Rear wheel hop when braking

[jcd9730]

I've been getting some noticeable wheel hop when braking. I'm 90% sure its from the rear, feels almost like when I turn traction control off on my Cobra and stomp on it and the rear loses traction.

It does this always, but it's most noticeable at about 25-40 mph, maybe just cuz of braking harder. I have rear drums, so no rotors that could be warped.

Could this be from the trailing arm bushings? I have not replaced those yet. Or track bar not adjusted correctly? I would think if either of those were the case it would be unstable all the time, not just braking.

[LockDoc]

Originally Posted by jcd9730

I've been getting some noticeable wheel hop when braking. I'm 90% sure its from the rear, feels almost like when I turn traction control off on my Cobra and stomp on it and the rear loses traction.

It does this always, but it's most noticeable at about 25-40 mph, maybe just cuz of braking harder. I have rear drums, so no rotors that could be warped.

Could this be from the trailing arm bushings? I have not replaced those yet. Or track bar not adjusted correctly? I would think if either of those were the case it would be unstable all the time, not just braking.

Does it pull one way or the other or feel like it wants to drift when you brake fairly hard?

There are a couple of things that could cause this. One is brake shoes that are saturated with brake fluid, or a drum that is out of round, or bad shock absorbers. OK, that's three, my fingers got carried away...

LockDoc

[jcd9730]

It pulls slightly. I need to adjust it a bit, but it's not that bad.

I have new shocks, not even a year old. From the ECE drop kit. I put new drums on about 2 years ago, as well as all new drum brake stuff. I'm pretty sure my shoes are clean as well, though I guess I will check again when I adjust. Is there a way to tell if the drums are out of round?

[LockDoc]

Originally Posted by jcd9730

It pulls slightly. I need to adjust it a bit, but it's not that bad.

I have new shocks, not even a year old. From the ECE drop kit. I put new drums on about 2 years ago, as well as all new drum brake stuff. I'm pretty sure my shoes are clean as well, though I guess I will check again when I adjust. Is there a way to tell if the drums are out of round?

Only way I know would be to chuck them up in a lathe and use a dial indicator on them or take them to a shop that turns drums, they should be able to check them.

How much is your truck dropped, and did you install shock relocators on the rear?

LockDoc

[57taskforce]

Gear oil leaking thru the outer seal and into the drum will cause this as well.

[Justin@EntropyRad]

wouldn't hurt to check the track bar and bushings like you mentioned. My buddies truck does it, and he has discs too

[davepl]

Originally Posted by 57taskforce

Gear oil leaking thru the outer seal and into the drum will cause this as well.

^^^ I was about to say that. Generally when I've had that happen it causes the wheel to lock up (and not release until the pedal is), as opposed to wheel hop, but I imagine anything's possible.

[jcd9730]

I had the drums turned. Not nearly as much bouncing when braking, although it is still there.

No leaking fluids at all. Replaced the bearings and seals a year ago or so, so they had better not be leaking! Doused both sides in cleaner. Not sure why its still somewhat bouncy. I don't think it is a wheel balance issue, since its only when braking.

[cleszkie]

Installing the brake shoes improperly can cause the drum brakes to lock up or act "grabby". There is one brake shoe that has a longer brake lining on it than the other in a set. I can't remember if this one goes on top or bottom, but it definitely makes a difference. I run all disk now, so that bit of info has been deleted from my brain.

[jcd9730]

Yeah, the bigger shoe goes in the front. I've had the shoes in there for awhile with no problems, so I doubt it's that

[jcd9730]

I should just do disk like you did. I hate drums.....

[Acorn]

The big (primary) shoe goes in the back.
The small (secondary) shoe goes toward the front.

[jcd9730]

Yeah you're right, I said it backwards. Big shoe on back since front shoe does more work.

[davischevy]

Did you check the pinion angle after you dropped it? I had a terrible vibration when braking and it turned out to be too much pinion angle.

[RichardJ]

Have you checked your front brakes?
The front disc brakes should be doing 60-70% of the braking. It does not sound like the fronts are contributing much at all to your overall braking.
It is also possible the proportioning valve is not reducing the pressure to the rear brakes as it should.

[jcd9730]

I didn't check the pinion angle myself, but the support bearing for the two piece driveshaft broke awhile ago. I thought the pinion angle was the problem, but I had a shop replace the bearing and check the pinion angle, and balance the driveshaft. They said the pinion angle was good, and the driveshaft was balanced. So I wouldn't think it is the pinion angle.

My fronts should be fine. New everything, minus hard lines. The proportioning thing could be an issue. But I notice I'm getting some vibration from the rear while at freeway speeds as well as braking so maybe the rear just needs to be balanced better or something

[LockDoc]

Originally Posted by LockDoc

Only way I know would be to chuck them up in a lathe and use a dial indicator on them or take them to a shop that turns drums, they should be able to check them.

How much is your truck dropped, and did you install shock relocators on the rear?

LockDoc

I think you overlooked a couple of my questions in this post....

LockDoc

[jcd9730]

Haha sorry! 5" in the back, and I used the relocators that came with the ECE kit. Used the track bar from it as well.

[LockDoc]

Originally Posted by jcd9730

Haha sorry! 5" in the back, and I used the relocators that came with the ECE kit. Used the track bar from it as well.

OK, thanks. The reason I asked, for those reading this that aren't aware, if you lower your truck quite a bit and don't use the shock relocators the shocks will lay at too great of an angle and will not work as they should....

LockDoc

[leddzepp]

If nothing else toss a couple bags of concrete in the bed. That always cures the rear end hop for me. With no weight in the bed my LWB truck bounces all over the place.

[jcd9730]

Yeah I have wondered if it's a weight thing. I've had a lotta bounce for a long time but my rear wheels were too big for the hub so they were always off. Now that I've got hub rings I'm trying to fix the rest