speed on rollers

John C.

just done 40.2 mph on my rollers with 52-12 gearing , I know some of you will have done a lot higher speed but i'm well chuffed. I was a bit worried when the HRM went over 200 .

whyamihere

I can't get much over 40, but only because my rollers start slipping on the floor if I try!

derekwatts

I reached 54mph on my rollers once, with a resistance unit attached too! But to be fair I think the belt was slipping at that kind of wattage, so it was as good as riding free rollers. Well it shows what kind of cadence the legs can reach I guess! Wish I could do that on the roads...

AntLockyer

On the turbo I have done 207rpm which = about 70mph

If I'd done that on rollers I would have fallen off.

John C.

207 WOW thats fast, to get any faster I think I'll have to bolt the rollers to the floor and maybe loose about 30 years of age.
Is there a formular for working out my cadance from my speed knowing the gearing was 52-12.

whyamihere

You can work backwards, yes.

Take your speed in km/h and divide by 0.06 to get your speed in metres per minute. Take the circumference of your wheel (the number you put into your computer divided by 1000, it will be around 2) and divide your metres per minute speed by this. You now have roughly the speed in RPM of your rear wheel. Divide that by 4.33 (52/12=4.33) and you have your pedalling RPM.

Example of 40mph:
40mph = 66km/h (roughly)
66/0.06 = 1100 metres per minute
1100/2 = 550 RPM
550/4.33 = 127 RPM

Obviously this is just an approximation, but it should get you pretty close.

DaveyL

Sheldon Brown's gear calculator says 52x12 at 120 rpm is 41.8 mph.

whyamihere

DaveyL wrote:

Sheldon Brown's gear calculator says 52x12 at 120 rpm is 41.8 mph.

For what wheel size though?

John C.

Wow I only posted the question 1/2 an hour ago Must admit I should have thought about Sheldon and it's a standard 700c wheel with a 23mm tyre on it. Many thanks.