Brake judder.

I hope you guys can give me some input on this because I'm running out of ideas. I'm having pretty hars vibrations/shaking in the steering wheel only when braking.
It's not hub run-out or debris between rotor and hub.
Rotors are new, had same problem with old brakes.
Guide pins are clean and lubed.
Inspection of the lca bushings didn't show anything, they aren't dry or visibly damaged.
Ball joints and tie rod ends checked out OK.
No play in wheel bearings.
The thing with this judder is that it isn't always as present, some days it's just the faintest shimmy just when I apply the brakes, some days it's really bad.
If I brake hard the brakes sometimes shakes but sometimes doesn't.
I think it has to be a bushing or joint but how do I find out what/where?
I was also wondering if worn guide pin bushings could make this happen? If the caliper can shift a bit like when opening a drawer that jams half way...

If the rotors are new, are the pads also new? If so, how did the old ones look? Any play in the CV axles? Any vibration when you accelerate from completely stopped, or when turning? Any idea if the source of this is the front or rear?

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Yep, pads are new. I'm pretty sure that the old pads looked normal, they weren't completely worn out when I replaced them.
Haven't thought about the axles other than checking that the flange bolts were tight.

There is no vibration when accelerating, turning, cruising or engine braking, only when the brakes are applied. I'm 99% sure it's from the front because I can feel it in the steering wheel and I have also pulled the e-brake when going slow and it slowed down smoothly.

I’d take a second look at the rotors. I would remove them and check that the mounting surface is smooth and nothing to cause a miss match of the machine surfaces. I’d also check them for any minor warpage. I once had a set of new, off the shelf rotors on a BMW (am I allowed to say that here?). That did the same thing while breaking. I had a machine shop turn the rotors and the problem was solved.
I’d also check that the brake calipers are free to travel as needed.
JMHO, Steve.

Did you install slotted rotors?

The hub/rotor faces are very clean, one side is new the other cleaned.
The rotors are not slotted nor drilled.
I guess it could be the rotors but I had the same symptoms before I did the brakes, I replaced the rotors when I noticed that one wheel bearing had some play in it.
And the strangest thing is that I can sometimes brake without even a little shaking, so I really doubt it has anything to do with the rotors. Calipers or guide pins maybe, or lca bushings. Maybe even a cv-joint, but why would that only vibrate when braking, not accelerating, how would the rear (against the normal rotation) of the joint be more worn than the front?
Maybe it's a wheel/tire issue, right now anything is possible

Did you find the problem? I have the same thing -- replaced the rt rear caliper and pads and rotor. It's as if there is still air in the line. I can bleed it and get air bubbles out and problem goes away for a few brake cycles and then returns. I've bled several times and always get more air bubbles. I believe the "judder" is caused by the air in the line collapsing. Where's the air coming from -- a bad rebuilt caliper?? But no external leaks. Any help appreciated. Thanks

DAH said:

Did you find the problem? I have the same thing -- replaced the rt rear caliper and pads and rotor. It's as if there is still air in the line. I can bleed it and get air bubbles out and problem goes away for a few brake cycles and then returns. I've bled several times and always get more air bubbles. I believe the "judder" is caused by the air in the line collapsing. Where's the air coming from -- a bad rebuilt caliper?? But no external leaks. Any help appreciated. Thanks

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Not sure how or if this idea would work with the ABS pump/motor but, because the brake reservoir is higher then the brake calipers and Professor Wizard tells us that air bubbles like to rise in a fluid, why can’t you pressure bleed the system from the brake caliper to the reservoir?
Just a WAG.

Steve.

OK, problem solved!
This was driving me crazy so I decided to remove the rotors and took them to a friend with a lathe. Turnes out that the backside of one of the rotors was like a sine wave. The thickness is uneven but only on the backside, we used the dial gauge on the outside only.
It was not enough to leave spots where the pads wouldn't make contact, but enough to shake the caliper from side to side while braking.
It puzzles me that it didn't shake every time I hit the brakes...

The good thing is that I now have checked all brakes and bushings and subframe bolts etc etc. And the calipers are super clean now

Edit: I'm willing to bet that the vibrations I had with the old rotors were from a bad wheel bearing, I replaced the RH side wb when I did the brakes.

nokivasara said:

OK, problem solved!
This was driving me crazy so I decided to remove the rotors and took them to a friend with a lathe. Turnes out that the backside of one of the rotors was like a sine wave. The thickness is uneven but only on the backside, we used the dial gauge on the outside only.
It was not enough to leave spots where the pads wouldn't make contact, but enough to shake the caliper from side to side while braking.
It puzzles me that it didn't shake every time I hit the brakes...

The good thing is that I now have checked all brakes and bushings and subframe bolts etc etc. And the calipers are super clean now

Edit: I'm willing to bet that the vibrations I had with the old rotors were from a bad wheel bearing, I replaced the RH side wb when I did the brakes.

Click to expand...

WooHoo!!! Great work, nice to have also inspected and cleaned the entire brake system lol

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