So the MINI had her first shot at autoX today, and unfortunately the day was dampened by what felt like underwhelming brake performance. Upon braking for a corner, the pedal would grind like the ABS was working, but I never thought I was braking nearly hard enough to invoke ABS. I tried braking smoother and earlier, and it would still trip ABS intermittently. I swear it even happened a few times before I had even made any steering input! I'm fairly sure I can stop harder on the street without issues... What gives? Is the ABS threashold fairly low on the MCS, or am I just not used to it? I've got HPS pads and stock rotors.

 

lots of stuff went unanswered here: Ambient temp?; Track temp.?; Weather?; Tire type (Compound); And most importantly, did you try to negotiate the track with ASC/DSC on AND off. I've noticed that the DSC setting is overly aggresive and kicks in early when wheel slip is observed by the system. Try running the track with DSC off.

 

Wouldn't ABS cutting in early be a sign of the brakes doing their job over effectively and outbraking the tire performance? If you are still able to lock a brake up then I would doubt that its a braking problem. Probably an all season tire? I don't know, just thinking...

 

Ah, my bad... I should have included more info. I was on summer tires. Ambient temp was fairly low (45-50), but track temp should have been a bit higher as it was sunny all day. All runs were made with ASC off. There were two other guys running MINI's, and both had slightly better (street) tires. I made a point of observing their braking points, and found that I had to brake somewhat earlier. I asked one of the MINI drivers about the ABS, and he indicated that he rarely has any ABS intervention. I know that's a fairly vague approximation due to variable driving styles and the difference between tires, etc, but it might be worth something.

As far as over-effective braking goes... This is where I'm stumped. In street driving with the same tires and similar ambient conditions, I can generally get the car to slow down very rapidly without any ABS intervention. I didn't feel like the car was braking nearly as efficiently during my runs, nor did I ever hear or feel it starting to lock.

I don't know what to think... Maybe the brakes are just boosted more than I'm used to, and require a very light touch? Maybe my tires just suck? Who knows. I'll have to do some experimentation this weekend.

 

What about the surface? I was at an autocross and the parking lot had lots of tiny gravel and sand.

 

Fairly clean and smooth for a North East autox surface, actually.

I know the subject is rather taboo, but is there a way to disable ABS without destroying anything? I've seen it done on Subarus... I just hate when cars try to "think" for me - I'm the driver, I'm in charge!

 

Could one of the wheel speed sensors be unpluged? You would lose all the ABS, DSC, and flat tire monitor and have lots of warning lights to go along with it.

 

Yeah, I thought of that. But since I turn ASC off anyway for autox, it might not be a huge loss.

 

This is one of the things I do not like about Hawk pads and a reason I'll never use them. I've never heard a great review on them.

I have a friend with a 350z who purchased some Hawk HPS pads. Immediately he was noticing a clunking noise under braking that he had never heard before. It seemed like it was the ABS and sure enough, it was...he had never encountered it in his car before so the way it came on was a little surprising at first. Well, once we knew that he was engaging ABS, it was a still a surprise. The braking didn't feel any better, in fact it felt slightly worse. The difference was now worse braking and engaging ABS...before on stock pads, better braking and ABS still wasn't reached. Though the initial bite and feel of the HPS's made braking before threshold FEEL better.

He decided to try and use them on the track as well and nearly ended up crashing due to them suddenly fading. Luckily he made a correct choice to go into the run-off area. He never had this problem before, even on stock pads!

Now the area that he did mention they were better durring street driving at less then threshold braking. They really do grab quite well and as long as you are not engaging ABS with them, they aren't too bad. But really, thats not why we buy performance brake pads. My guess why they do this, is they do have a good CF thus modulation early in the pedal does give that better feel and less braking effort is required to obtain shorter distances. But towards the limit, the pad doesn't allow as much "slip" on the rotor...it just wants to grab, and that just doesn't work.


My opinion, switch to a different pad...don't turn off ABS its just saving you from locking up the wheels.

 

I use Hawk HPS on the track with my Miata and have no problems but it doesnt have ABS. *shrugs*

What exact summer tire are you using? I have had a MINI here at work engaging the ABS early like that and it ended up being the tires. We swapped tires from another MINI on it and the problem went away. This was on the street not the track, obviously and both sets of tires were 'all season'.

 

HPS = High Performance Street
Not really meant for track use. Any pad will fade once their temp threshold has been reached.

Back on topic.
Give it another autox before you make any changes. These days the ABS pump and controls usually controls brake bias/distribution also so disabling ABS might have worse consequences for your braking as it will throw the brake bias off.

You mentioned that it would "grind". When ABS engages, you usually feel pulses in the brake pedal when it engages. Not really a grind. I usually associate a grinding sound/feel with heavy abrasion associated with hard at-the-limit braking.

Might also consider asking a knowledgeable fellow autoxer or instructor to ride along and give an opinion.

 

Seeing as how I'm the only one who mentioned the HPS on the track I figured this was aimed towards me. Yes what you state is the obvious. But one would assume that they would hold up at least A LITTLE better then an OEM pad! And the way they faded on him was the scary part, normally you can tell when the brakes start to go...but these were braking decently (as good as the HPS does) on one turn, then on the next (after the longest cool down portion of the track) they were suddenly GONE. The same distance to slow down from 120-80 it wasn't even below 100 yet...

I'm just sharing what I've personally seen with this pad besides the other mound of negative reviews I've been personally told about it.

If the OP still has some OEM pads left and knows how to change his own pads, I'd swap the OEM's back in and see if he still has the same problem. Also try some 60-0 braking starting the braking with a known point and compare results before and after.

 

My experience exactly with the Hawk HPS. Like everyone else, I am at a loss to explain how a brake pad could make the ABS kick in earlier, but somehow the HPS has figured a way. I'm going to try the CT Bobcats.

 

I've used Hawk HP+ pads in my dedicated autox car, and I notice that they are very sensitive to how you apply them - If you jump on the pedal real hard they lock fairly easily, but if you squeeze them gently they will generate impressively good stopping power before locking. I tried squeezing the pedal in the MINI and it did help, but not entirely. The rest of it could just be down to me being too forceful with the brakes since I'm used to the relatively un-boosted pedal in my other car...

I would agree that Hawk pads do seem to be very grabby though.