[Blown353]

Small boosters inherently have less assisting power because the internal diaphragm area is signifantly smaller than a larger diameter booster. Often they try to compensate for this by running dual diaphragms but they still don't have the effective diaphragm area of a larger single diaphragm booster; even using grossly simplified math (i.e. throwing out the lost area to the center plunger and spring assy) a 7" dual diaphragm booster has only 80% of the surface area of a single 11" booster. Thus it will need more vacuum to provide as much assist as the single 11". This is why I don't like small diameter boosters. If your situation has major clearance issues my preference is either to run manual brakes (which is doable if you properly size your caliper piston area to the MC bore size, but some calipers like PBR's don't lend themselves to manual use) or run a Hydroboost. I've never been a big fan of supplemental electric vacuum pumps either.

A hydroboost will cure all your weak brake issues and then some, TONS of assist power available. I got mine from Paul at Hydratech and would buy from him again without a second thought. Great guy and great product.

How much vacuum are you making? Small diameter boosters typically don't like under 16-17 in/Hg because of their reduced surface area. I've had mixed luck with large diameter boosters (11") working decently all the way down to 11-12 in/Hg.