Comments on: Gear Inches of Brompton with Single Speed, 2 Speeds, 3 Speeds and 6 Speeds

By: Phil Langford

Phil Langford — Sun, 07 Apr 2024 17:41:03 +0000

Hi. 33.1 inches on a tape measure lines up with 0.84 metres on the metric side of the tape. However, the 33.1 inches refers to the equivalent size (diameter) of the front wheel of a penny farthing. If you pedalled that penny farthing for one complete turn of the front wheel, it would travel 2.64 metres. This is the continental way of measuring the size of a gear.

By: rik headey

rik headey — Sun, 29 Oct 2023 23:08:35 +0000

re 3 speed
54 teeth = +8%
50 teeth = standard
44 teeth = -12%
I think?
But what combination creates -18% please?

By: M@

M@ — Tue, 03 Oct 2023 02:49:58 +0000

In reply to Rabi Dunamalijevs. The formula for gear inches calculations does not include pi: (Chainring Teeth / Cog Teeth) x Rear Wheel Diameter (wheel & tire) = gear inches

By: Rabi Dunamalijevs

Rabi Dunamalijevs — Tue, 04 Jul 2023 13:26:54 +0000

In reply to Steve Bungay.

pi is missing.
50/11*16*3.14=72.7*3.14=228.39 in
50/13*16*3.14=61.5*3.14=193.20 in
50/15*16*3.14=53,3*3.14=167.44 in
50/18*16*3.14=44.4*3.14=139.48 in

By: Jeff

Jeff — Sun, 05 Feb 2023 02:17:46 +0000

Hi, What are the corresponding number of cassette tooth that you used for the Stormy Archer 6 speed/-12%? I’d like to figure out what my gear inches using a different chainring. Thank you!

By: Steve Bungay

Steve Bungay — Tue, 09 Aug 2022 11:59:52 +0000

In reply to Mark Piotrowski.

Chainset teeth / cassette teeth x wheel diameter” = length of gear in inches
50/11*16=72.7
50/13*16=61.5
50/15*16=53,3
50/18*16=44.4
This is quite a narrow span. 44.4″ is quite long for climbing. 72.7″ is quite short for flats and downhills.

By: Mark Piotrowski

Mark Piotrowski — Sat, 02 Jul 2022 11:00:02 +0000

Hi I wonder if you can help me out here. I have a new P line. 50 chainring with 11/13/15/18 cassette. Please advise have I calculate the gear inches?
Kind regards

By: Frank Hooper

Frank Hooper — Sun, 06 Sep 2020 22:15:30 +0000

In reply to Ricky Do. Thanks for explanation - ie, multiply the gear inches by 0.0254 to convert to metric, then by π to go from diameter to circumference :-)

By: Ricky Do

Ricky Do — Sun, 26 Jul 2020 13:04:57 +0000

In reply to Rick. Hi, Gear inches and meters of development are equivalent terms used in America and Europe respectively. In the calculations, gear inches use drive wheel diameter instead of circumference.

By: Rick

Rick — Sun, 26 Jul 2020 12:56:15 +0000

Hello Ricky.

I’m confused by the gear inches and metres travelled table at the link above. The inch and metres measurements are not equivalents. For example, with the Brompton 6 speed standard and 1st gear, 33.1 inches equals 0.84 metres, not 2.64m. This is way out, across the whole table. What am I not understanding?

Regards