g741.org

yesterday after some spring maintenance on the brakes, as I sat pushing the pedal with the cover removed I noticed mass deflection of the mc.

with the aid of a steel plate and a depth gauge, I measured .060 of deflection at the fill cap. I slid under the truck in search of loose bolts and cracked cab mounts. every thing was good. I went to the next truck measured 0.80 of deflection. and on down the line. the least amount of deflection measured was 0.050 ...

now I know why the brakes always feel a bit spongy. the 3/16th ] bracket that runs from the lower bolt of the mc to the opposite wall of the cab mount is not up to task of supporting the mc.

a new master cylinder support bracket is needed. a big chunk of angle iron tying the three mc bots to the cab mount to cab bolt and a couple triangles tying it all together.

I would suspect this flex is noticed more on trucks with a dual master and a larger bore.

no thoughts ?

I know, I know.......... whats .060 of deflection on the master at the fill cap........

..............about 1.5in of pedal travel

* estimation not maths accounting for actual pedal ratio *

I hadn't noticed any flex as described but will make it a point to check further. I deemed my brake overhaul 100% successful but would like to explore this further to see if I can achieve an even stronger pedal than I already have.

Thanks for the post- I'll weigh in again once I check mine out.
Gary

I'll take a look at mine. I do recall replacing the pedal bushings made a huge difference in eliminating slop, so I can see how a bit of flex would multiply.