Brake question

[Harry Moon]

Does anybody see a technical or operational issue with using 1.1/2 inch wheel brake cylinders on the front brakes as opposed to the original 1.3/8?
I'm installing the larger axle on my C60L with the wide brake shoes, the original wheel cylinders are the same physical size as the commom rear brake cylinders, WC4511, but instead of the larger bore they have the same smaller bore as the WC4517. Can't find a part # and as the units are in excellent condition I'm thinking of rebuilding them. But I have some 4511's in stock and they fit but does this change make a difference? I have to think they did it that way for a reason as it would have been simple to use the same rear cylinders but they didn't....

[rob love]

I believe it was so the front wheels don't lock up as easily and thus negate your steering during a hard brake application. But generally, for the easy life these trucks are going to lead now, it shouldn't matter. That is.....until it does.


The engineers may have designed them this way based on the likely loads of the front vs rear axle.

[Bob Carriere]

In the absence or even existance of a brake equalizer valve they used the large wheel cylinder to get more force on the front wheels who do at least 60% of the braking.... but as Rob pointed out..... with out a heavy load in the rear to make greater demand on the front braking system you are probably alright.

Now if you have the booster brake system I would definitely stay with the larger front wheel cylinder..... this is a Trump recommendation not based on hard facts.

Cheers

[rob love]

Originally Posted by Harry Moon

.... they have the same smaller bore as the WC4517.....

Do you mean 4571? That was a common cylinder on the Fords.


Bob: I think what he is trying to say is that instead of using the 1-3/8 cylinders on the front he wants to use 1-1/2. But it seems to me the 20" tired vehicles used 1-1/2 all around, didn't they?

[Harry Moon]

Yes its the 4571, just went by memory. wonder why even when they went to the big brakes on the front they used the smaller wheel cylinder even going so far as to use a different 1 3/8 than on the smaller front brake trucks.

[Bob Carriere]

Do you have one on the C60L????

[Lynn Eades]

What size bore is the Master cyl.?
My guess is it is 1 1/4" (Thinking out loud. Not really relevant)

For the 1 3/8" bore wheel cylinder there will be less pressure applied to the shoe, than with the 1 1/2" bore cylinder, for any given pedal pressure.
Basically you will get used to it, either way.
The linings you choose will possibly make a more noticeable difference.

I will also make use of the Trump indemnity, Just in case (Thanks Bob!)

[Phil Waterman]

Hi Harry

Without getting out my hydraulics hand book, I want to say that going with large wheel cylinders is going to effect how much peddle travel will be needed.

As has been said how hard or soft the brake linings are will effect braking more. To me softer is better, preference to waring shoes instead of drums.

With all three of my CMPs brake adjustment is the biggest factor in brake performance. It's the difference between being able to lock up all 4 wheels if needed. Stopping without pumping the brakes.

But to Bobs question does the truck have brake booster?

Cheers Phil

[Harry Moon]

Yes the truck has the original brake booster. The existing brakes do work fine but I picked up this axle with the larger brakes and it is in such good shape I want to do the upgrade. No real reason other than the challenge.

[Hanno Spoelstra]

If you use the larger diameter brake cylinders, for the same amount of brake pedal pressure, greater pressure will be exerted to your front brakes and thus they will brake harder. You would not want to do this, especially not if you use softer brake linings also. You risk your front brakes locking up when braking, which leads to loss of control.

Go by the specs in the book, I’d say:
http://www.mapleleafup.net/vehicles/.../chevspec.html

H.

[Tony Smith]

Originally Posted by Harry Moon

Wonder why even when they went to the big brakes on the front they used the smaller wheel cylinder even going so far as to use a different 1 3/8 than on the smaller front brake trucks.

All weight trucks use 1 3/8" bore wheel cylinders on the front, but their physical dimensions are different. Trucks with 6" hubs have 3.5" wide brake shoes, while 5" Hubs have 2" wide shoes.

To ensure the centre bore of the cylinder is aligned with the centreline of the shoe, the wider shoes have physically larger castings (the same casting as the rear brakes, but bored to 1 3/8").

[Harry Moon]

I just wonder if there ever was a part number for the larger brake cylinders with the 1 3/8 bore?

[Tony Smith]

C118q-2192

[Harry Moon]

Originally Posted by Tony Smith

C118q-2192

I was thinking of a modern equivalant like the WC4571 etc

[Tony Smith]

No modern equivalent. You have to make one up. See This post