I have a bb30 frame (cannondale caad10). 10 speed ultegra. praxis chainrings with a p2m & rotor 3d+ cranks. Just installed last week. Just yesterday I took it easy for the day and kept it in the small chainring. What I noticed when using the small chainring for my rides, the chain would rub the inside of the outer chainring when I'm in the 3rd to smallest cog in the cassette. This is my washer setup:

non drive side = 1 mm 'clear' washer (one of those plasticy ones), rotors - i think - 11.5 mm spacer, seal, then bearing. drive side = 11.5 mm spacer from rotor, seal, bearing. Last night I added a 1 mm 'clear' washer to the drive side. It helped just a hair, but there's still some rubbing going on.

My question to you folks, and maybe I should put this in bicycle mechanics, can I keep adding 1 mm washers till the chain doesn't rub? I know that will affect q-factor and all that, but I'm not concerned about that.

What chainrings do you have on there?

This can happen if you have too large of a jump between your large and small rings.

Praxis Works chainrings - 53/39

Update from this mornings small chainring ride... now only the last two cogs cause the chain to rub on the outer chainring. Not *as* bad but still wondering if I should (could) add one more 1 mm washer to the drive side without causing any other issues.

This is an issue on Short Chainstay bikes as well. Not much you can do about it.

Except adding thin chainring spacers. LeTour makes 0.6mm for running 9 speed chains on 10 speed cranks. 1.0mm aren't uncommon, and Wheels Manufacturing used to have 0.4mm which they seem to have discontinued.

I had chain rub on the last 3 cogs running a Campagnolo 9 speed chain on my "9 and 10 speed compatible" FSA Carbon Pro Compact 50-34 (allowing no useable overlap between rings running a 13-23 cassette) with 40.6cm chain stays until I shimmed it back to 8 speed spacing. After that all cogs ran fine even the small x small I eschew.

my infinito with chorus crank and Q-rings also rubs the inside of the large ring from 36 to 12 and 11. I solved the problem by not using those combos.