I'm a little confused about gear inches on some models like the Espin Reine. It has a 11-36 cassette in the rear and a 15 tooth in front which works out as a low gear of 11 inches and a high gear of 37 inches, this doesn't seem right. I usually have a low gear in the upper 20s and a high gear at about 90s, or higher, on my non electric bikes. Most electric bikes seem to have a normal range when I do the calculation, so what am I missing.
Gear Inches
- Thread starter Black47
- Start date
fooferdoggie
Well-Known Member
looks like it is geared like a Bosch drive where you get bout 2.5 chainring rotations for every crank rotation. but you may not be able to find the exact ratio.
Gear inches is determined by (Front chain teeth/Rear chain teeth)*wheel size this will give you the distance traveled in one revolution of the pedals, which is why I was confused. The 2.5/1 makes sense, so on a 15 tooth front chain it would really be equal to 37.5. The reason why I was interested was so that I could compare different ebikes with something I was familiar with on non electrics. I noticed as I got older with bad knees that it was difficult for me to use the 48 tooth on my triple and that the 38 and 28 were much easier for me to use if the gear inches were close. Two of the ebikes at the top of my list are the Giant LaFree with a 38 tooth front and the Espin Reine with a 15, so they were pretty hard to compare. I had tried out the Giant and found it very comfortable, and was trying to figure out if driving the extra distance to try out the Espin was worthwhile. So thanks to you and fooferdoggie for the information, much appreciated.
stanmiller
Active Member
Gear-Inches is a valuable metric for gauging climbing effort. Lower numbers are better for your knees.
Granny Gear Inches: Ride Now, Save Your Knees For Later
https://bikepacking.com/plan/granny-gear-inches/
Turns out it is 2.8 times, not 2.5 which makes it equal to a 42 tooth front, so the very lowest gear is 32 inches a little bit higher than I like normally but it probably won't be a big deal with the power assist. But it will add a bit of drag when not using the assist, something I'll need to check on tomorrow when I go for a test ride.
Nova Haibike
Well-Known Member
I do not know how many more teeth an Acera derailleur can actually handle, but Shimano is conservative in the ratings. With a dropout extender you could go even bigger. 9-speed cassettes are available in 11-40T, 11-42T, 11-46T, and even 11-50T.
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