Brake drag

[gummycarbs]

Is there a spec for brake drag, like the rotational force spec for wheel bearings? I've searched 'Mud and looked through my PDF FSM files, and I can't find an answer.

It takes something like 45 pounds of force to get my front hub turning with the brake caliper installed, which seems excessive.

 

[Malleus]

0.0

 

[george_tlc]

You have discs in the front, assuming the pads are not excessively thick (or doubled up shims, aftermarket too thick etc) then the pads should be 'barely' kissing the rotors at their highest point (once settled).

I presume you understand that the disc system is 'self adjusting' - your foot causes the pistons to push the pads against the rotor and the rotor high spots will push the pad/piston away from the rotor (just barely away).

If you have just installed new pads etc, then I'd mount the wheel on (to get more mass) and give it a few spins by hand to settle the piston/pads at their neutral position.

If you have a sticky piston (time for a rebuild or new loaded calipers) then it can cause the pad to continue dragging on the rotor. Obvious from excessive pad wear versus the other 3 brake locations. On the front it would also tend to pull the vehicle to that side.

cheers,
george.

 

[inkpot]

If your rotors are pretty fresh and you are running 100 series pads, it is pretty tight in there until you get some road miles on it. Some folks kiss grind the pads on a belt sander to "break them in" prior to installing them.

 

[gummycarbs]

Thanks for the input. I think I might pick up some NAPA reman calipers, since I don't know the full history. The parts all seem reasonably new, but there's enough old Birf grease built up on the caliper body that I think they're original.

 

[zoojp]

Are you sure it's the brakes? Try pulling the caliper and turning before you throw parts at it...it might be something else.

 

[Dave 2000]

Pull the pads and then measure force needed to turn disc, remember you are pulling a large amount of hardware around with you.

Regards

Dave

 

[gummycarbs]

Yes, I did a Birf repack with new seals and bearings about a month ago. I followed the FSM for bearing preload, yielding around 10 Lbs rotational force. Put the calipers on and it goes way up.

I've never had disc brakes that don't drag at all, but I've never had disc brakes that drag this much. It's not like they're seized, it just seems excessive.

 

[gummycarbs]

Well, this changed my mind about the NAPA calipers!

Last weekend i replaced back calipers and rotors on my '97 LC. I got the NAPA Eclipse exactly as shown by cartercd above. POS! Problem 1:The rubber sleaves to keep water and mud out of the bracket slides ( dont know the official name ) were so flimsy, floppy, and over sized, that they would pop off the retaining rims and expose the metal to the elements in every possition. I ended up pulling the rubber sleaves off the old calipers ( dont know if they were oem or not ) and installing them on the new eclipse calipers so that they wont get contaminated and jam after the first year. Problem 2: When they remanufactured these units they sandblasted them violently with a very course abrasive. the mating surface for the banjo fittings were so pitted from the rough sandblasting it was impossible to get the the fittings to seal. I had to pull both of them off and polish the banjo mating surface and reinstall. Problem 3: On both units the bleed valves were torqued in so tight I was afraid I was going to strip them getting them lose for the bleed, only to discover that the machining on the threads of the bleed fittings was so poor that they wobbled once slightly loosened. Perhaps the threads in the casting were eroded from the sandblasting. I know you cant tell the quality of the metal by looking, but the metal just had that poor quality look on hardware you might buy at walmart. I should have pulled the bleed fittings from the old calipers.... Problem 4: the rubber plug on the back side of the bracket plunger was so flimsy and fit so loosly that they would fall out with any vibration. I again pulled the caps off the old calipers to use so the plunger chamber would be protected from contamination The rotors seemed just fine. In spite of the above worries I proceeded with the install and they seem to work just fine. Both my 80s are DDs with occasional rought back country use. I havent had much better luck with Auto Zone stuff and maybe a little better from Orielly. I was hoping for a better experience from NaPA. On my LX450 i have Oreilly calipers with 100k on them with no problems. I suspect all the reman stuff is coming from overseas and it is just the luck of the draw which supplier cut which corners on the batch you order from.

I can get a Toyota seal kit for about $35 per side (04479-60020), or a Carlson kit for $6.28 on RockAuto. I'll clean and inspect today, and plan on rebuilding them if the drag continues.

 

[Tools R Us]

Do the pistons compress back correctly? If so what are you attempting to "fix" it's normal for brakes to add some drag. Has it been driven since it was worked on, to settle, allow the brakes to seat in position?

 

[gummycarbs]

The previous owner had brake work done, and I've been driving it for months. There is plenty of meat on the pads and no ridge on the rotors, so I believe work was recently done. But the amount of hardened Birf puke on the caliper leads me to believe that the caliper hadn't been rebuilt.

As I said before, the drag seems excessive, which is why I asked if there's a spec somewhere in the FSM.

 

[Malleus]

Well, this changed my mind about the NAPA calipers!



I can get a Toyota seal kit for about $35 per side (04479-60020), or a Carlson kit for $6.28 on RockAuto. I'll clean and inspect today, and plan on rebuilding them if the drag continues.

I wouldn't let that put you off NAPA calipers. I've bought several sets there and have not had that experience. Nobody's perfect and sometimes crap slips through the quality control net.

 

[Tools R Us]

... But the amount of hardened Birf puke on the caliper leads me to believe that the caliper hadn't been rebuilt.

What difference does that make, if it's not a rust bucket, the pistons aren't sticking, it's good to go. Most of the rigs I know of have never had the calipers messed with. If the dirt bothers you clean it off!

... As I said before, the drag seems excessive, which is why I asked if there's a spec somewhere in the FSM.

What problem is it causing? When driving is there a huge cloud of smoke, rotors glowing red, etc? If not, there probably is not a problem to "fix".

 

[gummycarbs]

If not, there probably is not a problem to "fix".

Gee, maybe that's why I asked, "Is there a spec for brake drag, like the rotational force spec for wheel bearings?"

 

[Tools R Us]

Gee, maybe that's why I asked, "Is there a spec for brake drag, like the rotational force spec for wheel bearings?"

Realistically there can't be, it's highly variable, new/old pads, seated or not, etc. Really the same applies to the wheel bearings, the whole fish scale thing is best left to fishing.