Caliper pistons dumb question

[WAC1972]

I am replacing the pads on my rear and was wondering if both pistons are supposed to be able to back off or is one side stationary?

[naturbar]

piston on both sides move - i just did my rear 07 RSTD last week. you will need to compress the pistons all the way in (use "C" clamp and old shoe to compress). but first crack open the lid on rear master cylinder (stuff shop rag around it) but in order to open the lid you will need to remove the allen screw which holds it in place and remove the metal bracket. you're doing this so the fluid can back up into the reservoir when you compress the pistons. any further questions fell free to call me 336.465.8259.

 

Buz

[LilBeaver]

Make sure that when you do compress the pistons you press them evenly all the way around. What I do is hang on to an old pad or two and put the old one on of the pistons and put pressure on the old pad - to try to ensure equally applied pressure on all parts of the pistons (and to not mess up the new pad).

 

Also, make sure you clean those pistons really well BEFORE compressing them back into the caliper. You really don't want that kind of crap buildup to make its way into your caliper, the fluid or to create an issue with the seals.

 

[V7Goose]

First, there is no need to open or even loosen the cap on the master to compress the pistons - the cap is vented (that is the only way the system can work). And on a side note, this is exactly why you should never add fluid as your brakes wear. The system is designed so that you can never run too low before the pads are fully worn out, and if you ever top the system up before changing to new pads, you will have a mess when you do compress the pistons. If you ever find a master cylinder BELOW the minimum level, then there has been a leak.

 

Second, try to avoid the use of a C-clamp to compress the pistons, and if you do use one, you MUST use something like an old brake pad over the pistons so that they are compressed evenly. It is VERY easy to cock a piston in the bore if you push it in from just one side, and this can cause real damage to the slave.

 

The fact is that slave pistons must move easily (or else the brakes will constantly drag). Almost always you can easily compress the pistons with nothing more than your thumbs if you use one on each side of the piston and just apply steady pressure. If they are not moving, then they are probably slightly cocked already, and you want to be very cautious of using a clamp to just force them in.

Goose

[WAC1972]

Thanks for all the info. I got it done....