STX Rules and Setup Questions

[smg1138]

Anybody else had trouble with ABS kicking in during autocross? Was at an especially bumpy venue Sunday and had issues with ABS engaging and screwing up my braking. Apparently I wasn't the only one as several people plowed through cones when it happened to them. The old Miatas without any ABS were totally fine though. Is there any way to actually disable ABS without screwing something else up?

[M0nk3y]

Originally Posted by strat61caster

Got part numbers on that? The white line I've got is awful to keep tight and adjust in any reasonable amount of time. I've been meaning to do a 'custom' on the front.

Did OSH hardware out of the bins on the rear for $60-$80 iirc but the front will see a bit more stress...

6516K26 - Threaded Rod
60745K851 - Rod End Linkage

Associated washer and nuts
94895A820
90107A032
91030A435

I went threaded Rod mostly because of sizing I needed, couldn't really build it any other way at the time

[strat61caster]

Originally Posted by smg1138

Anybody else had trouble with ABS kicking in during autocross? Was at an especially bumpy venue Sunday and had issues with ABS engaging and screwing up my braking. Apparently I wasn't the only one as several people plowed through cones when it happened to them. The old Miatas without any ABS were totally fine though. Is there any way to actually disable ABS without screwing something else up?

I've only had issues with abs when I've done the pedal dance, it's well behaved with just the 5s button press, but the lots out here aren't too rough. I switched back to no pedal dance at the last event and picked up time after doing 4 runs with pedal dance.

It sounds like you might be hitting ice mode, especially if you're doing the pedal dance.

[smg1138]

Originally Posted by strat61caster

It sounds like you might be hitting ice mode, especially if you're doing the pedal dance.

Yeah, I had pedal dance enabled. I always thought that was supposed to be better than the button press. Didn't realize ice mode could kick in though.

[DocWalt]

I also had ABS issues at autocross when using pedal dance. I only did the 5s press for autocross.

[strat61caster]

Originally Posted by smg1138

Yeah, I had pedal dance enabled. I always thought that was supposed to be better than the button press. Didn't realize ice mode could kick in though.

Sounds like it was ice mode then which matches blown braking zones more than just simply blaming the abs.
Yeah I had to step back and look at how I was braking, maximum attack on the pedal was a recipe for a blown brake zone. Now I try to be gentle on the brakes and I think it's made me faster, not upsetting the car, more time to gauge the corner means I'm less prone to over braking. I loved the pedal dance because it really let's you get awesome rotation under trail braking, but it can bite you not just with ice mode.

I think the hypothesis is that the abs goes into 'single channel' mode, so if one wheel is light and you try to brake like say a dab of left foot mid sweeper to settle the car without backing off the gas the abs kicks in and doesn't let you feed in enough brake pressure, I think this may be a factor if you have a long trail brake zone as well, reducing how quickly you can slow down. I think it's less of a problem when the course is more track like where you're not blending inputs as much (and I'm sure surface plays a part too) but a tight course seems to bring out the downsides of the mode.

I still want to mess with it more, but I can see going back to 5s press because it allows the abs to be more forgiving and versatile. I think it's valuable to master and understand the mode if nothing else than to break the habit of overly aggressive brake application and to really feel what it's like to unload the rear and rotate on braking. There's nothing wrong with aggressive braking, but you have to understand when it works and when it doesn't.

[Racecomp Engineering]

I'm thinking about doing the Subaru non-brembo 4 pot/2 pot calipers on my own car this winter. I'm not a dedicated autocrosser but if I do the swap I plan on doing a lot of testing. It's an approx 7.9% shift in brake bias to the rear which I think may help with ABS issues on tight auto-x courses and rough surfaces. I'm not sure it's ideal for the track or high grip tires, but this car won't be that hardcore. Slight reduction in unsprung weight for a bonus.

- Andrew

[strat61caster]

Originally Posted by Racecomp Engineering

I'm thinking about doing the Subaru non-brembo 4 pot/2 pot calipers on my own car this winter. I'm not a dedicated autocrosser but if I do the swap I plan on doing a lot of testing. It's an approx 7.9% shift in brake bias to the rear which I think may help with ABS issues on tight auto-x courses and rough surfaces. I'm not sure it's ideal for the track or high grip tires, but this car won't be that hardcore. Slight reduction in unsprung weight for a bonus.

- Andrew

Depends on which mode you would be using, I think it wouldn't make a difference for regular 5s push because the car had a mind of its own and distributes brake force front to rear as it sees fit according to CSG based on it's sensors regardless of how you alter the system. With pedal dance that might show some improved stability in a straight line (which would reduce the amount of trail braking you get, right?) but it won't change the behavior of an unloaded wheel or what the computer senses is slipping.

Edit I should clarify that I agree the car will feel different, I just don't think it will change the funky behavior at the limit of the system which seems capable of overriding whatever modifications were done to it. Autox is all about making the driver comfortable to drive at 10/10ths, I don't think there will be a huge performance benefit of undeniable physics, but the driver confidence could pay dividends for sure.

[e1_griego]

Most people I've talked to who've had issues with 'ice mode'/panic mode braking problems have gone to a more aggressive rear pad and that's solved it. Something about the rate of deceleration front to back and if the front is decelerating at a higher rate it freaks the computer out. I know the camaros have a big problem with this, too.

I know going to more aggressive front pads caused a ton more issues on my car than running the same pad all the way around. Any issues I have now are generally the results of bumps or really shitty surface.

I am planning to go to a more aggressive rear pad soon just to test.

[smg1138]

Originally Posted by strat61caster

Sounds like it was ice mode then which matches blown braking zones more than just simply blaming the abs.
Yeah I had to step back and look at how I was braking, maximum attack on the pedal was a recipe for a blown brake zone. Now I try to be gentle on the brakes and I think it's made me faster, not upsetting the car, more time to gauge the corner means I'm less prone to over braking. I loved the pedal dance because it really let's you get awesome rotation under trail braking, but it can bite you not just with ice mode.

Yeah, I guess it was ice mode, not just normal ABS. I had never really experienced that before. Most surfaces I've autocrossed on are reasonably smooth, so it's never been an issue. I probably brake later than I should sometimes, but I've gotten spoiled by my Winmax W3 pads. I can modulate those things like no other pad I've used before. Guess I never took into account a course where you're going downhill and there's a big ass bump right before a 90 degree turn with a wall of cones. lol Gotta love autocross!

[cjd]

Originally Posted by e1_griego

Most people I've talked to who've had issues with 'ice mode'/panic mode braking problems have gone to a more aggressive rear pad and that's solved it. Something about the rate of deceleration front to back and if the front is decelerating at a higher rate it freaks the computer out. I know the camaros have a big problem with this, too.

I know going to more aggressive front pads caused a ton more issues on my car than running the same pad all the way around. Any issues I have now are generally the results of bumps or really shitty surface.

I am planning to go to a more aggressive rear pad soon just to test.

This is interesting. I've not had/taken time to try PD beyond discovering my driving + setup does NOT get along with it. I'm definitely locking up a wheel with the same approach to braking and disabled ABS so I think I understand why the computer is freaking out... Maybe some day I'll figure it out. My braking unquestionably needs attention.

[strat61caster]

Originally Posted by cjd

This is interesting. I've not had/taken time to try PD beyond discovering my driving + setup does NOT get along with it. I'm definitely locking up a wheel with the same approach to braking and disabled ABS so I think I understand why the computer is freaking out... Maybe some day I'll figure it out. My braking unquestionably needs attention.

ABS is still active during pedal dance, it just acts dumber. You're not locking a wheel.

[cjd]

Originally Posted by strat61caster

ABS is still active during pedal dance, it just acts dumber. You're not locking a wheel.

I am with ABS disabled. With just PD, it's ice mode all the way.

[DocWalt]

with ABS disabled doesn't the brake bias go bonkers?