My 81 4wd goes thump-thump-thump when I step on the brakes; more rapidly and more intensely from higher speeds, but on a smooth road I think I feel it pulsating with each wheel rotation all the way down to a stop. I have early V6 calipers (S12W) and Landcruiser rotors. I've done the following:

- Took apart and reassembled the front hubs, tightening the wheelbearings for maybe a little more drag than called for.
- Measured front brake rotor runout. It was just barely within spec on the outsides of the disks; I couldn't get my dial indicator lined up to check the insides.
- Replaced both rear brake cylinders (one was half-siezed) and shoes. One of them is leaking now, however.
- Had both rear drums machined.
- Replaced both rear axleshafts in an unrelated job.
- Replaced alloy wheels with OE steelies. The new tires are a lot smaller and not dryrotted.

I don't believe this issue was present before I upgraded the brakes. I remember testdriving this truck up to 85 and testing the brakes; weak but no thumping.

What else can I do? Rebuild the front calipers? Replace the front wheelbearings even though they're tight and smooth? I'm running out of ideas

 

This only happens with brake application ??

Or could it be you only feel it transmitted through the brake pedal??

Over the years all kinds of vibrations transmitted through the brake pedal having nothing to do with the brakes.

Any uneven brake pad wear??

Have you looked for a bubble or broken belts on any of the tires??

Does this happen the same way no matter the position of the hubs??

 

Only happens when braking, and it can get quite severe, shaking the whole truck. It's sometimes audible, too, in a dull thud sort of way.

Pad wear... I'll check that.

Tires...I replaced them and the wheels, and the thump's still there. Forgot to list.

Hubs...I don't think they make a difference, but I will drive with them locked and see what happens.

 

Sounds like rotors to me. maybe you can get them resurfaced ?

 

I was guessing that you already went with new rotors as that is the first thing I would have done to get rid of a brake pulse.

So my Question is are these new Rotors and if so are They Toyota rotors??

If used did you at least have the rotors cut??

Then maybe you just installed a bunch of used brake parts of unknown quality degrading the brake system??

There are so many junk China built rotors and drums floating around I get Toyota Rotors for my own vehicles if someone else wants cheap I warn them of how fast the rotors warp.

One does what one will .

As you state it was fine till you down graded the Brake system.

 

I bought new Wagner rotors for an 81 Landcruiser. I've measured runout and it's just within spec on the outside; couldn't measure the inside. The pads are worn slightly and evenly as of a minute ago.

Alright, I get that something in the brake upgrade got screwed up, and that I have to go back in and take apart the hubs. I'll have the rotors machined on the hub, to eliminate that variable. Only question is... is there any chance my wheelbearings are to blame? There's no play in the hubs that I can detect, no grinding or howling noises, but I really don't want to do this job twice. At the same time, money's tight and 100 bucks for wheelbearings is an expense I'll only pay if I have to.

 

Did you check the wheel bearings when you had them out?

You did repack the outer and inner wheel bearings in the course of this work.

If the bearing are not adjusted correct it would be possible to increase any movement when the brakes are applied.

Only you can tell if the bearings are worn How did they feel after they were cleaned prior to repacking .

It is something one picks up doing it over the years but used bearings should feel no different then taking new ones out of the plastic wrap .

No roughness no play what so ever

Forget anything when the bearings were installed Such as bending the locking tab.

Per chance did something come apart in your rear brakes??

You did recheck them as well??

If this is a thumping more then a pulse you might want to check the rear brakes.

Where you told to go with new drums?? Did yours clean up to be round and within specs??

Only so much one can do not up close and in person.

Good Luck!!

 

I do not know the firs gens but am wondering is the Landcruiser brake upgrade compatible with what you have. Also I have received wrong parts from the parts store and maybe that is an issue. Earlier I was suspecting warped hubs but seen you measured them.

 

You know with all these so called Brake Up grades I have yet to see any real numbers.

I hear more often of troubles just like the OP has.

 

Yep, I checked and repacked them with plenty of good grease.

Nope, and I've reassembled the hubs twice. First to replace axle seals and rotors, second time when I swapped my front diff.

I checked the rears and had the drums machined. The shop said they were just barely out of round. I replaced the rear shoes and cylinders and nothing changed about the thumping.

What kind of numbers would you ever see? The vented rotors decrease the likelihood of warping (I don't have statistical data to say by how much). The calipers provide more pressure, but it's mostly the booster that improved brake assist drastically.

 

do you do a lot of hard braking?

Its possible you cooked the rotors with some really hard stops and then kept the pedal down on hot pads. Rdesulting a hard spot on the rotors. You often hear this as "warped rotors" but its not warping, its a hard spot on the rotor.

 

I bedded them in using the 60-5 hard stop method, but was diligent in not actually stopping; I'm well aware of the hardening. Other than that, I don't remember any hard stops since then. I have however towed upwards of 5500# GCW. Slow and gentle but that's still a lot of weight. Think that could've hardened them?

 

that is a lot of weight for the stock disks. I surmise you are right thats a lot of heat and then holding at a stop light, makes sense. In fact for towing like that I would want a much bigger truck. Obviously it works but this may be the margin where you get burnt. Perhaps get a 4 disk conversion, but honestly I big v8 GMC Yukons with double the brakes as being a much cheaper alternative. Nobody wants them because they drink gas and that makes them cheap.

 

Well, they're not stock disks (vented off a Landcruiser), and it was thumping before I did those heavy trash hauls.

I called a local brake and wheel specialist who happens to have a SFA Yota with the same brake upgrade. What are the odds? Anyway, he said that even if .008 runout is within spec, then 1. that's my problem right there, 2. the wheelbearings have to have detectable play to contribute to this, and 3. he only machines these together with the hub, which is good news to me.

To be confirmed once the thumping is actually gone, but it sounds like all this came down to was cheap rotors and overly generous runout specs.

Alright, last question: other than OEM Toyota, what are people's opinions of various rotor manufacturers? I've used exclusively Brembo and ATE on BMW's (a much fussier beast than any Toyota) and never had issues with them.

 

I have been using Duralast Gold (Autozone) for 12k miles, and am 100% satisfied with them (on the 4runner). On my other car, Audi, I only use OEM, wear out quickly but they are incredible.

 

I went with vented LC rotors for mine too. did you go to a double dia booster?

 

My son could tell you, but they are all made in China today. Most stores only stock the cheapest available. He just put $10k worth of cheap Chinese chassis parts into a scrap metal bin rather than mess with them when the boss bought another warehouse.

 

Yep, small-diameter dual-diaphragm. Makes a world of difference.

 

After having the rotors machined (on the hub) and reinstalled with the same wheelbearings...

This.

We'll see how long they go before warping again, but I do believe they were warped out of the box.

 

Ok; Brake rotors seem to have three sources. Brembo is from Europe. Akebono is made here in the USA. The rest all come from China and have varible levels of quality and may be hit or miss to runout.