Hills – drive up them hard, or spin until you are fitter?

[jimboalee]

good stuff - thanks! Im sure you will redirect me to many previous topics for this question, but '66" gear' << I imagine this is about gear ratios, but how is it calculated?

A 66" gear is a 39 to 16 ( 39/16 x 27 ). The 52" gear will be a 50" in reality, 39 to 21.

But don't expect to get up a 25% gradient on 50" on your 15lb racebike unless you are a trained elite rider who can output 500odd Watts for half an hour.
Bike manufacturers put 23 and 25 sprockets on for the wannabes. This sells more bikes.

 

[Lazy-Commuter]

good stuff - thanks! Im sure you will redirect me to many previous topics for this question, but '66" gear' << I imagine this is about gear ratios, but how is it calculated?

It's "gear inches", which is kind of a bit like ratios, sort of .. it's the diameter of the drive wheel multiplied by the ratio, or somesuch. As ever, Sheldon said it best.

Edit: although jimbo says it pretty good as well.

 

[Joe24]

Ive been up some very steep hills on my 72" fixed, how does this magic number 7 with all your calculations work out with that then?

 

[Crankarm]

The 'Magic' number 7 in cycling is 7 Watts / kg.

This is the power requirement to ride up a 25% gradient.

I don't care what the on-line calculators might say, ask any experienced cyclist how difficult it is to get up a 25%.
It is also the attainment level to be a reasonable pro in sustained level cycling.

As some of you will already be aware, the gear ratio to climb a 10% is (1/weight of bike)x1000.
For every 1% increase in gradient, reduce the gear length by 1".
Thus, a 15lb bike will have a 66" gear for a 10%, and a 52" gear for a 25% hill.

A pro rider of 68 kg on his 7kg bike will need 7W x 75kg to get up the 25%, or 525 Watts. This power is OK for 29 to 30 mph sustained riding.

I ride a bike that is 24lb, so it MUST have a gear of 42" to get up a 10%. The total vehicle weight is 100kg, give or take a couple; so to get the Dawes Giro 500 up a 25%, I need to find 700 Watts from somewhere, and the gear to do that is 42 minus 15 = 27 ,,, lo and behold that's a 1:1 ratio, 30 ring to 30 sprocket.

I haven't got this gear, so getting up a 25% is a no-no for me. In San Fran', the bike did have a 1:1 and I got up the hill.

I used 750W just reading this post. Time for another bun .

At the w/e on my road bike I did 4 laps of a 14 mile route which takes in two hills one longish and not so steep say 1 in 10 about 2 mile long which I maintain 20-22mph and the other a short killer about half a mile long with about 1 in 3 for about 100m on one part. I breeze up the steeper on 39x19 at 11mph getting out of the saddle with 3 larger sprockets to spare. I weigh a lardy 76kg/12st approx and am 5ft 9". I would like to get my weight down to 70kg/11st to improve my power to weight ratio. Marco Pantani weighed 59kg/9.5st . But alas he is now dead.

Would second using Sheldon Brown's gear calculator.

You should spin but not like a windmill but also don't push heavy gears as you'll knacker your knees and back. Cadence should be about 80-95 revs or what ever is comfortable to move you forward. Thinking of gently flowing water helps me.

 

[jimboalee]

I used 750W just reading this post. Time for another bun .

At the w/e on my road bike I did 4 laps of a 14 mile route which takes in two hills one longish and not so steep say 1 in 10 about 2 mile long which I maintain 20-22mph and the other a short killer about half a mile long with about 1 in 3 for about 100m on one part. I breeze up the steeper on 39x19 at 11mph getting out of the saddle with 3 larger sprockets to spare. I weigh a lardy 76kg/12st approx and am 5ft 9". I would like to get my weight down to 70kg/11st to improve my power to weight ratio. Marco Pantani weighed 59kg/9.5st . But alas he is now dead.

Would second using Sheldon Brown's gear calculator.

You should spin but not like a windmill but also don't push heavy gears as you'll knacker your knees and back. Cadence should be about 80-95 revs or what ever is comfortable to move you forward. Thinking of gently flowing water helps me.

I'm finding it difficult to find the stretch of road you describe. I didn't know you had hills like that near Cambridge.

1 in 10 for two miles goes from sea level to 1050 ft

Can you tell us a grid reference.

A 1 in 3 will have two chevrons on the OS Landranger. Can you give a grid reference for that?

 

[PK99]

.. yup you'll ALWAYS struggle in the mountains carrying your weight.. there is a formal scientific law but I cant be arsed to look it up

errm, gravity?

 

[Crankarm]

I'm finding it difficult to find the stretch of road you describe. I didn't know you had hills like that near Cambridge.

1 in 10 for two miles goes from sea level to 1050 ft

Can you tell us a grid reference.

A 1 in 3 will have two chevrons on the OS Landranger. Can you give a grid reference for that?

I didn't say the route was in Cambs .

 

[threebikesmcginty]

In San Fran', the bike did have a 1:1 and I got up the hill.

I think I know the one - I had trouble walking up it.

Seen the Youtube film of the fixed gear boys in SF?....gasp!

 

[jimboalee]

Another short story about hills. This one involves two Frenchmen and an eight horsepower motorcar.

Two Frenchmen went on a roadtrip to evaluate the hills which would be part of a bicycle race around their homeland. The car weighed about 850 kg and was 8 hp, or 6 kWatts. The thinking was, - it is ten times the weight of a cyclist and his bike, and ten times more powerful, so logic says the cyclist will climb the hills at the same speed - due to similar power to weight ratios.
Depending upon the climbing speed and how the motor was labouring, they graded the hills from 4 to 1 with a Haute category for the really bad ones.

One tenth of 6kWatt is 600 Watts, and one tenth of 850 kg is 85 kg. 600 / 85 = close as dammit to 7 Watts / kg.

This was then taken as an unwritten benchmark for a racing cyclist. It still is.

If one was not aware of this, consider yourself "Not yet a serious cyclist".

And also, listen to Eddy Merckx "Don't buy upgrades, ride up grades".

 

[buddha]

... Thinking of gently flowing water helps me.

You're lucky. Thinking of "gently flowing water" makes me want to pee

 

[Crankarm]

Gently flowing water as it is moves calmly effortless smoothly down river like your riding style lite on the pedals smooth and easy mimicking the real power of flowing water .

 

[jimboalee]

Ive been up some very steep hills on my 72" fixed, how does this magic number 7 with all your calculations work out with that then?

Here's a little test you might like to try.

1/ Find your MAX heart rate ( that's if you've got a HRM ). Mine is 185, which is OK for a fifty year old.
2/ After warming up, cruise at the speed which is appropriate to 50% MHR. Mine is 14 mph.
3/ Double it.
4/ Look up on your curve ( that's if you are a serious enough cyclist to have evaluated your Cd and roadload velocity/power curve ) to see the power requirement for the ' 2 x cruise' speed.
Mine would be 28 mph at 550 Watts.
5/ Weigh the vehicle ( you and your bike, everything ) in kg.
6/ Calc your W/kg factor. Mine is 5.5W/kg - no where near pro racer's ( but then I'm a fifty year old oncewozza )

 

[rich p]

Here's a little test you might like to try.

1/ Find your MAX heart rate ( that's if you've got a HRM ). Mine is 185, which is OK for a fifty year old.
2/ After warming up, cruise at the speed which is appropriate to 50% MHR. Mine is 14 mph.
3/ Double it.
4/ Look up on your curve ( that's if you are a serious enough cyclist to have evaluated your Cd and roadload velocity/power curve ) to see the power requirement for the ' 2 x cruise' speed.
Mine would be 28 mph at 550 Watts.
5/ Weigh the vehicle ( you and your bike, everything ) in kg.
6/ Calc your W/kg factor. Mine is 5.5W/kg - no where near pro racer's ( but then I'm a fifty year old oncewozza )

Gordon Bennett!

 

[SimonC]

Here's a little test you might like to try.

1/ Find your MAX heart rate ( that's if you've got a HRM ). Mine is 185, which is OK for a fifty year old.
2/ After warming up, cruise at the speed which is appropriate to 50% MHR. Mine is 14 mph.
3/ Double it.
4/ Look up on your curve ( that's if you are a serious enough cyclist to have evaluated your Cd and roadload velocity/power curve ) to see the power requirement for the ' 2 x cruise' speed.
Mine would be 28 mph at 550 Watts.
5/ Weigh the vehicle ( you and your bike, everything ) in kg.
6/ Calc your W/kg factor. Mine is 5.5W/kg - no where near pro racer's ( but then I'm a fifty year old oncewozza )

'kin hell! I thought I was a serious cyclist, racing and sportives etc for last 25 years, but dont do any of this stuff, who does?

Each to their own jimbo, but not for me im afraid, its not going to make me any faster

 

[swee'pea99]

Gordon Bennett!

+1