[Aualexa2]

Hey, guys.

I'm new to the M2 world as I usually track my GT4. I took my M2 to NJMP Thunderbolt last weekend and had the brake pedal hit the floor after only 4 laps on track. It was barely enough track time to get the brakes warmed up. I was able to safely get off the track and had the brake fluid flushed by the trackside shop. Of note, I had srf flushed a week prior to the event by my local shop (who I trust 100%). When they flushed it at the track, they got a lot of air out of the driver side front caliper. The brakes felt great the next session, but later in the day, they went to the floor again. This was more than just brake fade. I'm planning on having a full flush done again including bleeding the abs unit in case air somehow got in there. Is there anything else that I should be considering?

More background: There are no puddles of brake fluid anywhere, so I don't think there are any leaks. The car is basically new with only 3000 miles on it. No previous track use. Stock pads.

Thanks in advance for any suggestions.

Alex

[ZM2]

Originally Posted by Aualexa2

Hey, guys.

I'm new to the M2 world as I usually track my GT4. I took my M2 to NJMP Thunderbolt last weekend and had the brake pedal hit the floor after only 4 laps on track. It was barely enough track time to get the brakes warmed up. I was able to safely get off the track and had the brake fluid flushed by the trackside shop. Of note, I had srf flushed a week prior to the event by my local shop (who I trust 100%). When they flushed it at the track, they got a lot of air out of the driver side front caliper. The brakes felt great the next session, but later in the day, they went to the floor again. This was more than just brake fade. I'm planning on having a full flush done again including bleeding the abs unit in case air somehow got in there. Is there anything else that I should be considering?

More background: There are no puddles of brake fluid anywhere, so I don't think there are any leaks. The car is basically new with only 3000 miles on it. No previous track use. Stock pads.

Thanks in advance for any suggestions.

Alex

It's the pads. Our brake calipers get extremely hot and the stock pads can't cope with hardly any track work.

My personal preference in the stock calipers are PFC 11's.

[Aualexa2]

Thanks for the info! It's hard to believe they can be THAT bad! Crazy.

[5.M0NSTER]

Just curious. Do you track your GT4 with stock pads?

[Aualexa2]

Originally Posted by 5.M0NSTER

Just curious. Do you track your GT4 with stock pads?

I did for the first two track seasons I owned the car. I've since switched to girodisc rotors and ferodo pads.

[ZM2]

Porsche's are definitely better sorted for the track out of the box (esp a GT4), but I can fit all my tires in my track prepped BMW and I think it looks better than a Porsche.

[5.M0NSTER]

Originally Posted by Aualexa2

I did for the first two track seasons I owned the car. I've since switched to girodisc rotors and ferodo pads.

Wow, that's actually pretty impressive! Most cars which weigh over 3300lbs + can not pull that off.

As ZM2 said it's very easy to overheat the stock pads. Over 800F they fade bad. If you plan on tracking the M2 you'll need 1500F + capabale pads like the PFCs 08 or 11 to be able to finish a session.

If you're on stock rubber or something like Micheling Pilot Super Sport or 4S you can stick with 08 compound. A bit less initial grip which doesn't overpower the tires on initial apply. If you run semi slick or slick you can go for something like PFC 11 with more friction.

[omasou]

How would stock pads cause the pedal hit the floor? Sounds like air. If they aren't using the computer to do a complete bleed maybe there's still some air in there from the first bleed? Though not sure how they introduced air?

[ZM2]

Originally Posted by omasou

How would stock pads cause the pedal hit the floor? Sounds like air. If they aren't using the computer to do a complete bleed maybe there's still some air in there from the first bleed? Though not sure how they introduced air?

Part of my head thought this too, and if you got the stock pads hot enough to get the pedal close to the floor you probably smeared pad material on the rotor.

But, he said he trusts his shop, and we all know you def can’t run stock pads on the track anyways, so those should go anyhow.

[Aualexa2]

I think the most likely cause is air that was introduced into the system. As I said, I trust my shop. Certainly, no one is perfect, so it could be their fault. Any other thoughts about how air could be introduced? Fluid was fresh srf, so it shouldn't boil.

Pads and rotors are fine and have plenty of life left on them.

[ZM2]

Originally Posted by Aualexa2

I think the most likely cause is air that was introduced into the system. As I said, I trust my shop. Certainly, no one is perfect, so it could be their fault. Any other thoughts about how air could be introduced? Fluid was fresh srf, so it shouldn't boil.

Pads and rotors are fine and have plenty of life left on them.

Does your shop know to cycle the ABS unit when flushing/bleeding?

[Aualexa2]

Originally Posted by ZM2

Does your shop know to cycle the ABS unit when flushing/bleeding?

I'm heading there tomorrow and they're going to flush the system and cycle the abs unit. They didn't do it when they flushed it last week. Does it need to be done with every flush? I thought it was only if air got into the system.

Btw, I appreciate everyone's responses

[M2joey]

Originally Posted by Aualexa2

I'm heading there tomorrow and they're going to flush the system and cycle the abs unit. They didn't do it when they flushed it last week. Does it need to be done with every flush? I thought it was only if air got into the system.

Btw, I appreciate everyone's responses

Yeah, something other than pads is going on there. Your foot should not have gone to the floor. I know an instructor that was driving his completely OEM M2 incredibly hard with no issues, other than wear.

Edit: Driving with DSC On will certainly heat the OEM pads up. It is certainly possible to get them overheated.

[Aualexa2]

Well, there was definitely air in the abs unit. More came out when they cycled the valves in the unit. Should be all set. I still don't think it was my shop that originally introduced the air. The only other possibility was that the dealership bled or flushed the fluid prior to delivery and they messed it up. My car had sat on their lot for several months and the dealership "freshened everything up" prior to delivery.

[Aualexa2]

Is it possible that some cars are coming from the factory with air stuck in the abs?

This is basically the exact thing that happened to me. Wondering if people are attributing it to crappy pads/rotors when the problem is actually air in the lines.

[Drop the hammer]

When I did my second flush (right after a track day), I had air bubbles come out of rear rotors. This was after bmw dealer changed my brake fluid (prior to the track session). I’ll only trust a fluid change to my own doing now.

[jritt@essex]

There are two types of brake fade:

1. Pad fade= The pads exceed their maximum operating temperature, and the compound can no longer generate friction. The pedal remains hard, but the car doesn't slow down. This is most commonly experienced when someone runs OEM road pads on the track.

2. Fluid fade= The brake fluid exceeds its boiling point, and air bubbles are formed in your brake lines. This is the culprit in this instance. This typically happens on stock fluid, but may very well happen with aftermarket fluid if the rest of the brake system cannot handle the temps being thrown at it. Many times it takes several bleeds to get all of the air out of the system, and yes, it definitely gets trapped in the ABS system.

To the OP...
A) Thanks for your support on the Ferodo pads (we, Essex, are the Ferodo importer and distributor for Ferodo in North America). We offer Ferodo DS1.11 in the OEM M2 shapes. I'm assuming that's what you're running on your GT4. You can see them here: https://www.essexparts.com/my-vehicl...W/M2/F87%20All

B) Make sure you are running a high quality fluid. A good recommendation is Ferodo Super Formula fluid, which we are currently running a promo on. If you spend $100 with us, you get two bottles for free. It is an excellent fluid with an extremely high boiling point, and you can't go wrong with it.

If you go to a superior fluid with Ferodo pads and you're still boiling it, then you'll know you're discs aren't able to handle the heat you're throwing at them. Think of your brakes like a chain...hot discs leads to hot pads, leads to hot pistons, hot calipers, and hot fluid. If the discs don't have the thermal capacity or ability to shed heat, that's the next place to look.

In the link above you can see our brutally effective complete AP Radi-CAL brake kits. If it comes to that, give us a call and we'll get you fixed up. In the meantime, make sure your fluid and pads are correct as the top priority. Good luck out there!

[eeyang92]

OP, I just had this happen to me recently when I went to Thunderhill. First lap was okay, but by my second lap my pedal nearly touched the floor (as I was getting the brakes warmed up). I am running SRF as well.

The interesting thing is that after the second lap, my pedal actually started getting firmer and then besides a slightly squishy pedal, I had 100% performance from my brakes for the rest of the session. It was like this at the beginning of every session.

Fairly certain I have air in my system, and it's sounding like it's probably in the ABS if I didn't see any bubbles come out when I flushed it just a few weeks ago. Guess I'll need to go to a shop that has the equipment to flush the ABS system.

[5.M0NSTER]

In a different thread user Caduceus said this:
"I think the need to do this is over-rated. What matters is what fluid is in contact with the back of the pistons inside the brake calipers. This is what boils under heavy use and leads to vapour in the lines and a soft pedal. Brake fluid is not a recirculating system. There’s no return line from the caliper. So boiling fluid and vapour inside the caliper doesn’t end up in the ABS unit, or the master cylinder and it isn’t conductive enough to transfer the heat along a considerable length of brake line.

In a perfect world, the entire system would be full with clean, fresh SRF. But for all practical purposes, as long as that’s what is coming out of your caliper bleed nipples and there isn’t air trapped in the system further upstream (which would be soft all the time, not just when hot), you will be fine."

And mythoughts were:

Yeah, I would generally also agree. The reservoir holds 250cc if fluid. The ABS unit has accumulators which hold about 4-6cc. Calipers and lines hold about 50 CCs. The only way you get contaminants or boiled fluid into the accumulators is under ABS pressure decreases from the calipers. And it’s a lot harder to get into ABS when the pedal gets soft. Then from there the boiled fluid would go back up to the master cylinder when the driver releases the brake. But the bottom line is the few CC’s in the ABS unit are not that much.

He is still correct, and I stand by my previous statement also. For what it's worth.

[eeyang92]

Originally Posted by eeyang92

OP, I just had this happen to me recently when I went to Thunderhill. First lap was okay, but by my second lap my pedal nearly touched the floor (as I was getting the brakes warmed up). I am running SRF as well.

The interesting thing is that after the second lap, my pedal actually started getting firmer and then besides a slightly squishy pedal, I had 100% performance from my brakes for the rest of the session. It was like this at the beginning of every session.

Fairly certain I have air in my system, and it's sounding like it's probably in the ABS if I didn't see any bubbles come out when I flushed it just a few weeks ago. Guess I'll need to go to a shop that has the equipment to flush the ABS system.

Just an update on this:

Today I did a "complete" flush - I drove around and activated ABS a few times, and then slowly pumped my brake pedal while having the cap open and under pressure (not sure if this did anything, but did see some bubbles come out, but that could have been from the reservoir) and then slowly bled all 4 corners.

The result was a firm pedal (I almost hit my face on the wheel the first time I braked) - so I did have some air in my lines, quite possibly in my ABS or MC as during my last flush I did not attempt to clear either of those.

I had bought the phoenix reverse bleeder as I was getting desperate but it turns out I didn't have to use it. I may give it a go if my pedal becomes soft again.

[5.M0NSTER]

Good work! sounds like you had trapped air somewhere in the system. Looking forward to how it feels on the track next time you’re out.