How many rear gears can be used with each chain ring?

RogerLittlewood

I’m on the verge of ordering a new Specialized Allez road bike but not sure whether to get the 16 or 18 or 24.
I know not all of the rear gears can be used on each chain ring but can anyone tell me -
The 16 has two chain rings, 52 and 39 and an 8 speed 12-25 block. How many of the gears will I be able to effectively use while on the 39 ring and how many when using the 52 ring?
The 18 has two chain rings, 50 and 34 and a 9 speed 12-25 block. How many of the gears will I be able to effectively use while on the 34 ring and how many when using the 50 ring?
The 24 has three chain rings, 52 and 39 and 30 and an 8 speed 12-25 block. How many of the gears will I be able to effectively use while on the 30 ring, how many when using the 39 ring and how many when using the 52 ring?
Thanks
Roger

rake

it depends on how the chainline is set up, but a rough guide stay two away from the extreme end of the block which is the opposite side to the chainring your using.

RogerLittlewood

Thanks Rake.

rake

for most riders its more usefull to have 50/34 chainrings for average hill terrain. it gives slightly lower ratios, but can still take you to 40mph + with a swift pedal. much better for hillclimbing. i havent found anything i cant get up on 34-25 gear.

ChrisSA

You can always change the cassette.
I have a 12-27 (10 speed) and a 50/34T chainset. I can use all the cassette in each chainring apart from the outers in each situation.

Go for the 18, and see if they'll change the cassette to the best range for what you need. Compact chainset won't work to well on the 16 speed.

Dodger747

Every single one. All you need is to set up your gears correctly. Don't let anyone tell you that certain gears can't be used, especially given trim...

neeb

Dodger747 wrote:

Every single one. All you need is to set up your gears correctly. Don't let anyone tell you that certain gears can't be used, especially given trim...

+1
Chainline isn't quite as important as it might have been 20 years ago, as chains are a bit more laterally flexible and ramps etc. make shifting easier. You should be able to use all of the gears, it's just that efficiency (to a rather small extent) and chain wear (to a larger extent) will be worse if you regularly use extreme chainlines. In practice what happens is that you shift the at the front when you are getting towards the "wrong" end of the cassette, so you should only need to use severe chainlines briefly in unusual situations, e.g. if you are caught out on a sudden steep hill while still in the big ring.

kettrinboy

On my Giant FCR2, which has a triple chainset 52/42/30 and 9 speed cassette 12-26 i regularly use all nine speeds on the 42 middle ring with just a little rub on the front mech(no trim)on the 26 cog,i think i could use all nine on the granny and big ring if it was just for a short period, but the chain has done over 5000 miles so is pretty flexible now,cross chaining is ok if your say halfway up a steep hill and dared,nt change rings,a few hundred yards wont hurt,but doing it for miles will prematurely wear the chain and sprockets.

Bozman

+1 for all, but.....
I've got a Look with 53/39 - 12/25 and it's perfect with no noise or rub throughout all 20 gears, but i've got a Viner with 50/34 - 11/23 and i get issues(clicking where the chain meets the chainring) on 50 - 23 and the nxt couple of sprockets down.
i tried everything i knew to solve it but i couldn't, i even swapped the chainset and wheels etc from my other bike to check but it remained, the problem eased after the chain had done a few hundred miles but it is still there and i've given caring now.

RogerLittlewood

Thanks everyone for the information. I’ve ordered a Specialized Allez 24 which will give me a 14 gear different gears span over the three chain rings which should be plenty. I’m looking forward to experimenting with which gears I can use.
Roger