Are chainrings speed specific?

The compact philosophy is based around the 10 speed cssette, 12-27. Yes you can fit a compact 10 speed crankset, but use a 10 speed chain with your 9 speed cassette. You may also need a "compact" 10 speed front derailleur.

For a 9 speed bike, if you must go compact, it is far cheaper to use 9 speed MTB 110pcd cranksets. I was shipped a Sugino 38 tooth inner 110pcd in error recently, it is for 8 or 9 speed. 🙂

What crank length are you intending to run with the compact crank?

neon said:

i.e. 10 speed and 9 speed. I want to put compact cranks on my 9 speed bike. I know the 10 speed chain is narrower than 9 speed. Does this effect chainring selection?

Campy requires a compact specific front derailleur, for their compact cranksets. Shimano doe's not.

You CAN use "10spd" chainrings with a 9spd chain with no problems.

mikesbytes said:

What crank length are you intending to run with the compact crank?

175mm

neon said:

175mm

175 is a longer crank, generally used with a slower spin and suits taller gears. If you do go down the compact crank, you may find that you run out of gears at the top end.

mikesbytes said:

175 is a longer crank, generally used with a slower spin and suits taller gears. If you do go down the compact crank, you may find that you run out of gears at the top end.

A 175 crank is suited to a rider with longer legs in the first place. For someone with long legs 175 is not a slow-spin crank at all.

Also, most of riders out there will not run out of gears with a typical modern compact crank, say 50/36, 110 BCD combination. Most of folks would in fact be better off having the compact (50/36) instead of the racing standard (53/39) setup. I think there arern't many of those that really need the gear higher than 50*12 or 50*11 to ride.

My personal *ideal* crankset is going to be 48/36 with a 12-27 cassette. Plenty of high, plenty of low for everyday riding. May not be enough at the high end for a hard race, but I don't care because I don't race. I have already used 48T chainring with a standard Shimano front deraileur (130 BCD double) and it shifted OK. No problems there...

I'd advise anyone considering going compact to choose 50/36 rather than 50/34 because the "jump" between 50 and 34 is too big. If 34 is *really* needed, then I'd go 48/34....

cluster blaster said:

A 175 crank is suited to a rider with longer legs in the first place. For someone with long legs 175 is not a slow-spin crank at all.

Also, most of riders out there will not run out of gears with a typical modern compact crank, say 50/36, 110 BCD combination. Most of folks would in fact be better off having the compact (50/36) instead of the racing standard (53/39) setup. I think there arern't many of those that really need the gear higher than 50*12 or 50*11 to ride.

My personal *ideal* crankset is going to be 48/36 with a 12-27 cassette. Plenty of high, plenty of low for everyday riding. May not be enough at the high end for a hard race, but I don't care because I don't race. I have already used 48T chainring with a standard Shimano front deraileur (130 BCD double) and it shifted OK. No problems there...

I'd advise anyone considering going compact to choose 50/36 rather than 50/34 because the "jump" between 50 and 34 is too big. If 34 is *really* needed, then I'd go 48/34....

A long descent with a 12 x 50, @ only 40mph, requires a fairly high cadence to maintain. I see no advantage in a higher cadence 48, unless you don't come close to 40mph. The jump between a 34-50 vs 36-50 is too big for either, without simultaneously changing cogs, unless you are going downhill or just cruising. So why not get the climbing advantage of the 27 x 34? My ideal gearing, would be an 11-27 x 34-50, with a short cage rear derailleur. Shimano comes closest, but I ride Campy and have to settle for their 12-25, because a 13t cog spins me too much at 40+ mph. Anyway, the BEST gearing is what suites the individual and where he rides.

lks said:

Anyway, the BEST gearing is what suites the individual and where he rides.

Absolutely, I run 53/42/30 11-21 with 170mm cranks. Probably not that common.

The 42*11-21 runs sweet when crusing in a pack, stops that constant annoyance of going up down up down up down on the chain rings. When the going speeds up, the closer cogs on the 11-21 elimates gearing gaps while running on the 53. Don't use the 30, buts its only about 100gms to keep it, so it might as well be there.