Rear Disc Brake Upgrade Update

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Jglew82

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Dang, I'm almost sorry I asked about the parking brake on this swap, but nonetheless, the responses have been entertaining :)
 

bigpapiray

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Very interested in this.... I ordered front calipers/pads (RockAuto Power Stops) and absolutely hate the drums that won't adjust properly.
I tow a 2100# car on a 20' trailer & braking sucks as I've had to manually adjust the rear shoes twice ..... but that only lasts so long before having to re-adjust. I mostly stop using the trailer brakes..... Lol.
My pig is a 97 maroon/purple same as yours though
 

bigpapiray

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I know quite of few forum members thought that is was a waste of time to convert to rear disc brakes.

I reported what I found with a much improved pedal feel. Nos so hard of pedal etc.

I have driven this for several months and contemplated to going to bigger rotors and 4 piston etc because I thought it should be better than what I was feeling but have been too busy to do anything about it.

However I knew I did not do anything with the disc/drum master cyl and I knew that was not right.

So I decided to check the caliper pressures knowing that the rear and fron should be about 1000-1100PSI

Mind you that this is a K3500 with a hydroboost.

I purchased a pressure gauge and checked it and found the rear disc was only 475psi and the front was only 675 psi

I was shocked and happy at the same time.

I installed a new disc/ disc master cyl with a 1 1/8 bore which should be correct for the conversion with no residual or prop valve.

I installed the new MC and the readings are now 1050 in the rear and 1100 psi in the front.

I took it for a drive and was delighted as it feels like a newer truck with a very nice normal feeling pedal and unreal stopping power from what I was experiencing.

No more hard pedal feeling and no more dull feeling pedal. It has the feel you should expect a truck to have even though it was an older truck. To me 4 wheel disc brakes should feel the same on any year truck because the brakes do not know a thing..

It pays to check things more closely and the pressure gauge told the story.

Converting to Disc Brakes all the way around with a new correct MC with the correct bore size changed this truck stopping power 100%

I let a buddy of mine drive it who has a 2015 GM 3/4 ton and he says it feels and stops as good as his truck

Best thing I have done to the truck as far as safety is concerned.

Go ahead naysayers and attack!!...but for those who want to do this conversion I would be happy to share info
What parts did you use in the entire swap? Do you have a complete parts list?
 

Supercharged111

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One issue with the E-Brake/Parking Brake is that the cable can freeze in the winter. I have had this happen on 2 vehicles in my driving career. 1 of them is my 89 GMT400. I have a manual 5 speed. While I do use the parking brake in the summer I will not use it in freezing weather. First winter I had this truck the cable froze and it took me 5 tries to rock the truck to pop the brakes loose. Back in the early 90’s I had a car that the first 3 times it froze I was able to rock the car to release the parking brake. The 4th time I had to get a ride home and go back later in the afternoon to get my car. After that I never used the parking brake.

I do not like that the brake cable can hold water and freezes in the winter time.


Sent from my iPad using Tapatalk

They freeze in the rust belt too. With rust. You use it and it doesn't release. Before I left MI, I never used a parking brake on an automatic car.
 

arrg

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Gibson

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The pistons in a disc brake caliper are much larger than a drum brake wheel cylinder and need more volume to move.

That is an idea that just keeps being repeated so often that many think that it's true,, but it's false.
Actually the pistons in a caliper move very little, only a few thousands of an inch, they are already dragging on the rotor even when they are in the relaxed position.
The difference between brakes off and brakes on is just an increase in fluid pressure, the motion of the piston is so small that the rubber boot is the return force,, perhaps a couple of ounces.
 

454cid

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That is an idea that just keeps being repeated so often that many think that it's true,, but it's false.
Actually the pistons in a caliper move very little, only a few thousands of an inch, they are already dragging on the rotor even when they are in the relaxed position.
The difference between brakes off and brakes on is just an increase in fluid pressure, the motion of the piston is so small that the rubber boot is the return force,, perhaps a couple of ounces.

The boot is not the return force, the square seal on the piston does that.
 

John Cunningham

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The only thing that matters is how much pressure you are putting on the front and rear discs
You need about 1100 PSI to the front and rear and you do not need a prop valve.
Find the Master Cyl. that will give you that pressure and problem solved.
You dont need a lot of fluid volume for disc brakes
The Master Cyl should not be a step bore with two diameters contained within. One last thing is to make sure the brake rod seats within the MC and is the right length.
You have to pay attention to the rear step diameter. It could be different from a hydroboost like my truck or a vac boost.
 
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