GrantG

Agree and while I have no direct experience with either on the GT4, I would guess the Michelin racing slicks made for the CS are significantly faster than R7's.

Phokaioglaukos

The words in Porsche's mouth is not to use racing tires--they say nothing of DOT or street tires. Hoosiers are sold for racing, that is how Hoosier describes them and warns against their use on public roads.

Use Hoosiers at your own risk. It may be a risk you are willing to take, but recognize it as the risk it is.

GrantG

I understand your concern, Chris. But remember the manual specifically mentions "Slicks" in the context of "Racing Tires" and both OEM tires are also associated with Racing in their marketing (and the Dunlops even have "Race" in the model name).

I think one way to clearly distinguish Racing Slicks from the allowable Track tires is that they don't even share the same sizing conventions. For instance, the Michelin Slick on the Clubsport use the sizes 25/64-18 and 27/68-18. Pretty different from the 265/35/19 and 295/30/19 nomenclature on the Hoosiers (same convention used for road tires), for instance.

DeerHunter

My guess is that overfilling the sump, while providing protection against oil starvation at high Gs, will also create more windage that reduces efficiency (i.e. mileage). To me it's more interesting (and puzzling) that the manual recommends that optimum oil level for the track is one bar down.

Manifold

To throw more data (and confusion) into the mix, here's the website for the OEM Cup 2 tire:

http://www.michelinman.com/US/en/tir...rt-cup-2.html#

And here are some quotes from the website (bold added):
So where do we draw the line between R-comp versus slick, street versus racing tire?

GrantG

See my post above (#48) - if it uses "Street Sizing and is DOT approved" then it's ok.

If it uses "Racing Slick" sizing and is not DOT approved, it's not ok.

It's possible that Porsche could disclaim a warranty repair if one is using Hoosiers, but I think the customer would have a very strong case if one chose to fight that decision. Certainly the safest thing to do is use one of the 2 OEM tires in OEM sizes on OEM rims, but I don't think using other DOT tires is very risky (unless Porsche clarifies their warranty coverage to the contrary).

ML///

One other question, do you think the Porsche track app will be available for retro fit without the addition of the sports chrono? They mention in the video that this is the best and simplest way to get data. I did notice that the GT4 clubsport did not have the sports chrono. I want to be hopeful that this is possible.

HiWind

Space left for when the oil gets hot i.e. about .5L

BGB Motorsports

I think it's more because the uprights are radically different and therefore the bearings are. The strut style suspension puts more stress on bearings. The new uprights and bearings should have a long and useful life.

Bill Verburg

Nobody seems to have picked up on a big change on the CS no seen on the street GT4

The whole front clip is from a 991Cup including twin master cylinders and then added adjustable racing ABS not seen on the Cup cars

Manifold

Personally, I see the GT4 CS as having only moderate similarity to the regular GT4 (just as I see the GT4 having only moderate similarity to the other street Caymans). The CS and GT4 share essentially the same engine, but most everything else is quite different - suspension, brakes, transmission, wheels, tires, etc. It's track-only race car versus combo street/track car - different machines for different purposes.

bigkraig

It can be optioned either way, the larger fuel cell requires the balance bar braking system

PistolPete

Bill Verburg

yes there are 2 fuel cell sizes but the front clip is the same w/ either. You get twin masters and balance bar from the 991Cup either way.

For some reason they call it "2-circle brake system"

The cabin air seems to be simplified too.

<3mph

Another video (hopefully not a repost)