jabo

Hey Tom,

Glad to hear you're getting out driving again.

Mid-engine seems to be gaining credibility these days.

I really do miss SDR AX even though I have run hundreds of laps at COTA, I don't get to do that nearly as often as when I used to AX once a month.

We are trying to build some momentum to do more AX here in Hill Country.

If you ever get out to Austin, let me know.

In any case, when I helped with the Performance Driving Schools, we had to try and change everyones assumptions about tire pressures. Most folks had assumed that the higher rear pressures still have the result that they do for 911s. We found that on the skidpad, and other situations, the mid-engined cars actually need the opposite bias, preferring more pressure up front to get the oversteer required to achieve pitch/catch mode.

I also found that, in lieu of a proper LCA adjustment to get more aggressive camber up front, the pressures are a reasonable substitute.

It may not work for everybody, but I liked the change in the feel of the car.
While the rear end does come around a bit more easily, I prefer that to the push/slide I would get up front otherwise.

Good luck seeing what works for you, against the likes of all the converts to boxster/cayman setups. AG, CV, MR&JR etc. All tough competitors, as you well know.

Cheers,

JB

majormojo

I'm getting ready to order some new tires for the upcoming season ('11 Cayman S, running in SS. Only mod is H&R front stabilizer). It's Canada, we won't be running till early May usually. Last year I ran RE-11 OEM size on OEM wheels because that's what came on the car when I got it and I was focused on learning the car itself.

The wheels I'll be using are 18x8.5 and 18x10 Champion RG5. I'm leaning fairly hard toward the Hankook RS-3(v2) in 265/35-18 and 285/35-18. But it also occurred to me to try the StarSpec in 275/35-18 F&R for a square setup. Seems like that should help to balance out the limited front camber and it's still wider than OEM at the rear. What do you guys think of that idea? Anyone tried it?

Conditions here are generally cool compared to many locations in the US like AZ or TX, etc. We don't get the really hot days here so getting and keeping tires warm is usually more of a challenge than keeping them cool. My understanding is that the new RS3 does better at cool temps than the old one did, so maybe it's a better choice now? I will also do a number of track/HPDE days, but my priority is on having the right Autox tire, a good track performer is a bonus.

sjfehr

I'm running Dunlop ZII* on my 09 Boxster S and highly recommend them. I'm running a little narrower wheels than you are (18x8 & 18x9), but the size tires I'm running should mount well to your wheels.
255/35-18
275/35-18

I haven't run the R-S3v2, but others who have put them on heavy cars like ours have complained about the soft sidewall and a squishy feel. The ZII* has a much stiffer sidewall. You might consider Bridgestone RE71R (RE11 successor, just came out 2 weeks ago but did very well at the Dixie tour) and Rival S (soon to be released).

Paul Hagger

I thought 255s would rub on the struts/fender liners when mounted on the front of a 987.

Any issues?

sjfehr

Nope, no issues at all. May depend on the particular tires as there is some variance in dimensions, but 255/35-18 ZII and ZII* are OK at OEM offsets on my 987.2S. Not a lot of clearance, but no rubbing.

XPC5

8.5 fronts seem really narrow for anything more than a 245/255 tire. It may suffer in steering response and grip/wear. The 275 or 285 will work well on the 10".

sjfehr

I'm overtired with 255/35-18 mounted on 8x18, but have gotten fantastic performance out of it, no issues at all. This size is recommended by the mfg for 8.5" wheels or wider, but you can't tell by looking at it that I'm overtired, it visually looks right. I'm running probably the stiffest side-wall summer tire on the market, though (Dunlop ZII*)- really stiff sidewall tires take overtiring much better than softer sidewall tires like Toyo R1R, Hankook R-S3 or Michelin MPSS.

I wouldn't try 275 R-S3 on an 8.5, but ZII* should take it. Now, whether it will fit without rubbing is another issue entirely! There's also rake. If you try to run square tires, you're going to end up with the front rotating less than the computer is expecting and it can cause ABS/PSM/etc issues. That's why I'm running the sizes I am- the F:R rake ratio is very close to OEM. Balance is very good, btw. You don't need more front tire.

majormojo

I agree, those are my main concerns as well. According to data on TR the 275 ZII* is +0.1" F and -0.7" R different in diameter from stock. I'm not sure if that's enough to throw off the computer or not. From the same data the diff on your setup is -0.5" F and -0.7" R, so only 0.2" diff from stock vs 0.8".

For the fit, I guess the worst case scenario is that I can't get it to work and I have a spare set for the rear...

XPC5

Don't sweat the tire diam. difference F/R. I have run 3 987's with both square and staggered size/diam and PSM/ABS behaves basically the same. If anything equal diameters add more rear brake effectiveness which will help trail braking. The larger, taller rear mainly helps power down, which in our case is 'modest'.

majormojo

Cool. Anyone have thoughts on whether a 275/35 will fit up front? Wheel is 18x8.5 ET50.

majormojo

OK, so I've pretty much used up my first set of RE-71R's. 255/35-18F and 275/35-18R. I've got almost 120 runs and 4000+ km of street driving on them. But I can't get another set of 275's for over a month now either in Canada or USA. So I have a set of 4x 265/35-18 coming this week, going to try a square setup. Not thrilled about the narrower rear, but there isn't another option. I'm thinking that to counter the wider front and an expected resistance to turn in, I should add a bit of toe-out up front (currently 0), maybe 1/4" or so. Thoughts?

j patterson

FWIW I ran a set of MPSS at 1/4" toe out -- -1.2 camber in front and corded them on the inner edge. 11 track days and about 15000 street miles. They were still well out of the treadwear markers in the middle of the tire. Rears are still good for another event or two. I'm going back to zero toe at front but keeping the -1.2 camber as the outer corners still wear faster than the middle of the tire despite running as high as 40psi hot. Driving style is of course a factor. I expect that lot of my inner edge wear came under braking.

2XIPA

They did on my Spyder using AD08R's. Shims from Suncoast solved the problem.

majormojo

I had no issues with 255 RE-71R on my 987.2. On 18x8.5 ET50 wheels. I'm getting the new tires mounted this week. If I decide to change the toe it will only be at autox events, I won't keep 1/4 toe out for street driving. I have a test&tune day this Friday, going to try it out.