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I have not done a lot of Auto-X in many years but back in the mid '90's I did a full on campaign for three years running a MK1 MR2 in CS, actually ended up 3rd regionally in my last season. I learned early on to document everything because there are so many variables. I kept a log book that noted alignment settings, the MR2 was very adjustable but I really found that toe, both front and rear, really affected how the car felt on course, Temps,weather, venue, and tire pressure. Because I stuck to the same tire season after season, there were not many choices back then, I was able to hit the track with a good set up and concentrate on learning the course instead of fiddling with TP and alignment settings. I also found it interesting when talking to other MR2 drivers how different we liked our cars set up but would all be pretty darn close in our times. It just goes to show that what works for one person may not work for another. With all that said it sounds like the OP has a good base line so just document all the changes you make and you will soon be able to show up at an event and know what you should be running for TP right off the bat.

Cheers,
Jim
 

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Discussion Starter · #22 ·
So I finally had my first auto x on the z2s. I have the pro kit and the sway bar kit front and rear, with the rear at the stiffest setting. I also got 2 degrees rear camber and 1.3 up front. I hAd a very balanced car with the michelins but I could not get front traction with the z2s. It was understeering and squealing up front and could not get any front grip. I had 40-37 psi then adjusted the rear to 35. The back got better but the front was consistently fighting for traction. It was sunny with temps 25-28 degrees all day. The sidewall triangle markers were right on the spot so there was no sidewall roll but it seemed there was a lot of scrubbing on the front edges. Any input would be appreciated.
 

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A stick of chalk makes the world of difference.

Your goal is to adjust the pressure so that the chalk wears off on the shoulder at the ideal point on the tire. Once you get it tuned in to that point the rest is just minor adjustments.
 

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So I finally had my first auto x on the z2s. I have the pro kit and the sway bar kit front and rear, with the rear at the stiffest setting. I also got 2 degrees rear camber and 1.3 up front. I hAd a very balanced car with the michelins but I could not get front traction with the z2s. It was understeering and squealing up front and could not get any front grip. I had 40-37 psi then adjusted the rear to 35. The back got better but the front was consistently fighting for traction. It was sunny with temps 25-28 degrees all day. The sidewall triangle markers were right on the spot so there was no sidewall roll but it seemed there was a lot of scrubbing on the front edges. Any input would be appreciated.
I'd check the front sway bar for binding. The best way to do this is to remove one end of both front end links and see if the bar will rotate freely. I've found most aftermarket bars require the bushings to be shaved down or the brackets shimmed out with washers to prevent binding. Liberal amounts of grease helps there, too. Good idea to check the rear bar while you're at it.

What was your front pressure at? Could the front suspension be hitting the bump stops and causing the car to push? Are you giving the car too much steering input?
 

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Discussion Starter · #25 ·
Hi. The front pressures were between 40-42 all day. I do tend to over drive the car a bit as well. I think my problem is that I don't give enough steering input and step on the gas too hard so the front washes out because of too much wheelspin. But I drove the same with my pilot sport a/s 3s all winter for the slush series the same way and there was much better front grip.
 

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Hi. The front pressures were between 40-42 all day. I do tend to over drive the car a bit as well. I think my problem is that I don't give enough steering input and step on the gas too hard so the front washes out because of too much wheelspin. But I drove the same with my pilot sport a/s 3s all winter for the slush series the same way and there was much better front grip.

A few more thoughts that may or may not be the answer, but IMO, worth investigating....

Ultimate grip with the dunlops should be a good bit higher than the a/s tires. More grip = more body roll and suspension jounce than before. Something in the front suspension could be bottoming out or binding now that the grip level is higher. For example, you might be relying heavily on the front bump stops in corning. Bumpstops are highly non-linear and hitting them can cause sudden loss of grip on one end of the car.

The dunlops have traditionally been known as a tire that is not terribly forgiving once you're past the point of peak grip. They like to be driven a bit more precisely than some of the other extreme performance summer tires. Your a/s tires may have been more lenient with large slip angles and excessive throttle while turning. Driving style plays a huge role. It can take some time to adapt to the tire's behavior.

Different tires like different amounts of camber. That is quite a bit of rear camber. -0.5 deg more than stock out back with -1.3 up front sounds like more grip was added to the rear of the car than the front. If everything else checks out (sway bars, suspension travel, driving style, etc). I'd look a reducing the amount of negative camber in the rear if adding more front camber is not an option.
 

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Discussion Starter · #27 ·
The only thing I guess would make it change this much is the rear camber. I just had that changed because I was going to order the front kit from groundcontrol ,but then they told me it does not work with stock springs. My initial setup was going to be 2.5 up front and 2 in the back. I just don't want to pay another 90 bucks to get it re aligned at the moment. I guess I can try the moog camber kit, which will give me 1 more degree up front
 

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The only thing I guess would make it change this much is the rear camber. I just had that changed because I was going to order the front kit from groundcontrol ,but then they told me it does not work with stock springs. My initial setup was going to be 2.5 up front and 2 in the back. I just don't want to pay another 90 bucks to get it re aligned at the moment. I guess I can try the moog camber kit, which will give me 1 more degree up front
I do alignments at home with a setup similar to this:

Wheel Alignment Guide - How To Align Your Car At Home - Hot Rod Magazine

Cheap camber gauges can be made with a 12" digital level (~$30 at Home Depot), a ~20" long piece of square tubing (steel if you want the magnetic base from the level to stick), and bolts + nuts.

Vinyl tiles with grease between them make good alignment plates if you're working on the floor.

If you autocross much, additional front camber will pay for itself in terms of reduced/more even tire wear.
 

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I do alignments at home with a setup similar to this:

Wheel Alignment Guide - How To Align Your Car At Home - Hot Rod Magazine

Cheap camber gauges can be made with a 12" digital level (~$30 at Home Depot), a ~20" long piece of square tubing (steel if you want the magnetic base from the level to stick), and bolts + nuts.

Vinyl tiles with grease between them make good alignment plates if you're working on the floor.

If you autocross much, additional front camber will pay for itself in terms of reduced/more even tire wear.
Very good ideas for the DIYer.

I run 45/35 on the street on the stock tires for best handling and even tire wear.
 

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Discussion Starter · #32 ·
Found the sweet spot with the dunlops at 43front 37 rear.
 

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Discussion Starter · #34 ·
The dunlops have a stiffer sidewall. At 37 even in hard cornering the wear Is still at the top of the wear mark indicators so there is no sidewal roll at the psi.
 

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On stock tires in vegas heat on stock pressure, after 2 runs my psi jumped to about 44psi

Sent from my SAMSUNG-SM-G920A using Tapatalk
 

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I have been AutoXing for a few years, won a local champ in stock class in a mazda 3. Started AutoXing the ST this year, I have done about 80 runs over many events this season and have been doing AWEFUL. So I have been running the z11 star specs on advice I have gotten from 3 people to run front between 36 and 41 and rear 34 to 38. Finally on Sunday I went 43 in front on wet and 41 in rear. I was much happier. As the day progressed and the track tried out (and things got hot) the car performed better and better. Eventually I as it got hotter I could tell I was loosing a little up front so I checked the tires after the heat and the front was at 50 and rear at 43. I lowered the front to 46 and the rear to 41. BEST the car has performed. It was finally what I was expecting from the car. Great rotation in the rear, planted front no pushing, predictable and FAST.
So for my 2 pennies I am going to start my next event at 45 and 41. :)
 

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I've been running 35 Front and about 33.5 Rear with the stock Good Year F1 in the Rio Grande region. Turn all ESC off or you'll never get close to "limit driving" in this car. Last weekend my ESC was stuck on and really took the life out of the car when it decided "you need help" and ruined a couple lap times.

With dry and about 80 F conditions. They tend to get hot if I'm ripping out laps with little down time and I use a masonry / weed sprayer to cool them and the inter-cooler. Watch that video above on tire pressure and bring a grease pencil or chalk next time you go. You should see an arrow or on the Good Years a winged shoe, which represents the ideal scuff limits per the tire and adjust the pressure to make the chalk scuff at that indication level.
 

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Well I haven't seen this temp range covered yet.

Ambient temps were 36f this am. Ran 38f and 35r. The ambient temps reached 46f. Maintained the same temps thought out. I liked how it felt so I kept it there through out. Stock f1 and steeda RSB with bilistein coils
 

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Discussion Starter · #40 ·
Seems like the sweet spot with the z2 is 43 front 37 rear in about 65-70 degrees in the dry. I run my Michelin pilot sport a/s 3 in the wet at the same psi and the car rotates really well
 
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