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Clemens:

Shahab has it figured out

It is a street tire...  a kumho street tire at that.... So yeah, jello side wall...

 I ran 42psi on the fronts with the MX's....  BS so NO camber...........  Run 38 PSI and -3.2deg...    Fixed.  :) 

m3kerry:

I talked with Terry Fair about it and he said he has stills of his car getting that kind of movement.  I plan to up the pressure in the fronts from 35 to 38psi and test a few tire guages on the tire...

Yea, but that guy doesn't know squat! I think the video is showing the tire movement more readily than any still picture can, and its unusual enough that it makes some people cringe... but if they video'd their own tires it might be just as alarming.

Here's the pic of a 265/35/18 Bridgestone RE01R on an 18x10" wheel. Like the Kumho, this model isn't known for a super stiff sidewall. This tire is also moving a lot under load.

Here is a Yokohama AD07 in 265/35/18 on an 18x10.5" wheel. Its also using -4° camber in front and still moves a bit on the wheel under load (1.3g lateral on this road course)

Now consider your 255mm tire isn't as well supported on a 9" wheel as either of those 265's used above (but its still a pretty good fit). Then factor in the Kumho sidewall. We've found the Yokohamas to be fast at only 28-32- psi, and we rarely need to go higher than that, but our current AD08 is a 245mm tire on a 10" wide wheel. On an E36 you aren't ever going to fit much more than about a 9.5" wheel and 255mm tire without some rubbing, using the current (and unfavorable to the E36) fender rolling rules.

m3kerry:

The car ran 2nd fastest raw time of the day for non open wheel cars in a field of 100 and paxed 4th.  Field included several nationals trophy winners.  So, the car ran fast.  The tire temps were good 130 to 140 and even accross the tire (130 inside, 135 middle, 140 on the outside).  Tires never rolled over past the triangle markers on the outside edges.

Well from the pyrometer numbers it looks like its keeping the outside plenty warm, so running less negative camber would likely make the outsides hotter still, and probably lower front end grip and worsen tire wear. We ran -4° on our STU M3 for 3 years and every set of tires wore perfectly on the front, inside and out. We always tell E36 racers that think we're crazy - test for yourselves. Usually the drivers that can keep the tire temps even across the fronts with a lot less negative camber in front just aren't pushing the car hard enough...

Terry, I bought some AD08's today to try to get the car to become "alive" again in slaloms.  The XS's are a great budget tire and we did have a chance to put the car in the top three at the Eastern States Championship in STU but I feel like the AD08's and a light weight battery are the next upgrades.

 Thoughts on moving from $600 tires to $850 tires for the stiffer sidewalls.

http://www.flickr.com/photos/misin4mati0n/3628910846/sizes/o/in/set-72157619676181919/

I tried the 245-35-18 XS on an 18x8.5" wheel. I felt it was much better than the (taller and perhaps wider) Azenis I replaced. Started at pretty high pressures, around 35 if you believe my pressure gauge. It was spot on for the first few runs but it was pretty high and I didn't bleed off enough when they got hotter. You can see the sidewall flex in the (giant) picture above, or here:

http://www.flickr.com/photos/misin4mati0n/3628581884/sizes/o/in/set-72157619676181919/

http://www.flickr.com/photos/misin4mati0n/3627635015/sizes/o/in/set-72157619676181919/

They sure were sticky though! 

Thought I would add my video here too as a counter example of XS sidewall action. Mine don't flex much at all as you can see in the video below - nothing like above.

My setup is 285/40/17 on 17x10 with 34psi

http://www.vimeo.com/5167877

Very happy with XS performance.

Something looks really wrong in your video. I can't believe that could be normal. Could the tire simply not be seated properly on the wheel? Poor fit perhap?

The Nebulizer:

Thought I would add my video here too as a counter example of XS sidewall action. Mine don't flex much at all as you can see in the video below - nothing like above.

My setup is 285/40/17 on 17x10 with 34psi

http://www.vimeo.com/5167877

Very happy with XS performance.

Something looks really wrong in your video. I can't believe that could be normal. Could the tire simply not be seated properly on the wheel? Poor fit perhap?

You need to get closer to those cones

SIMMONS-RACING:

You need to get closer to those cones

I don't think so in most places. The slalom I was a little cautious (and sloppy). The course is a bit misleading from that angle - many of the right turns were more limited by the outer cone so I was purposely off the inside cone. I am also focusing more on learning proper angle and speed than I am about brushing cones. Here is the same run from in car...

http://www.vimeo.com/5183258

(Sorry, to get off topic.... But, you can see the grip of the XS tires in this video too.)

The Nebulizer:

SIMMONS-RACING:

You need to get closer to those cones

I don't think so in most places. The slalom I was a little cautious (and sloppy). The course is a bit misleading from that angle - many of the right turns were more limited by the outer cone so I was purposely off the inside cone. I am also focusing more on learning proper angle and speed than I am about brushing cones. Here is the same run from in car...

http://www.vimeo.com/5183258

(Sorry, to get off topic.... But, you can see the grip of the XS tires in this video too.)

 Getting slightly further off topic, and then exiting the discussion....you need to get closer to those cones (obviously I'm familiar with the course).  If you had, you might have beaten Kevin on Sunday!

Back to your squirmy tire discussion.

It seems likely that you just arent running enough pressure in the tires.  Heres some RE-11's with 35 psi:

It looks damn scary, but tires are made to deflect.  It keeps the contact patch on the road more evenly. Also, it is technically this deflection that generates grip, it just looks scary on a softer sidewalled tire where the whole tire deflects instead of just the tread. 

Here is the odd thing, somewhere in this thread or the one over on bimmerforums, someone posted to check my air gauge.  I did, it is 8psi low.  Yes, low.  So, in the videos in this thread, I am not running 35 front and 32 rear, but 43 front and 40 rear.

Now, your attached pic really looks close to the deflection I see in my tires.  I also, have gone back to look at some pics  of the car with r888's on it and they move across the wheel too.

 So, I don't think that there is anything wrong with what I am seeing.  I don't think there is anything wrong with XS's either.  I have a set of AD08's being shipped (back ordered).  At this point, I am going to have the order canceled and probably go back with another set of XS’s to make the rest of the year.

The XS’s died over the weekend.  I put about 200 runs on them and daily drove them about 5000 miles.  Saturday they were hooked up ( 30 runs in 100 degree heat) and fast at a school I taught (www.autocrosstraining.com) but Sunday it was John Force burn out day, as they would not let me lay down any power.  I ran them full thread down to about 2/32’s left on them or less.

I am open to thoughts on what to buy from here.  The car has one more divisional to run this year and a national tour stop.