xt derailleur and 48 tooth chainring

I think shimano states a xt front derailleur can handle a maximum of 22 teeth difference between
chainrings (44-32-22). But could it handle a 26 teeth difference (48-36-22)?

 

"gerrit van wijk" <[email protected]> wrote in message
news:<[email protected]>...
> I think shimano states a xt front derailleur can handle a maximum of 22 teeth difference between
> chainrings (44-32-22). But could it handle a 26 teeth difference (48-36-22)?

It could handle that tooth difference, but not stock with the 48 tooth chainrings. The curvature of
the outside plate is matched to the chainrings it is designed for, so the one for your compact
drivetrain will be more curved than a 48 tooth chainring. This will force you to mount the deraileur
high, and decrease shifting performance as well as ability to shift accross that difference. You can
change this, however, by using a grinder to rework the curvature of the outer chainplate. I have
managed to get a deraileur to shift from 24 to 52 teeth this way. Look at Sheldon's site for more
details on this.

Whitfit.

 

On Sat, 12 Apr 2003 13:58:01 -0400, whitfit wrote:

> "gerrit van wijk" <[email protected]> wrote in message
> news:<[email protected]>...
>> I think shimano states a xt front derailleur can handle a maximum of 22 teeth difference between
>> chainrings (44-32-22). But could it handle a 26 teeth difference (48-36-22)?
>
> It could handle that tooth difference, but not stock with the 48 tooth chainrings. The curvature
> of the outside plate is matched to the chainrings it is designed for, so the one for your compact
> drivetrain will be more curved than a 48 tooth chainring. This will force you to mount the
> deraileur high, and decrease shifting performance as well as ability to shift accross that
> difference. You can change this, however, by using a grinder to rework the curvature of the outer
> chainplate. I have managed to get a deraileur to shift from 24 to 52 teeth this way. Look at
> Sheldon's site for more details on this.

There's more than one model of Deore XT front mech. I have one I use with a 24/36/48 crankset that's
made for "full size mountain" cranksets. It shifts fine. On another bike with the identical gearing,
I'm using a 105 braze-on front mech; that works fine too.

In my experience, the big deal with front mechs is the middle and outer rings. I like small
grannies, and I've never had a problem related to the size of the granny ring. I wouldn't think the
difference between a 22 and a 24 T inner ring would matter much, especially since with tiny grannies
you only use them with the 3 or at most 4 large outer rings, which give the chain an ascending angle
as it heads towards the back of the bike, reducing the chance that the chain would drag on the
"heel" of the shifter cage.