[Msquared]

Wasn't sure whether to ask this in the 1LE forum or the Suspension/Brake forum. Asking here because it's probably specific to the Brembo calipers and this where the track junkies hang out.

I was doing a PDE event at World Wide Technology Raceway (formerly Gateway) today in my 2020 SS 1LE (all stock) and I suddenly lost my brake pedal completely. Luckily it was at a fairly innocuous corner and I was able to cut across it in the grass and come back on track with no damage.* Trundled back to the pits where we discovered that both bleeder screws (inner and outer) on the RF caliper were very loose and fluid was just geysering from them every time I pressed the pedal. We were able to screw them back down and they didn't leak any fluid. I topped off my reservoir and had no issues driving home.

So now the question is: why the hell did this happen, and how do I make sure it doesn't happen again?! For context, this is a 2020 car with lots of autocross use and 10-12 track days in its history. I last flushed the brakes before the SCCA Time Trial at Autobahn at the beginning of August. I competed that weekend, SCCA Solo Nationals, and a bunch of other autocrosses since then. There's no way I left those screws loose this whole time, or the failure would have happened a long time ago. This caliper is on the corner that gets the most cornering and braking load at this track, so it stands to reason it gets the hottest. Can heat cycles cause the bleeders to loosen and back out like this? Nobody I know has ever seen anything like this before. One obvious answer is "Tighten the bleeders tighter." However, I don't want to strip the threads in the caliper. What sayeth the forum members?

*Discretion being the better part of valor here, as there is a wall awaiting those who enter this turn too fast and push out of the exit.

[2SS Capt]

Originally Posted by Msquared

Wasn't sure whether to ask this in the 1LE forum or the Suspension/Brake forum. Asking here because it's probably specific to the Brembo calipers and this where the track junkies hang out.

I was doing a PDE event at World Wide Technology Raceway (formerly Gateway) today in my 2020 SS 1LE (all stock) and I suddenly lost my brake pedal completely. Luckily it was at a fairly innocuous corner and I was able to cut across it in the grass and come back on track with no damage.* Trundled back to the pits where we discovered that both bleeder screws (inner and outer) on the RF caliper were very loose and fluid was just geysering from them every time I pressed the pedal. We were able to screw them back down and they didn't leak any fluid. I topped off my reservoir and had no issues driving home.

So now the question is: why the hell did this happen, and how do I make sure it doesn't happen again?! For context, this is a 2020 car with lots of autocross use and 10-12 track days in its history. I last flushed the brakes before the SCCA Time Trial at Autobahn at the beginning of August. I competed that weekend, SCCA Solo Nationals, and a bunch of other autocrosses since then. There's no way I left those screws loose this whole time, or the failure would have happened a long time ago. This caliper is on the corner that gets the most cornering and braking load at this track, so it stands to reason it gets the hottest. Can heat cycles cause the bleeders to loosen and back out like this? Nobody I know has ever seen anything like this before. One obvious answer is "Tighten the bleeders tighter." However, I don't want to strip the threads in the caliper. What sayeth the forum members?

*Discretion being the better part of valor here, as there is a wall awaiting those who enter this turn too fast and push out of the exit.

I'm guessing there is a torque setting somewhere for the bleeders, if you are on the track, I'd make sure you are set correctly...

[Baddawg53]

Yikes!! That's frightening, think I'm adding to my pre-track day checklist to check caliper bleeders now...

I cannot think of a reason why this would happen. Trying to think back to every time I've cracked open a bleeder screw, and I can't think of any time where it seemed as if a bleeder was backing out.

Really interesting stuff, thanks for sharing that...

[Msquared]

Originally Posted by Baddawg53

Yikes!! That's frightening, think I'm adding to my pre-track day checklist to check caliper bleeders now...

I actually meant to include this in my OP, so thanks for writing it. I think if nothing else, this is a good lesson. It's obviously super-easy to do if you're even swapping tires for the track day. As 2SS Capt wrote, I need to find the torque spec for those bleeder screws and make sure they are all set at it.

I cannot think of a reason why this would happen. Trying to think back to every time I've cracked open a bleeder screw, and I can't think of any time where it seemed as if a bleeder was backing out.

This is where I'm at, too. And it's especially odd that out of all eight bleeders, only the two on the RF caliper became loose, and they both did it at the exact same time (if either had backed out first it would have caused the same failure).

[MT-SS1LE]

I haven't bled mine yet as I don't track it, but the factory service manual calls for 17-20 Nm (13-15 ft-lbs) of torque for the front OE Brembo caliper bleeders. That's a lot more than you would think and much higher than I've seen for other vehicles with "normal" brakes. My guess would be you didn't have them tightened down enough. I would use a good, accurate torque wrench and check them all.

[Baddawg53]

I've actually never torqued a bleeder screw in my life, also you used the car plenty after the last bleed. It's really odd. After I replied last night I began thinking about things like sabotage... Have you made anyone mad lately? Like you said, both bleeders on the same caliper, it's definitely weird.

[m6-lt1]

Only thing I can think of is you over torques them and they failed or you under torqued them. I too was afraid of stripping the threads so I have bought an inch pound torque wrench and use it specifically for torquing my bleeder screws. It actually does feel like you’re going too tight when torquing them but that spec above is provided by GM.

There is a former SS 1LE owner that claims he and others have had brake failure on track and they let GM know about it. Not sure if this was the cause of their failure though.

[DaveC113]

Glad you're ok @Msquared!

Interesting timing... I just had a bleeder loosen too, inside front. Luckily for me it only leaked a very small amount of brake fluid, the master looked full.

For torque, at 13-15 ft lbs I almost surely wasn't using enough. I also double checked the torque values and got 10 ft lbs for bleeders and 15 ft lbs for banjos, but it seems like 10-15 ft-lbs is the range for 10mm Brembo bleeders. In either case that's probably more than I used as I don't want to strip out the threads, otoh leaking fluid and/or brake failure is also bad. I'll have to see if I have a torque wrench that covers such a low value, I have a tiny one for diffs and two large ones, lol.

[MT-SS1LE]

Best thing is to use an INCH-lbs torque wrench since they usually fall within the range GM calls for. Your standard 1/2" or even 3/8" torque wrench is going to be outside the torque range needed. And you don't want to be using a torque wrench at either extreme of its range if you can avoid it.

[TransamGTA350]

Sorry that happened to you. Scary and glad you're OK.

It does sound like the bleeder screws weren't tight enough. I have not used a torque wrench on mine (probably should after hearing this), but I go pretty tight with them. I do 10-12 track days per year and get the brakes very hot at times (have come in with the stock front pads smoking on more than one occasion) and never had an issue with the bleeders loosening.

[Eric10905]

OP, glad the 'event' ended well, as it sure could have been worse.

I also have no clue on why they would loosen. And both on a single caliper is beyond strange.

I had a different issue with a caliper and bleed screws where I ended up replacing the entire caliper. I guess I am second, third, the recommendation to use a inch # torque wrench. I bleed twice a year (or more) for tracking and now use that torque wrench religiously. I actually go a little lower than the recommended values 'cuz it just feels like so much torque on them.
And likewise... going to add checking these before each event.

[bishopts]

If it wasn't sabotage or neglect then it had to be related to heat. Front brakes get hotter than rear since they do more of the braking, then dissimilar metals expand and contract at different rates. So steel screws and aluminum housings with the application of fluid pressure could be the culprit.

[p47dman]

Use a flare nut wrench. Or get a flare nut crows foot to go on the torque wrench. You will not round the corners using these.

[Msquared]

A few responses to those who've replied. First, thanks for the well wishes. All really is well. I actually got into a novice's car to begin coaching after getting my car roadworthy for the drive home. If that doesn't prove I wasn't rattled by the brake failure, I don't know what would!

The thought of sabotage actually briefly crossed my mind, LOL, but the only person I know of who hates me enough to do that wouldn't have the slightest clue how to do it. Also, getting to the inside bleeder screw would probably require removing the wheel, which didn't happen. OTOH, my wife might want to collect on our life insurance policy...

I know the well-known person whose 2020 SS 1LE crashed at a track due to one corner's brake failure. It wasn't because of this problem. That is confirmed.

Okay, so putting the car on jackstands this evening and checking all the bleeders, all the others are snug but not close to the spec. My current hypothesis is that although they weren't loose to begin with, they were never actually tight enough. They survived the heat cycles of one TT and the autocrosses, but the extra brake load on the RF that my local track causes just made that corner's bleeders work loose through the expansion and contraction of heat cycles. I still find it incredible that both bleeders loosened at basically the same time.* I'm still open to other hypotheses if anyone comes up with them.

I have a good in/lb (also reads N.m to the tenth) torque wrench, and this will go on every bleeder before every track day for sure! BTW, 13-15 lb/ft is 156-180 in/lb. And I did verify the specs that MT-SS1LE gave us in my copy of the FSM. Regarding p47dman's advice about using a flare nut wrench, I won't actually put the final torque on these things while the catch can hose is still attached to the bleeder. After any bleeding is done, I am using a hex 1mm socket on my torque wrench. I definitely won't use a 12-point socket, though, for the same reason you mention.

*Although I know for sure that at least one of the two bleeders loosened to the point of leakage between Turns 2 and 3, I only really know that the other loosened somewhere between there and my crawl back to the paddock. But that's close enough to call it "at the same time."