The Stovebolt Site Forums The Shop Area The HiPo Shop Front Disc Brakes too tight.

So I noticed after putting this disc brake upgrade together the left front is very tight. I can spin it by hand, but it seems to me it would be the cause for a serious overheating problem. The pads are all square to the rotor, so there is no angle problems. The pad closest to the engine, when letting off the brake I get enough clearance to slip a piece of paper between the pad and the rotor. The other side seems to be my problem because it is very tight to the rotor. Here are some pics.

http://forums.devestechnet.com/forum/technet-members-gallery/556-front-disc-brakes-too-tight


Maybe I put this together wrong or something? Also can I remove the caliper assembly without having to disconnect and re-bleed the brakes? Thanks!

Sounds like the caliper is hanging up on the slides. What kind of lubricant did you use? Also, are the O rings seated ok in their grooves in the caliper?

I used white lithium grease on it and the O-rings are in their grooves. The problem is, the movement of the floating caliper is fine. Its just maxed out on the outside. Its EXACTLY as if the pad is just too thick by about a paper width.

Do you know what brand pads come with the kit? I have seen issues with some brands of brake pads and shoes where they either put too thick of friction material on them, or use too thick of a shim on the backing plate. Perhaps a little experiment might be in order, swap the outboard pad from the left side to the right, just to see if it makes any change.
That brings me to your second question. Yes, you can remove the caliper without taking the line loose, just make sure you have a hanger of some sort (I make them from wire coat hangers) to hang the caliper up with.

You could take the calipers off and measure the distance from the bracket to the rotor, see if both sides are the same. You could also measure the thickness of the brake pads from side to side. Couple ideas...

on my kit I found one of the adapter brackets was a little different than the other, just slightly. Must of been the ...offset... when they pressed them. (I'm referring to the bracket you have painted black)

one wheel was a little tighter than the other when I hand spun the wheel.
I didn't think anything of it and just drove.
Maybe I should of been more concerned.

When I let off the brakes the calipers do let off a little. I did not install the residual valves.

Since everything is square, no need for shims that I can see, the only thing left with the calipers floating properly, is to take off a smidge of padding from the outside pad. But I am no expert. Maybe you guys know something that I don't about why that would occur. You know how it is.. if you are unsure, post on The StoveBolt!

Dads very similar. The left wheel there is drag, but no more than you would get if you adjusted your drum brakes properly. On the drivers side, there is considerable drag. I cant really fault the calipers bracket since everything is straight. The pads are exactly perpendicular to each other. I can slip a piece of paper between the rotor and pad on the side where the piston pushes against it, but on the side that is stationary, the outside, the pad is HARD against the rotor.

A friend came over today and said to me, he would just drive the truck and forget about it. He felt that over a few miles, the brakes would settle enough to be just fine. Since we are talking about a frame with no sheet metal on it yet, it will be quite some time before that happens, and as he said, the rotor will turn blue from heat if I let it settle in. Its pretty tight. Pushing the frame back and forth is hard because of it. Just not sure what to do is all.

Get a friend to help you push the frame! 😉

I don't believe you installed anything incorrectly or there is any real problem. There is residual pressure in the caliper which can cause the brake to be a little tight. Normal driving causes the caliper to release from the rotor and it should perform fine. Since you are not driving the truck it is difficult to determine if you have a problem or not. If it was running and driving and it pulled to one side or one side seemed to heat up significantly you would then have a problem. Of course you cannot totally rule out a manufacturing error on aftermarket parts, it doesn't take much to cause problems.
Fred

I have this habit of watching PowerBlock TV on Spike on Sunday mornings. Last Sundays had a thing about putting front disc brakes on a project very close to the same. I watched intently and then got out my calipers and checked everything the way they did. Turns out I dont need shims, everything measures straight and true, but the problem is just that there is about a paper width too much meat on the static side brake pad. Thanks for the input everyone!

The outboard pad on mine touches ever so slightly. I can spin the wheel with just a hint of contact so I think it is OK. If I were concerned, I would probably put a sheet of sandpaper on a hard flat surface, a piece of glass would be good, and take a bit off.

Dennis

That's my plan unless I get others opinions to the contrary Dennis. Yep, just shave a bit off, and we are GTG. Unless there is a reason not to?

Did you get your install done in a 1/2 hour like they did on power block?

As Shakespeare says, "Much ado about nothing"! The pads are supposed to drag just a little, to aid in wiping water off the rotors after hitting a puddle, etc. Did you apply the brakes, then check for clearance or freedom of movement? Nope, didn't think so! Do about 10 brake jobs in an 8-hour day, and repeat that for a few years before you start getting anal about the thickness of a piece of paper.
Jerry

No, its not dragging 'just a little'. After applying the brakes ad nauseum, the drag is substantial. My concern is it will turn the rotor blue from overheating the first time I drive it. Its the other side that is dragging just a little. So far the only thing anyone has mentioned is to take a little off that brake pad with a flat sander or something. First time dealing with disc brakes, maybe thats something that everyone just does when installing brake pads.

Sounds like the bracket is a few thousands out of spec, or the piston, or the hub/rotor/bearings .......
Just touch the pad to the belt sander and make a mental note to do it again in 30,000 mi when you replace them.
Check it again after the test drive.

You might want to check the pushrod adjustment in the Master cylinder. It sounds like the fluid may not be returning fully when you release the brake pedal. Also make sure you have the rear brakes adjusted correctly. If the disc brakes are not releasing fully, driving and applying brakes will heat them up to the point they will freeze on you.

If the floating caliper is free then the problem is pressure, try to break your pigtail to the caliper and see if it frees up then. I've seen older pigtails get so tight - I know yours is all brand new etcetc - that the resistance will act like a residual pressure valve and will let the caliper only partially release.
This is assuming you didn't force the pads onto the caliper, that the floating caliper was free and the rotor would spin right up until you connected the brakes lines and applied pressure.
Make sense?

Britcon and ojh, your suggestions do make sense, but the issue is with the outboard pad, not the inboard. That would make it a slide pin or hardware issue rather than hydraulic. Bad part is that we're trying to diagnose this over the internet, rather than in person, and can only really give guesses as to what the culprit could be. Could be something as simple as needing to drive it to get the pads seated in and cycle the caliper on the slides to get them to move freely.

Yes, Bill hit it on the head.. even the people who come over and look at it are saying one of two things..

1) forget about it, when you take it out on the road, it will settle in, or..

2) Take that pad over to the disc sander and take a bit off.

Its SOOO close to just leaving it alone, but with my experience with DRUM brakes, this would be way too tight to just ignore.

Thanks guys!

What's it going to hurt to take a 1/32 or so off the pad on the belt sander? Nothing. Take a box of a 100 brake pads, think they will all measure the exact same thing?

I would wait until you're ready to drive it, see what it does. If it seems to be a problem, then perhaps sand it.

...been trying to stay out of this thread but here goes.
I've had basically the same problem twice in the last 3 years and both times it was the PAD. (to thick)
When I retired I delivered parts for Advance Auto Parts for several years and, as most of you can guess, on more than one occasion, I picked up pads for return that were boxed wrong, labeled wrong and even mixed pads in the same box. Whew, there, that's my story.

...I've enjoyed reading some very good answers/thoughts though!
Not much else I can add to what's been said.

I know what you mean.
The thing about a floater is that it'll retract until the pressure equalizes, in the OP's situation one pad is still in contact with the rotor. If he had a fixed caliper and just one set of pads remained in contact the problem/solution would be entirely different.
I've seen this happen where the brake fluid isn't compatable with the hoses, the pads won't release. After replaceing the hoses I've cut the old ones to see inside and they are all but closed.
The calipers' pressure would escape after pedal release until a certain value, it might have been 10 or 15lbs pressure required to push the fluid back thru the hose - I don't know - but once the pressure in the caliper reached a value equal to the pressure required to push it back thru the lines it would retract no further. On a floating caliper this would let just 1 pad remain in contact, right?
Again, Very hard to diagnose with out touching, any of us can be right.

The thing is that the piston is retracting, and is puling the inboard pad away from the caliper. So that eliminates any kind of hydraulic issue. It has to be either a mechanical issue or a case of a dimensional problem with either the pad itself or the bracket.
BTW, I'm pretty sure from his other posts that Deve is running DOT 5 silicone fluid.

Gotcha, good point. I'd still break the line. The fixed piston side has relaxed because it isn't seeing 1200psi, if the silicon fluid had swelled the hose then the pressure might drop to 20, a 100?psi to release the piston further. Break the bleeder, see if there is pressure and then you'll know.
When he assembled the floater he'd have known if the pins were interfering, when he put the pads in they probably just plopped in and the thing rattled around on the pins or would've taken it apart to see whats what.
Again, I'm probably wrong but before I go grinding pads down I'd break the bleeder to see if there is pressure.

There is about paper-thin airspace when you let off the brakes on the piston side. Nothing touching. Its the outboard side. Plan is to just shave a bit off. I just haven't gotten to it yet. When I do, Ill report back. Thanks everyone!

Interesting, but probably totally normal, sanding these beasts down isnt easy! Nice that they are that tough. But, I sanded them down very slowly and I am sure I didnt take enough off. But, I noticed if I didnt really tighten the crap out of the Allen head retainers but rather went a little easier on them, it seems that everything works really smooth. Not too smooth.. you can feel about the same drag as you should with drum brakes, but smooth enough to not feel there is a problem. I am thinking I need to just keep those retainers a little loose. But be very aware of it, then as I drive it, crank them down after everything has settled in.

Does this make sense to anyone? Thanks for the posts!

Are you talking about the slide pins? Those should be torqued to 38 ft/lbs.

Run them Deve. If the rotors don't machine them to specs in short order, you will smell it. It smells hot.
Carl

Yes Bill. My hands are calibrated for precisely 38 ft/lbs, but if I do that, I get a very tight wheel. Backing them off about a 1/4 turn makes everything happy. Looking at it further, there is a spacer that goes through that hole. Maybe it is too short by about that much? You never know what you are going to get from these kits.

The plan is to just leave it backed off until I drive it, then get my 1/4 turn back as it settles in.