There's plenty of information/discussion on NAM about what modifications are legal for what class.

I thought it might be fun to hear how stock class drivers dialed their cars in. Some of the choices they have for adjustments are alignment, tire choice (and mixing of sizes), tire pressure, shocks, shock settings....what am I forgetting?

Anyway, we're all bored during the off-season, so I thought this would be a fun topic to discuss. I'll start it out with this one:

When you run your Mini on a cold day, how do you go about dealing with the rear tires not heating up as fast as the fronts?

(Hopefully this will be a fun and informative thread. No right or wrong answers, just lots of good discussion)

 

Maybe this wasn't a good idea.....

 

Well, I was hoping the thread would take! I'm just not a really good participant, since my stock class Mini is amazingly stock Oh well.

I went to '05 nationals with only a set of SSR's and 710s. I have never even had my car aligned.

Early this year, I put on a set of Koni FSDs, and decided to run street tires all year since I was sick of changing wheels at events - so I put some Azenis on a set of holey's.

Over the winter, I'm hoping to get an alignment (now that my '04 has a whopping 18k miles on it), a catback, and a new set of 710's.

And as for cold events, I just run 5-10psi less in the rear than I normally would, and make sure I'm hanging on tight for the first couple of turns

 

I think it's a good idea, but I'm lurking and watching since I don't think I'm much of a resource. I run Azenis on holeys also, since I'm just learning and trying to get seat time. I run 'em at 40 f and 36 r, and other than that, it's pretty much an H stock Cooper. I'm consistently about 2 secs behind the guys with 710's.

 

satay-ayam: So what alignment settings do you plan to go with?

Bulfrog: Switching to race tires is worth almost 2 seconds over your Azenis....so you're really not that far off.

 

most around here when going from street to track.. take two turns out of the driver side wheel alignment .. making it toed out approx 1/8". That and going to the V710.

For me since i run in SM due to pulley change and adding camberplates. I went and had the car squared. Which means no Toe front or Rear. also with 1.5 camber front and rear. and 5% of caster. I did this as to be my Neutral setting and make adjustments from there. As for Tires im running 225/45/15 Toyo Ra1's in front and Hankook Rs2 205/50/15 in the rear. I've also had to replace the Front wishbone bushings twice (still under warrenty).

Before squaring the car i was running mid 20th place in raw time.(same tires) After squaring I've been in the top 5 last 4 time out.

 

So what's everyone's opinion on rear toe-out?

Does it help in the middle of a corner (like a big sweeper)? Or does it only help with corner entry and exit?

 

I started off autocrossing with my '02 Cooper with a set of Azzini's on the five spoke Cooper sport wheels and a rear sway bar from DiD's Cooper S. Now I've got an '05 S with LSD but I still run on the same Azzini's on the same wheels (That tells you how little autocrossing I've done over the years).

For what it's worth, I used to run tire pressures about the same front and back until I discovered that turns are quicker with higher pressure in the rear tires. It was downright eye opening the first time I tried it! Give it a try Bullfrog, try 38 front and 40 rear.



(that's my car with daughter's bf)

 

So why are turns "quicker" with higher pressure in the rear? Please explain what the car does differently.

Also, Johnna, why does your car have CS on it? Shouldn't it be G-stock (or H-stock)?

 

My MCS is in SM now, so this doesn't exactly apply..but I'm going to join in the fun anyways....:-P

When I was bone stock, I would always run higher rear tire pressures, 55-60 psi sometimes. My theory was that I was actually tuning the spring rate of the tire, so I wanted to stiffen up the rear as much as possible to dial out some understeer (same idea as stiffer rear sway bar or springs..). It seemed to work for me, but I have heard a lot of guys say that for a stock MINI, you want to run your front tires higher because they are "working harder"..... To me, basic vehicle dynamics tells me that by stiffening up the rear, it increases weight transfer to the rear in a corner, trying to get the outside rear tire to "work harder".....What do you guys say????

Jason

 

By turning quicker, I mean that there seems to be much less understeer. The car comes around in a tight turn more easily. I'm quessing that the harder rear tires have less traction so they loosen up the back a bit. In anycase my time improved by a couple of seconds.

I've been autocrossing with the BMW Club in Denver. They use different class designations than the SCCA. A stock Cooper runs in DS (street tires) or DR (racing tires) A stock Cooper S runs in CS or CR. I like the BMW Club because they typically get in 3 morning practice runs and 3 afternoon real runs Which means more seat time. During the morning runs, most people take in riders. It's a good way to get extra course time and advice.

 

Johnna -

I read a number of places where people suggest running higher pressures in the rear. We'll have a test-n-tune in March, so I'll give it a try. Makes sense, some people run them up as high as 48.

 

What Johnna says makes sense and I've heard that most people raise the rear tire pressure to free up the rear end while cornering.

But.....just to keep the discussion going, I'm going to argue for running lower pressures in the rear.

1. Every tire has an optimum pressure window that's about 5-6 psi wide. If you want to reduce traction you can either raise the pressure so it's outside the window, or you can reduce the pressure so it's outside the window. Either way, running a pressure that's outside the ideal window will reduce the traction of that tire.

2. When the weather is cold and you want your tires to heat up as fast as possible, you reduce the pressure so they will "bend" more and heat up faster.

3. Everyone complains that the Mini's rear tires don't heat up as fast as the fronts for obvious reasons.

Taking all this into consideration, wouldn't it be better to run less pressure in the rear?

(again, I'm not saying I'm right or wrong.....I'm just trying to stimulate some interesting discussion)

 

Sounds like an idea worth testing. If it works both ways, you could alternate over and underinflation to ballance out the tire wear!

However, If the goal is a consistant amount of reduced traction, I would think that overinflation would have less temp change and remain more consistant. Besides, I don't think I'd like the sloppiness that would come from underinflated tires.

 

I want to find out where it is, and then just go a bit more agressive. The car already seems loose enough from just playing with tire pressure, I don't want to make it scary. Also, I like doing track days now and then, and don't want something that will be too scary to drive 90mph into the braking zone of turn at the end of the straight.

I've been autocrossing the mini for 3 years now (quite a few years in quite a few cars before that), and until late this summer, I had always run less pressure in the rear tires. Then I tried running the rear's higher, and really liked it. I was mad that I hadn't tried it sooner, the car was amazing. But, I know that some pretty fast guys run lower pressure in the rear than the fronts, so maybe the looser rear end makes up for my sloppy driving, who knows.

 

I wish our new 2006 was "loose enough". It pushes like a pig. From just eyeballing it, I think it has a lot of rear toe-in. But I'm going to wait on the alignment until after I install the shocks and front sway bar.

 

I haven't made any adjustments yet, but my 06 MCS had 1/4" toe in when I checked it.....sounds like I'm not the only one.
Jason

 

Front sway bar? From what I've read, people are generally using stiffer rear sway bars to reduce understeer. Are you thinking of a softer front bar?

 

Thing on the tire pressure for when its cold. for discussion let's say when the tire is warm (at running temp) the air temp in the tire is 100 degs and the pressure is 40psi. On a nice day 72 deg outside which the starting temp for the air in the tire. For every 10 degs its 1 psi. I would do my first run 2-3 lbs below what my idea goal for psi is. Simply because i use my first run to get to know the track and i wont push it. On a cold day 40's or lower , I will run 5-8 lbs low because of the same effect.

As for Toe out in the Rear. This depends on where an how you unload the rear of the car. Different driving styles and Techniques will make it work differently in the corners for different drivers. If your Dive bombing a corner with hard braking and quick turning. This normally will cause the inside wheel to be off the ground. So by the outside tire bing toed out this will make the car want to understeer to turn easier by making the rear end swing out. Also if you start to tramline or wiggle it makes it a tad be harder to get back in control.

 

Johnna: You can't change the rear sway bar and be legal for G/H-stock. But you can change the front, along with the end links.

Mugami: Great point on tire pressure. If you start low, the pressure "might" come up so it's back in your ideal window....which wouldn't be good. But I don't really understand your description of the effects of toe-out in the rear....sorry. For example, you talk abotu tramlining.....I thought tramlining was when you had too much negative camber which causes the car to follow the big grooves in the road?

 

Hey Mitch, don't know if you remember us, Michele and I came up to one of your events with Morris back in September, we have the black MCS JCW, Michele ran in ladies class and I had an Orange SRT4 that Morris drove. Anyway, since then I've made several strides toward a drivable MCS since we were out there. Even though our car is STX/DSP car, I found alignment to have a significant effect on these cars. When we started off I had the car set up very similarly to the SRT4, that is about neutral to slightly toed in in front and about an 1/8" toe out in the rear. Not having any experience with the alignment, I was starting with something that worked in another forced induction car. WRONG answer, the Mini was almost undrivable. Sevearly tail happy in slaloms and unpredictable turn in everywhere else. At this point I've settled on about 1/16" total toe out in the front and neutral to about a 1/16" total toe in in the rear. Since I've added camber plates, I haven't been able to do more testing on setup and I'm sure these numbers will change more next year. I have also found that slightly higher tire pressure in the rear helps as well. The Mini really responds well to a slightly oversteer setup and became very predictable. On street tires (Hankook RS2s) I've been running about 26 in the front and 29 in the rear and that seems to feel pretty good. Next season will be the first on 710s as we'll be heading into DSP class and I'm sure I'll be starting from ground zero on pressures again. I'll add more as I think of it.

Dudley

 

This discussion is about tuning your MINI for stock class autocross.

Probably it would have been best started in H-stock or G-stock forums for more interest. Don't forget to look in both those forums.

Per Schroeder recently spent the last autocross season driving the Grass Roots Motorsports MC in H-stock class all the way up to Nationals (I think he finished 10th overall). He has since traded it in for a new 2007 MC to start the process all over again. But he published his stock class legal mods done to his MC in GRM magazine.

On tire pressures-
Which pressures work for you have to do with your driving style, the surface, your course design, your tires, your suspension and alignment setup, etc. If you want to do your best you will need to use ALL of your tires. Borrow or buy a tire pyrometer and check tire temperatures (probe is more accurate than Infrared) right after a run. Look for even temperatures on the inner, middle and outer parts of the tread front and rear. You WILL find that in most cases the tires are much hotter on the outer edges in the front and almost cold in the rear. Chalk your tires to find out how they are rolling over with your runs. Adjust tire pressures according based on your collected data. I run Kumho V710 front 33-34 psi and rear 30 psi and try to finish in the top 5 out of 100-130 drivers each month in raw time.

On alignment-
Stock MINI toe settings are not good for autocross. You will find toe in for the front AND rear. You can use any alignment but if you change it to help autocross you can wear your tires a bit more- nothing major. For all stock class racing you can try setting toe to front 1/16" toe out and rear to zero toe. You can't change front camber which runs about -0.5 degrees. Rear camber can be adjusted a little (about 0.5 degrees) in later model MINIs 2005+ but not in the early models.

Your biggest upgrade for stock class racing-
Has got to be tires. If you are serious you need R-compound tires. Consider the Kumho V710 in 205/50-15 or 215/40-16. I don't recommend using 17" wheels for stock class autocross. The best H-stock rim is the 7 hole wheel or holey. The best G-stock rim is the SSR comp (expensive and light) or Rota Slipstream (custom ordered in MINI OEM specs by 18racing.com), or AK monzas (no longer made), or stock X-lytes (hard to put 215/40-16 tires on them though).

Other legal upgrades-
Fresh drop in Air filter- used only for autocross days
High quality synthetic motor oil
Any Cat-back exhaust (check out the Helix13 exhaust for the MC)
Shocks of stock size
Driving school for you.
Schroth harness or CG lock to hold you in place.

 

Maybe it's just my sloppy driving Really, I wouldn't be suprised if our two cars, both which have not been aligned, are set quite differently.

The other thing is that if you're coming from another car, the Mini is essentially guaranteed to have less front end grip. It is a front heavy car with no camber, it's only going to go around sweepers so fast.

 

Actually Per Schroeder is getting rid of his HS 2005 MC for a GS 2007 MCS. He drove one in Europe and was rather impressed with it from what I hear. Per's write-up on his HS experiences with the MC should be must reading for anyone starting out racing their MC or MCS in HS or GS, as the wheel and tire combinations and the suspension setups are the same for both classes.

Are you sure about the 15" wheels being "best" for HS? Seems like nearly everyone at Nationals was running 16x6.5 wheels, mostly SSR's and Rotas (same as GS). Since 16" wheels were a factory option on MC's, you can run them in HS and put the wider, shorter 215/40 Kumho (or 205/45 Hoosier) on them. In reading about Per's HS Mini experiences over the years and talking locally to Jack Burns (he finished 3rd at Nationals in HS this year), they seemed to think that a 16" wheel/tire setup was .7-.8 second faster than the equivalent 15" setup. I ran the stock 15" holeys the last two years as I was getting started with my Mini in HS, but if I campaign it next year, I'll go with a 16" wheel and tire setup (I'll probably be racing my Mustang in FS most of next year though). After some experimenting and asking other Mini drivers, I ended up in the neighborhood of 45 psi front and 55 psi rear turned the quickest times on my MC with Kumho 710's.

FWIW I finally had my HS MC aligned in the middle of the 2006 season. IIRC I ended up with -.5° to -.6° camber per side in front and the minimum in back, -.3° to -.5°. I had the toe set to 1/8" out in front and 1/16" out in back (stock was toe in front and back). I have the exact numbers out in my shop but it is too dang cold to run out and get tehm right now. Judging by a local fellow HS competitor who turned pretty consistent times, the alignment was worth .2-.3 second on a 40-45 second course. I haven't noticed any abnormal tire wear yet, but I have run as much as 1/4"-3/8" toe out on other FWD autocross cars in the past.

-Keith

 

Yea, hopefully I'm finalizing the order this week.

I've got a bunch of stuff written up on the car at:
http://www.grassrootsmotorsports.com (click on project car updates, find the 2005 Cooper)

Although I don't have any advice on the cold pressures, as Nats taught me that what I was thinking wasn't correct. Grrrrrr.

Per