BRAKE HELP!!!

[adam996GT3]

I want to apologize for the long post, but I want to be as thorough as possible since myself as well as many instructors at the track are truly stumped.

My car is a 2015 M3, with 11k miles and manual transmission. It is a weekend car so mostly just sits in the garage. My track set up is pfc 08 pads and apex wheels, 9.5 x18 and 11x18 on 275 and 305/35/18. Tires are nt01 that are nearing the end of their life. Other than that, the car is all stock and no suspension upgrades.

So here is the story, on Tuesday I do the usual track prep routine and swap the pads and wheels to track set up. I drove around the neighborhood a few times to bed the brakes in and then left the car alone until the track day. Saturday morning I make the 2 hour commute to the NJMP. First session go out, first few laps feel fine and then after laps 3 or 4 I start to feel a shudder under heavy braking. The best way to describe it is it feels like I am driving down a cobblestone road when braking. I continue, but after it progressively becomes worse my instructor advises that we come off the track. We visually inspect everything and all looks fine. The pads have ton of life, as they should since they were brand new pads when I put them on. Instructor advises I go bed the brakes in. I go to the road and perform about 5, 60 to 10 mph stops and the brakes feel fine while doing this, no shudder at all. Seems it's only happening when brakes heat up and under heavy braking. Go out for my second session, all feel well for the first 2 laps and then once I am warmed up and getting on it, same thing. After the session, the instructor advises I put the oem pads on. I do so and go out for my third session and same issue after the brakes warm up. Instructor then recommends that we call it quits which puts my track weekend to an end. I then drive home and under normal driving, no shudder at all. I even take some on/off ramps at speed and can't replicate the shudder. I can't seem to figure out what's going on. Some suggested my rotors are warped. Others suggested that there may be oem pad deposits on the rotor, but visually I don't see any build up on the rotor and I would assume I scrubbed those when I installed the pads, drove to the track, drove on track, and finally bed them at the track. Could it possibly be the settings I was driving on? I love the rev matching feature so I drove in sport engine, sport plus suspension, and sport steering. Any advice would be greatly appreciated.

[CanAutM3]

It is a long shot, but what you are experiencing could be unrelated to the brakes. Being a 2015, your F8X is nor as new as it was, so you might be experiencing bushing wear in the front suspension. I had this on my 2015 F82 after 4-years in, the bushings in one of the front suspension links had gotten loose. It was most noticible on track when the tires were properly warmed up. I would get rather intense shudder and vibration under braking. In normal street driving, it was barely noticible. I would recommend jacking up your car and checking for play in all of the suspension links.

[adam996GT3]

Originally Posted by CanAutM3

It is a long shot, but what you are experiencing could be unrelated to the brakes. Being a 2015, your F8X is nor as new as it was, so you might be experiencing bushing wear in the front suspension. I had this on my 2015 F82 after 4-years in, the bushings in one of the front suspension links had gotten loose. It was most noticible on track when the tires were properly warmed up. I would get rather intense shudder and vibration under braking. In normal street driving, it was barely noticible. I would recommend jacking up your car and checking for play in all of the suspension links.

That has been a thought of mine as well. I was planning to get out my trusty pry bar and apply it to all suspension components to see if there is any play or excessive movement. Also to inspect all bushings. Thanks for the advice.

[gum2012]

Do you use your ebrake between sessions? I used to do that between sessions and it was creating deposits (same rumble noise) being lava hot sticking to the rotors lol.

[Suds]

My take is you are scraping off the OEM brake material from the brake rotor, power through it. You could actually see material coming off the surface of the brake rotor. I have run PFC08’s for 40 track days or so on F82s. On my 2015 the front wheel shake got pretty bad while the OEM brake material eventually wore away off the brake rotor, braking was smooth after that. I no longer change back to OEM pads and run PFC08’s on the street.

[ATX_M3]

I agree with suspension investigation recommendations. I've been tracking on PFC 08s for a while and I have some weird noises and vibrations due to deposit build up when I switch back to OEM pads but nothing on track.

Other than the noise, my experience with PFC 08s is they are better feeling with more heat in them.

[fanatic1]

Originally Posted by gum2012

Do you use your ebrake between sessions? I used to do that between sessions and it was creating deposits (same rumble noise) being lava hot sticking to the rotors lol.

The e-brake is a separate system, you can use it between sessions w/o issue

[CanAutM3]

Originally Posted by gum2012

I used to do that between sessions and it was creating deposits (same rumble noise) being lava hot sticking to the rotors lol.

On your M4 ?

Because the handbrake on the F8X is a separate drum-shoe system inside the rear disc hub that can be used without issue between sessions.

[pshooter]

My guess is you have uneven transfer layer on the rotors If you are swapping between street and track pads.
My experience has been that you need to find compounds that play nice together (Ferodo 2500 and DSUNO is one I know of) or aggressively clean the rotor (Heavy scotchbrite on a 4"grinder or bead blast) to remove old pad material. A full metallic pad will clean them as well and leave no deposits.

Uneven transfer layer will only show up when the rotor is HOT.

[CanAutM3]

Originally Posted by pshooter

My guess is you have uneven transfer layer on the rotors If you are swapping between street and track pads.
My experience has been that you need to find compounds that play nice together (Ferodo 2500 and DSUNO is one I know of) or aggressively clean the rotor (Heavy scotchbrite on a 4"grinder or bead blast) to remove old pad material. A full metallic pad will clean them as well and leave no deposits.

PF08 are compatible with the stock pads. I've never had any issue with them.

Originally Posted by pshooter

Uneven transfer layer will only show up when the rotor is HOT.

That's not my experience, once there's an uneven layer of pad deposit on the rotors, it will shudder with every moderate to heavy brake application.

[adam996GT3]

Originally Posted by gum2012

Do you use your ebrake between sessions? I used to do that between sessions and it was creating deposits (same rumble noise) being lava hot sticking to the rotors lol.

I actually don't use the e brake between sessions. I leave the car in gear when parked

[adam996GT3]

Originally Posted by CanAutM3

PF08 are compatible with the stock pads. I've never had any issue with them.

That's not my experience, once there's an uneven layer of pad deposit on the rotors, it will shudder with every moderate to heavy brake application.

The brake shudder happens only during heavy braking. When I drove home I never felt the shudder. For safe measure I am going to check the suspension components this weekend and if there is nothing obvious I will be ordering a new set of rotors.

The car does sit a lot. I probably drive it only once every 2 weeks and sometimes once a month. The rest of the time it sits in the garage. Additionally sometimes I will take it out to only wash the car and when I go to pull the car out the pad is stuck to the wheel. So having the stock pad deposits on the rotors is likely and due to the fact that I didn't properly bed the brakes, the track driving with the pfc pads likely compounded the issue.

[DRLane]

Originally Posted by adam996GT3

The brake shudder happens only during heavy braking. When I drove home I never felt the shudder. For safe measure I am going to check the suspension components this weekend and if there is nothing obvious I will be ordering a new set of rotors.

The car does sit a lot. I probably drive it only once every 2 weeks and sometimes once a month. The rest of the time it sits in the garage. Additionally sometimes I will take it out to only wash the car and when I go to pull the car out the pad is stuck to the wheel. So having the stock pad deposits on the rotors is likely and due to the fact that I didn't properly bed the brakes, the track driving with the pfc pads likely compounded the issue.

Remove the rotors and resurface with a Flexhone. This will remove any pad residue, and surface rust that's not removed by the pad. At least start here before replacing them...

https://www.amazon.com/Brush-Researc.../dp/B007SOW0WC

[jpy1980]

This wouldn't be ABS related, would it?

[USSEnterprise]

I have the same issue on my Lotus Evora. See thread here: https://www.lotustalk.com/threads/ev...3#post-6035049

I do believe it's related to brake pad material transfer on the rotor. Inokinetic did a good writeup on this issue, read here: https://www.inokinetic.com/innovatio...ding-padsrotos

Definitely use the flexhone drill attachment and clean off all your rotors, then rebed your track pads in. Having to do this constantly before each track day (all 4 rotors will have to be taken off so you can hone both sides clean) will be a chore, but try that, before spending money on rotors themselves. Your suspension is fine.

[Spun Crankhub]

Are you able to replicate this on the street or only heavy braking at the track? Maybe try to locate someone with a spare set of confirmed true rotors to rule that out.