Joe Ricard

When I autocross my kart I do not care about PAX because I am the fastest thing on 4 wheels that day.

Actually have a guy say Sure you can go fast it's a go kart. I handed him my rib vest and said go ahead take a run. EPIC FAIL. Yea easy huh? go sit down.

PedalFaster

This:

...illustrates the silliness of this:

Even if two drivers go equally quick in equally prepared cars, if they switch cars odds are they won't tie each other, especially if those cars have significantly different behaviors.

Indexes are by necessity compromises and approximations. That doesn't make them inherently bad, in my opinion, but I do think that making them more complex by adding more variables will just add false precision.

sjfehr

I didn't mean it literally, there are far more variables involved in swapping cars than just index, but I hope you understand what I was getting at.

Classing and index don't need to be perfect. In fact, perfection is impossible. I did a statistical analysis on a couple of the more homogeneous classes at nationals two years ago and worked out that to be statistically acceptable, we need to get the accuracy of classing & index to within 0.3 seconds. 0.3 seconds is a realistic goal, but neither classing nor index is anywhere close to that right now.

As to the variables, only statistically significant variables need to be accounted for, and most of them are quantitative in nature. If the statistics say r-comps are 1.5 to 2 seconds quicker on concrete relative to street tires, that's a pretty significant factor, don't you think? High altitude states have issues with differing affects of air pressure on turbo vs NA cars. Things like that are easy to calculate and index for and there's no reason we shouldn't be doing it. Course design is the one dependency I don't think we can accurately index for, but we can account for that in classing- we end up with 4 or 5 indexed classes split by course dependencies. If within each of those classes, subclassing and indexing puts every car within 0.3s of "the car to have", I would consider that a tremendous success and a massive improvement on the status quo.

mopar bob

Well it looks like more sizes for RE71rs are coming out. I talked with Tire Rack and 245x35x19 is coming out with no est yet. 305x30x19 for the back still not on the list. So I guess I will keep burning up my RE11's for now.

sjfehr

I've got a fresh set of 255/35-18 & 275/35-18 RE-71R in my kitchen right now just waiting to be mounted. I'll let everyone know how it goes. I do know showing up to the last event on 120-run ZII* left me a second behind where I usually am compared to the guys on RE-71R & RivalS. I think part of that is that I've worn down to the slow rubber on my front tires and they're starting to fall off in speed. I'm going to use up the last of them on a local time trial this weekend.

cretinx

I have 245/40/18 and 275/35/18 waiting to be mounted.

If 19s do show up that's what I'll run next year.

mopar bob

I just bought a set of RS3 v2 255 35 18 and 285 35 18. I wanted RE71r but they still didn't have a size that works with my 997 C2. Sjfehr bought the 275 RE71r for his Boxster but that tire is under rated for a 911 that needs a weight rating of 102. I needed a better tire for the Tire Rack tour that is this weekend in Colorado. I just drove them home and all I can say so far is that they have a better ride on the street than the RE11's.
I do have a question for the folks that have run the RS3 v2. What tire pressure should I start with. The Lotus guys are running around 25 psi but that weighs nothing.

sjfehr

The RE-71R are each a full 1" wider than the ZII* I had on of the same size; you can go smaller and not lose anything. In fact, I'm really worried I'm going to need spacers to keep from rubbing (getting them mounted today!)

Personally, I wouldn't worry about the weight rating on these tires. It's a function of tire heating, and if you're not driving your 911 fully loaded at 180mph on a blisteringly hot day, it's moot: these companies do tradeoffs in the ratings more for marketing purposes than anything- given the heat produced from these sticky high performance tires, they would either need to reduce the speed rating to be able to increase the weight rating or vice versa.

burglar

Sell those rs3 and get the re71 or Rival S. Or ask for a one second head start.

cretinx

Odd, most of us have found RE71r sizes that work with our C2s.

The 275/35/18 is plenty in the rear.

mopar bob

Dam guys cut a rookie a break. I'm looking for my first 900 point race and to stay there, that is my goal this year. I will be running a Evolution I school again Friday to get seat time and to work on my lines. There is a Evolution II in Denver in a month or so and I will be there.
As to the tire pressures I'm thinking of 34 front and 38 or 40 in the back.

Paul Hagger

Do you think the 275/35 would be plenty in the rear on a 996 GT3? Stock size is 295 and I'm very skeptical about downsizing so significantly.

mopar bob

I thought that the 996 GT3 guys were running 305 or 315's. As for the weight a Boxster is rated at 97 back and the RE71r is 95 close and I would run it. My 997 is 102 in the back 6 steeps down and a little far. All my weight is over the back wheels and they wouldn't even sell them to me.

cretinx

The Rival S comes in GT3 sizes - 255/305

sjfehr

1 of my new RE-71R had a damaged/defective bead Wonder how my Boxster would on 3 good tires and 1 snow tire, lol.

e: the good news is there is no rubbing. Once mounted, the RE-71R were only slightly wider than the ZII* I had one before. TireRack says they'll have the replacement tire to me in 1-2 business days. Also, TMPS really hates having 3 summer tires and 1 winter tire installed.