'39 - '48 Master Cyl...rear hyds on a '32
 

Anybody got a loose '39 - '48 mast cyl they could measure the stroke for me ? And the '32 rear axle in my p'up causes the '40 backing plates to be rotated which in turn places the wheel cylinders at an angle, I'm concerned that some air might be trapped in the lower portion of the rear cylinders. Is there a way to bleed the rears or is this maybe me thinking
too much.

Thanks,
Charlie ny

Re: '39 - '48 Master Cyl...rear hyds on a '32
 

Hi Charlie,


I just measured an old 39 master I have. I put it in the vice and measure a 1-1/4" stroke.

Re: '39 - '48 Master Cyl...rear hyds on a '32
 

Regarding the air pocket you will have with a non-horizontal wheel cylinder, I don't believe you will have a problem if you do a proper brake bleeding. The small amount of air will be absorbed into the high pressure brake fluid, think carbonated drinks.

Pump the master cylinder increasing the fluid pressure and then bleed. You'll get most of the air entrained fluid out. I like to keep a newly bled system pressurized over night by blocking between the front seat and the brake pedal; and then if spongy, i.e. air is in the system, bleed it and re-bleed.

The bleed valve in the picture below will be in the same circle as the brake line but is hidden.



https://i69.servimg.com/u/f69/19/88/31/04/air_po10.jpg

Re: '39 - '48 Master Cyl...rear hyds on a '32
 

I have a steep entrance to my garage. I always used it to get the cylinders more horizontal. I never tried it level!

Re: '39 - '48 Master Cyl...rear hyds on a '32
 

Hi Charlie,
Yes you will have trouble getting the air out of the rear wheel cylinders. I have had trouble with bleeding the rear brakes on two 32s & some 34s with rotated backing plates. I could not get a good pedal after pressure bleeding or reverse bleeding. If the brakes are assembled if you could jack the rear up high enough to get the cylinder level, that would work or maybe with the vehicle facing down a incline. What I do now when assembling these brakes is to carefully remove the front piston & cup tilting it so there is a slight gape at the top to let the air out. You could also unbolt the backing plate & twist it level to bleed the brakes then reassemble.

Phil.

Re: '39 - '48 Master Cyl...rear hyds on a '32
 

If the backing plates will rotate on the housing enough you could mark them and re-drill the holes. Since they need to be bled anyway if you re-drilled another pair, you could probably swap them in a day, maybe 2 if you need longer brake lines.

Re: '39 - '48 Master Cyl...rear hyds on a '32
 

Thanks guys....I jacked the butt of my '32 up to almost get the backing plates horiz,
I did get a couple pfft's out of each cylinder. It's hard to believe that made a difference but it did. Went around al 4 corners again, very nice solid pedal 1/3 down. Now on to the vibration at 50 - 60 mph.....if it's not this it's that....if not that it's this....all something.
Mucho appreciato.
Charlie ny

Re: '39 - '48 Master Cyl...rear hyds on a '32
 

On modern cars, the wheel cylinders are alway are fully compressed and the adjustment spreads the bottom of the shoes. With the early brakes with the adjustment at the sides, the wheel cylinders expand. Turning the side adjusters all the way in would help get the air out. Readjusting the brakes would be a pain.
I thought about redrilling the plates. I decided it would not work due to interference with the spring mounts.

Re: '39 - '48 Master Cyl...rear hyds on a '32
 

This should serve to convince folks that even a LITTLE bit of remaining air AIN'T "GOOD ENOUGH"! DD