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New Dunlop ZII Star Specs


mthomas
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So got the CC out and headed over to tire rack for a new set of shoes. I've been running PS2/PSS's and a well used set of NT05's (they came with some wheels I bought), but I was recommended Z2's for the performance/money. To my delight they are on clearance right now, but it seems there is a new Z2 (Star Spec) out. I googled around and there's not much info on them. Has anyone run them? Thoughts on alternatives? Right now I'm HPDE2, but hope to be in 3 or 4 by the end of the life of the tire. They'll probably be used up by next spring, so I don't think ambient temps/heat would be too big of a consideration??

 

http://www.tirerack.com/tires/tires.jsp?tireMake=Dunlop&tireModel=Direzza+ZII+Star+Spec&partnum=34WR7Z2SS&vehicleSearch=false&fromCompare1=yes

 

I have a little off topic question too. I've read that you need to put about 500 miles on a street tire to break it in. In the past I've been able to do this, but this'll be the first set that pretty much goes straight to the track. If I leave them on for the road trip I'll put ~150 miles on them. Should I have TR shave/heat cycle them?

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It is possible (likely?) they will chunk on track if not properly heat-cycled. Tire Rack has more info on the technical details, but mileage isn't as important as getting enough heat into them and then letting them thoroughly rest. I have seen the Z1 star specs chunk on track from taking them out with stickers still on and not breaking them in. But I ran several sets of them with never an issue by always breaking them in on the street first.

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Accoding to Dunlop Japan's promotional video, the Z2 Star Specs get up to temperature significantly faster than the original Z2's and are roughly 1% faster on a road course:

 

 

I ran Z2's for a while on my FR-S and didn't have any problems with chunking, but I did about 100 miles on them before taking them to an autocross event, and much more before a track event.

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It is possible (likely?) they will chunk on track if not properly heat-cycled. Tire Rack has more info on the technical details, but mileage isn't as important as getting enough heat into them and then letting them thoroughly rest. I have seen the Z1 star specs chunk on track from taking them out with stickers still on and not breaking them in. But I ran several sets of them with never an issue by always breaking them in on the street first.

 

The confusing thing is that Tire Rack has two steps of instructions. One for 'competition/race' tires and one for 'street'. The competition instructions basically recommend a heat cycle and complete cool. The street guidance is mileage based and mentions getting rid of the mold release. It makes me wonder if their recommendations are based on the difference in compound or the difference in use.

 

"Many tire manufacturers use very aggressive tread compounds for the Track & Competition DOT-legal tires they’ve developed for autocrossing, track days and road racing. And just like other high performance parts, these tires will provide more consistent performance and last longer if they are properly broken in.

 

The first time Track & Competition DOT tires go into service is very important. All tires deflect under load and their tread rubber compounds repeatedly stretch and relax as they roll into and out of contact with the road. This stretching breaks some of the weaker bonds between the tread rubber molecules, generating heat. If new Track & Competition DOT tires are initially run too aggressively, too hot or too long, some of the stronger bonds will also be broken which reduces tire grip and wear.

 

Putting new Track & Competition DOT tires through an easy initial heat cycle and then not running them for a minimum of 24 hours allows the rubber bonds to relink in a more uniform manner than they were originally manufactured. Heat cycling actually makes Track & Competition DOT tread compounds more consistent in strength and more resistant to losing their strength the next time they are used."

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R comp rubber stretches a lot more than street tires. That is why heat cycling is more important for those.

 

For street tires, just be aware that your first session will not produce great grip until that slick layer of mold release is off the tire. No need to do any special mileage requirements for street tires. I have used several sets of 200 treadwear tires that go straight on the track and no chunking problems. We even used a set of sticker Falkin Azinsis for a 24 hour race last weekend and no problems with weird tire wear.

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  • 10 months later...

I am running these on my track only civic, and I didn't do any break in and they seem happy as can be. I was a little cautious my first time out to get the lube from the molds off the tires.

 

Quote from an instructor last time out on the track while using these tires "what kind of slicks are you running?"

 

Harry's lap timer says I was getting around 1.1 Gs in my best corners with these guys. Great tires.

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