https://www.s2ki.com/forums/showthread.php?...&threadid=93503

Posted this in Under the Hood Forum = wanted to direct your attention to it as well.


Help - ABS Premature Engagement
It seems as if my ABS has been prematurely kicking in during otherwise routing braking situations. I am a bit concerned about this and am looking to see if anyone else has experienced this before. I must emphasize that I am NOT driving agressively enough to warrant ABS engagement. Furthermore, I have modified the braking system a bit which may be relevant to the topic at hand -

1) SS Brake Lines
2) Drilles/Slotted/Cad Plated OEM Rotors
3) DOT 4 "Super Blue" Fluid
4) Porterfield R4S pads (very light wear)

I have experienced ABS engagement during the following scenarios -

1) Light-to-moderate braking over uneven (e.g. "rippled") roadways. This is where I first noticed it occuring.
2) Moderate-to-hard braking on dry, smooth roadways. Pedal not even close to being pushed all the way.
3) VERY easy to engage ABS during wet-weather conditions; again, light-to-moderate braking.
4) Does not matter if braking in straight line vs. corner
5) Even after I've "warmed" up the pads during an extended drive I experience the same thing.


I would also add that a few months back (with identical brake system setup) during Fall Colors '02 I never experienced this at all, even with "vigorous" braking. I am trying to determine the casuality of this. Much colder weather in the Washington, DC area lately? Pads not adequately warmed up? It hasn't been that cold in the area; never below 20 degrees or so. Car is parked inside so there isn't any ice or moisture buildup on rotors.

Help! Thanks in advance for your suggestions.

 

Have you checked the tire tread? On S-02's, the sticky rubber seems to wear off just before the wear indicators. ABS was activating all the time just before I replaced my last set.

 

From time to time (i.e. once every few months, maybe a few times in a row over a span of a week), I notice this too. I'm like "What! Why did I just get ABS just now?" -- I have Porterfield R4-S pads too... might be a connection there.... My S02's all have a lot of life though and the rears are brand new. I agree about the way that ABS tends to be sensitive to braking on undulating surfaces.

 

You have made your brake system a bit more powerful (able to lock the wheels up with less brake pressure) and this combined with cold/worn tires and or uneven road surfaces can activate the ABS system.

Remember ABS works by sensing wheel rotation using sensors on the wheels. When one (or more) wheels start to lock up it kicks in and releases the brake pressure to the wheel in question by pulsing. Worn pads or glazed rotors would make the system less likely to kick in because it would make it harder to lock the wheels up.

Changes in suspension (Shocks, springs, etc...) will also have an effect. If you have made your suspension less compliant when a wheel hits some bumps it will spend less time contacting the road and therefore more apt to lock up.

Check your tire pressure also.

 

Hey all - thank you very much and hank you all for the suggestions. Some further information.

1) Am running OEM wheels/tires
2) Shocks are great all-around. Car has about 20k miles on it and I don't beat it.
3) I have NOT checked my tire pressure lately. I will do that this evening. While that may be a contributing factor, I don't think it is the primary cause.
4) All tires are in great shape with plenty of thread.

I will pull the ABS fuse tonight and see what happens. While swapping rotors might certainly help out (thanks for thinking of that), I want to avoid the time/expense of doing that right now because I know they were working properly before with these rotors. It is true that I have made the braking system more powerful, but the fact that the ABS engages during light braking indicates to me that there is something else amiss!

Any other suggestions would be more than welcome! Thank you all!

 

Wanted to provide some further information based on what I posted in "Under the Hood" -

Thank you all so much for your feedback. Some more points of clarification.

1) The ABS light has NEVER come on.
2) The rotors are in tip-top condition. No need to be resurfaced/reglazed.
3) The pads are in excellent conditions.
4) I "feel" the ABS engage through the pedal. Feels just like it would during "normal" engagement, albeit under these anomolus circumstances.
5) Pedal feel is normal (i.e.; extremely firm), even with the SS brake lines.
6) I have not tracked the car with this particular setup, so I don't think the system has gone through any undue hardship.

All roads are leading towards pulling the ABS fuse and seeing what happens next. Please, keep the suggestions coming. I am confident that I can resolve this issue with your help and feedback.

EJ