Ryan996TT

So usually when I’m backing up or just generally moving at slow speed and braking, I’ve been getting the brake pedal vibrating intermittently for a couple seconds at a time. Sometimes it throws PSM/ABS lights and tells me brake failure drive to workshop. The brakes work fine, this issue keeps popping up at low speeds.

I initially thought the brakes needed to be bled, as perhaps it was an air bubble in the lines. However I’ve never experienced that and I’m not sure what that feels like.

My local Indy shop who kept the car for days waiting to experience this intermittent issue said that they didn’t think it was cause for bleeding the brake lines and didn’t suggest we go that route. They checked the brake sensors and saw they were newer. They couldn’t figure it out in the hour I paid for and I didn’t feel like going down the rabbit hole on it so I took it home.

Anyone experience this or have any ideas?

k9turbo

check your rotors. it's not common for them to warp, but it happens and might well cause pulsing/vibration etc.

Ryan996TT

Ive considered this, but vibration is only at very low speeds and it happens for a couple seconds here and there. If rotors were warped pedal would always vibrate under all braking.

Mike Roblin

Yea but the faster they are rotating the higher the frequency and you might not notice it as much. The lower speed allows for a slower pulsation and potentially it is more noticeable.

Carlo_Carrera

It’s the rotors. Sometimes a few very hard stops from high speed will lessen the vibration.

Ryan996TT

I'll try a couple hard stops to try and lessen the vibration. That usually shuts my noisy brakes up whenever they get loud.

However, I just can't wrap my head around it being the rotors if it's only happening sometimes for a couple seconds at a time. If it was indeed the rotors, wouldn't it be consistently happening?

I had to leave it at the shop for days just so they could wait for it to happen again....it doesn't happen all the time.

pancing

Is it a judder? Or is your abs engaging? I for one cannot get my abs to activate, my wheels just lock up. What size are your wheels?

Ryan996TT

Yes, a shudder would be a better way to describe it. Happens for like 2 seconds. My shop said they think its the ABS engaging, and they checked the brake sensors and said they're both newer.

Wheels are aftermarket 19 inch.

2fcknfst

This.

And Mike noted that as speed increases, the vibration frequency will change as the rotor is spinning faster, the pulse widths get shorter, so it may not have the same effect on the pedal, but that does not mean it is not warped. Also of note, the larger the rotor is, the more pronounced the vibration (warp) is at low speeds.

Ryan996TT

Noted. This seems to be consensus and I'll check them out then.

ABORh911

I bet the vibration would completely go away at warp speed!

2fcknfst

If you have access to a good brake guy, or machinist, and enough meat left on the rotors, you should be able to clean that up pretty easily.

pancing

If it happens right at the moment before the car stops your abs is engaging. If you have your stock rims available throw those on and see if you can get it to happen. Or you could pull the abs module up front and see if it still happens.

That would rule out warped rotors.

I do hope it is just warped rotors in your case tho anything else would be more expensive than brake job.

Ryan996TT

:

Thanks for your (and everyone else's) input!

Ryan996TT

Lol @ your sad face for Polk County haha I'm in Orlando...

Yeahhh I hope I don't have to end up spending a lot on this one... my shop seems to think that it def is the ABS engaging...and it does indeed happen prior to stopping at slow speeds. Good info...thank you.