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Suspension Questions Chassis, Brakes, Springs, Shocks, Swaybars, Tire, Rims Etc Suspension Questions Chassis, Brakes, Springs, Shocks, Swaybars, Tire, Rims Etc

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Old 06-29-2019, 02:49 PM   #1
tomthegtrplyr
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Default Front Disc Brake Drag - Bizarre!

So I just lived this bizarre tale with my 56 that I have named Christine....
Took my front wheels off to put back a sheet metal screw that fell off, made sure the others were tight - no big deal right?
Put the wheels back on, went for a spin.
Immediately began smelling the unmistakable odor of brakes getting hot...
E Brake was not engaged..I didn't go far - drove right back to the garage.
Both front disc brakes (I bought the common conversion kit) were hot and obviously the calipers were stuck, right?
Well..This car was completed 2 yrs ago, and the brakes have several hundred miles on them with zero issues.
I took the wheels off, put them back on, and now the calipers were stuck? How can that be??
I checked the prop valve and the brake sensor tells me it is centered.
Took the wheels back off and yep - you couldn't turn the rotor without a lot of force.
Hmmm..so I opened the bleeders on the calipers, and that didn't help.
The right was a bit tighter than the left..I figured the next step was to buy new calipers and pads (the rotors were warped now anyway, might as well),
put it back together, bleed the whole system to insure the prop valve was indeed centered (which it must be as both back and front bleed out well - no "trickling" on the rear drum wheel cylinders).
FYI- the rear end is all stock 1956 Chevy.
After all that - the front calipers were still waaayyyy too tight. I really didn't gain anything with all that $$ and busted knuckles.
So, I did what my Dad taught me. I got away from it, had some beer, and thought about it.
The next day I went out and stared at the problem, and then I recalled that the only time they really locked up when was I tightened the caliper pins.
So I loosened the caliper pins and voila! The rotor turned with not so much force. This was evident on both left and right.
Now in all this I noticed that the inside of the rotor on the left side had gouges in it like when the pads wear down to the rivets. That was weird as the pads were new and had all kinds of meat. I'm still not sure where the gouges came from as the rotors came in the conversion kit and were new.
So that was bizarre problem #1.
After taking the caliper on and off a few times I decided that maybe, just maybe the kit I bought (got it from Car Parts Warehouse - they were the most competitive at the time) was not properly engineered.
Maybe this caliper drag had been occuring the whole time and for some God forsaken unknown reason it just decided to rear it's ugly head that day.
I've been working on cars since 1970 or so and I've seem some really weird crap, so I understand just about anything is possible when you tear a car apart into a million pieces and then put it back together again using a lot of parts that were never meant to go on that car in the first place.
So...I developed a theory.
What if the caliper mounting bracket was either engineered incorrectly or perhaps tweeked from the factory, and even with the inner caliper piston fully retracted, the inner pad maintains excessive force against the rotor?
Or maybe there was supposed to be a shim I missed.
So I took the caliper pins out, and inserted a common flat washer in between the inner caliper bushing and the caliper mounting bracket.
Then I tightened the caliper pins and the rotors did not lock up.
I did this to both sides, re-bleed the brakes as I had loosened the brake hose banjo fitting just to make sure it was not a residual pressure issue.
When I got done, the rotors turned with a lot less force.
Put the wheels back on, and it appears everything is spinning at about what you would expect.
Took it for a spin, carefully incresing speed, windows down, sniffing the air.
Got it up to 70 MPH briefly, drove for about 2-3 miles, got back to the garage and all appears to be functioning normally.
I did do a hard stop, and I'm not 100% confident the back brakes are working like they should, but it appears I made some serious progress.
If Christine gives me any more fits like this, I may have to call a Priest..
Just sayin'..
Has anybody ever experienced anything like this??
If anybody is fighting a problem like this, maybe this trick will work for you.
All I know is today is my birthday, and I am too old for this sh*t....
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Old 06-29-2019, 06:18 PM   #2
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Have you checked your pushrods between brake pedal/booster and booster/master cylinder? They both need a slight amount of slack. Too long and brakes can't release completely....

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Old 06-30-2019, 04:42 PM   #3
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Hey Ace,
I appreciate the comment, but at one point I loosened the m/c from the booster and had the brake hoses off the calipers and there was still drag.
It seems to operate correctly with the spacers.
If it locks again I will try shortening the rod.
I am open to any and all comments and suggestions.
Thanks.
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Old 06-30-2019, 05:29 PM   #4
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Quote:
Originally Posted by tomthegtrplyr View Post
It seems to operate correctly with the spacers.
If it locks again I will try shortening the rod.
I am open to any and all comments and suggestions.
Thanks.
It may be the brackets are bent or not offset correctly. Install the caliper without the opposite pad and see if the caliper will slide on the pins enough to give at least 1/16" clearance between the pad and rotor and check the clearance to make sure the pad is parallel to the rotor.
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Old 06-30-2019, 10:58 PM   #5
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Thanks Don.
I didn't realize caliper bracket bent or incorrect offset was such a common thing...
This is very feasably my problem.
Excellent suggestion!
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