The Stovebolt Site Forums The Parking Lot Big Bolts brake improvement

I'm thinking it might be nice to improve the brakes on my 1950 4100 a bit; I'm hauling some heavy loads and sometimes it feels like there's more pedal travel than I'd like. The truck has an odd mixture of parts on it. The wheels are 16", 8 lug. Grigg helped me identify the rear axle as a Dana 70. The front drums look like 12" the rears 14", and there's a relatively newer looking master cylinder and power booster on the fire wall. When I had the inspection done, there looked to be a fair amount of meat on the shoes, and not much by way of available adjustment at the shoes. I'm wondering if I may not be using the full length of the master cylinder, and I could use a longer rod, and/or maybe attach the rod further down the pedal to get a bit more travel. Or maybe a bigger bore master cylinder might help. Barring that, I can get a disc brake conversion kit for the Dana 70 rear fairly easily, but I'm not sure what I could do to upgrade the fronts (I think it was Grigg that was suggesting it might be a custom fab job to convert the fronts to discs). Any ideas, input on thngs that worked well, or poorly, would be appreciated.

Be sure to bleed the brakes before going in to anything complicated on the lots of pedal travel thing. it could be just a little bit of air.

My next guess is that you have a master cylinder with too small a bore for the wheel cylinders. Assuming you have 3/4 and 1 ton stuff I would expect to see a MC bore around 1" to 1.25"

Then you may look at the linkage, unless it looks ____ed up / unsafe to start with, then fix that first.

Start simple and go from there....

Something else that you may to check out are the drums. It might be possible that they could have been turned so many times that they are now way oversize on the inside diameter of the drum.

I am not sure, but I can think of at least a couple of theories that could cause oversize drums to reduce braking performance. Not to mention that if they are extra thin, it's possible they could cause catastrophic brake failure.

John

True, oversize drums can actually swell when perssure is applied and cause a soft pedal. Then they break and the pedal gets really soft.

I guess another possibility is spongy rubber lines; I'll have a look at the lines, too.

May be check that the shoes are adjusted and nothing is stuck. Sounds like its worth getting right.

Mark I'd love to see some photos of this truck! Can you post some somewhere? Or email them to me and I'll post them where they are visible to anyone you want to see them.

I'd like to see the front fenders, hood and grill to see if they are the same as a 3800 or a 4400. Then I'd like to see the fit of the front wheels in the fender wells.

And I'd like to see how the rear axle is mounted under the rear of the truck.

I hope the pictures aren't too much to ask. I'm really interested in what they look like.

Finally got back to this. Tried the simpler things first. No air in lines, adjustment looks OK, shoes seem OK as do drums. So we tried swapping the old MC (1 3/4) with the biggest bore substitute we could find that would fit on the booster; that was 1 7/8". Unfortunately that gave no noticeable improvement (of course all I guess you'd expect would be a decrease in pedal travel to around 87% of what you had before, which isn't a whole lot). So I'm still looking for suggestions. Maybe the key is figuring out what the front axle/brakes came from. Any ideas would be appreciated.

Pictures?

I've got the front brakes off now. The friction material measures roughly 1.75" x 11" (actually a bit under 11"). I'm thinking that this is consistent with the front brake for a 3600. I see that the front for the 3800 is nominally listed as 12" x 2". It almost looks like you could use the 12" x 2" shoes instead of the 11" x 1.75", simply by turning the drum and extra 0.250" deeper (but retaining the old backing plate, wheel cylinders, drum). Does anyone know if this more-or-less drop-in replacemen/upgrade is possible?

Thanks,
Mark

Your figures don,t add up. You can,t go cutting masive material off drums to modify things. If your rear are the 2 wheel cyl. type they have 2 adjustments. If you get the adjustments right & all the air out of the system you will have a good pedal.

He has at least a newer Dana 70 rear, and perhaps a different front.
I agree, don't modify drums.
The difference in 1/4" of brake lining width should not be a significant improvement unless you are pushing your brakes to their limits stopping your truck now. Doesn't sound like it's worth the aggravation to do anything with them to me.

I agree, if you have all the air out of the system and good drums, lines, and properly adjusted shoes you will have a good firm pedal.
Could it be possible that someone has a wheel cylinder installed upside down and the bleeder screw is not on top, therefore trapping air in the cylinder?
If that checks out OK then I would bleed the brakes several times and with different methods trying to be 100% certain the air is out. Try pumping the brakes to bleed, and also try a vacuum bleeder.

Grigg

Can you adjust the brakes to where the wheel won't spin without using the pedal?