Crank Question

[Buddy2004]

Hi,

I have a MTB that I am using as a road bike until I have the $$ to buy a proper road bike. The bike (21spd) I have is about 10 y.o. and has a crappy Shimano altus crank...........This is really worn and I want to replace it along with the rear deraileur, but without spending too much on what is a 'temporary' bike (wife, mortgage allowing!). I checked out e-bay and saw a used shimano deore crank going cheap.....basic questions I have are:

1. I have seen cranks advertized as e.g. 9 spd.....the rear derailleur / sprocket in part dictates the total no. of speeds, so why doesn't one crank fit all speed bikes?

2. Anyone have a clue if a shimano deore crank would fit a 7spd sprocket?

3. Anything else I should know about selecting cranks / rear deraiileurs (I realize that the bottom bracket I have may need changing to fit a different crank)?

4. If I change the crank and rear deraiileur is it likely that I can get away with the current shimano altus front derailleur?

Thanks in advance for your help!

 

[boudreaux]

Hi,

I have a MTB that I am using as a road bike until I have the $$ to buy a proper road bike. The bike (21spd) I have is about 10 y.o. and has a crappy Shimano altus crank...........This is really worn and I want to replace it along with the rear deraileur, but without spending too much on what is a 'temporary' bike (wife, mortgage allowing!). I checked out e-bay and saw a used shimano deore crank going cheap.....basic questions I have are:

1. I have seen cranks advertized as e.g. 9 spd.....the rear derailleur / sprocket in part dictates the total no. of speeds, so why doesn't one crank fit all speed bikes?

2. Anyone have a clue if a shimano deore crank would fit a 7spd sprocket?

3. Anything else I should know about selecting cranks / rear deraiileurs (I realize that the bottom bracket I have may need changing to fit a different crank)?

4. If I change the crank and rear deraiileur is it likely that I can get away with the current shimano altus front derailleur?

Thanks in advance for your help!

1) cranks don't have speeds. 2 it works. 3) it's a good bet you will need another BB. You can get hosed real bad on used octalink cranks. Morons install them wrong and bugger the spline interface. I've returned 2 bad ones and will never buy another used one without seeing it first. 4) you don't have to change the RD unless it is worn out or damaged.

 

[e_guevara]

1. I have seen cranks advertized as e.g. 9 spd.....the rear derailleur / sprocket in part dictates the total no. of speeds, so why doesn't one crank fit all speed bikes?

2. Anyone have a clue if a shimano deore crank would fit a 7spd sprocket?

I have yet to find a crankset that has "real" compatibility issues with the number of sprockets and/or chain.

3. Anything else I should know about selecting cranks / rear deraiileurs (I realize that the bottom bracket I have may need changing to fit a different crank)?

There are several crank-BB interfaces in the market. Most common is the SQUARE-TAPERED. Most low- to mid-end cranks use this interface. High-end Shimano cranks use a proprietary OCTALINK interface (toothed/splined). Truvativ uses ISIS, similar to Shimano's OCTALINK.

4. If I change the crank and rear deraiileur is it likely that I can get away with the current shimano altus front derailleur?

I see no reason to shred your FD. Just have it aligned and the stops adjusted with respect to the new chainring.

HTH.

Cheers