Knowing gear ratios

User avatar
Derny Driver
Posts: 2073
Joined: Wed Nov 21, 2012 12:18 pm
Location: Wollongong

Re: Knowing gear ratios

Postby Derny Driver » Wed May 24, 2017 6:49 pm

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.

User avatar
Alex Simmons/RST
Expert
Posts: 4388
Joined: Fri May 02, 2008 3:51 pm
Contact:

Re: Knowing gear ratios

Postby Alex Simmons/RST » Thu May 25, 2017 8:56 am

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 :D
Image

madmacca
Posts: 362
Joined: Mon Aug 03, 2015 5:13 pm

Re: Knowing gear ratios

Postby madmacca » Thu May 25, 2017 11:53 am

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 :D
Image


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

User avatar
bychosis
Posts: 5060
Joined: Sat Jan 14, 2012 1:10 pm
Location: Lake Macquarie

Re: Knowing gear ratios

Postby bychosis » Thu May 25, 2017 1:08 pm

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.

User avatar
Alex Simmons/RST
Expert
Posts: 4388
Joined: Fri May 02, 2008 3:51 pm
Contact:

Re: Knowing gear ratios

Postby Alex Simmons/RST » Thu May 25, 2017 7:10 pm

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.

User avatar
Duck!
Expert
Posts: 6351
Joined: Tue May 21, 2013 8:21 pm
Location: On The Tools

Re: Knowing gear ratios

Postby Duck! » Thu May 25, 2017 7:23 pm

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.

User avatar
CKinnard
Posts: 2455
Joined: Mon Jun 30, 2014 10:23 am

Re: Knowing gear ratios

Postby CKinnard » Thu May 25, 2017 7:41 pm

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.

User avatar
bychosis
Posts: 5060
Joined: Sat Jan 14, 2012 1:10 pm
Location: Lake Macquarie

Re: Knowing gear ratios

Postby bychosis » Thu May 25, 2017 10:55 pm

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.

Who is online

Users browsing this forum: No registered users