I was at an autox school/test n tune on Saturday with my 06 MCS, for the straight line braking exercise I pulled the ABS fuse. I experienced a couple of issues with this, although another MINI owner (she was driving her 04 MCS) had zero problems with pulling the fuse.

First off, although ABS was definately disabled, it seemed to dial in WAY too much rear bias (even in the rain). I wonder if with the EBD also being disabled it defaults to full rear bias? That for sure doesn't seem like a very safe failure mode. It actually felt like I was trying to stop the car using only the E-brake. Lots of fun trying to keep the car pointed in the correct direction, but not the end result I was looking for.

Second issue was that the car would buck real hard under part throttle constant speed. It was actually hard to drive thru grid without looking like a fool .

Has anyone else experienced this? I actually think the stock ABS does a nice job and would normally not worry about it for autocross....but it would have been nice to run without it for this training exercise.

Jason

 

Probably not a real big surprise to you I suspect. The short wheelbase nature of the MINI offers little gain for rear brakes.

A couple things you might consider to do:
1. Up the ante in the front to balance it some.
2. De tune the rears with some real crappy pads.
3. Try putting some weight in the rear.

I'm the first to confess that the rear kits sold are mainly for looks not for function. And I'd urge any buyer to pair them with proper front kits for best results.

 

I think the Mini ABS is pretty decent for autocross, as far as ABS goes - it's intrusive, but not that intrusive

I don't think it's actually even legal to pull the fuse (or use a blown one) for a stock class car. Fun stuff to try at a test and tune, though.

 

Thanks for the reply Todd, I might pry a bit more on this topic if you don't mind...

Believe it or not, I am actually very surprised at this- my reason being that conventional street car design is very conservative when it comes to brake bias- traditionally way too much front bias. I suspect that the MINI engineers would have the basic hydraulic system on our cars designed so that without ABS, CBD, EBD (or any other cool sounding acronyms), the bias tends to be more forward than ideal. My experience this weekend disagrees with my theory, humm....

When the ABS is functional on my car, during straight line braking the fronts will try to lock first, which is pretty much what I'd expect. Pull the fuse and everything changes. I guess EBD must be working ALL the time, not just in "special cases". Maybe the system is designed for rear bias, and expects EBD to "bring it up front" under all situations.

I guess to sum it up- I am surprised that my car goes from Front Bias to Rear Bias with the pull of a fuse.

Jason
p.s. Todd, I assume you were kidding with suggestion #3 below

 

Who said I was running in stock

I'm actually running in Street Mod so I could run without the fuse legally.

Jason

 

I'm not really surprised at the systems effectiveness at all. The design is "max rear braking" whenever possible. That comes from both ABS and EBD.

Given the short wheel base and agreed common nose heavy design of most cars the MINI does quite well with the rear brakes. So long as the systems are ahead of the driver.

Kidding? Not at all. Finding the right amount might take some time but knowing that you'll get more from the rear brakes with two people in the back seat the same holds true of track use. Much the same reason hard cores move the battery to the rear, fuel cell behind the axle etc. etc. And you did notice the height/pitch/dive sensor on the rear suspension right?

With a front of 1650
Rear of 1200
Total 2850
Frt % 58
CG 20
Wheelbase 92
Braking G 1.0
Frt dynamic 2270
Rear dynamic 580
Front % 80

Put 200 in the rear and you have
76% or a 4% rear gain

Plug and play:
http://www.tceperformanceproducts.com/dynamic_dist.html

While not exactly the same as brake bias it works with it. Combined with a stiffer front spring and stiffer rear shock you migh slow the weight transfer some and pick up a bit of rear work.

Is all of it really worth it? Not sure.

 

As long as we are talking about moving weight to the rear and taking it off the front I am totally with you- move that cg back! I thought you were suggesting that I ADD total weight to the vehicle to make it stop better-which isn't exactly the best solution...

Anyways, it looks like the ABS/EBD system is much more performance tuned than I gave it credit for and does a better job of maximizing the rear brakes for available friction. I guess I'll have to practice my non-ABS threshold braking in another vehicle

Jason

 

Both. Moving it is ideal but I'd not give up on the rear weight add-on either. While the total is up 200lbs if it makes the rears work more you might be surprrised. Easy enough to try it.

 

I pulled one of the DSC fuses once. The speedometer didnt work, ABS was gone, and the milage didnt accumulate. I put the fuse back after a few miles.

About that rear vehicle level sensor, that is only for the DSC right? When I installed the 4 rear control arms, I had to remove the lever and bracket. I taped up the arm in the aproximate neutral postion. So far there seem to be no ill effects. Anyone else want to weigh in?

 

Sure it will make the rears work more- it is going to take more work to slow down the heavier car :D

Tire load sensitivity normally dictates that adding weight is bad! Cf falls off as normal load increases.

An extra 200 lbs to get moving, change direction in corners, and to slow down would be a huge disadvantage!

Vehicle dynamics are not new to me- my inital post was trying to understand more about the specific systems on the MINI which I still do not completely understand.

As far as the level sensor, I was under the impression that it was strictly to control the auto leveling headlights...

Jason

 

I believe the leveling sensor that you are referring to is only used for the leveling function of the Xenon headlights.

 

All the fancy, three-letter acronyms relating to the braking system are all controlled by the main ABS module. Pulling the fuse disables them all.

The height sensors attached to the suspension arms is there only for the Xenon headlight leveling system.

 

The braking system in this car is waay too complicated! I read through my wheel chock (Bentley) about the system ubercomplicated. At each notch in complexity I see added around me I shudder. This design is generated by a culture & technology that cannot design a stable computor operating system nor build a reliable mobile phone network. I don't believe that we aren't capable. It is the marketing people that cease the development prematurely. Hence it is all about profit.

I can only hope that it was engineered beyond the "It seems to work, hand it over to marketing. There are enough TLA's installed to impress even this jaded market!" "So has anyone got any ideas on the sunroof wipers?"


@nabeshin You pulled the wrong fuse (I know, I tried pulling that one first!)
You have to go for the main one under the hood, it is one of the square ones, 20 amp, I believe.

 

This may be of interest.. if the ABS is disable by other means than the fuse. It will remain Front bias. If your updating your brake pads. Try not inserting the sensor that goes in the Front Passenger side. This sensor went bad on mine so i had no ABS. The car would lock the Front brakes first when i was Autoxing. That was until I had it fixed. Now and then I will disable the system depending on the coarse by disconnecting that sensor

 

I've seen the same thing happen on other cars. From what I understand, when you pull ABS you need to add a brake balancer.