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Optimum gear-inch range

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Optimum gear-inch range

Old 05-15-21, 06:45 PM
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Pinigis 
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Optimum gear-inch range

We are working on a new bike, and I think that I may be going a bit too far in one respect, so I need a realty check. What would you consider to be your optimum gear-inch range?
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Old 05-15-21, 10:56 PM
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It all depends on where you ride your bike. If you commute in the plains, few gears can be fine. If you take your folder into a hilly area, you need low gears or else you walk. On my principal folder I have 1.1-8.4m of development. Around home base, outside of winter, I mostly use 2-5.7m. Higher gears are nice, but not essential, in a downhill ride or to show off. The gears below 2m are needed in the mountainous areas or in winter. The gears below 1.4m or so cannot be used, in my case, in a sustained manner, just in surges. I.e., maybe having to walk rather than having them would not have made a big difference.
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Old 05-16-21, 02:45 AM
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I believe that my Airnimal Joey frame (a folder) that I built up years ago came with a 52T chainring, I built it up with a 11/32 Sram eight speed cassette, that bike has 24 inch wheels. For most things that was adequate, but it lacked the gearing for uphills. The frame could not be fitted with a front derailleur for a double or triple, thus it was a 1X. At one time I tried a compact double crank on it, but it was a major hassle to get off the bike and shift the front by hand with a greasy chain.

If I was anywhere in Florida, the above gearing would have been more than adequate. Agree with 2_i, it all depends on where you are and what you are trying to do.

Eventually I decided that if I was going to ride that bike much, it needed wider range, I fitted a Sram Dual Drive (now out of production) which is a three speed rear hub that can take a cassette. Dropped my chainring size to 39. I usually am using my Dual Drive in third gear which is an "overdrive".

The bike with Dual Drive has a range of 20.8 to 112.3 gear inches. Quite happy with that. That said, I have three non-folding touring bikes, so I have expectations for low gearing.

The bike before I installed the Dual Drive had a range of 37.8 to 109.9 which was not good enough for hills.

To compare this to my rando bike that rarely carries much of a load, that bike has a range of 25.1 to 126.8, but the highest two gears are only used on downhills to maintain momentum for when I cross a valley and start up the hill on the other side.

There is some flex in my tall seatpost extension and steerer tube extension on my Airnimal, my rando bike does not have that flex. I think I like slighly lower gearing on a bike that has that flex, the stiffer frame on my rando bike can have slightly higher gearing.

I am 67 and just a hair below the "overweight" BMI, about 6 ft.
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Old 05-16-21, 11:16 AM
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30 to 90 gear inches with 8 gears or more.
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Old 05-16-21, 11:34 AM
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On a folding bike with 20 inch wheels an 11 to 34 rear cassette with a 48 teeth chainwheel would give a nice rangr from 28 gear inches to 87 gear inches..
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Old 05-16-21, 06:58 PM
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It depends on the usage and riding conditions.


For the more speedy folders (eg. Bike Friday Pocket Rocket), I have 25.7 - 94 GI.
Its done everything from mountain rides to the weekend fast rides with road bikes.
Where it looses out is the high gears for surges and downslopes (where the road bikes can attempt to get away with their higher GI )
Solo flat runs are no issue as I find that 94 GI is enough to not over commit to a long stretch and I am able to reel in any RB rider so long as he's not a 130 GI churning monster.
Nothing to complain about for the low gears.


For loaded touring, I've found that 26 - 88 GI is enough for the high gears due to the slower pace.
Downslope, its a good time to just coast down.
However, I'd really like to be able to go down to 22 or 24GI on the low side (though with 26 GI, I only occasionally need to get down and push )



My current Change Bike (gravel bike setup ) is SRAM Rival 1x 44T + 10-42t cassette. (29 - 123 GI )
For touring, I just need to swap the chainring down to a 38T ( 25 - 106 GI ) ; or even a smaller chainring if necessary.

Last edited by pinholecam; 05-16-21 at 07:01 PM.
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Old 05-16-21, 07:12 PM
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I have about 40-100 inches on my pocket rocket.

It is good for a travel bike but the high end is a bit anemic. It is at least 25 years old, so, I could rectify with any easy albeit expensive change from 8 speed to 11 speed getting the 11 cog
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Old 05-17-21, 03:07 AM
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My gravel 1x11spds is geared for 24.4-102.3". It is setup for cotswold hills, muddy single track etc.
My road folder 2x9speed is geared for 29-90". close ratio cassette for frequent smooth changes
M gravel folder 1x9speed is geared for 24.4-80". pretty similar to the gravel bike but 2 harder gears are missing; as I do not ride this on hard (child seat), it does not matter.

24.4" is needed when climbing a hill which a child in the back seat while towing another one
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Old 05-18-21, 12:58 AM
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Optimum depends on budget (# of speeds) & terrain. For life on the cheap in hilly Vancouver, I've given my 7-speed Dahon an 11-34t cassette which pushes the jumps to get 309% range, & a 42t chainring. 25-76" range gets me up almost all hills at the price of coasting on long descents. If you can afford Microshift Advent X (budget 10-speed, 11-48t, 436% range), you can build an all-world 20" bike: 48t chainring, 20-87". For less than 10-speed, and given that you're an online business, I'd suggest making chainring size an option - maybe cassette as well. Folks on the prairies may be best served by a corncob.
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Old 05-18-21, 01:49 AM
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Originally Posted by Antifriction View Post
Optimum depends on budget (# of speeds) & terrain. For life on the cheap in hilly Vancouver, I've given my 7-speed Dahon an 11-34t cassette which pushes the jumps to get 309% range, & a 42t chainring. 25-76" range gets me up almost all hills at the price of coasting on long descents. If you can afford Microshift Advent X (budget 10-speed, 11-48t, 436% range), you can build an all-world 20" bike: 48t chainring, 20-87". For less than 10-speed, and given that you're an online business, I'd suggest making chainring size an option - maybe cassette as well. Folks on the prairies may be best served by a corncob.
Maximising the range is one thing but not the only thing to look at. One of the big thing to consider is progression. for example, like you I run a 11-34T on 20" wheel but on a 44 rather than 42 and it not far from yours however, mine is 9spd making the gear spread closer than yours and that is important in therm of comfort. When I run the helios on 7spd 11-32, I found the changes horrible as the steps between gears were too big.

As my folding gravel was a budget built, I purposely set the gear spread to match my big gravel and start from roughly the easier compromising the harder gears however, the gear progress is the same on all my bike so no nasty gear change/jump when going up hill of on the flat... down hill does not matter.

Note that on a budget, the cheaper is previous year road racing groupset. TT racers like to have the latest piece of kit and sell their old one on ebay etc. these kits on a folding 20" bike tend to give commuting bike ranges (27.5/29" wheel -> 20").
2nd hand shimano 105 on a folding bike is affordable

Note : 10-speed, 11-48t will not fit well; yes the cassette fit but it requires a long cage derailleur which will drag on the floor with a 20". I test fitted a acera long cage (with 11-36 on my daugther 20" frog52 (seeable on GCNTech Show @ 17.34)) and it was 12mm from the floor (midd tyre level). I tried a new 2020 Sora medium cage, it was a little better, ~50mm clearance... so I went for a new 2020 short cage Sora (it is longer than 2015 sora short cage) , and I got the right clearance with a 11-34T cassette

Last edited by Fentuz; 05-18-21 at 02:01 AM.
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Old 05-19-21, 05:16 AM
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I have 14-72.6 gear inches measured with the effective diameter of the tire when loaded. It's equal to 1.12-5.79 meter Development if I calculated correctly. I'm usually comfortably around 75 rpm to 85 rpm and average at 77rpm, so I prefer lower gearing. This gives me a maximum of 29.5kph and minimum of 5kph, or 4.5kph at 67rpm.

The difference between 75rpm and 85rpm is 13.3%, so I will try to keep my gear spacing below this percentage. I custom mix my cogs to get small 7% to 13.3% spacing at the top and up to 21% at the bottom. Changing cadence between 67rpm and 85rpm is 27% but very tiring. 12 8.3% 13 7.7% 14 7.1% 15 13.3% 17 11.8% 19 10.5% 21 14.3% 24 16.7% 28 21.4% 34

My normal speed is on 7th gear which is 58.1 gear inch. At 75rpm it is 21kph.
I would increase to 85rpm when shifting up.

If I ever change from 10 speed to 11 speed, I would try changing the 15 to 17 cogs to 15 16 18 to reduce that 13.3% gap to 12.5% although it may not seem like much.

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Old 05-19-21, 05:51 AM
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Originally Posted by Fentuz View Post
Note : 10-speed, 11-48t will not fit well; yes the cassette fit but it requires a long cage derailleur which will drag on the floor with a 20". I test fitted a acera long cage (with 11-36 on my daugther 20" frog52 (seeable on GCNTech Show @ 17.34)) and it was 12mm from the floor (midd tyre level). I tried a new 2020 Sora medium cage, it was a little better, ~50mm clearance... so I went for a new 2020 short cage Sora (it is longer than 2015 sora short cage) , and I got the right clearance with a 11-34T cassette
GCN Tech show
As a few companies are starting to use Microshift’s 8 speed Acolyte (12-44t) groupset on children’s mountain bikes with 20” wheels, I recently installed their 9 speed Advent groupset with their medium length rear derailleur and a 11-44t block on a Tern Link D8. With a smaller replacement chainring added (think it was a 46t?) the range is fine for the hills around here - I live in a city full of volcanoes. As I expected from the kiddy MTBs, derailleur clearance to the ground is sufficient for road and trail use with 20” wheels. With some Big Apple tyres on order that should also help increase that clearance too. I’ll post a photo if you want?
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Old 05-19-21, 01:32 PM
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Over 100 years ago three-speed bicycle drivetrains were set somewhere near +33% +33%, i.e. -25% 1/1 +33%; about a total range of 178%. This has been common to hub gears from Sturmey-Archer, Fitchel&Sachs (SRAM) and Shimano and has been continually produced and accepted by cyclists ever since. Sounds like an optimum - of sorts.
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Old 05-23-21, 10:58 AM
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Fentuz: the Advent X system includes a derailleur, and it's medium-cage. I have a medium-cage Tourney on my 20" Dahon; 43t capacity - more than enough for the 37-tooth range of the Advent X - & ground clearance is 70mm.
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