## Knowing gear ratios

Derny Driver
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### Re: Knowing gear ratios

Alex Simmons/RST wrote:
Derny Driver wrote:I currently have a lady who can run 8 laps like clockwork on a 94 inch gear, she has done it many times and is always within a second of her target. We need to take 8 seconds off her pursuit time, so I have twice put her on 95 inches and she can only manage 3 laps before blowing up in spectacular fashion. My job is to problem solve what is going on - nevertheless my point is that a gear inch on a track bike, in certain cases, is quite a jump in my opinion.

At those speeds, 1 second per lap quicker requires 15-20% more power. That's the problem. increase power that much and time to exhaustion goes from a handful of minutes to less than a minute.

Cheers Alex. Im trying to get there in tiny increments over a 12 month period. But its a massive challenge.

Alex Simmons/RST
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### Re: Knowing gear ratios

Derny Driver wrote:
Alex Simmons/RST wrote:
Derny Driver wrote:I currently have a lady who can run 8 laps like clockwork on a 94 inch gear, she has done it many times and is always within a second of her target. We need to take 8 seconds off her pursuit time, so I have twice put her on 95 inches and she can only manage 3 laps before blowing up in spectacular fashion. My job is to problem solve what is going on - nevertheless my point is that a gear inch on a track bike, in certain cases, is quite a jump in my opinion.

At those speeds, 1 second per lap quicker requires 15-20% more power. That's the problem. increase power that much and time to exhaustion goes from a handful of minutes to less than a minute.

Cheers Alex. Im trying to get there in tiny increments over a 12 month period. But its a massive challenge.

Try this

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### Re: Knowing gear ratios

Alex Simmons/RST wrote:
Derny Driver wrote:
Alex Simmons/RST wrote:At those speeds, 1 second per lap quicker requires 15-20% more power. That's the problem. increase power that much and time to exhaustion goes from a handful of minutes to less than a minute.

Cheers Alex. Im trying to get there in tiny increments over a 12 month period. But its a massive challenge.

Try this

Graeme O'Bree built his bike out of washing machine parts. But obviously someone has been raiding the sawmill for parts for that bike.

bychosis
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Location: Lake Macquarie

### Re: Knowing gear ratios

It might be more relevant know 'gear inches' for MTB riding with all the different tyres sizes available at present. It is no good saying "I can climb that with a 32f-28r, you'll be right on yours" if you are on a 26" bike when your mate is trying to work out what gear is necessary for his 29", 27.5+, or fatbike. The outer diameter of the wheels is quite difference and can make a big difference to gear ratios and 'gear inches' would even it out because it involves tyre diameter.
bychosis (bahy-koh-sis): A mental disorder of delusions indicating impaired contact with a reality of no bicycles.

Alex Simmons/RST
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### Re: Knowing gear ratios

bychosis wrote:It might be more relevant know 'gear inches' for MTB riding with all the different tyres sizes available at present. It is no good saying "I can climb that with a 32f-28r, you'll be right on yours" if you are on a 26" bike when your mate is trying to work out what gear is necessary for his 29", 27.5+, or fatbike. The outer diameter of the wheels is quite difference and can make a big difference to gear ratios and 'gear inches' would even it out because it involves tyre diameter.

The thing that makes most sense is rollout. Gear inches is kind of a strange way of looking at it since it refers to a wheel's diameter rather than its circumference.

Rollout tells you how far the bikes travels for one full turn of the crank.

Duck!
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### Re: Knowing gear ratios

Alex Simmons/RST wrote:
bychosis wrote:It might be more relevant know 'gear inches' for MTB riding with all the different tyres sizes available at present. It is no good saying "I can climb that with a 32f-28r, you'll be right on yours" if you are on a 26" bike when your mate is trying to work out what gear is necessary for his 29", 27.5+, or fatbike. The outer diameter of the wheels is quite difference and can make a big difference to gear ratios and 'gear inches' would even it out because it involves tyre diameter.

The thing that makes most sense is rollout. Gear inches is kind of a strange way of looking at it since it refers to a wheel's diameter rather than its circumference.

Rollout tells you how far the bikes travels for one full turn of the crank.

Yup. Gear inches is an ancient throwback to the days when diamond frame bikes were appearing alongside and ultimately supplanting penny-farthings (big-wheel bikes). The gear inch calculation gives an equivalence to a theortetical big-wheeler, eg a 90" gear would approximate the rollout of a 90" wheel.
I had a thought, but it got run over as it crossed my mind.

CKinnard
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### Re: Knowing gear ratios

As said above by many, gear inches were more important for single speed bikes, when one needed to get the optimal gear for most of a race duration and circuit.

Today, with advances in exercise physiology, and total usable road bike gear numbers up from less than 10 to 18, top riders think more in terms of watts and rpm.

bychosis
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### Re: Knowing gear ratios

Duck! wrote:
Alex Simmons/RST wrote:The thing that makes most sense is rollout. Gear inches is kind of a strange way of looking at it since it refers to a wheel's diameter rather than its circumference.

Rollout tells you how far the bikes travels for one full turn of the crank.

Yup. Gear inches is an ancient throwback to the days when diamond frame bikes were appearing alongside and ultimately supplanting penny-farthings (big-wheel bikes). The gear inch calculation gives an equivalence to a theortetical big-wheeler, eg a 90" gear would approximate the rollout of a 90" wheel.

I didn't realise the origin of the calc, but did recognise it accounts for different wheel sizes. Still, the idea is all about comparing gear ratios And taking into account the wheel diameter.
bychosis (bahy-koh-sis): A mental disorder of delusions indicating impaired contact with a reality of no bicycles.

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