Ongoing brake problem

[JD Cross]

I'm having trouble with my NSX brakes again and need some help.

At 147 k km I replaced my front rotors with StopTech slotted rotors and OEM pads.
The rear rotors measured 20.4 mm compared to new at 21 mm and min allowed of 19mm so left them in and just replaced the rear OEM pads.
I broke the new pads in using the procedure outlined on the StopTech website

I developed severe juddering on the front rotors at highway speeds due to either pad material build-up or warping so had them turned by Burrard Acura.
The problem went away but returned soon after.

StopTech offered to replace the front rotors under warranty so I went with plain StopTech rotors this time in case the slots were part of the problem.
They also recommended their PosiQuiet pads which I also installed.
They also recommended just driving the car normally without a high speed break-in procedure.
This was done at 161 k km, about 3000 km ago.
The rear pads only have 17 k km on them so I assume they are fine and not the problem

The problem has returned.
The juddering is pronounced under braking at 120 km plus and the whole car vibrates.
At city speeds the braking is normal.

What should I do next?

 

[solidol]

What should I do next?

I don't think this is because of your brakes. I would look at ball joints wear - especially in lower control arm on the passenger side.

 

[anesthesia]

I would look at the calipers, sometime it can somewhat if you may lock or fail to release fully, if not properly lube when doing a brake job, just a thought. The other thing I would look at are your tires?

 

[B2FiNiTY]

Check if your pads are wearing evenly.

 

[JD Cross]

Check if your pads are wearing evenly.

Will do

- - - Updated - - -

I would look at the calipers, if not properly lube when doing a brake job, just a thought. The other thing I would look at are your tires?

Calipers were lubed when the rotors and pads were changed and the tires have 6 k miles on the fronts and 2 k miles on the rears.
I think both of these items are okay.

 

[Honcho]

Jim-

Does the shudder only occur when pressing the brakes? Roman may be right, but if it only occurs at a certain speed, I would take another look at the rotors and calipers. A suspension issue (loose ball joint) would be apparent at any speed. If your brakes are original and have never been rebuilt, it is possible one of the front pistons is stuck, causing uneven pressure on the pad and a "flutter" at higher speeds.

Paul

 

[JD Cross]

Does the shudder only occur when pressing the brakes? Roman may be right, but if it only occurs at a certain speed, I would take another look at the rotors and calipers. A suspension issue (loose ball joint) would be apparent at any speed. If your brakes are original and have never been rebuilt, it is possible one of the front pistons is stuck, causing uneven pressure on the pad and a "flutter" at higher speeds.

The juddering only happened when braking from 60 mph or more.
Slowing from say 30 mph all is smooth.

I'll be taking the car to my Vancouver dealership in May we'll take a look at the suspension, rotor wear, pad wear, run-out and rotor thickness variation.
The calipers have never been rebuilt and you are right that should be done regardless.

 

[solidol]

Given all the data you have shared unless you have sticky caliper your brakes won't cause this. I think the reason you see it happening at 60 is that your ball joints can still withstand pulling forces at lower speed.

Now the only question I have is how much pressure do you apply on the brake pedal to cause this? IOW light touch on the brakes or heavy braking?

I'm very curious what the actual reason is.

 

[sparky]

For what it's worth my slotted Stoptech's (front and rear) do not exhibit this problem, over several years of use. Occasionally at very low speeds a slight shudder, but definitely not at high speed, they are perfect.

I can't see rear brakes having anything to do with your front brake shudder issue, so I'm inclined to agree it may be suspension looseness that is only evident under load, e.g. a ball joint, perhaps the compliance bar? Or, trying to think outside the box: could the front ABS be faulty ?