To switch from two rings to three on a mountain bike what is involved?

Question

If I want to switch from 2 rings to 3 on the front of my mountain bike do I also need to change the front derailleur along with the shifter?

Answer 1

yea you would have to change the derailleur as well as shifter to match b/c both are calibrated specifically for a double in this case.

Answer 2

There are several things involved, first is to get the big ring and mount it to the crank. Other items to pay attention to are what length rear derailleur do you have? With 3 front rings you will likely need a slightly longer chain, a short cage will not work, so you'll need to get a long cage rear derailleur and either a new chain or add a few extra links. Next when setting up the front derailleur you will need to reset the high limit s***w as it was set for two gear operation.

Here is some help on the adjustments:

http://www.sheldonbrown.com/derailer-adj...

EDIT:

Silverbullet, Down hill bikes, the big gear is normally replaced with a bash ring, after you remove the bash ring a big ring gear can be put in it's place. Some people I know of will convert their three speed cranks to either two spd (22 & 32) and sometimes one (32t) for racing, depending on the course.

EDIT2:

Your front shifter  and derailleur should be three speed compatible.

The replacement of the rear derailleur is based on what cage length you have.

Answer 3

mtbkr has answered the question, but I have one in return.  How did you end up with a mountain bike with only two rings?  Three rings is standard on every MTB I've looked at.....

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tnx mtbkr.   Never went in for downhill.  My few offroad races have been cross-country.  Protecting the gears while bouncing off stuff makes sense.