,

 

suspenders?

 

Get a harness. That'll keep you from sliding off your seat.

 

And wear Depends.

 

And check your pads! They may be worn or glazed, shifting your brake balance to the rear, causing the back to shimmy and dance.

That's what happened to me recently at Laguna Seca... once I swapped the front pads, everything was A-OK again

 

The mini is not the most civilized threshold braking machine. On the surface, a short wheel base and very good braking numbers tell part of the story.

By comparison, I could brake very hard deep into corners - just an experiment, not the fastest way thru a turn - with my 99Si. But, the si broke records for the longest braking distances while the mini is on par with pure sports cars...perhaps the mini has more rear bias than other front drivers.

I played with many different pads and brake setups and this trait never went away. Alignment settings will have some affect especially if there is a zero or toe out condition in the rear...conversely, if you have extreme neg camber and toe out up front, the ABS may be sense a lack of brake torque on the front axle while maintaining rear brake torque.

Brakes are very sensitive to tire compound as well...tires are resonsible for the mechanical keying that help determine brake torque.

 

Reduce rear rebound in the shocks. When the weight transfers to the front under braking this will cause the rears to droop quicker under braking and keep more contact patch on the ground. But it will lessen your ability to rotate while trail braking into the corner.

 

thanks for all the useful input guys, I should elaborate more on this experience, when I was at the track last month, I lost a lot of time trying to catch the rear end under hard braking, the rear end just steps out everytime when I hard brake. When I mean hard brake, I'm really really putting a lot of force onto the brakes at the last minute just before the turn in, I think any members who has been to the track will know what I mean. Could it be my brake setup, currently I'm running Stoptech BBK up front with just regular brake pads, I also have stainless steel brake lines front & rear. If I switch my pads to eg. Ferodo DS2500 front & rear plus rear slotted rotors, would it solve the problem, since the braking bias will be more balanced, where as right now, the front brake is a lot more powerful or will a set of R compound tires work too?Any input would be helpful?

 

Tires play a key role in threshold braking...powerful brakes require sticky rubber...at some level, you have to match the brakes to the tires.

Tires are said to provide the bulk of stopping power since mechanical keying is what determines grip. However, if the brake system is not optimized for the tires, braking distance and predictability will suffer.

What tire type are you running? When I had my BBK installed, I used pads to match my DOT R-Cpomounds at the track and then changed these back when I re-installed the my street tires. Track type pads/BBK can also be over-worked, over-heated, if the the tire compound is not correct...the tire does less work, understand? As another example, I never found a need for a BBK at Lime Rock, but did at Watkins Glen. Tim Allen would love a BBK, but they are not always the best choice - nice looking for sure!!!

Also, Maitlandimports offer another possible area to look at...shocks. And, if you have installed heavier spring rates in the rear - heavier than the front - you will also experience some instability in the braking zone.

You may have a few areas to look at, but starting over, or going back to some baseline you know is a good idea. Then make one change at a time.

 

Some brake modulation might help.

 

Could also be a question of bad bushings, front and rear.

 

ABS working?
This could really just be your driving style.
If it's swinging around under hard braking in a dead straight line, then you have an issue where one side of the front, and or rear is not working properly. I gather you have bled all the brakes by now? New fluid?
Do you have DSC? Even in the off position, you should feel it working under these conditions.

 

This may be the issue. You should be braking hardest early in the brake zone, and releasing the brakes as you near turn-in. At turn-in you should be getting the car to take a set and transitioning to throttle. You can't do that if you are still braking hard.

The car will wiggle on occasion during threshold braking. As you release the brake pedal it will track true. I'm currently using Hankook F200s C30 compound.

Alan

 

This problem could definitely be caused by my driving style but since it has never happened to any of the past cars I owned, therefore I guess this driving style is absolutely not suitable for the Mini. I checked all the bushings and suspension setup, everything seems to be nice and secure. Therefore, I will be putting a set of Ferodo DS2500 pads f&r and racing brake fluids next week, hopefully it can solve the problem.

 

That is true and mimics my experience...but the mini is a better braking car than any other front drive I have ever driven on the track.

If you are participating in HPDE events you don't have to worry about covering your corner , so, slow in, fast out.

I do not trail brake the mini...I am faster braking in a straigt line.

 

How old of a car do you have and how many miles?

 

It might also be the road surface. On some worn asphalt surfaces, it can get squirmy under hard braking.

I love the modulation my hawk pads and slotted rotors give, I can hardly drive regular cars anymore with their "on/off brakes."

 

my car is a MY06 with approx 20,000kms, no accidents ever.

 

ya, I'm gonna try upgrading the rear brake setup with a set of Ferodo DS2500/ DS3000 w/ slotted rotors & high temp brake fluid, hope this can solve the problem, will keep you guys posted.

 

...not sure how this will help you. From my limited understanding, if the back end is "loose" under braking, you've already lost tire adhesion – adding more brake is not going to help, and will just make it worse. You need more grip (either via tires or suspension changes), not more brake.

 

You have to look at your tires and brakes as one system. If you add more braking than the tires can handle - friction circle - your tires will lose traction during braking and your brakes will over heat.

You have to improve your tire's mechanical keying - stickier tires...if you are running stock run-flats and upgrading brakes you can expect the braking problem you describe...there may be another cause(s) but tire/brake relationship is fundamental.

 

i have been watching this thread since the beginning. i started a similar thread quite a while ago. there have been several similar threads since then. i have tried every suggested cure. no success. i have changed front/rear pads to change the bias. i have changed damper settings (as suggested by maitland, although i only have single adjustables). i have installed the Alta PSRS (it helped, but did not eliminate the problem). i have used multiple alignment setting (with particular attention paid to toe). i have checked all suspension bushings for wear and replaced most of them. the car is still unsettled during threshold braking. it is not comfortable, but the car isn't going to swap ends. as i said in another thread, my solution to date is "big ***** and soft hands".

 

Bean, sometimes I also think that way too, there is no cure but have you ever thought why only limited number of Mini owners can experience this problem, is it because not everyone has ever braked this hard or is it because there's some common modification that we did to our cars while others didn't. This is the only puzzle that I can't solve because if every Mini owner say its a common problem than its definitely 100% big ***** soft hand.

 

among my track rat buddies, the common denominators seem to be: sticky r-comps or slicks and very high tq brake pads. one friend found out what i was dealing w/ when he switched to HT 10 pads w/ his V710's. he runs stock rotors and calipers. another friend w/ slightly less aggressive pads and Ra1's/Nitto NT01's doesn't have these issues. any GP or R56 owners w/ this problem? i'm curious as to the effects of the aluminum trailing arms. i will be adding these as a part of my race car build.

 

Big *****, soft hands

ABS could be causing some of this since it is very active when I threshold brake.

Short wheel base may be another contributing factor.

Rear toe should be studied with the rear of the car raised 5 degrees...or a little more to simulate brake dive...and front tow out will really aggrivate this condition and lengthen braking distances. Rear camber should also be studied along with toe.

Another are that I have thought about, but have not played with due to the time and expense involved, is the rear trailing arm bushinf orientation to the trailing arm. This bushing is installed vis a large bolt into the trailing arm. When I replaced these, I followed the instructions very carefully; the bushing and the trailing arm must be aligned one way only according to the Bentely manual. But I wonder still about how this bushing might work if it is rotated a bit in either direction...it could be disasterous, or it could help the condition we are feeling, but perhaps slow the car's turn-in ability.

Where the rear role centers move to during braking - specifically the relationship between CofG and roll center at threshold braking might be an interesting study...

And high and slow speed damping characteristics - along with the integrated bump stops - will affect braking stability - written above.