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Discussion Starter · #1 ·
At the autocross this weekend I had a little incident that I am trying to blame on the ABS. I was blasting down the back straight in 3rd gear coming up on a tight Z-box (maybe a bit too fast) and hit a bumpy patch of pavement. The car's brakes felt strange and the car became unresponsive to steering and I ended up plowing pretty much the entire Z-box (8 cones at once, my new record!).

The suspension bounced a few times and I thought that this may have triggered the ABS sensors. The brake pedal felt very strange (kinda light), but wasn't the tell-tale pulsation of ABS. Since the brakes didn't work as I expected, I ended up plowing right through a sea of cones.

The car was really neutral the rest of the day so this one incident had me confused. Any ideas on what could have caused this? Car is a 95 NA with ES suspension mods and alignment.
 

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If you're turning the wheel and the car is going straight, it's not the ABS that's killing you, but it could be contributing. You probably went in too hot, couldn't slow down enough for the turn but turned the wheel anyways. Before you turned the wheel you were probably in ABS. The moment you turned the wheel (possibly quickly), the front tires locked. With the wheel turned and the front tires sliding, even with ABS they might not start turning again, because it's the lateral load causing them to slide, not the brakes. So ABS probably tried to compensate even more (it sees the wheels not spinning and lets off the brakes further) to no avail.

I had a similar thing happen when i first put ABS on my yellow car. It's definitely more effective the straighter you're going, and fairly ineffective in sharp turns. It's still better than making your tires square though :)
 

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Discussion Starter · #6 ·
I'm almost positive I was going in too hot. The ABS suprised me though because every other car I've autocrossed hasn't had ABS installed.

It's fun when there is a lot of 3rd gear action at the auto-x (got to 6000+ rpm in 3rd) and I think I got a little too excited and didn't want to slow down.

Apparently there is a video floating around out there of my cone killing action. I'll try to find it and post it so you guys can see :)
 

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I've only had one bad episode with ABS. I knew I was right on the edge all day long in the corner, and my last trip through I was a little further to one side. Hit the bump just a teeny bit further and instead of the chirp of the tire briefly locking as I went over it, I got the ABS grind and departed course at quite a bit of speed. Once the ABS starts doing it's thing, you definitely can't stop as well on paved surfaces. Appears that despite only one wheel actually locking, it starts pumping ALL the wheels, resulting in a loss of braking ability.
 

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I have an early '91T with ABS. I've always felt it was way too intrusive; I can get it to come on with hard braking on dry pavement (on street tires though).

My brakes have been upgraded to '93T-up spec, and I'm using Porterfield pads front and rear with Goodridge lines.

Am I just an embarassingly crude driver?
 

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Hsun Chen said:
I have an early '91T with ABS. I've always felt it was way too intrusive; I can get it to come on with hard braking on dry pavement (on street tires though).

My brakes have been upgraded to '93T-up spec, and I'm using Porterfield pads front and rear with Goodridge lines.

Am I just an embarassingly crude driver?
If you're locking up the tires on dry pavement, you need better tires and smoother braking inputs. :)
 

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Unless I hit a bump with a wheel, I'm able to lock them without the ABS activating on dry pavement. They must all stop turning at the same time (or close enough). It does happen on occasion at autox events. Coming from a long straight into a real tight corner usually. I'll start braking, smoothly increase braking, and eventually they'll lock. Porterfield R4-S pads, TRD SSB brake lines, '91 dual piston front calipers, Motul 600, and 215/245 (on 7.5"/8.5") Michelin Pilot Sports.
 

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Discussion Starter · #11 ·
If any of you guys happen to come to the autocross in Tucson... it's affectionately known as the "gravel pit". Our lot is large, but it has a lot of gravel and some bumps in spots :eek:

Getting airborn is fun sometimes, but usually it's annoying as I have to run weird shock settings to compensate for the rough surface (give up time everywhere else).
 

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I had a '93 turbo with abs.
The one autox I got it to there was a place on the course w/ some funky elevation changes. Right at the end of a straight w/ a long hard stop. Running right on the edge the tires would chirp there on the brakes.
So one tiny chirp and the abs would kick in and the pedal would start shaking and 25%-50% of stopping power was gone.
So having driven only no abs cars I did what I always do when it locks up. Let off a little and back on and the stupid shaking was still there w/ massively reduced stopping.
Since then I don't trust cars with abs. I figure I might as well learn to stop without it and be a better driver.

Those with abs. Does that sound accurate? I've been wondering if maybe the car had a faulty abs system.
 

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Blueroo said:
If you're locking up the tires on dry pavement, you need better tires and smoother braking inputs. :)

Shinomori said:
I had a '93 turbo with abs.
So one tiny chirp and the abs would kick in and the pedal would start shaking and 25%-50% of stopping power was gone.

So having driven only no abs cars I did what I always do when it locks up. Let off a little and back on and the stupid shaking was still there w/ massively reduced stopping.

Those with abs. Does that sound accurate? I've been wondering if maybe the car had a faulty abs system.
That is what my '91T does. I would be fine if when ABS kicked in, the brakes actually continued to slow the car well. On my car, it's like you hit gravel. Just like my old '91 Taurus SHO - it would go from poor overall braking (way undersized brakes) to ABS response/no longer slowing down much at all.
 

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You guys do realize the alternative to ABS kicking in is your tires completely locking up, right? As soon as that chirp happens you're pretty much done. I think a little more practice would help. The ABS system isn't perfect, but if you learn to work with it, it can be helpful.
 

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I have a 93 turbo with ABS, and have hit ABS numerous times during autox, but I never really had any trouble with it. By the time the ABS came on I was pretty much ready to get off the brakes anyway.

And now that I think about it, I don't really remember it being a problem during a HPDE either...yeah wrong forum for that sorry. ;)
 

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rnoll98 said:
You guys do realize the alternative to ABS kicking in is your tires completely locking up, right? As soon as that chirp happens you're pretty much done. I think a little more practice would help. The ABS system isn't perfect, but if you learn to work with it, it can be helpful.
It's just annoying on the real bumpy courses (well, that'd be all of them around here :) ) where I'd rather let the one wheel hitting the bump lock, than to have my braking drastically reduced on all 4 wheels. Overall though, I think the MR2 ABS system is excellent, and worth having.
 

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The part that really bothered me about the abs was that it wouldn't go away if I let off the brakes and got back on em.

With regular brakes if they are sliding you let off a little and stop sliding and then you can start braking again. My buddy was driving a na w/ regular brakes on ____tier tires and he could way way out stop me in that corner because he could get to braking again if he chirped the tires. In his car I could match or beat his braking.

Not being able to stop freaks me out.
 

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Shinomori said:
The part that really bothered me about the abs was that it wouldn't go away if I let off the brakes and got back on em.
Exactly. The ABS on my '91T seems to work against me for autox, because if you go over its threshold and trigger it, it's over. You can't do anything to continue braking/setting up for the corner.
 
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