Box Hill would kill me

[killyridols]

167 rpm max cadence!!!!

[killyridols]

just like i said.

[quote="Sean Hogan"][quote="killyridols"]just like i said.

[Dombo]

Geek alert:

Distance travelled by a 700c x23 wheel in one rev = diameter x pi = approx 720 x 3.142 = 2.26 metres per rev
Max speed = 32 mph (51kph)
= 51/60 kpm = 0.85 ie 850 metres per minute
The diameter of the wheel and tyre is a constant so 850/2.26 = 376 revs of the wheel to travel 850 metres or 1000/2.26 = 442 revs of the wheel to travel 1km
sprockets and chainrings allow us to "gear up" our pedal revs to wheel revs so 52 x 12 has a factor of 4.33 ie 4.33 wheel revs per pedal rev. Our 39 x 25 climbing gear produces a 1.56 wheel rev per pedal rev.
So at Sean's max speed of 51 kph, (850mpm) his wheel is turning at 376rpm. If his max rpm at the crank is 167 this suggests a gear ratio of 376/167 = 2.25
Assuming a standard set up he is riding on 52 x 23 (52/2.25 = 23 approx), or 39 x17
If a compact 50/34 then he's on either 50 x 22 or 34 x 15
On a 52 x 12 at 167 rpm you are moving 167 x 4.33 x 2.26 = 1634 metres per minute, ie 98 kph or 61 mph.

So we can deduce that with all that fancy kit, wide flat roads and a tailwind the boy still hasn't figured out his gears.
Best ditch the Di2 me old son and get a fixie

[Dombo]

I have a Shimano Flightdeck that calculates virtual cadence from the gear indicator and roadspeed. Unfortunateley it is a POS and the left hand sensor is stuck on 30 chain ring (I have a triple as I'm old and live in hilly Surrey). I therefore get some pretty impressive cadence numbers on the downhills.

[Grahame]

I'd suggest that the max cadence registered is a false reading, probably causes by rotating the crank abckwards and forwards past the sensor whilst freewheeling downhill?

[Dombo]

Oh, is it not like Surrey? Or the Swiss Alps?

[Phil H]

I have hit that sort of cadence downhill on the fixie commuter (that's about 36mph on a 42x15). Can't say it was a lot of fun though.

[Phil H]

As an experiment I put my bike on the turbo (Garmin has magent on the back wheel so can get speed and cadence) and tested to see what I could pedal to. On 50/11 that was 55.7mph at about 158rpm. And a new back tyre. Wouldn't fancy trying that on the road though.

[url=http://www.sheldonbrown.com/gears/]Sheldon's gear calculator[/url] will give you "mph at 100rpm" and stuff. Always useful - if you can't be bothered to set it up yourself in Excel.

[Dombo]

.

[Dombo]

[quote="Sean Hogan"]Lol...er. Box Hill would be Cat Hors mon ami.

[Elliot M]

[quote="Dombo"]Geek alert:

Distance travelled by a 700c x23 wheel in one rev = diameter x pi = approx 720 x 3.142 = 2.26 metres per rev
Max speed = 32 mph (51kph)
= 51/60 kpm = 0.85 ie 850 metres per minute......: