Disc Brake Conversion - Wheel Drag

[LBC TITAN]

Hello All,

I've completed my front drum to front disc conversion a few weeks ago, but I have a problem. I had the hubs turned down to fit the rotors of a Chevy S-10, I repacked the bearings, installed 20" brake lines, and installed the Scarebird Corvair brackets.

The rotor and hub spins fine up until I start tightening the lugs on wheel and then the wheel doesn't turn freely, feels like it's dragging, what do you think is happening? The wheels are American Racing 15" rims with BF Goodrich T/A Radials 205/60/15 tires, I've checked the clearance on the rim and it is not coming in contact with the caliper.

[cnicol]

Is the back of the rotor touching the knuckle? Tie-rod end touching the rim?

[LBC TITAN]

Nothing is touching the rotor at all, but you maybe on to something about the knuckle. I will check tomorrow and let you know.

[terribleted]

Is it the caliper not fully releasing? Did you adjust the master cylinder push rod length for clearance? This is generally necessary when installing disks and a dual master. The rod length tends to be a little long and therefore holds the master cylinder piston slightly depressed which can cause a brake drag. there needs to be a around 1/8" slop in the push rod before it contacts the master cylinder piston.

[azdave]

Is it the caliper not fully releasing?

Read his first post more closely. He hasn't even touched the brake pedal yet. He says when he tightens down the lug nuts the wheel binds on something.

[LBC TITAN]

Is it the caliper not fully releasing? Did you adjust the master cylinder push rod length for clearance? This is generally necessary when installing disks and a dual master. The rod length tends to be a little long and therefore holds the master cylinder piston slightly depressed which can cause a brake drag. there needs to be a around 1/8" slop in the push rod before it contacts the master cylinder piston.

I already have a dual master cylinder with the disc brakes so the Mc is not an add on. I did in fact bled the entire system before test driving. I used to be able to push the car around s with the hand brake off now it takes more of my limited super powers. The disc brakes are definitely t touching the rotor as I turn it.

How do I adjust the Mc pushrod?
I'm thinking about purchasing the Monte Carlo 1975-77

[cnicol]

The disc brakes are definitely touching the rotor as I turn it.

How do I adjust the Mc pushrod?

Your statement confuses me. The brake disc and the rotor are the same part. Did you mean to say the brake pads are definitely touching the rotor?

Now I'm wondering if the caliper lacks the freedom to float or float far enough to not be pushing hard on the rotor. I'm going to bet this is the problem. Of course the problem could be in the bracket's position relative to the rotor (bracket shimming or machine work) or the rotor's position relative to the caliper (rotor shimming or machine work). Did you machine the hub?

As for the MC pushrod: There's a clevis and lock nut up by the pedal. 1/8" free play is way too much in my experience. I'd shoot for something on the order of .010" or less. (while still having actual clearance)

[LBC TITAN]

Yes I meant to say the pads ate touching the rotors.

[LBC TITAN]

Yes I did machine the hub to fit the rotor and added liner wheel studs (1/4").

[cnicol]

Now I'm wondering if the caliper lacks the freedom to float or float far enough to not be pushing hard on the rotor. I'm going to bet this is the problem.

If you can push the pad back with levers (indicating free fluid flow back into the MC, Rotor/Caliper misalignment is almost certain. Were there any indications in the instructions for further machine work or shims for the bracket or rotor? Are you sure you have the right rotor?

[terribleted]

Now I'm wondering if the caliper lacks the freedom to float or float far enough to not be pushing hard on the rotor. I'm going to bet this is the problem.

If you can push the pad back with levers (indicating free fluid flow back into the MC, Rotor/Caliper misalignment is almost certain. Were there any indications in the instructions for further machine work or shims for the bracket or rotor? Are you sure you have the right rotor?

This is a good possibility. If the rotor lines up a little too far inboard or outboard and the caliper can not move enough to compensate, the pad on that side could be binding. Cinicol...my 1/8" or so slop is at the pedal , where the shop manual specifies 1/16-1/4".

[64powerglide]

When the inner pads wear down a bit it will probably be just fine. Sounds like it's real close to being free now, drive it a while and then see how they are.

[LBC TITAN]

Is it the caliper not fully releasing? Did you adjust the master cylinder push rod length for clearance? This is generally necessary when installing disks and a dual master. The rod length tends to be a little long and therefore holds the master cylinder piston slightly depressed which can cause a brake drag. there needs to be a around 1/8" slop in the push rod before it contacts the master cylinder piston.

Terribleted,

After installing the new mc for a monte carlo I had to cut the rod as it was too long. Wow what a difference these disc brakes makes!

With the mc being off and no applied brake pressure there is still a drag on the rotor.

When it cools off I will go back and investigate more, but thanks for all your help.

[TravisFowler]

I had this problem when I purchased disc brakes for my 59 Impala. Turns out the pads the vendor supplied with the kit were wrong. The inner disc brake pad is thinner (less brake material) than outer disc brake pad. It drove me nuts until I went ahead and got pads from the local O'reillys and compared them to what came with the kit. The pads from O'Reillys solved my problem.


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