You are correct but if I would have the proper setup for this size, I would try it. The price is just too good to not do it. It has the proper W rating and might be better in the rain than NT01. I am just burning too much tire on the track to not consider more economical options.

 

Imagine how fast you would have been if that tire was on a 9

 

And if you can't keep the back under you after a couple of laps, how much have you saved? Sure, it's worth a shot. Chalk it up to a learning experience if things don't go as expected. For me, if I'm looking for a 2:01-2 pace at Thunderhill, and I've got a I tire I have to drive my *** off to run 2:04......I'll just run crappy, heat cycled Hoosiers/similar and accept that's all I can get.

I'd have to go back and look at my notes, but I've had a whole host of tires on the 8.5 X 18's up front over the years and the 7.5 + 9 X 17's still provided the benchmark.

I've looked at enough data to know where I get and give, and ultimately we're only talking ~.5 sec. But over the years, no matter the external conditions, when I've got good tires on the heavy old POS Cup 1 replicas I've got a known quantity.

For comparison sake, what are your benchmarks on the tracks you run? Specifically, Lime Rock and Watkins Glen. Have a guy from out here who now lives in the NE, and I'm trying to debunk how slow he thinks the Porsches are relative to an E46 M3.

 

I'm no one to bench mark off of, mediocre at best, but I do know basic Physics

you get the best performance from any given tire when it is mounted on the widest possible wheel for which it is speced. Conversely you will get the most comfort from, the narrowest wheel. The reason is the different slip angles that result from the different configurations.

Comparing lap times is difficult at best because there are so many variables that cause deviation one way or another.

Comparing generic Porsche to a specific BMW is a waste of time, perhaps compare published lap times from races which identify specific cars. As always a good driver in a mediocre car will win.

 

Again, I do not know this tire but would give it a shot. As with each change to the car setup, I would take it easy to find out what it is capable of doing (and not doing). I did this with every tire change when I worked myself up from Falken Azenis to Yoko AD08 and finally NT01s. I am considering myself an experienced driver on the track.

However, without trying I would never find out what they are capable of doing. Looking at the initial investment, the risk / reward ratio would fit my bill.

The good news is that there are plenty of good tires out there.

 

Again, I do not know this tire but would give it a shot. As with each change to the car setup, I would take it easy to find out what it is capable of doing (and not doing). I did this with every tire change when I worked myself up from Falken Azenis RT615 to Yoko AD07/08 and finally NT01s. I am considering myself an experienced driver on the track.

However, without trying I would never find out what they are capable of doing. Looking at the initial investment, the risk / reward ratio would fit my bill.

The good news is that there are plenty of good tires out there (including the ones I mentioned above). I forgot to list Dunlop Starspec which I never tried but know that they are quite popular at our track.

 

Very interesting thread. I don't have much experiance at all but most of what I've heard from others is that the widest possible wheel for the tire is the best solution, which is in line with what Bill says above. But there are many factors to consider when choosing a tire. What people tend to forget is sometimes the height of a tire. A 245/40/18 for example is much taller than a 255/35/18. In my view, the height is more of a limiting factor than the width, as the tire usually rubs on top, rather than on the sides (if that makes sense). So a 255/35/18 might actually rub less then a 245/40/18 for example. Again, the problem is that most manufacturers have only limited tire sizes in the narrow range - i.e. 235-265.

My concern is also with the F/R width ratio. On the turbo the standard tires are 225/285 (F/R). The gives a front to rear ratio of 79%. Most of what people tend to believe is that this is the absolute minimum required. But if this is far from ideal, why did Porsche have these sizes on the turbo? My reasoning is that as long as you are around 80% then you should be fine. Also, if you have the front tire mounted on a wide wheel, then the actual footprint might be larger than the front tire size indicates. Thus the real world ratio F/R might be more like 82-83% rather than 79%. For a widebody, I think the limiting factor is the front tire size. In the rear, it is possible to fit a 315 tire on a 12" wheel with rolled fenders. The tire fits perfectly on this wheel with a good stretch. The problem is finding a good size front tire so that the F/R ratio mentioned above is not too far off...

 

Just a note if anyone is interested I have a set of FISKE 8.5 and 10x17 for sale $2500 plus shipping not cheap but track strong forged wheels and can confirm they fit NB 993 with 245 fronts and 255 or 275 on rears.
Excellent condition were used as storage wheelss on my race car not raced on, have center caps if using for street car.
Thanks
Rich