Front brake shudder

[GlanzaAtHeart]

Hi team,

Back at it with another brake system issue.

I am having some brake shudder on the pedal and steering wheel that's directly related to wheel speed.

I have:
- Rebuilt all calipers in the last 2 months
- New pads/rotors late last year
- Put the rear of the car of jack stands with the wheels off and "driven" the car up to 40-50 and braked, there is no brake shudder.
- Put a straight edge on the front discs and couldn't find anything?

What would I go checking next? Thanks in advance.

[GDII]

You will need to check for brake rotor run out. If the rotor isn't sitting flat on the hub then it won't be rotating evenly.

To test you need to get a dial gauge. Or borrow one as they are not cheap. Also check your hub faces are clean and also running true.

[GlanzaAtHeart]

You will need to check for brake rotor run out. If the rotor isn't sitting flat on the hub then it won't be rotating evenly.

To test you need to get a dial gauge. Or borrow one as they are not cheap. Also check your hub faces are clean and also running true.

Would the wheel not seat the brake disc to the hub? Fair point. Yeah thought I might need a dial gauge. The grooved/drilled rotors I got probably don't help when using it haha. I'll see if I can borrow one. Thanks for the tips, I will see how I go.

[GDII]

The wheel does bolt it down but slight variations in the rotor and hub mating faces can't be cancelled out by bolting the wheel on.

Znoelli state in the fitting instructions (I'm sure other manufactures say this too) that you should do a run out test and check what it is. If you take the rotor off and turn it one stud more (72°) then try again. It can make it better apparently. But it sounds like you need to see what the run out is and what the max spec is.

[GlanzaAtHeart]

Had a go today trying to reseat the hubs, which I did and turned the rotors by 72 degrees.

Test drive was better after slamming the brakes a few times, however still there. I don't know what it is.

Car will be going into a workshop next week as I just don't have the time to look at it any further :/

[GDII]

If it was me I'd try rotating again but you really need to get out a dial gauge to test the runout is in spec each rotation you make.
Clearly it is not in spec and rotating it 1 step showed it is the rotor or the rotor to hub interface.

[GlanzaAtHeart]

Got the rotors machined by a local workshop, ended up solving all my issues.

I spoke to them, there wasn't any immediate damage they could spot with the rotor, but a large amount of surface rust buildup so maybe it was that?

Unsure what really caused this but glad it solved it.

[GDII]

That's good. I'm sure there was more than just the rust otherwise they wouldn't have machined them.