Road Cycling - Gear selection

I have a 53/39 chainring, and a 23 to 12 cluster. If I select the 53 chainring, with the 19, then one turn of the pedals will turn the rear wheel 2.78 times. I will get the same result if I select the 39 chainring with the 14. My question is this: Is there any difference between the two ? That is, do my legs have to work harder turning the big chainring, or am I able to accelerate better with the smaller ?

first of all, you shouldnt have the chain crossed over from the left chainring to the cogs at the extreme right of the bike.

For examble i dont use my 39x15 combo, i use my 52x19 instead.

Brendon

.
T --- 53T | - 39T
12 | 116.1 | 85.4
13 | 107.1 | 78.8
14 | 99.5 | 73.2
15 | 92.9 | 68.3
16 | 87.1 | 64.1
18 | 81.9 | 60.3
19 | 73.3 | 53.9
21 | 66.3 | 48.8
23 | 60.6 | 44.6

units are in gear inches..

53-19 and 39-14 combos have the same mech advantage.

Just think of it as your transition gear combo.

PS: @ 53-21 and 39-13 your chain will start to rub your Fder. and will be too twisted.

So if your speeding up, shift from 39-14 to 53-19/18(you can go 3 cogs bigger at a time). When slowing down, shift from 53-18 to 39-14/15.

That's what I do.

first of all, you shouldnt have the chain crossed over from the left chainring to the cogs at the extreme right of the bike.

For examble i dont use my 39x15 combo, i use my 52x19 instead.


Ummm.....Isn't that exactly what you just jumped all over him for doing?

Seriously, you only need to avoid the most extreme combos (big ring, big cog, small/small). This guy is just a bit anal-retentive.

Yes, the 2 gears are pretty much the same. the only difference is in what gear you may need to shift into next.

Hi

Thanks for all of your input. I wasn't really considering a severe crossover - it was just that the combinations I quoted both yielded the same ratio. I was more interested in whether there was any mechanical advantage or disadvantage according to the chainring selected.

For the anal-retentive amongst us, please see 'Defecation a key to BETTER HILL CLIMBING' in the Road Cycling forum.

There is no diff in power exertion. We've often wondered about that in fixed gear riding. The only benefit is a slight weight savings by using the smaller ring combo........on a fixed gear bike, that is...

George!

One advantage, albeit a minor one, of using the 53/19 is that your chain will last longer. I won't go into the math (cos I can't remember it all :) ), but because bigger cogs are bigger (chain is further from the axle), and they have more teeth, the chain has less force applied to it and it is spread over more links, thus reducing wear.

I have a question though; is it OK to shift both derailers at the same time? ie can I go from 39/15 to 53/19 in one fell swoop? This is pretty much the same as going up to 39/14, but puts me on the big chainring at the same time.

Why?Arent you afraid of hurting your chain?

Originally posted by Jonny B
I have a question though; is it OK to shift both derailers at the same time? ie can I go from 39/15 to 53/19 in one fell swoop?

if the chain would slip, you would loose power suddenly and when it bites after a second or less, imagine what will happen.

Female opera singer?

Gear selection posted to the left, just above Drinky Crow...