Brake Caliper Rebuild Kits - 02-04 R6 Blue Dot

First, are there any better kits/parts other than OEM?

Second, How do I know when the pistons are too far gone?

Third, Why are the "Upper" pistons and seals a different part number than the "Lower" pistons and seals when I look up the parts??

 

Look at manual to see if there is OD measurement and limit. If answer is no at least do a visual for pitting or gauling and replace as needed. There are other vendors for piston search the threads as I remember seeing 2 or 3 listed.

 

JPBRAKES and Braketech are 2, have to search and see if they have them for that year.

 

Thanks for the info!