I guess I can expect a variety of answers depending on tires/drop/suspension brand/chamber/etc...

After putting a few hundred miles on the H&R street, Ive finally figured out where the breaking point is. Anyone have a general idea how many G's they are pulling?

Would it be reasonable to generalize and say about 1.0 with aftermarket suspension? Or is this waaay to general

 

It all depends on if you put gumball tires on it and the surface you are cornering on. Goodyear Invitca's, no. Hooser DoT slicks, no problem. Something in-between, probably.

Even an 85 CRX with Jackson Racing springs, Tokitco shocks and P7's broke 1G on a skid pad. Really ticked off the Corvette development team. They beat it a couple years later.

Go buy a G-Tec and find out!

 

I just realized the types of cars that actually can pull 1g. For example, the 911 GTs and Z06s pull about .98 (wow).

Hmmm, let me simplify my question, anyone know the oem skid pad specs for the R56?

According to this website, the old JCW GP mini pulled only .83 (yikes, worse than the civic Si)

 

The biggest thing is tires (and alignment). Crappy runflats on the pathetic OEM alignment are responsible for the skidpad number above. Put even a decent street tire on a JCW GP comparable to what the EVO has and it could be over .9.

Anything over .9 on street tires is pretty darn good, getting above 1.0 is doable with street tires, but takes a bit of work.

That's a cool chart.

- Andrew

 

Hi,
I usually run an APP on my Android phone called DynoMaster hooked up to a bluetooth GPS that gives hits at 5 Hz when I run autocross. This gives me position, velocity, heading, accelerations (lateral and longitudinal), and an estimated horsepower. All of this is recorded and downloaded to an Excel sheet I built which tracks my runs and compares them. I have hit in the .9 g's several times, and all of these are at about 30 mph.

I also have a KAT Matrix battery powered 3 axis accelerometer that I put on the speedo when I do some of the twisties. It doesn't record anywhere, but it gives an active readout at about 10 hz. I have hit well over 1.15 g's lateral on some tight twisties at about 50 mph.

My S is lowered on NM engineering springs with Koni FSD dampers. I maxed out the front negative camber (about -1.4) and run about -2 for the rear camber. I am on my summer tires now - Conti Extreme Contact DW's at 205-55-16.

So yes, one can certainly do better than .83 g's. But that may have been on a wet skid pad.
Cheers,
Greg

 

I have a G-Tech Pro RR recording accelerometer, and have also hit over 1.0 g on sticky street tires during autocross runs.

The problem is, you can't compare those numbers to the skidpad numbers that the magazines publish. The magazines use a standard 200-ft skidpad, and the numbers they publish are lateral accelerations that the car can maintain over a long period.

The 1.0 g and higher numbers that you and I are seeing are easy to hit for a few tenths of a seconds during a rapid transition, but we'd never be able to maintain that kind of lateral acceleration around a 200-foot skidpad.

 

Well said Scott. Dynamic is very different from steady state. Besides, it is dynamic that matters, and it has a lot more to do with the driver skill than anything!

 

See my sig pic for my best (gravity cavity turn at the Dragon)

below are if i recall correctly as each new peak got a new sig pic
wet autoX ~0.9
dry trackday ~1.2
dry autoX ~1.25
other dragon run ~1.3

as mentioned above lots of things factor into this, don't forget about shape of the road (a contributor on my 1.41)

suspension setup is: 16x7" slipstream, 205/50 f1 gs-d3, hsport springs, SS front sway bar, SS+ rear sway bar

all are dynamic mid turn peaks not magazine style skid pad numbers

i don't remember exact alignment but w/o camber plates i could only get to ~-1-1.2 camber all around (driven by lowering)
zero toe front and rear

 

I don't have anything to add other than this was an awesome thread to read through!

 

Scott,
I agree that making a hard turn in an autocross is not the same as running on a skidpad. However my skidpad experience tells me that it is likely that the way the magazine comes up with the g value is something like this: they hold the steering input constant and slowly increase increase speed until the wheels lose grip (usually understeer on these cars). They can either use the max record speed (if they know the radius of the turn) or an accelerometer to get the max g value. They probably repeat the process several times and take the average.

On a standard 200 ft diameter skid pad you need to be traveling about 40 mph to see 1 g lateral acceleration. The friction force between the tire and the road surface will be the same (assuming the same tires and nearly the same road type) as in making a tight 60 ft radius turn at 30 mph in an autocross event. That force is due to the normal force on the tire which is due to vehicle weight and the lateral acceleration of the center of mass and the height of the center of mass (all of which are the same in both cases). What I am saying is that both events are dynamic and the forces at the instant of wheel release will be the same (if the car and road surface are the same).

At the end of the day is 0.83 a believable number for a skid pad test of a Gen I JCW - I expects so. Is your 1.2 in autocross the result of different dynamics - I don't think so. As you said you have sticky summer tires, probably stiffer suspension, and may be lowered and weigh more. I didn't see the 1 g accelerations until I had lowered my Mini and put on the summer tires. So I expect if either of us did the standard Tire Rack skid pad test we would be closer to the Cayman than the JCW. If the Cayman isn't seeing 1 g then it is the road surface they are using.

Cheers,
Greg

P.S. - I always enjoy reading your posts - could it be that you might be an engineer?

 

The difference between the autocross readings and a skid pad reading is that in a tight transition on the course, you can very quickly go from the extreme limits of adhesion in one direction, through the neutral center position to the extreme limits of adhesion in the other direction. This is a big overall change of direction in a short amount of time, which is what gave me my brief "spikes" up to 1.2 or 1.3 g when watching the playback. I've never gotten sustained readings that high during a sweeper or single turn.

If a set of Falken Azenis, some coilovers, a little bit of negative camber and my mediocre ability were to legitimately get me into the 1.2-1.3 range when a factory GP is only around 0.8 g, then the factory engineers have left a LOT on the table that they didn't have to.

Thanks for the compliment. I'm a naval officer, but my undergrad was in computer science & engineering, and I have a master's in applied physics. I retire in about 3-1/2 years and am still trying to decide what I want to do when I grow up.

 

I guess some chamber plates and control arms are in order to take advantage of 225 tires. Running -0.8 degree up front and -2.2 degrees in the rear is clearly not ideal on a car that understeers so much.

Only reason I asked is because every since lowering on H&R streets, ditching runflats, and getting wider tires the mini corners soo much better than the oem setup. I guess it would be nice to know how much better.

People can dyno their cars to see if their aftermarket performance parts actually resulted in a change/increase in HP. And although you dont need a sensitive butt to tell that aftermarket suspensions actually improve handling, numbers are always great just to compare oem to aftermarket. All I could do is say, with oem suspension/tires, I can take this on ramp at X speed, where as now, I can easily take it at X+ speed. I guess i am happy with numbers somewhere between 1.0 and 9.0.

Does anyone know how many G's an oem mini s is pulling? Couldnt find it on miniusa.com or after googling it. I know i ran into it somewhere...

 

You don't want ANY where that much rear camber. Try a half degree. The rear geometry just about matches body roll. The .8 up front is probably pretty good. Have you pulled the pin to see what range you can adjust? I just slotted the holes to go from 0 to -.9. Very happy.

Scott, growing up is not really necessary. Never bothered myself.

Dynamic cornering involves dynamic weight transfers from steering and brake inputs. That is what allows much higher that the static skidpad numbers derived as described above. You can only compare numbers on the same skid pad. Same day, same surface temps. Same wind.

 

 

Generally,to reduce understeer, you increase front camber.

Suspension tuning is both a science and an art with lots of trial and error. Since alignments are not cheap, we cannot have too many variations. I can only tell you some starting points where many of us Minis in the NE track circuit start with so there it is somewhat easier to narrow down to a setting you like better based on your driving style.

I would try the following as a starting point:
front camber: -1.6 to -2.2
rear camber: -1.2 to 1.6

Toe as close to zero as possible.

To get a more neutral balance, generally, for FWDs like Mini, you will need a little more camber in the front. A little toe out can help in turn ins but this can be bad for your tires and gas mileage. Also, you can experiment a little with differential tire pressures as well.