C6psi

So I have had a braking issue since last October that I can’t seem to resolve. During hard braking from above say 90+ mph the car wants to rotate severely to the left. ABS seems to always be present when the car wants to rotate. From lower speeds you can feel a tendency to pull left but not as dramatic. The issue started immediately after rebuilding the front calipers after both leaking overnight at the track. The day before the pulling to the left was not present. So logic would dictate that it would be the calipers right…and maybe so but at this point I have rebuilt twice and still have the issue. I am accustom to rebuilding high pressure pumps and hydraulics so just hard to believe I mucked this up as they are incredibly easy to rebuild. Anyone have any thoughts on another coincidental issue that could be the culprit? Just a list of what I have tried to resolve the issue.

-Checked wheel bearings (I have had two failures there over the past few years)
-Bleed brakes
-Different: Slicks (all 4), Wheels, Rotors, Brake Pads
-Pulled ABS fuse, still pulls to the left and caused me to spin twice while testing.

Car is track only with no active handling (deleted Yaw sensor and SPS). Brakes are Stoptech ST60 up front and ST40 rear.

SouthernSon

Sounds as though you have done the most obvious but did you change pads? Soaked pads are no good.

Sorry, just saw that you did that, too.

Gary K Sr

I deal with brake problems four days out of five- check the calipers and the hoses. Sounds like the left side is doing most of the braking so there may be a problem with the right. If nothing there, check the tie rods both inner and outer.

sccaGT1racer

Make sure you also check the ball joints, tie rod ends, control arm bushings . Under braking load you could have a bushing giving up.

SouthernSon

You know, if there is ANY speck of contamination in that left caliper it may not be releasing. Doesn't take much to close off the port. I have had that problem before. Also, IIRC, some O-rings have an orientation front to back.

TKOGTO

Was the pad change done with the same compound? It's a long shot but if the new pads are more aggressive, car could be going into Ice Mode. When this happens, the car has a tendency to snap one way or another, especially as mph increases.

Reggie Dunlop

This.
Or a defective line feeding this caliper.

C6psi

I will give all another check when I get it in the air again, only thing that leads me away from these components is that the braking issue was like a switch. One day the car drove great and the next day it was trying to kill me.

C6psi

According to the rebuild procedures from Stoptech it did not indicate nor could I see a taper. The first rebuild I just submersed seals in brake fluid but on the second I got the assembly lube just to make sure there was no chance of an issue. Which port are you refering to? Where the brake line attaches to the caliper?

C6psi

I was running XP24's up front and swapped to another set of older XP24's, XP20's and even back to the street pads. I did purchase a new set of rings and pads of a different brand to try for my next trouble shooting session. This trouble shooting at the track is just getting expensive though.

C6psi

This could be tough to catch if the damage or defect is not visible. If checking pressure with a gauge the line would show the same as the others even if the line had reduced flow volume. If the line had a restriction of flow it could cause a balance issue left to right for sure.....will inspect the lines more closely.

C6psi

Sticking piston on the right? So if I were to have a tie rod issue your thinking the TOE out would increase significantly causing the car to dart left or right. Not up to speed on the result of a sudden increase in TOE?

FASTFATBOY

Uneven pad wear will show.

Did you check the rear bushings and alignment eccentrics?

sccaGT1racer

When you have a internally collapsed hose the fluid flow will be reduced. open the bleeders and see if they are both dripping at equal rates. Then while bleeding under pressure inspect for equal output. You may have to get a pressure gauge to verify if you cant find it with the above methods.

96CollectorSport

I'm just going to throw this out there - are you sure it was the caliper that was leaking? Any chance the fluid came from a shock? If one of the shocks is dead it could cause the car to pull under hard braking.

speedracernc

I didn't see any mention that you checked the rear brakes. If one of the rear brake calipers is sticking that could also cause the car to want to rotate. I would also closely inspect the rear brakes if you haven't already done so. Good Luck!!

STANG KILLA SS

x2 on rear. your description of trying to kill you and spinning sounds more like a rear brake. however the tendency to pull one way sounds more like a front.

also your wheel sensors can be watched live with a diagnotstic tool. it would tell you exactly which wheel was showing the slower speed than the others, and the problem corner

C6psi

To be honest I have only been able to drive the car for maybe a total of 25 minutes at 75% over several events since the braking issue so no chance to notice uneven pad wear. Will check the rear bushings and all ball joints as suggested.

C6psi

I do recall while bleeding with a Motive bleeder that the flow seemed consistent around the entire car as I try run the same pressure while bleeding. I will inspect the hoses more closely tonight.

C6psi

Funny you should mention as one of my rear Pfadt's bleed out one event after the issue started and I replaced the set with a new set of LG G2's before my last outting...no glory. Brake calipers leaked up front and coil over in the rear leaked. Was sure the bleeding coilover was causing the lose of traction making the car want to spin.