Singlespeed & Fixed Gear - downhills

Just over a week now riding my fixed and loving it.superb.What im wondering tho is pedalling action for downhills.Im basically using the fixed for the whole winter, to help my racing for next year.

Im riding a 42-16, which seems adequate for this time of year, good for the flats as im not hammering it just now and gets me working on the hills, but the downhills....?im fine up to about 30 ish mph, not too sure about cadence (still got to put on my astrale) but think I start bouncing about 160, or there abouts.

Do you guys try and pedal down hills at speed or sort of 'float' at the same cadence as the cranks are moving, so that your not really putting any effort, but sort of getting pushed??....OR just east off until your not bouncing.

one of the nice things about a fixed gear is that you can calculate your speed if you know your cadence, gearing and wheel size. well, i guess you can do this with a geared bike too, but then you have to know what gear you're in.

for example, using sheldon brown's gear calculator at http://www.sheldonbrown.com/gears/ we see that 700c at 42:16 gives you 5.5 meters rollout (aka meters development), which is approximately 18 feet rollout.

if you were doing 160 rpms, with 18 feet rollout, you would have been travelling at approximately 2,880 (160 * 18 ) feet per minute, or 172,800 feet per hour, or about 32 miles per hour.

you can flip the equation around with:
speed = cadence * rollout
cadence = speed/rollout

doing 30 mph, you were doing 2,640 feet per minute.
cadence = speed/rollout = 2,640 / 18 = 146.7
so at 30 mph your cadence was 146.

so.... if you can do all this math in your head you don't really need to put that astrale on your fixed. :D


as for pedaling down hills... i can't really help ya. on the two very steep downhills on my way into work i get off and walk when i'm riding brakeless... both have traffic lights or busy stopsigns at the bottom. everything else (easy downgrades) i tend to ride for speed and flow with traffic, not spin or cadence.

[ edit 5 minutes after posting - yes i know i'm a nerd. :p ]

This is weird to think about, because I never think about the mechanics of my pedaling action while I'm flying down a hill. :) It really depends on the situation. Most of the time I take it easy and depedal, other times I put power into the pedals until I can't spin any faster, and yet other times I let the bike spin my legs as it goes. I do the latter a lot when I'm tired. If you can't spin comfortably at 150 rpm, though, you need to work on your spin :)

meant to say, dont have a computer on the bike yet either so kinda guessing the speed..... :eek:

I find when I start to bounce, the best thing is to focus on rounding out the "front" of the pedal circle--say 1 o'clock to 5 o'clock. This usually means adding more force.

Of course, sometimes I just resist the whole way down and go slow. But learning to smooth out the spin has made me go faster with less effort on flats and up hills as well.

I find when I start to bounce, the best thing is to focus on rounding out the "front" of the pedal circle--say 1 o'clock to 5 o'clock. This usually means adding more force.

Of course, sometimes I just resist the whole way down and go slow. But learning to smooth out the spin has made me go faster with less effort on flats and up hills as well.

I agree with both those statements and often do either of them...

..back when I had a front brake..I'd just take my feet out of the pedals and 'coast'...haha.. a little squirrely at times ;)

When I finally got my front brakes fixed I rode the brakes endo and had the rear tire in the air.

All I could think was how cool is that to be in such awesome control.











Then of course I lost it, nearly went over, panicked, let go of the brakes, dropped the rear tire, went into a tail slide, got my foot kicked out of the pedal, jumped from the bike, sliped on my look soles and fell on my @$$. Once I was sure no one was looking I curled up into a ball and rolled around in pain.

Of course, I'd never admit this out loud. But we all learn.

See, brakes causing accidents instead of preventing them!! :D

A young friend of mine who raced in Belgium a couple of years ago said someone over there told him to just relax you legs and let them fly with the pedals. Guess that would work up to a point. Seems to me that in extreme cases your legs could be moving fast enough that the slightest misalignment, while spinning so fast or when trying to regain control, could cause you some instant joint damage.
FWIW,
Raymond

I think of myself as cowardly with respect to long steep downhills. I have admiration for those TDFers who go hell-bent-for-leather down the steep mountain passes however. I ride a 70 inch gear and was curious how I would react when I came to the long down hill on the escarpment for the first time. I ended up copping out and clamping on the front brake for most of the descent.

I do not have a cadence monitor anymore, but I think that I have hit 150 to 160 without a problem going down most of the shorter steep hill around here. I am comfortable doing this, and after awhile I came to the point where I could do them all brakeless by resisting the pedals until a point in the hill when I could unweight my pedals completely and "let her fly."

In the case of the long steep hill though, I guess I was afraid that a cadence much above that would result in my legs not keeping up with the pedals and disengaging, on one side before the other, and then heading for the rhubarb at 35 mph +.

My question is:Can control always be maintained despite the cadence if you are supple enough, or is there a limit?

I personally feel there is definitely a limit..