Sleeping at the wheel on Prepared rule changes.Sponsors car purchased 18 X 10s all the way around for their 944.Switching from the bias ply on 16s and going to A-6 in the 285-30-18 size.24.9 inch tire with 10.6 contact patch.
We have previously ran the car on the 275-35-15 - but only on 8s -never stretched out properly.
Always wanted a few more mph with our current gear setup-this would do it.
Slightly larger contact patch-Double the amount of competitive runs from a set of tires.
Have got this years 16's-for nats-covered in the corner-but have won three more tires that haven't been collected.
Just thinking out loud and looking for input.
JJackson

There are a number of things to consider.
IMO the A6 is better on asphalt than R35 slicks...tho I have no proof of this.
On concrete I think R35 slicks are better.
A6s are heavier. I think there are 18inch wheels that are as light as 16 ....but bring lots of cash for em'. Is your camber is adjustable enough to get what the A6s need without spending/modification.
The W/T combo will raise your ride height/CG. No big deal if your ride height is adjustable enough to compensate.

It's a lot of money to get a slightly larger contact patch and more speed in
gears (at a loss in acceleration) that may or may not pay off on the clock.
It's kinda like switching to Avon tires at about 100 bucks a tire more each. They may be quicker at the cost of fewer heat cycles and no contingencies.

A DP buddy is trying Avons while another DP buddy is letting him do the research...but watching.

I've never had the disposable income to test everything I'd have liked to.

Interesting question. My Boxster ran 16x10s with Avon a15 compounds. Awesome combo for cold weather with lots of people approaching me after last years San Diego tour asking questions about Avons after we did so well as a couple SCCA rookies. Heck it was Evans first SCCA event ever and he beat national level car and driver first day out of the chute in a poorly developed FP car.

However in warm weather, over 70 degree, the avon a15 compound doesn't hold up well at all.

Back on topic. So Erik is changing to 18x12 and 18x10 with huge A6s on the FP Boxster. I think he must know something as that's direct opposite I was going. 285 front and 3xx something in rear.

We have EP champ in our region as well and he has switched to bigger wheels and A6s the past two years. He runs on cement here a lot too.

Hamiltons have gone to huge A6 setup as well on their 914. Seems to be working?

.
huge A6 setup as well on their 914. Seems to be working?

Hoosier slick that were running is a very predictable-loose tire-As in vague turn in,predictable slip.A6 has incredible initial turn in and very predictable,precise tire- with more competitive runs per set.Like the car with bias ply suspension settings more than I like the car with the a6 camber settings.
We'll see how sponsors car with the 18s perform-they are geared similar to us with similar hp.
Not gonna make that kind of change before nats.Need to learn how to drive the car now-Cars fast-driver makes too many mistakes.JJackson

18s don't fit well on a 914, particularly in the front, due to the larger diameter of the tires. With slicks, common 16" tire diameters are 23-24". For 18s, it's more like 25-26" (I think it's similar for DOT tires), which you'll have a hard time fitting under the bodywork. I think they'll also hit the inner fender well/chassis near the strut towers. I saw a 914 track car with 18s on it, and while cool, it seemed to be running at a fairly high ride height, which in my mind cancels any advantage the 18" wheels would bring.

Scott

Not that this makes any difference, but my rears are 18x10's.. Fits under HPH flares with a 285 tire pretty good.