Bicycle Mechanics - Using Only 4 Gears on a 21-Speed
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07-08-08, 08:14 PM
I am riding a Mongoose Switchback 21-speed hybrid. I only use 4 gears, because if I use any of the others, I feel that I am pedaling my keester off and going nowhere. Should I change the crank gears of the rear cassette? Also, if I change the front crank, I surmise that they should be bigger and if I need to change the rear cassette, should they be smaller?
Any info is greatly appreciated.
Which gears are you using? Tell us which front gears (small, medium, large) and which rear gears. That will help a bunch.
Joshua A.C. New
07-08-08, 08:47 PM
Some quick terminology:
Chain ring: gears in the front, attached to the crank.
Sprockets: gears in the back, attached to the rear wheel.
Crank: the arm that connects the pedal to the chain ring.
Kiester: Yer butt.
OK, so the deal is, the bigger the difference between the circumference (measured in teeth, since teeth are all the same size) of the chain ring and the sprockets is what makes the acceleration higher or lower and the top speed lower or higher, respectively.
If you're using the top four gears, therefore, there are two ways to change that: put on a larger chainring or a smaller set of sprockets. I'm on a super-crappy internet connection right now so I can't check to see what your gear ratio is, but my guess is that you've got something like a 48 tooth big chain ring and a 12 tooth small sprocket. That's a gear ratio of 4:1. If you're riding on flat roads all the time, you probably spin out pretty easily, so you'd want to put a big road chain ring on there — something like a 52 tooth ring.
Since I don't know much about your bike, I can't offer any really specific advice, like what chain rings would fit, or even if they're removable (because if they're not, you'd have to change the cranks, too). But that's pretty much what you need to do.
07-08-08, 09:43 PM
I am sure the chainrings are rivetted to the crank, so it would be necessary to buy a new crank assembly with bigger big ring $50, a crank removal tool $15 and a pedal wrench $12. You will also have to raise the front derailler up the seat tube a bit to clear the big ring
07-12-08, 08:17 PM
Thanks all. Mr Phil, I haven't ridden in a while since I am taking an on-line class for college. The next time I ride, I will double-check what gears I am using.
Joshua A.C. New: Thanks for the proper terminology. I knew what I wanted to say, but not how to say it. Thanks for putting me on the right track. I have a Schwinn Varsity 14-speed that I found in the dumpster where I live, so I will check that the chain ring is on that bike.
AndrewP: Thanks for the info on price. There is a local bike shop that I help with in October hauling parts in crates to the "local" bike swap meet. I say "local" because it is the Lehigh Valley Velodrome, which is about 2 hours away. He maybe able to get me the proper equipment at a discount price and teach me how to change out the crank and chain ring.
As long as your cranks aren't going around more than 100 times each minute, don't wory about it.
You SHOULD be pumping your legs around at a decent rate. It's far easier hurting your knees by slow and strong pushes than it is by over-revving them.
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