Brake studder or hop

1113 Views 5 Replies 3 Participants Last post by mckinnej, Mar 11, 2020

mckinnej

Discussion Starter · Feb 6, 2020

I originally posted this in the brake and suspension forum, but didn't get any responses. Trying again here hoping someone is paying attention. I do have a small update though. I bought a dial indicator to check the runout on the front, just to make sure, even though I have new rotors. I do feel a very slight amount of that uneven braking feeling you get when you have excessive runout, but as I said, it's very slight. I don't feel that it's causing the shaking that I'm getting. I'm hoping I can get good weather and a weekend to match up so that I can check it soon. Get an eyeball on the brakes too and maybe see what's going on. Anyway, here's the original post.

Hi all. I'm new here, but have worked on cars all of my life. I've done a lot of brake jobs, but I've never encountered anything like this.

I have a 2004 Frontier XE: 2-door, 4-cyl, automatic. I bought the truck new. Now it has a tad over 80,000 miles on it. The factory drum brakes always squeaked and/or made a grinding sound. They looked fine visually, so I just lived with it. It finally started sounding more like a metal-to-metal sound, so I assumed they were wore all the way down. I decided to do a full brake replacement all the way around, so I ordered pads, caliper kits, and rotors for the front, and drums, wheel cylinders, and shoes for the rear from Rock Auto. Didn't try to get anything fancy. Just factory replacement stuff.

The install was pretty straightforward. Neither the pads nor the shoes were worn to the metal, not even close, so I'm not sure where the grinding sound was coming from. Basically it didn't need a brake job, but the money was already spent, so I pressed on. Once complete, the pedal was a bit low and not as firm as I expected, so I bled the system again and adjusted the rear brakes to get a slight drag on the drums. That took care of the pedal, but now I get this weird hopping in the rear when I apply the brakes. It isn't too bad when the brakes are cold, but it gets worse as they get hot. The back of the truck jumps pretty hard when I hit the brakes for a quick stop. It almost feels like wheel hop that some cars experience under hard acceleration, but when I'm stopping. I've never seen anything like that.

At first I thought it had to be the front brakes, but with new rotors and pads, and now with a few hundred miles of burn in, they should be good. Besides, the front isn't where the shaking is coming from. The steering wheel remains steady during braking. The brakes are quiet too. No squeaking or grinding. At least I fixed one problem. :-/

Now I'm wondering if I got the adjustment too tight or the ABS is acting up or maybe some combination of the two, but I'm not sure. Any ideas? Thanks.

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rogoman

· #2 · Feb 7, 2020

mckinnej said:
The install was pretty straightforward. Neither the pads nor the shoes were worn to the metal, not even close, so I'm not sure where the grinding sound was coming from. Basically it didn't need a brake job, but the money was already spent, so I pressed on. Once complete, the pedal was a bit low and not as firm as I expected, so I bled the system again and adjusted the rear brakes to get a slight drag on the drums. That took care of the pedal, but now I get this weird hopping in the rear when I apply the brakes. It isn't too bad when the brakes are cold, but it gets worse as they get hot. The back of the truck jumps pretty hard when I hit the brakes for a quick stop. It almost feels like wheel hop that some cars experience under hard acceleration, but when I'm stopping. I've never seen anything like that.

Now I'm wondering if I got the adjustment too tight or the ABS is acting up or maybe some combination of the two, but I'm not sure. Any ideas? Thanks.

To begin with, adjust the rear brake shoes so that there is no drag at all. I always leave extra clearance for drum brakes because when you do several backups the self-adjuster will set it to the proper clearance. If it's too tight, will it contribute to your problem; maybe yes - maybe no.

Make sure the parking brake is properly adjusted; 6 - 8 notches on the pedal stroke should do it. There should be no drag when parking brake pedal is fully released.

Bleeding Brake System
● If master cylinder is suspected to have air inside, bleed air from master cylinder first.
● Turn ignition switch OFF and disconnect the ABS/VDC connector or battery cable.
● Bleed air in the following order.
– Left rear brake
– Right rear brake
– Left front brake
– Right front brake
– ABS actuator/VDS

If you're still having your "jumps", it could be a problem in the ABS system. Temporarily disable the ABS system by disconnecting the ABS connector. Drive the vehicle to see if it clears up the problem.

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smj999smj

· #3 · Feb 7, 2020

I would have the drums turned on a lathe. I've had a couple of incidents of brand new brake drums that were out of round right out of the box. They don't make them like they used to!

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mckinnej

Discussion Starter · #4 · Feb 13, 2020

rogoman said:
To begin with, adjust the rear brake shoes so that there is no drag at all. I always leave extra clearance for drum brakes because when you do several backups the self-adjuster will set it to the proper clearance. If it's too tight, will it contribute to your problem; maybe yes - maybe no.

Make sure the parking brake is properly adjusted; 6 - 8 notches on the pedal stroke should do it. There should be no drag when parking brake pedal is fully released.

Bleeding Brake System
● If master cylinder is suspected to have air inside, bleed air from master cylinder first.
● Turn ignition switch OFF and disconnect the ABS/VDC connector or battery cable.
● Bleed air in the following order.
– Left rear brake
– Right rear brake
– Left front brake
– Right front brake
– ABS actuator/VDS

If you're still having your "jumps", it could be a problem in the ABS system. Temporarily disable the ABS system by disconnecting the ABS connector. Drive the vehicle to see if it clears up the problem.

Thanks for the advice. I've done everything you listed there, twice, except bleeding the ABS. That might be the culprit. I'll give that a shot when I have time and the weather cooperates. Getting those two things at the same time has been a challenge recently.

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mckinnej

Discussion Starter · #5 · Feb 13, 2020

smj999smj said:
I would have the drums turned on a lathe. I've had a couple of incidents of brand new brake drums that were out of round right out of the box. They don't make them like they used to!

If the bleeding doesn't help, I'll give this a shot. Probably get both the rotors and drums turned to be sure. Sad that we have to deal with so much Chinese junk these days. Thanks for the advice.

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mckinnej

Discussion Starter · #6 · Mar 11, 2020

I fixed this. I made a dumb rookie mistake. I got the brake shoes on the passenger side backwards. Not sure how I did that because I spotted it right away as soon as I slid the drum off for a little visual inspection last night. A quick teardown and reassembly took care of it. No more stutter or hop. The lining on the front shoe from the original shoes was significantly shorter than the rear. The lining on the replacement shoes was the same length on both shoes, but the front was shifted down on the backing plate by an inch or so. I had them correct on the driver's side, but backwards on the passenger side. This caused the rear brakes to be uneven which could have caused the stutter directly or triggered the ABS because one wheel was braking more than the other. Weird problem that thankfully had an easy solution. Thanks everyone for you advice and help.

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