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Tire lock-up with race ABS

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I have had the Ford race ABS module for a few years and it has worked flawlessly. During a track day last month I lost the right rear under heavy braking when the tire locked and sent me spinning into the infield. Pirelli DH had a flat spot right down to the cords.

I then did another track day two weeks later and after two full sessions got rained out but no issues with braking. A few weeks ago I did a hillclimb so speed and brake effort was low but video confirmed I locked the right rear into the first turn on one run and the right front on another.

Has anyone experienced this with the race ABS? How can I tell if the unit is faulty? The whole dash lights up when you install it so no specific warning light to alert me if there is an issue. Any other ideas? I bleed the system after every event.
 

Mad Hatter

Gotta go Faster
5,237
4,227
Santiago, Chile
Dont know if this helps, but once we found a shorted cable to a ABS sensor. Made me Lock up the fronts and toasted a new pair of tires with massive flat spots. Have the TC off in a track tune so all the lights are always on as well.
 
I have had the Ford race ABS module for a few years and it has worked flawlessly. During a track day last month I lost the right rear under heavy braking when the tire locked and sent me spinning into the infield. Pirelli DH had a flat spot right down to the cords.

I then did another track day two weeks later and after two full sessions got rained out but no issues with braking. A few weeks ago I did a hillclimb so speed and brake effort was low but video confirmed I locked the right rear into the first turn on one run and the right front on another.

Has anyone experienced this with the race ABS? How can I tell if the unit is faulty? The whole dash lights up when you install it so no specific warning light to alert me if there is an issue. Any other ideas? I bleed the system after every event.
What track/corner did it happen first? How old were the tires? I've done it before, worn out tires on a shake down run. If the tire doesn't have any grip, it can't be unlocked.

Does the ABS light turn on/off at start up? If the ABS is failed the light ABS light will be on and stay on.
 
What track/corner did it happen first? How old were the tires?
It happened braking hard into Lightning turn 7. I jumped on the pedal and the rear immediately locked and started a long, slow slide into the runoff area. The tires were used Pirelli DH so not that great. I ran Pocono Grand course after that and no issues. The front lock up was probably at 70 mph but with A7's. Tire temps are pretty low with hills so grip is also not ideal.

I'll have to inspect the ABS sensors but since it happened both front and rear I would be surprised I knocked out both. Just odd this suddenly started happening. I always ran used Pirelli's and never had this issue.
 
It happened braking hard into Lightning turn 7. I jumped on the pedal and the rear immediately locked and started a long, slow slide into the runoff area. The tires were used Pirelli DH so not that great. I ran Pocono Grand course after that and no issues. The front lock up was probably at 70 mph but with A7's. Tire temps are pretty low with hills so grip is also not ideal.

I'll have to inspect the ABS sensors but since it happened both front and rear I would be surprised I knocked out both. Just odd this suddenly started happening. I always ran used Pirelli's and never had this issue.

Make sure their isn't too much dust/debris built up on the sensor tips. Hydraulics/valves can wear out and get sluggish.

Used tires are tricky and IMO Pirellis can be deceiving even if they look good they can have no grip depending which track and car they were on. You could have had 3 tires that were run for 20 minutes in a practice session and 1 that was beat on for an hour in a race in 90 degree heat and all look the same but they have very different levels of grip.

T7 at Lightning, did you do something different that lap, pass a car, brake early, brake in the shadow of the bridge, morning session, with dew still around, have a little bit of lateral load still in the car when getting on the brakes.

The hill climb happening is not surprising to me. ABS can't defy physics. Uneven/different surfaces/age/lines, cracks, sealer, etc are all going to play a part and if it can't make grip, its not going to stop. Instead of going to Icemode, it locks up.

If you've got data, you log /look at the wheel speeds, and if the ABS is active, and if it is failed.
 
T7 at Lightning, did you do something different that lap, pass a car, brake early, brake in the shadow of the bridge, morning session, with dew still around, have a little bit of lateral load still in the car when getting on the brakes.
I did make a decision to try and brake later and I jumped quickly and hard on the pedal. It felt like I was on ice or there was fluid on that line.

If you've got data, you log /look at the wheel speeds, and if the ABS is active, and if it is failed.
Wish I had that level of data. That may come later but no help on this one.
 
Used tires are tricky and IMO Pirellis can be deceiving even if they look good they can have no grip depending which track and car they were on. You could have had 3 tires that were run for 20 minutes in a practice session and 1 that was beat on for an hour in a race in 90 degree heat and all look the same but they have very different levels of grip.
Believe me if I could afford new slicks or Hoosiers for every purchase I would do it. I have to say the BFG R1S tires I purchased new 3 years ago are still working and have good life after at least 15 track sessions so they were not a bad deal but $500 for a set of Pirellis or Michelins is still tough to pass on for an amateur like me.
 
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I did make a decision to try and brake later and I jumped quickly and hard on the pedal. It felt like I was on ice or there was fluid on that line.


Wish I had that level of data. That may come later but no help on this one.
Was it on a different set of tires than other sessions? It could have been fluid or dirt or something. Next time out, look for the ABS light, if its on, ABS is not functioning. If the light is off and you get lock up, look into something you did differently either driving or setup. The rest of the lights about TPMS, or Service Adancetrac or other things don't matter.
Believe me if I could afford new slicks or Hoosier's for every purchase I would do it. I have to say the BFG R1S tires I purchased new 3 years ago are still working and have good life after at least 15 track sessions so they were not a bad deal but $500 for a set of Pirellis or Michelins is still tough to pass on for an amateur like me.
I understand. We sell off old tires and its a good way to keep things economical. But as drivers get faster, gain more experience and push harder more weird things seem to happen in my experience and to me that comes down to tires. This sounds like one of them potentially. Remember those are the only 4 parts of the car that touch the ground, work them accordingly.
 
Was it on a different set of tires than other sessions?
Interesting that you mention that. Yes, I switched from a set of Pirelli 305/660's to 305/680's because the 660's put me into 5th gear too early. Well-used set too.

You are correct......when you reach a certain level of confidence with the car and your ability it's frustrating to have a worn set of tires holding you back from setting your best laps and you end up pushing too hard.
 
179
308
Utah
One of the Spec-Z drivers in our area reported that when they used SRF in the Z cars it would ruin the seals in the ABS unit, with it leaking into the unit and causing lockups like you are describing. When they went to different fluid the problem went away.

Granted, I have NO experience with this problem, or if it applies to the Mustang. Just thought I might throw that our there.

I just got a new car (2014 Mustang GT) and it has the Boss 302s ABS, so I may learn more about it (hopefully not the way you have!). If I remember correctly the previous owner did report the same issue and gave me brand new rear calipers with the car, which I put on immediately. I clean the ABS rings and sensors often as well. I have only tracked the car about three days, and havn't seen any issue. Running Motul 660. Good luck with the fix. I am interested to hear the result.
 
One of the Spec-Z drivers in our area reported that when they used SRF in the Z cars it would ruin the seals in the ABS unit, with it leaking into the unit and causing lockups like you are describing. When they went to different fluid the problem went away.
Well that's interesting. I only used Motul the first two years I tracked the car. I introduced SRF during flushes last year and into this year. I also mixed in some Brembo fluid recently that I bought from a friend but I noticed it was very dark, almost like it was old fluid. It was a new bottle so I figured it was normal but now I wonder if my fluid choices are causing this issue. My right rear caliper is also a cheap Autozone rebuild so I'm swapping that out to OEM this weekend.
 

Norm Peterson

Corner Barstool Sitter
939
712
Exp. Type
HPDE
Exp. Level
5-10 Years
a few miles east of Philly
Yes, I know many who use SRF on all kinds of cars with great results. I was surprised to see the post from one of our Spec-Z drivers. Again, I didn't want to imply that the problem here is SFR for sure, but I thought I would put it out there as a possibility.
I was surprised at that as well. Though I guess there could be fluid - seal material compatibility issues in the ABS system just like there can be with transmission fluids and synchromesh materials.


Norm
 

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