i pulled the rims off for some paint last night. spent a lot of my youth working on dirt bikes and now mountain bikes so it was very easy. now thinking into the future, when i put 'em back on ... will i have to remove the brake calipers to get the wheels back in place? it was an awful tight fit getting them out.

second question, if i do remove the calipers is there any mechanism for making sure they're centered on the rotor. the discs on my bicycle have a whole procedure for alignment, dunno if this exists on the gs.

thanks!  

Yes you should remove the caliper FIRST when removing the wheel. I'm suprised you actually got it off with it on...

And the caliper floats back and forth on the caliper carrier's pins (thats the part you bolt to the fork leg). So it's "auto centering".

To be more precise, you don't need to disconnect the caliper from the brake line, you just need to move it away from the retaining arm. You need to remove only the nut with the cotter pin like in this picture.
http://www.angelfire.com/mt2/mikesgs500/chain/DSCF0193.JPG

that makes sense. do i just disconnect the front caliper from the fork to get it out of the way?

if its a stock rim and tire sizes front and rear? why would you need to pull the calipers?   not once have i had to do this, front or rear. just dont move the brake levers so you dont close the pads. :dunno:

okay, now i'm confused again  

Ok, I'm far from an expert, but I took off both wheels to put new rubber on this summer. For the front, I romoved the caliper from the fork, and let it hang by the brake line. For the rear I diconnected the caliper from from the bracket that connects it to the rear axel, unlike diconnecting the bracing arm like miket did. Once I did this, I put scraps of wood between the brake pads to keep the pistons from pushing out if the brake levers were touched. This was pretty painless, the front was a cakewalk, but you might want someone to help you putting the rear back on. I don't know if this is the easiest way, but it worked for me. Best of luck.

What JamesG is stating, and I agree, is that it would be easier to unbolt the front caliper from the fork leg, and let it hang out of the way of the front wheel to remove the front wheel.

miket is speaking of the rear wheel, and I agree with him, you shouldn't have to even touch the rear caliper to remove the rear wheel or the brake stay. The rear wheel should just roll out straight back.

And Blueknyt is stating that you don't have to remove either of the calipers. Which I know you can do, it just seems easier to get the caliper out of the way first. It's just another option of how you can do it.

As far as preventing the pistons from moving, I have found it easier to remove the front brake lever, because I don't have anything to wedge in between the pads (and I don't like to use a screwdriver, because either I need to use it or I don't want to deform or mar the pad surface). As for the rear, well either I put a block of wood under the brake arm or I just really careful to avoid it.

thanks for the clarifications! i will pull the front caliper off before putting the wheel back on then.