I had my first track day with my '04 MCS at Lime Rock last Thursday. Total of ten days at LRP since 9/98. Did some of the first DEs there with BMWCC on the late '70s. Anyway, my MCS ran great and could easily pull 911 SCs and NA 944s on the short main straight (max @110 mph). The braking zone was where I had to give it all back. Under hard braking sometimes with the ABS doing its thing, the back end would get real loose. The tail wag was observed by a following Spec Miata. Rather than risking a trip into the weeds, I started to gently squeeze the brakes on and off to not upset the balance of the car before and on turn in. Naturally, the resulting exended braking distances cost lots of time. It felt like the weight transfer to front with the H Sport (progressive) springs was excessive and lightened up the rear too much. Once settled into the turn the car was basically neutral.

Here is whats under the car;

No DSC (we do it the old fashioned way)

H Sport springs 195# front & 300# rear (progressives)
H Sport rear (comp) swaybar - set on end hole (softest)
H Sport Lower Control Arms
stock aligment settings (i.e rear camber - neg .75)

Tires - Goodyear F1 GS D3s, 215x45x17 on Slites
Tire Pressures cold; 36#s front,34# rear. Hot; 40#s on two fronts & outside rear, 39#s inside rear

Brakes - Ferodo 2500s front/rear track pads, SS brake lines, Motul SB, Tyrol caliper stiffners. Pads were re-beded the day before.

FWIW - Usual mods under the hood, Dyno'd 169hp @ wheels

So what is the course of action to correct the problem? Linear springs (eibachs)? More rear camber? Alignment? Ideas......

Cheers,

 

I just ran Moroso in West Palm Beach and I was having to brake from 140 to 60 for a turn at the end of a long front straight. (Turn 2a) I had no issues.

I used PBR Metal Master Brake Padsin the front with Cross Drilled Zimmerman Rotors. In the rear I ran the stock brake pads with Corss Drilled Zimmerman Rotors. I was able to stand on the brakes while downshifting to the point that the ABS was pulsing.

In the back of my mind, before my fist session, I wasworried that there would be too much bite in the front. This was quickly forgotten once I was up to speed.

I wonder if maybe you are getting too much bite in the rear?

Of course the spring setup could be a problem as well but, by the #'s you are posting it seems like you would trnsfer the weight nicely.

Maybe try a lesser pad in the rear?

 

You might try less trail braking, and then getting on the gas much sooner. It's not as good, but could be okay at the end of a straightaway. I personally tend to trail brake less off a straightaway than in a tight complex (tracking a 951, not a MINI). It sounds like Jim5543 has the right setup, anyway

 

I personally think the H-Sports are too light up front for the very reason, or circumstances you point to. Pure handling balance might be great, but the braking zone demonstrates how important the entire handling package is.

I too noticed this little squirming under hard braking. I actually run a pound or two more pressure in my rear tires 36F cold and 37 or 38R cold - counter intuitive but it works. A bit more negative camber in the rear will also help - you didn't write what your front camber is set at???

Adding a more pressure to the rear and more negative camber to the rear, all else the same, will add a bit more understeer. The H-Sports simply allow too much weight transfer off the rear wheels during braking, period. Others will disagree; with 63% of the weight up front, weight transfer while braking IS a concern. And, as you've experienced, you're only as quick as your weakest link. Nothing is perfect, nothing is ideal, just more perfect or more ideal than your current set-up.

I've been at Lime Rock many times - last May I was on the course racing in reverse in a pouring rain storm...a bicycle race, 58 miles. First time ever on that track on a bicycle. Turn four, a roller coaster ride down hill in reverse was absolutely a white knuckled ride in the wet! This is typically the uphill before the chicane.


Good luck

Michael

 

Morefun writes:
It's entirely possible that there's something afoul with the car. I'd look at alignment first. It could have changed since it was aligned. Or, there could be something amiss in the brakes. I've seen sticky calipers, glazed pads and all sorts of minor problems that cause mystery handling under braking. Someone mentioned the possiblity of too much rear bias; that's could be it, too. I hope so - It's cheap and easy to fix

If these ideas don't yield anything, go back to the driver. You mentioned that it was your first school in the car. Is it possible that when you applied the brakes you may have been a bit too abrupt? Sometimes being too aggressive initially can upset the balance, transferring weight too quickly. And are you sure there was no steering input under heavy braking? Either of these, or a combination, could have played a part.

Hope this helps.

 

naparsei - On the first couple of laps, standing the brakes (as in my P-car) just scared the #@ out of me as the back end got real squirlly while traveling in a straight line. I resorted to trail braking and as I accumulated laps I (cautiously) became more aggressive with my initial braking point. The unsettled condition was a concern at every entry, not just at the end of the main straight...

Jims5543 - The pads were bedded in per Stop Tech's recommended method. I didn't "feel" any rear bias. PBR MMs are great street pads, but based on past track experience with them in 911s and a 944T they couldn't handle the temps and quit early . Feredo 2500s F&R, come highly recommended as a track pad for the MCS.

MEB - I tend to think that the front to rear spring rate differential with the H-sports is the issue for track use. What's your experience the PSS9s (also progressive)?

 

Was this your first track day period? or first in this car?

FWD cars tend to feel loose under heavy braking. Often what newer drivers think is a problem is just the way things are. After more experience in the car they get used to it.

My experience is that stronger front pads makes the wandering feeling worse. Stronger rear pads make it feel better, but tend to leave the rear locking up first - not what you want.

 

First track day in the MCS. A total of 10 days at Lime rock since 1998. Yep, front drivers are different. I autocrossed a GTI back in the '80s.

 

I'm still doing a little more research with regard to the PSS9 system. There is way too much info to include here regarding their progressive front rate springs - made by H&R by the way. The rates are 325 +/- front (it is unfortunate that a progressive rate is not given???) and linear 345 rear with a 115lb/in tender spring. That makes Bilstein's front rate, at its stiffest, 130lb/in heavier than the H-sports front rate - huge in a 2,500 lb car. My personal feel is that 300lb springs front and rear for this car for all around driving is the limit...so 345 feels a bit high. But, we can only use what the market offers.

Stability problems can be corrected in many ways. The endless permutations for all the cars in the world make a recipie impossible. But, that said, and I didn't mention this above, rear toe angles are very important...more so than the front. This is one area where I will play the most after dialing most everything else in. you can for example, have a wild toe out condition up front. This helps intial grip upon turn-in, but creates wandering at high speed on the straight. Well, you don't have to give up the intitial grip if you add in a bit rear toe-in as this will reduce some of the wandering. This advise so depends upon what else you've done too, and, where you drive. Rear toe is a piece of the puzzle, however...an important peice! I typically use a little rear toe-in to dial out a bit of oversteer with a car set up with heavy rear springs and a large rear sway bar...but it's more than that too; the degree or speed of rotation can be increased or decreased - after swaybar settings are achieved - as a way to fine tune oversteer, with rear toe angles. A little toe-in in the rear can also aid stability in the braking zone.

Just keep in mind, stability means unresponsive and responsive means instability. You have to find a happy medium for you, your car,and, and your driving venue.

Uhm...be careful when playing with the rear brakes; You may meet snap oversteer if you give too much biased to the rear brake with either better pads or bigger rotors or both...especially if you trail brake. Braking for me under most circumstances is like an on-off switch; I'm on them hard and then off. I personally feel more comfortable doing my braking in the stright rather than trail braking. But that's a personal comfort thing as well as a set-up thing.

 

My dear FPC friend ....
A few things...
First, 110 at the end of main straight? Maybe... , but what the heck are you looking at your speedo for!

So, are you getting this problem when braking in a straight line before you start your turn in at Big Bend? If so it just could be you getting on the brakes to late and too hard, or it is something wrong with the brakes in general. Having about the same setup as you have when I was there, I did not experience this problem with weight transfer with the H-Sports.

Do know that the Mini does start to feel like it's getting looser then it really is. If you are used to the P-car going into big bend, then you need to picture this. In the P-car you inside front wheel may lift while digging that rear into the track. The Mini inside REAR wheel lifts making it feel more like she's about to break away.



Also tires are very important to the Mini feeling squirmy. I would bet that getting those rears up to 38-40 cold with the fronts at 36 might make a huge difference. Soft rears in the Mini are very scary in deed.

I'll be there on the 20th with the CVC BMWCCA.

 

I have a similar setup to yours except:

EBC green pads on rear
Maddness sway bar on middle setting
Rear camber -1.5 deg
40 psi hot on all 4 tires, Yokes ES100 215-45-17
And the biggest difference, 2002 shocks (stiffer)

This is very solid under braking at the end of the straight (110 mph down to second gear). It does feel light if trail braking entering a turn but still controllable.

Stiffer shocks and more rear camber?

 

There is DEFINITELY something wrong with the car. Maybe suspension, but I'm guessing brakes. Check the rear brakes. This is assuming you were braking in a straight line.

 

I also have basically the same set up. I think that it being your first track day has more to do with it than something being wrong with the car.
You might try more rear negative camber. I'm at -2degrees. I also run a little more tire pressure on my left front. Big Bend tends to make my left front roll over too much.
Other than that, as long as the rear end doesn't come around and you can get used to trail braking, enjoy it The car is front wheel drive, keep the front pointed where you want to go and the rear will follow

 

I have a very similar set up to yours w/ H-sports front and rear, Ferodo 2500's, Madness rear sway on middle position. I have been hitting 118 on the main straight at Lime Rock (as confirmed by the S2000 and formula ford I was dueling with) and the *** end gets very light and squirrely under braking for Big Bend. I think it's the nature of the MINI beast and that tough corner (it's fun to watch Novices in Ferrari's go skating down the run-off and into the grass) and finding a happy medium between late braking and earlier braking for that particular corner.

 

What type of line do you use entering Big Bend? A double-apex, or a "carousel"?

My guess is you're hammering down the Main Straight and then trail-braking for the turn into Big Bend.

The solution is either to finish all your braking in a straight line, or take an inside line entering Big Bend and continue braking (if necessary) smoothly, with the car going in a relatively straight line.

But, either way, the key is to do your braking in a straight line. Trailbraking in a FWD car tends to make the rear end of the car feel squirrely. (Ever see a GTI lift its inside rear wheel completely off the ground in Big Bend?)

And, please, folks....learn how to drive a STOCK automobile on the track before you start modifying everything!! This takes away all of the variables some of us tend to blame when things don't feel right.

 

This is your own personal philosophy. It has no merit as far as my own philosophy goes.

 

Onasled hey you're out there! Yep, I glanced several times at the speedo out of curiosity and it was in the neighborhood.

I am most comfortable doing my braking in a straight line, turning in, then on the gas. It's not always the fastest but it works for me. I do know FWD cars are different than RWD, esp. rear weight biased P-cars. Back in the early "80s (my GTI days) left foot braking through the turn was used to balance the car. Anyway, in this instance it was quickly apparent that the car was not happy braking hard - period. After I changed my shorts, I tried various ways to tackle the problem, trail braking worked best but the instability remained.

The alignment was set at stock specs after I changed out the springs and lower control arms. Tire wear (@5,000m) on the street has been even.
At the track, the tires were chalked each time before a run session. As you know LRP has only one "real" left turn, tire wear was what you would expect, front left and rear outside worked hard, front right inside, right rear even and 1-2#s cooler. No shreading of tires like the recent photos posted after a NHIS DE. I would assume that with the 4 tires hot and 3 out of 4 at 40#s and the inside rear 38-39#s that I was in the ball park.

Increasing tire pressure in the rear seems counter intuitive, can you explain why it works?

It's possible that the rear pads are glazed. But if that was the case then they wouldn't bite. I bedded then in early one AM on RT 138 immediately after I installed them. I put @ 800 miles on them on the street so I re-beded them again the day before LRP.

5vr6fm... - FWIW I've been trying to carve Big Bend as a double apex since 1977.

 

Something funky in the rear suspension? Still sounds alignment related.

 

Big Bend is a very challenging turn.
Do you agree that Big Bend as a double apex in the MINI just seems all wrong?
I find that if I take it slightly late and keep the radius very tight I enter far ahead of what ever car was riding my tail down the straight.

 

Increasing tire pressure in the rear seems counter intuitive, can you explain why it works?


It simply adds, as I'm sure you know, a bit more stabilty to the side wall and tread. This alone, as I'm sure you know, will not cure everything. It was a suggestion. It will help a little, especially when you transition from full braking to power; the Mini can get a little squirely in on-off throttle conditions while entering or exiting turns. Well, my 05 does.

I really think the H-Sports are the problem. So much of what I wrote above is based upon personal experience and how I feel about what my car is doing. I'm just trying to help; Big Bend is a very technical turn - get it wrong and you lose lots of time coming out of the only left hander. It's also a fairly bumpy track, which doesn't help.

I find that if I take it slightly late and keep the radius very tight I enter far ahead of what ever car was riding my tail down the straight.

I prefer to enter big bend by braking as late as possible effectively lengthening the strait as you mention. However, I like to be on the far outside of the straight while braking so that I can carve a very long smooth arc thru the second half of the turn. This allows me to concentrate all my braking in one spot while creating a line that has a softer - faster radius. I won't beat most folks thru the turn because this technique consumes more time, but I will be traveling faster as I approach the left hander. And, this only works if you have a clear road ahead and don't feel you need to protect your corner. Essentially, I'm zigging while everyone else is zagging.

 

Thanks for the input guys! I'll have the allignment re-checked and I'll do some more playing with tire pressures. I decided on last Thursday's track day to leave tire pressure alone based on the even temps all around. I focused on learning the car. But even a Spec Miata (always beind me) commented on the wagging back end! Yes, I agree that staying outside and turning in late also works in Big Bend allowing you to carve one turn, but you have confidence in the car - which I didn't. More seat time coming up! MEB - do you remember the big bump that used to be at the first apex in Big Bend?

Cheers,

 

.... I actually think it's that overpriced oil catch can!

 

Some of the concrete inserts have nicely done away with some of the bumps and slippery blacktop...although, I can tell you that the bicycle race I mentioned in the rain above was not at all fun while traversing the concrete sections at speed on a bicycle. My first time on the track was in 1983 with the local SCCA club out of Albany, NY - the Knock-off Club. I had a pretty well set-up Ford Fiesta. Another short wheel based front driver with a very narrow window for stupidity. Fun in a scary sort of way.

As a note, I've not tracked the Mini. I might also feel very nervous going into Big Bend with my car squireling around. My only thought, knowing what I know about the car, and, based upon your comments, is take speed deep, hit the brakes like an on-off switch in a straight line and then gradually get on the power is fast as possible. Far easier said/written than done...just a re-hash of what's already been written, sorry. I know you get it. apologies.

 

Onasled - yea, that "What the hey, as long as I'm hanging around, throw in Alta CC" is probably the root of the problem. Whew. I still shake my at that experience. RW to customer, "bend over please"... My fault, I probably inhaled too much second hand smoke at FPC.


Cheers,

 

my second lap ever at Lime, at the end of the straight, with an instructor/passsenger (and in 3 class as I have had enough track time to warrant) was hairy. two cars ahead someone locked the brakes..smoke all over, so I got some un-anticipated heavy braking action. car was fine though, no squirrel action. I never felt right about BBend, and tried to concentrate on setting up wide to the right for the Lhander, clipping the apex apron for a good line and longer straight to the next right and gassing it up the hill.

for the above trouble, I would suspect toe out in the rear when brake loaded might be the culprit.