I have a 2006 SG. I tried to replace the stock front calipers with PM 6 piston models. We could not get the calipers to bleed out. My mechanic said my stock master cylinder was not large enough to push the brake fliud to both 6 piston models. What should one do to improve the braking and make it a bolt on job.

 

does pm make a master to push these pistons? if not maybe a proportioning valve would work

 

proportioning valve is used on cars to regulate pressure between the front and the rear. (I believe) I also think the HD braking system has an independent front and rear, so not sure how the valve you mention would help. Bottom line is you need a master cylinder that can push the required hydraulic fluid to work 6 pistons. I see this all the time on kids fixing up their cars, they buy fancy caliper systems, rotors, pads, and have gained almost noting cause the master cylinder isn't rated to support the caliper.

I'd contact the people selling the caliper and ask for the solution from them, I'm sure you are not the first to have this problem. What I am surprised is that they didn't inform you what would happen.

 

+1 They should have told you when you bought the calipers.