long descents and overheating

[gbs]

I am committed to my first visit to the Alps next Summer. Not being the bravest of descenders I wonder if I will be at risk of overheating the wheel rims. Is there any hard data on the issue? If I want to limit speed to 60kph is there an ambient temperature threshold above which overheating becomes a real risk?

If I opt for a disc brake solution what is the all in weight penalty (different frame and wheel design included) over conventional callipers?

 

[jazzkat]

I was in the alps last summer and I am now a bit of a wimp when descending. I had no problems, just don't hold the brakes all the way down, alternate front and back brakes, let the bike roll a bit then reign it back when it's starts getting too much. It tends to be pretty cool at the tops of the mountains even if its warm at the bottom. Take some spare blocks with you (or put new ones on before you go) but I doubt you'd need them.

Enjoy the views, there's plenty of people riding up and down the cols who don't see anything they are too busy staring at the road ahead!

 

[gbs]

@jazzkat: well, that is encouraging. Were you on yr fixed gear bike?!

 

[jazzkat]

@jazzkat: well, that is encouraging. Were you on yr fixed gear bike?!

No, I took my geared road bike. It would easily have been do-able on fixed but the descents would have been harder work than the ascents

 

[Pale Rider]

Another vote for cadence braking - let the bike go, pull the speed right down, repeat as often as necessary.

Particularly effective in the Alps, because I think I'm right in saying the descents are very long rather than very steep.

 

[Jimmy Doug]

I've cycled down the Gallibier and the infamous Troll road in Norway on a fully laden touring bike with old-style rim brakes. No problem. Don't worry - should be fine. Just look well ahead, and squeeze the brakes on and off regularly.

 

[TheDoctor]

If you sit upright on the bike - hands on the tops and straight arms - you'll struggle to get much over 50 kph just on air resistance.
Then you just need to brake hard for the hairpins and all is good

 

[oldfatfool]

Same as Jimmy, dropped off of the Lauterat, Bonnet and a multitude of other long steep descents on a fully loaded bike with cantis no real bother other than making sure the bike didn't get up too much speed when hairpins where looming.

 

[Jimmy Doug]

To be honest, I find braking in the wet scarier than braking going down (most) mountains - with rim brakes, that is. The worst thing about long descents is that after several minutes of braking repetitively you start to get achy fingers. Oh, and don't forget gloves and something to cover your ears! It'll be cold whatever time of the year!

 

[fossyant]

My clubmate did Alpe D'Huez with tubs - he did have to stop part way down as the tub glue started to melt. Sticky mess.

If you don't ride the brakes then you'll be fine.

 

[Jimmy Doug]

f I opt for a disc brake solution what is the all in weight penalty (different frame and wheel design included) over conventional callipers?

If you have the choice, I'd defo go for disc brakes. Much more reliable braking - and if they're hydralic it'll be easier on you physically. Worth the very small gain of weight. If I can cycle up Gallibier with 15kg of bags, I'm sure the small added weight of disc brakes shouldn't be an issue for you.

 

[swansonj]

It is well understood that the way to get down hills without overheating is to let your speed build between corners, to maximise the amount of your energy dissipated in wind resistance, and brake only for the corners.

Which is fine if you don't mind your speed building up frighteningly rapidly. I suspect the people who say they get down Galibier or Alpe by this technique with no problems are letting their speed go up to 40+ mph. Me, I am unashamedly unwilling to go down steep hills that fast. If you want to limit your speed to say 30, I submit you are indeed likely to have rim heating problems.

 

[User269]

Your hands/wrists will give out long before your rims.

 

[TheDoctor]

Got down Ventoux at a top speed of 34 mph using exactly this technique. On a Brompton.

 

[Fab Foodie]

Got down Ventoux at a top speed of 34 mph using exactly this technique. On a Brompton.

Chapeau!

I averaged 40mph with up to 49 on the straights on a TCR, never managed to wind it over 50 sadly. Wrists and forearms where screaming in pain towards the bottom ....
Bends were awesome ..... hot, clean, smooth, tarmac, good sight-lines, PR2s .... bliss.