to me that continuous light breaking controlling the speed of descent to a near constant will cause fewer problems than occasional heavy breaking, The energy that is dissipated ultimately as heat will be the same in both cases, but heavy breaking will result in much higher brake component temperatures during the period of braking, whilst continuous breaking will result in a lower equilibrium brake component temperature to be established.

    September 27, 2019 at 5:49 pm #950273
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    Griff500

    I am 4 years younger than you

    I am 4 years younger than you, also come from the Scottish climate, and now have a similar climate to you, with most of my riding in the South of France (Ventoux is my back yard), and Southern Alps. I have no problem at all with rim brakes on steep descents, but then I bought my bike in 2016. Buying now, I would go disc, and there is little point going for the half way house of mechanical disc. Mechancal discs are a compromise I suspect you will regret later.

    As an aside, my regular riding buddy is a fast decender, and recently swapped  back to his rim braked, carbon rimmed Colnago, after a couple of years on a disk braked Roubaix. A couple of weeks ago I had to scrape him off the road on the Ventoux to Bedoin descent. I think there is a lesson there for people who ride both rim and disc. (Having said that, the Colnago is a think of beauty, and I’d take it in a heartbeat over the Roubaix)

    September 27, 2019 at 5:27 pm #950271
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    CXR94Di2

    Hydraulic brakes far superior
    Hydraulic brakes far superior. I tend to brake hard then release to let brakes cool and brake again. Hydraulic brakes allow good feel and modulation of braking effort. If you hold and drag the brakes everything will begin to cook. I upgraded to Hope 4pot calipers, with longer pads.
    I use this technique for descents like off Mt. Teide, Ventoux etc.

    Also dont let speed get too high to start with, so shedding speed is easier

    September 26, 2019 at 6:29 pm #950269
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    Drinfinity

    Tredz spec sheet on the D50

    Tredz spec sheet on the D50 has Shimano mechanical brakes, which given the visible group set is Claris level, will be single sided . 

    September 26, 2019 at 5:46 pm #950267
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    ktache

    Paul’s Components make the

    Paul’s Components make the Klamper, which is probably as good as mechanical disks can get, teamed up with compressionless cables, Nokons or Avids.  Can’t be bad.  Bit pricey mind.

    September 26, 2019 at 4:16 pm #950265
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    HoarseMann

    Definitely go for the

    Definitely go for the hydraulic brakes. The tiagras have a cooling fin on the pads and as long as they are bled correctly you should have no issues with fading. You could upgrade to vented rotors too in the future (actually I think they might already be vented).

    If you are doing long descents and dragging the brakes, it’s best to alternate between dragging the front and then the rear, to allow for some cooling and give your hand a rest. The advantage of hydraulic is they require a lot less effort, so a much reduced risk of hand cramps, which can be a problem on long descents.

    I think the main reason tandems sometimes have mechanical drag brakes is because they use a friction thumb or bar end shifter to actuate the brake, and I don’t think you can get a hydraulic version.

    September 26, 2019 at 3:46 pm #950263
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    Sriracha

    Ask tandem riders what they
    Ask tandem riders what they use as the third drag brake. Last I heard they prefer a mechanical disk over hydraulic as cables don’t boil. Can’t see it will make much difference whether you “pulse” or not – physics tells you how much energy you need to lose over any given descent, and it’s all going out as heat.

    September 26, 2019 at 11:01 am #950261
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    maviczap

    Ha that’s my kind of descent!
    Ha that’s my kind of descent!

    You’ll be fine there, if you can cope with wet Scottish descents on rim brake, then discs will be a revelation.

    However I’ve had no problems using rim brakes in the Alps or Pyrenees, although only in the dry.

    Limiting factor is tyres with braking, as you’ve only got a small contact patch with a bicycle tyre.

    September 26, 2019 at 10:57 am #950259
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    IanEdward

    Quote:

    The mechanical ones will be single side actuation.
      

    Unless they are TRP Spyres, very common these days and actuate both pads.
     

    I think hydraulics are more sensitive to oveheating than cable brakes, I’ve certainly lost braking power on a steep, loose tarmac descent past the Bracklin Falls in Callander (little Scottish reference for you there!). Pulsing the brakes might work but is a pain as it effectively dictates how and when you brake, not ideal.

    I think the best suggestion is to do all your braking before each corner, then let the brakes off for a bit on the straights before repeating the process for the next corner. I did some descending in Spain and noticed how good the bike felt going through corners off the brakes! Not always possible if they are steep switchbacks though.
     

     

    September 26, 2019 at 10:40 am #950257
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    Drinfinity

    I’m even more jealous having

    I’m even more jealous having seen the video!

    September 26, 2019 at 10:04 am #950255
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    phototext

    Thanks guys. This link will
    Thanks guys. This link will give you a view of the descent https://youtu.be/qnMJEHsDZyI
    As an old fart, my gung ho attitude to descending is fading to vertigo, hence the worry about brakes. I am used to wet rim brakes in Scotland mind you.

    September 26, 2019 at 7:14 am #950253
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    Drinfinity

    Sounds like you have a great

    Sounds like you have a great plan with the Spanish pad!

    Hydraulic discs every time.

    The mechanical ones will be single side actuation. This means one pad is fixed, and as it wears down you have to adjust it out, otherwise it disappears inside the caliper and you have no braking. Not a problem on my kids CX bike where it gets checked over after every 30 minute race – less attractive for regular long descent.

    Tiagra 2×10 gearing will be an improvement over the Claris 2×8.

    If you are planning long descents and dragging the brake, it might be worth getting a new Ultegra finned disc or similar to dissipate the heat better, and finned pads.

    September 26, 2019 at 6:55 am #950251
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    maviczap

    Go for hydraulic, marginally
    Go for hydraulic, marginally less faff than cable, self adjusting, not susceptible to cable stretch.
    As for over heating then both will be the same, although it might be possible to boil the hydraulic fluid and loose braking ? But that’s extremely unlikely.

    Best way to avoid overheating is not to drag the brake, I wouldn’t do that with any braking system.

    Just let the bike roll, brake pre corner, then let it roll.

    If it’s a long straight descent, then pulse brake or alternate between front and rear to check your speed, if you aren’t a confident descender.

    It’s tiring on your arms to be constantly braking, and you’ll eat brake pads too.

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