I’m hoping you could help explain gear ratios and maybe shed some light on which gear ratios are unnecessary. Here’s the situation:
I have a customer that is using the Sram Red compact double (50-34). In the back she is using the new Sram Apex long cage rear derailleur. She is also using a Sram PG1070 10speed casettte in a 11-32. She is interested in switching out the 11-32 cassette to a 12-36. For some reason, I’m thinking that running a gear combination of 34 small ring to a 36 in the back doesn’t make sense. I think what that means is that she would essentially “spin out” OR her gearing in that given combination is too low. Her rebuttal was that her other bike was a road triple with a 22-32-52. However, she was running a 11-28 10sp to go with the triple. I’m wondering this:
Does she just not want to exert any effort climbing or is it useless to run a gear combination of 34-36?
Hopefully these questions make sense.
Congrats on the new book!
Thanks for writing. I need to rock some family style, but here’s a quick answer:
Gear ratios 101
Gear ratio is the size ratio between the front gear (chainring) and rear gear (cog), measured in teeth. When you divide the front gear by the rear gear, the resulting number tells you how many times the rear wheel will turn for every rotation of your cranks.
44 front / 11 rear = 4 (top gear for most mountain bikes)
36 front / 12 rear = 3 (a good DH/Super D top gear)
34 front / 17 rear = 2 (a common singlespeed ratio)
34 front / 34 rear = 1 (my Stumpjumper climbing gear)
22 front / 34 rear = 0.65 (low gear for most mountain bikes)
The lower that bold number, the easier it is to turn that gear, but the slower you’ll be going when you turn it.
22 / 28 = 0.79
That’s a very low road gear, almost as low as a mountain bike.
34 / 32 = 1.06
That’s a lot harder than her old gear. If I was used to climbing with a 22/28, I’d be looking for an easier gear too.
34 / 36 = 0.94
That’s still harder than her old gear, but easier than her current gear. If her drivetrain will handle that ratio, I say do it.
Picking the right gear
Asking which low gear a person needs is like asking how much they should be bench pressing. It depends.
We all need a gear we can turn without hurting ourselves or feeling completely miserable. That ideal ratio depends on terrain, conditions, genetics, goals, health, rest and whether you have infant twins.
My Mighty Tricross has a 34/28 (the lowest I could go with Shimano Ultegra). Last winter when the babies came, I could barely turn that gear up the 17% climb to my house. Now I can spin that gear pretty easily — and even upshift a few times if I feel like it.
This is important: If I didn’t have the easy low gear, I wouldn’t have been able to ride that bike very much. I would have lost my mind, and I wouldn’t be rocking now.
If your customer wants an easier gear, give it to her. The best bike is the one you get to ride. The best gear ratio is the one you can ride.
But: Don’t let her be lazy and use the ‘easy’ gear as a crutch. Encourage her to:
– Pedal with great form. Always.
– Learn to spin the gear quickly. No plodding along in defeated mode.
– Spend time in harder gears. That’ll make her stronger and increase her overall confidence in the hills. Eventually she’ll save the 34/36 for emergencies.
– Have fun!
I hope that helps.
(Tired today from yesterday’s climb: Enduro with 36/34 gear and 2.5 sticky DH tires up Sunshine Canyon.)
Know more. Have more fun!
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