Hard Pedal, Poor Braking Performance - Manual Drum Brake Setup

[SnowStorm34]

Hi everyone, in case you didn't see my introduction post, I have a small homebuilt tractor my grandfather made in the early ‘80s. It’s cobbled together mostly from automotive parts from the 50s and 60s.

Last summer I tried fixing the brakes on it (they hadn’t worked in a long time). I rebuilt the master cylinder, replaced the wheel cylinders, flushed the line, and adjusted the brake shoes. They work now, but not very well.

I have a rock hard pedal, yet there is not enough braking power to hold the tractor in place on an incline. I even tried over adjusting the shoes so they would drag- still didn’t work very well (though they did work better).

Here are additional details of the setup.

MC - From an early 60s Ford sedan. Rebuild kit sourced for a 1962 Galaxie. Single pot, 1” bore, manual.

Wheel cylinders - From a ’72 Suburban.

Shoes - I didn’t replace them, not sure what they’re from. I’ve attached a photo from when I had one of the drums off. I thought they were okay after cleaning them up. I'm certainly having doubts about that now!

Tractor in general - Weighs around 1600lbs, rear brakes only. Handbrake is mechanical and runs on a different system (it works fine).

I'm leaning towards thinking the issue is with brake shoes, but I would really appreciate a second opinion before tearing into them.

Thanks

 

[MercuryMac]

My first thoughts for you were; I think brake drums were made to turn fast so the shoes work better on the speedy swirling of the drums, but a farm tractor does not turn the drums very fast, so the shoes don't do as much stopping. [S
My second thought is to ask if all four of the wheel cylinder pistons were free in the cylinders. They will probably be aluminium and the cylinder is steel. They will probably have bonded together after sitting so long. If the pistons are stuck in the cylinder, you are not squashing the shoes out into the drums at all. Your shoes should be O.K., if you can get them to move.
Good Luck.

 

[Bamamav]

How did they work before? Could be the master is too large, might need a 7/8" or smaller to create enough pressure.

 

[Blue Eyed Devil]

My first thoughts for you were; I think brake drums were made to turn fast so the shoes work better on the speedy swirling of the drums, but a farm tractor does not turn the drums very fast, so the shoes don't do as much stopping. [S

Drums stop cars that are moving slow too.

The shoes alone wouldn't have anything to do with what you are describing, regardless the shoes in the pic, while old, look to have plenty of meat on them. If you have a rock hard pedal then it should be locking those wheels up no problem. If you really do have firm hydraulic pressure at the pedal, then something is making it build. If it isn't the pressure of the shoes to the drum, then there is another obstruction somewhere. The wheel cylinders in that pic don't look new. Remove them, disassemble and clean, then reinstall. May as well do the same to the M/C. While everything is off off blow some air through your lines to make sure there isn't an issue there. Brake systems aren't that complicated, especially what you have there. There are only a few things that can cause an issue like what you are describing. Get after it...

 

[smallfoot]

Yuppers, probably just an obstruction. The easy way to tell is leave the drums off and try pushing the brake pedal while observing the wheel cylinders. It won't take much pressure to move cylinders that aren't stuck. You'll see the shoes move. In fact if you aren't careful you'll push the ends off. If you don't see movement pretty easily, something is stopped up. I'll re-affirm that manual drum brakes work just fine.

 

[Dr Crankenstein]

Just my thoughts...

You have a MC designed to support 4 wheel cylinders, but only have 2... basically, the MC is delivering 4 wheel cylinder volume to 2 wheel cylinders, which will shorten the stroke and increase pedal effort, at least in my mind...

.

 

[DozerII]

As was said I think a 1"bore is to large for two wheel cylinders. The photo of the rear brakes is it from the right or left side of the tractor? The short brake shoe has to be on the front side.

 

[SnowStorm34]

Thanks for your replies everyone!

I should have made it more prominent in my original post, but the wheel cylinders have been replaced.

The image of the brakes is from when I first took off the drum. The original cylinders were seized- I replaced them with new ones (which are replacements for a ’72 Suburban).

How did they work before?.

They used to work well. With all the different components, I also was thinking the system might just be out of balance. However I asked my Dad and he remembers the brakes working properly before. Certainly better than now.

The shoes alone wouldn't have anything to do with what you are describing, regardless the shoes in the pic, while old, look to have plenty of meat on them.

Thanks for confirming that! I had originally thought they were fine, but I’ve been second guessing myself lately.

Yuppers, probably just an obstruction. The easy way to tell is leave the drums off and try pushing the brake pedal while observing the wheel cylinders. It won't take much pressure to move cylinders that aren't stuck. You'll see the shoes move. In fact if you aren't careful you'll push the ends off. If you don't see movement pretty easily, something is stopped up. I'll re-affirm that manual drum brakes work just fine.

I actually did exactly what you warned me to be careful of! haha… I don’t think I have an obstruction. The pistons move and I had a good flow of fluid when bleeding the brakes.

Just my thoughts...

You have a MC designed to support 4 wheel cylinders, but only have 2... basically, the MC is delivering 4 wheel cylinder volume to 2 wheel cylinders, which will shorten the stroke and increase pedal effort, at least in my mind...

I’m with you 100% on this. When bleeding the brakes I got a lot of pedal travel, but normally it barely moves.

The photo of the rear brakes is it from the right or left side of the tractor? The short brake shoe has to be on the front side.

This is a photo of the right side of the tractor. The smaller shoe is on the front side.

 

[sneakysnake]

When you replaced the wheel cyl did you keep the same bore? Thing is you want as big as you can get there and small at the master cyl ,without a booster.

 

[BlueNorther]

just looked on RockAuto's site and the rear wheel cylinders for a 1972 Suburban are speced at 1", same as your M/C.

you would need a large brake pedal ratio to operate the system.

I would find a 3/4" bore M/C, which would give you way more leverage.

 

[smallfoot]

Can you show us a pic of the brake pedal lever arrangement? Everybody is trying to help but let's start at the cheap and easy stuff before changing MCs and WCs. We could maybe try the lever ratio change without spending a cent. If this set up worked before, it's not likely it won't work now with a little trouble shooting.
When I assembled the brake system on the 31. I started with a mis-match similar to some of the suggestions on this thread, regarding bore size of the MC and WC and type of brakes, drums/disks, etc. I brought a mis-matched system into good working order with just a lever change on the pedal. Mine is 1" MC. 1- 1/8" Front WC, 3/4" rear WC. on manual drums. I have plenty brakes with a little longer pedal and shorter throw where the MC rod hits the lever, increasing the pressure ratio.
Anyway, that's a cool little tractor. Those shoes look like regular C-10 style brake shoes like the suburban. You could eliminate your thoughts of that with a simple shoe change and if you really want to be good on it, find some new drums or have the existing ones turned. Something simple is causing this if they worked before...

 

[SnowStorm34]

Can you show us a pic of the brake pedal lever arrangement? Everybody is trying to help but let's start at the cheap and easy stuff before changing MCs and WCs. We could maybe try the lever ratio change without spending a cent. If this set up worked before, it's not likely it won't work now with a little trouble shooting.

Certainly

When I assembled the brake system on the 31. I started with a mis-match similar to some of the suggestions on this thread, regarding bore size of the MC and WC and type of brakes, drums/disks, etc. I brought a mis-matched system into good working order with just a lever change on the pedal. Mine is 1" MC. 1- 1/8" Front WC, 3/4" rear WC. on manual drums. I have plenty brakes with a little longer pedal and shorter throw where the MC rod hits the lever, increasing the pressure ratio.
Anyway, that's a cool little tractor. Those shoes look like regular C-10 style brake shoes like the suburban. You could eliminate your thoughts of that with a simple shoe change and if you really want to be good on it, find some new drums or have the existing ones turned. Something simple is causing this if they worked before...

Thanks for this info. If I'm going to get back into the wheels, I'll probably get new shoes for the peace of mind.

just looked on RockAuto's site and the rear wheel cylinders for a 1972 Suburban are speced at 1", same as your M/C.

you would need a large brake pedal ratio to operate the system.

I would find a 3/4" bore M/C, which would give you way more leverage.

Thanks for looking that up. I still have the old wheel cylinders- they measure in at 1”.

When you replaced the wheel cyl did you keep the same bore? Thing is you want as big as you can get there and small at the master cyl ,without a booster.

I appreciate your advice. Would going larger on the wheel cylinders have a similar effect as going smaller on the MC? For sentimental reasons I like to keep visible parts of the tractor original (only if I can, of course).

Thanks again everyone, your input has been really helpful.

 

[smallfoot]

To test the longer lever theory, clamp a large pair of vise grips on that brake lever and give yourself a longer lever. Go out to the end and see if you can get better action at the wheel.

 

[Dr Crankenstein]

For sentimental reasons I like to keep visible parts of the tractor original (only if I can, of course).

Your grandfather should be well satisfied to know, you haven't "let it go to rack and ruin". (Make the necessary changes and his spirit is well kept.)

I would also try to increase the pedal ratio, working with what you have...

.

 

[sneakysnake]

Yes, If you can get bigger wheel cyl it should help.

 

[SnowStorm34]

Your grandfather should be well satisfied to know, you haven't "let it go to rack and ruin". (Make the necessary changes and his spirit is well kept.)

I would also try to increase the pedal ratio, working with what you have...
.

I appreciate you saying this. This tractor has a lot of sentimental value to it. I’d like to keep it running, but I'd also like to keep my own finger prints off it as much as I can.

To test the longer lever theory, clamp a large pair of vise grips on that brake lever and give yourself a longer lever. Go out to the end and see if you can get better action at the wheel.

Thanks for the idea! I gave it a shot. I still wasn’t able to lock up the wheels. Though in all fairness I was a little nervous putting the massive amount of pressure as I usually would on the vice grips.

Speaking of zero dollar fixes, maybe did I adjust the brakes improperly? I got them to a point where they started to drag and then backed them off slightly.

Yes, If you can get bigger wheel cyl it should help.

Thanks for confirming this. If I end up going back into the brakes I’ll look into getting something bigger.

 

[dutch]

I own a 63 Fordson super Dexta and there`s no way I can lock up the brakes...
Emergency stop would involve lifting my butt off the seat and stand on the pedal. I bet I`m quicker 0-25mph than 25-0 tho....

 

[BlueNorther]

the proper way to adjust those bakes, is to adjust them tight so the wheel can't be rotated then back them off 6 or so "clicks" keeping the adjustment identical for both sides.

the wheels should rotate freely with just a hint of drag noise. most people just adjust them tighter til they hear dragging sounds, but the problem with that is only one shoe may be moving and start dragging on the drum and the other shoe is hanging up with a bunch of clearance. by adjusting them until the wheel won't turn, you know they are evenly adjusted.

the adjustment must be made with the wheels on.

 

[SnowStorm34]

I own a 63 Fordson super Dexta and there`s no way I can lock up the brakes...
Emergency stop would involve lifting my butt off the seat and stand on the pedal. I bet I`m quicker 0-25mph than 25-0 tho....

I guess if I have one thing going for me, it’s that I top out around 12mph haha

the proper way to adjust those bakes, is to adjust them tight so the wheel can't be rotated then back them off 6 or so "clicks" keeping the adjustment identical for both sides.

the wheels should rotate freely with just a hint of drag noise. most people just adjust them tighter til they hear dragging sounds, but the problem with that is only one shoe may be moving and start dragging on the drum and the other shoe is hanging up with a bunch of clearance. by adjusting them until the wheel won't turn, you know they are evenly adjusted.

the adjustment must be made with the wheels on.

Thanks for the tip! I’ll try this next. Based on this I may have under adjusted them.

 

[Spooner]

You could change the pedal ratio by lowering the MC in the bracket and lowering the rod on the pedal by the same amount.