[sleepdoc]

I need a bit of input on my brakes.

My 74 3.2L conversion has rebuilt stock rears, venting set at .004. Rebuilt 320i calipers in front. New pads all around. New stainless lines. New 19mm M/C. Brass brake line "Tee". I am now post multiple bleeding sessions, about two gallons of fluid.

This is a follow on from a previous post.

The original problem was the calipers were binding and the pedal was getting hard as a rock and very high when the disks got hot, leaving all four corners locked.

cle2cont gave me the pivitol idea. Since I could relieve the lockup by opening a bleed screw at any corner, he suggested the MC wasn't returning to baseline and allowing the return of fluid. I recalled that I had lengthened the MC actuating rod to give a short pedal throw, so I shortened the actuator rod and now no more binding. Ok great.

I have a firm pedal and have been working the new pads so they are biting better and better.

My current question is about pedal travel. Looking at many posts about MC and 320 calipers it appears that the bigger 320 pistons require more fluid leading to a longer pedal travel until the pads hit the caliper. This also leads to some recomendations to go to a bigger MC (19mm) to fulfill the need for more fluid movement to keep the pedal travel about stock ( and requiring a bit more force).

I have no complaint about the braking behavior, it is pretty darn good, and no complaint about the amount of force needed to actuate the system.

I am perplexed however about the pedal travel. I have the rear venting adjustment up tight, and have adjusted the actuater rod longer and longer. In order to get reliable release of the brakes after hard use( ie no binding or locking up) the actuating rod must be set so that the pedal moves about two inches before calipers start to work, then firm and normal from there.

The acuator rod is supposed to be set so that there is 2mm freeplay before it contacts the MC socket it rides against. If I set it there the pedal would move maybe three inches to firm contact. There is plenty of pedal travel left so this doesn't seem dangerous, it just isn't right.

I have the sense that the calipers are working correctly and that the MC is not behaving as expected.

I wouldn't mind a small increase in pedal travel, one of you proposed that the 320 brakes reuire 25% more fluid and the 19mm MC supplied 23% more fluid at higher foot pressure. If correct this seems close enough so that the slight increase in pedal travel should not be irritating.

Your comments and ideas are awaited with appreciation.

best Mark