My set of Dunlop ZII's have about 130 runs and 2000 miles on them. I ran them for one last time (24+ runs at this past weekends Evo school) and have a new set of ZII's waiting to be mounted. We have a fun autocross event the end of this month and then our regions season starts after that.

How far can you run a tire and still be safe? It would be nice to keep the new Dunlops until the season begins but if its a safety issue (a tire blowing?) to run them further than its not worth it.

Also, other than the rubber probably being heat cycled a bunch of times is there still good traction left on an extreme summer tire left with no tread (in no rain...)?

Picture of my worn tires attached.

 

Is there any cracking on the rubber? Kind of hard to tell from the photo but looks like there might be in the center. I have heard of people running the Direzzas for a long time using them for daily driving as well as track autox duty. I'm using the zII's on my autox and track cars.

 

Possibly how long is not the correct question. How much do you allow them to wear and use them for autocross before calling them shot? Till they cord? These are only 1 year old.

 

People used to run the Z1s down to the cords and they were still good. I'm not sure the z2s stay sticky quite as far down into the rubber. We've found the heat cycles kill the z2s before the tire wear does. If you have a Co-driver you'll need to be spraying during the summer.

Those look to be about done though. I wouldn't run them at a national tour or anything but you could get another local event or two out of them. All depends on how fast you want to go. If it were me I'd probably swap off of them.

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I'll use the tires down to the legal minimum (1/32") for getting to and from the events, if its dry (like it is around here). If it were wet, I'd want more tread.

 

Pretty much.
Once you see cords - you know they are done ;-)

For street (non-R compound) tires, age (assuming less than 5 years!) and tread depth play at best a minor role.

There is nothing wrong with the last 1-2/32nds of tread - unless you are hit with a downpour and have to autoX over puddles. Plain wet surface doesn't matter, but you do need some tread if you have rivers running across the course.

The other consideration is getting to/from event safely. That's not a concern if you change the wheels at the event, but if you drive on them, you may want to check the weather forecast first.

a

 

Some tires (Toyo R1Rs for example) change rubber compound once you get down to the last little bit of tread. There's nothing wrong with the tire they're just not as fast anymore because the compound is much harder.

 

this has been on my mind literally all morning. 130 runs is pretty decent, esp on a jcw. are you flipping these tires regularly? i'm hearing these tires get harder at 2/32nds, but not confirmed

 

All tires "feel" harder once you shave off the outside tread.
The key is what happens to the actual tire compound with heat cycles, whether the wear is even (vs. outside front shoulder gets fried first), and whether a given tire model has different compound for the last 2/32nds of the tread.

On the last count, few street tires have multi-layered rubber compounds, most don't.
Original Bridgestone Pole Positions used to have super grippy rubber below 3/32nds, and competitive folks used to shave off down to it to go fast. It sounds like Toyo R1Rs may have harder compound at the base instead. Go figure. It doesn't appear that Direzza's do:
http://www.tirerack.com/tires/tires....el=Direzza+ZII

That leaves us with wear uniformity and heat cycles.
Both will work against you going faster at the last 2/32ns vs. on full (or shaved) rubber.
However, unless you are competing to the last 0.1's for a trophy or bragging rights, squeezing another day out of the current autoX tire set is definitely on the table.

a

 

Here's something that will really blow your mind. The R1R changes compounds depending on tire size. The 195/15 "pixie dust" tires a lot of people run have the sticky tread all the way down as well as (supposedly) the 235/40/17. The other sizes have stick rubber that turns into hard rubber once they're worn down.

The Z1s used to be good to the cords. I've heard the Z2s don't last quite that long but we've run them down pretty far. I've always been hesitant to run street tires down to cords after "peeling" up some rubber off a Z1 star spec on the STI. In defense of the tire it's a big heavy car with not so good camber. So now we usually start looking to swap off of them after hitting the wear indicators. The mini is pretty gentle on tires though and we have good camber (STX car) so we can get a whole lot of runs out of a set of Z2s. Probably 160+ pretty easily.

 

Safe for what? Only for a tire blowout or safe on the street?

It it was safe to use on the street then you can change them out now.

If your weather is always dry and you want to hold on to the tires that is fine to use them until one of them cords, but I would inspect them before mounting on the car and between each run. Having the new tires ready to mount is a good idea.

If you do cord during an event and you don't watch carefully you could be driving runs on a corded tire which is not legal by SCCA rules, further you will have to drive home on a corded tire if you do not change tires at the event.

Considering that, it's probably best to change to new tires soon.

 

yea i think they're still good for now, as long as they dont have too much shoulder wear