Today I took off the 175/65-15 Continental ContiPremiumContact 2's and put on 205/50-16 Dunlop Direzza Sport Z1 Star Specs on Rota Slipstream 16x6.5" wheels.

The Contis are competent tires that provide plenty of warning when approaching their limit by starting gradually to slide and then starting to run wide.

The Star Specs just track through the corner like you're doing 10 mph. I haven't a clue where their limits are or how well they communicate their approach. It would be illegal, anti-social, and quite possibly suicidal to explore their limits on public roads.

Are these more similar to r-compund tires where they just spin seemingly without warning until you adjust to them?

I can't wait for the next autocross. This MINI is taking 40 years off the way I feel about driving.

 

So I think you are saying you like them?

 

I think I'm gonna like 'em a lot at an autocross. Too fast for the street.

 

I've got about 14k on my Star Specs and still love them.

 

I think the Dunlops are generally very predictable, with good turn in feel. Grip is generally good, better than most street tires. On turns, they do communicate their limits with a deeper groan/squeal.

They do lose some traction when they are too hot. And they chunk at AutoX and the track!

 

Have you tried spraying them down to stop them chuinking/over heating? I've always been curious as to whether that will help. The stock Dunlops have the same tendencies - chunk at autocrosse and get greasy when hot. I wonder if it is one of the tendencies of the brand? Probably to general though...


Stupid DC heat is eating my tires...

 

After running both Hankook and Dunlop, I felt like both of them got oily quickly. The Continental tire and Kumho tires I have been running don't tend to have the same characteristics as far as oily feel or chunking, but the Continental Extreme Contact DWS has great wear, great grip, and so far no adverse effects.

 

Dunlop Z1 Star Specs are generally autoX tires so they are designed to have great grip when are lower operating temps (within the first minute). There is some tradeoff when you run a 30 minute track session when it can overheat.

I usually don't come into the pits during a track session unless they black flag me. I would not throw water on my tires as it may get on my hot brakes and crack them.

The best way to prevent some chunking for autoX and track is through:
1. proper camber
2. Shaving (down to 4/5 32nds) or just use them on the street first
3. drive more smoothly and reduce understeer and oversteer

 

Forgot to mention, Yoko AD08 and Bridgestone RE11, similar to Dunlop Direzza Z1 Star Specs, can also have the chunking problems under the same conditions.

 

You don't throw water on the tires. You use a garden sprayer to spray water on the tread surface. It is very effective between autocross runs on hot days with insufficient cool down time between runs. Overheating tires is bad for the compound even if they aren't prone to chunking. A cooked tire loses some grip forever.

See heat cycling.

 

Ok. I went out this evening with the explicit intent of finding a public road upon which I could make the tires work for a living. I headed for a hidden short road along a US highway that has a lot of 5 and 10 mph 90 to 135 degree turns. Upon the way I ran over a section of coarse pavement that made the tires growl. They did it whether I was going straight or turning though. So no indication of approaching limit there.

The road of my objective has very smooth ashphalt due to a newish resurfacing (US stimilus dollars at work). I made the tires claw the surface under braking, cling for grip mid-corner, and grasp for traction accelerating out.

No drama under braking, but the abs would have taken care of it anyway. Based on the one time I invoked it autocrossing on the previous tires it appears to be BMW's usual good system.

I got an unannounced slide out of the rear tires just beyond the apex as I did with the Contis when autocrossing. Easy to control and no tire noise. No sudden total loss of grip ala R-compound tires.

The fronts however were a big surprise. Acceleration was greatly aided by the tire's high grip level. While both turning and accelerating the front tires became super sensitive to minor bumps, doing a little deke to the outside of the turn and taking a brief spin in the air. Easy to control though.

Having a better idea of what to expect from the tires I took a detour on the way home over a more open twisty road. I hope no one saw me go by as I was doing a great impression of a WRC car. These tires are definitely too fast to enjoy responsibly on public roads.