Need Help School me on Bottom Brackets and cranksets

[jqualls]

I just bought my wife a 2012 Yeti Asr5 frame and I am considering transfering the build from a 2010 Trek Fuel EX9.9. I am pretty comfortable with working on my bikes with everything except the bottom bracket and cranksets. I figure its time I learn the ins and outs of BB's and Cranksets.

If I was going to transfer the Truvative Noir crankset that currently uses a BB95 bottom bracket on the Trek to the Yeti would all I need to get is a new GXP bottom bracket or other truvativ compatible BB for a 73mm shell. Is the spindle length going to be something that is a problem for my chainline or is spindle length pretty standard? Will I need to pull the crank off the Trek to measure the spindle to determine if it will be compatible on the yeti?

I have been doing some research on the subject and sorry if this is a jong question but I dont feel like a have a good handle on it yet so I am going to turn to the knowledge here to school me.

I am not sure if it is needed but the drive train is a 3x9. I would guess it might make a difference for spindle length but maybe only if I was changing from one drive train to another.

Thanks in advacne for the help.

[willmtbike4food]

First off, don't bother trying to learn all the ins-and-outs of crank/bb standards - you'll go crazy trying to remember them all, and just as soon as you think you have them figured out, there'll be a new 'standard.'

TruVativ GXP MTB cranks from 2010 are one and the same.

A BB95 uses a GXP MTB crank, and a 2.5mm spacer on the drive side between the wave washer and dust seal.

A BB90 uses the same GXP MTB crank, a 5.5mm spacer on the drive side, and a 2mm spacer on the non-drive side.

To use a GXP MTB crank in a 73mm bb shell, use GXP cups and no spacers.

To use a GXP MTB crank in a 68mm bb shell, use GXP cups and 2 spacers.

[jqualls]

Thanks for the straight forward explanation. That is basically what I was thinking but wanted to make sure I wasnt missing something.