Another Rookie Chevy Disc Brake Install with one major glitch

[Raskew]

I completed my Chevy disc conversion this evening and all went well until I installed the passenger side caliper. The caliper barely fit behind the rotor and it rubs too hard, not alllowing the Rotor to move without some major effort. If I push the piston in, it will free up the rotor a little. The Rotor rotates easily without the caliper installed.

The master cylinder is new from a 77 Bronco.

What could cause this rubbing? I'm wondering as I type this if the backing plates could be two different thicknesses. Could that cause a problem. I bought the backing plates from a junkyard and they look the same.

Any suggestions would be appreciated.

Rick

 

[ransil]

Did you take a grinder to the knuckle??
Some instructions say to remove 1/8" I had to remove mor than that I also ground the caliper a bit.

 

[TJK74]

Yep! you need to grind the knuckle a bit.

 

[kwspony]

are you sure that the spindles are the same??? I am doing the same setup and got the wrong spindles twice!!!! and the wrong caliper brackets as well.

 

[Raskew]

I have a Dana 30 and I didn't have to grind the knuckle, there was plenty of clearance as far as I could see. Has anyone else with a Dana 30 who has done this conversion not had to grind?

I measured the spindle, cause thats what I thought it was intially and it measures the same as the chevy spindle is supposed to except that is 0.001" smaller where the inner wheel bearing sits. That's not enough to cause a problem, is it?

The caliper brackets/backing plates look to be the same visually. Are there any dimensions anywhere on these?

Rick

 

[Raskew]

I just had an epiphany. I noticed when I bled the front brakes the front part of the master cylinder drained. I realized that the brake lines are crossed, but I thought no big deal I'll change it later. Now I'm thinking if the front MC reservoir is for the rear drums, then it must have a residual valve in it and this could be causing my brakes to bind.

What do you guys think?

Rick

 

[raleigh_bronco]

My backing plate was catching on the lead weights on the inner wheel used to balance the tires/wheels.


I also went up to the F250 camper special master cylinder and removed the residual valve from the rear reservoir.

 

[$$PIT]

I just had an epiphany. I noticed when I bled the front brakes the front part of the master cylinder drained. I realized that the brake lines are crossed, but I thought no big deal I'll change it later. Now I'm thinking if the front MC reservoir is for the rear drums, then it must have a residual valve in it and this could be causing my brakes to bind.

What do you guys think?

Rick

Sounds possible if you have already bled the system. Might as well swap the lines and find out since you have to do it eventually. Also, I did the conversion on a D30 and the caliper/knuckle clearance was real close so I went ahead and did some grinding, but it may not have been necessary.

 

[Raskew]

I'm gonna give that a shot tonight. Any other possibilities?

Rick

 

[chuck]

The res. valve may cause a little drag but if your lines are crossed you will have a low peddle.

 

[Raskew]

Does anyone have a schematic of the 77 Bronco braking system..Showing discs on front and drums in the back?

Rick

 

[66horse]

On the dana 30 part and grinding. I did grind. Now that I think about it I am not sure if I checked if I needed to.

Here is how you can figure out.

Put the calipers on without the brake pads. Then fully deflect the calipers. Do you get what I mean? Move the caliper its full movement. Watch the clearance between the knuckle and caliper. You will watch on the backside of the backing plate.


Good luck!

Steve

 

[Raskew]

Well I relocated the brake lines to there correct location at the MC and removed the residual valve from the large reservoir. I have speed bleeders on the calipers and when i open them on the passenger side residual fluid comes out and the brake unlocks and works fine as long as the bleeder stays open as soon as i close it and step on the brake it locks again. I'm stumped.....help!

Rick

 

[raleigh_bronco]

go in there and make sure the caliper is clearing the knuckle by atleast .100" min.

Mine passenger side wouldn't brake b/c it was binding against the knuckle... ground it down and she works great.

 

[Raskew]

i'll post pics tonigt, but i have .100" easy. Could a defective caliper be the problem? How would i test?

 

[raleigh_bronco]

i'll post pics tonigt, but i have .100" easy. Could a defective caliper be the problem? How would i test?

compare both calipers for piston extension. Are they both extended about the same amount. If one is further than the other you'll get a good impression of what's going on.

 

[Raskew]

I'm gonna have to check that on Wed. Where exactly does one have to grind the knuckle for the caliper clearance. If I'm between the front and rear wheel and looking towards the front of the truck, where am I grinding?

Rick

 

[chuck]

Well I relocated the brake lines to there correct location at the MC and removed the residual valve from the large reservoir. I have speed bleeders on the calipers and when i open them on the passenger side residual fluid comes out and the brake unlocks and works fine as long as the bleeder stays open as soon as i close it and step on the brake it locks again. I'm stumped.....help!

Rick

What is between that caliper and the M/C? If nothing a flex line is bad.

 

[Raskew]

There is a distribution block on the firewall and a fitting sitting on the top of the axle.

Rick

 

[raleigh_bronco]

Use this link for pics. You'll see exactly where to grind.

Very good Chevy Disc Brake Swap Link