got my new bike with a 180mm rotor up front, removed it and replaced with a 160mm one. My fork is a rockshox sid RL 29er. The caliper only had washer between the bolt head and caliper, NOT between the fork mount and caliper. Do I need some washer between the fork and caliper? The disc looks to be perfectly positioned with the brake pad.

thanks

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2013 rocky mountain vertex 29er
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the convex/concave washers are required for the 180mm post mount adapter. the adapter is thicker for the top mount than the lower mount. it angles the caliper relative to the fork leg, so the caliper will sit crooked relative to the bolt heads. the washers square things back up for the bolt heads.
when you remove the adapter to use the 160mm rotor, you leave the washers off.
this is all new for SRAM/avid brakes as of about 2012.5. it was a gradual rollout.

hey thanks for replying. I did found a bit of info and it seems its new with 2013 avid brakes, the CPS system is out.

as I understodd it, for a 160mm front brake, you bolt the caliper directly on the fork but you leave the CPS washer between the bolt head and caliper. FOr the rear brake, there are no washer needed at all.

Please let me know if its correct and if I can ride the bike safely without destroying anything. The front rotor is perfectly aligned in the brake pads.

thanks

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2013 rocky mountain vertex 29er
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Should be good to go then!

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Trek 5500 - 13.75lbs on a $1400 Budget
20 gram 1x10 chain guide

from what ive understood (and i have been wrong on occasion), you use the cps washers between the caliper and bolt head when you use an adapter (post mount -to- post mount) to go to a larger rotor. and that's it.