Looking to replace my existing 21" wheels on my 2009 GTS with something more suitable for light off-roading: primarily rock strewn desert two-tracks.

I was thinking to copy the Transsyberia size set-up of 265/65R 18R. Porsche went through a lot of testing to arrive at this size and it should therefore be compatible in every regard with my GTS? Right?

Tire rack offers an interesting selection of all-terrain tires, some of which include a snow suitability designation which might kill two birds with one stone. Here in NW Nevada we definitely get snow.

For example:

Goodyear Wrangler Silent Armor (http://www.tirerack.com/tires/tires....omCompare1=yes)

A "T" speed rating (118mph) is low for my GTS, but why would I ever drive over 100mph?

Wheels? How about the Victor Zehn's in Matte Black?

Anybody in my situation care to share some wisdom?

 

Have a new TS and it did not come with the BFG ATKO 265/65/18. It came with Goodyear Eagle LS2 OEPorsche (Shaved to 10/32). I go offroad with the TS. Look at the Michelin Lattitude Alpin XL in 255/55/18 VR. I have been riding them for the last 2k after riding the Goodyear for 1.2K. Better all around tire. I did put the BFG on the pepper but the noise was hellacious and I am getting too old to listen to tire whine. The Michelin will be fine for anything except rock climbing. I would also use the new Michelin LTX2 which is a better off road tire in my opinion and I have switched my SWB Gwagon to these from the BFG ATKO. Hope this helps.

 

Also look at the Nokian WRG2SUV. Unbelievable tire but difficult to get. ANd please know that though Tire Rack is very knowedgeable about on road and performance tires, they are generally poorly informed about off road (JMHO).

 

I have a Transsyberia on order with the full off road options package; and I, too, will be looking for a good set of rubber. Porsche used the BFG All-Terrain T/A tires on the rally cars; and those are excellent tires.

The Pirelli Scorpion A/T is one of Porsche's approved off road tires, although the Scorpion ATR looks even nicer. Both get very good reviews on Tirerack, although neither one is available in the 265/65-18 size.

I have a friend who swears that the Michelin LTX A/T2 are the best on/off road tires. Also not available in 265/65-18.

 

Quite right about the LTX A2 Only available as 265/60/18 and that is what is on the SWB (new rims!!)

 

cooper zeon LTZ 275/45R20, with 20x9 wheels off ebay cheap, that's what i have.

 

A 45 profile tire? Not much rubber between the rims and the rocks.

 

The Cooper has a thinner sidewall and lower sidewall. I would NOT recommend a 20 inch rim for any offroading. I drove 622 miles yesterday on my 255/55/18 and 32 miles was into logging track which is unpaved and mostly loose dirt and some small amount of shale with 2 streams. I would under no circumstances want less than this tire in terms of sidewall height and agree with Dutch that probably a 60 or 65 with a 265 would be ideal. I will say that the 590 miles on pavement though with my set up is a dream. Quiet and very confidence inspiring.

 

I mounted Cooper Discoverer Mud & Snow tires (255/55R-18 109S XL B) onto some takeoff 18" rims. Not Porsche approved since it is only "S" rated (up to 112 mph). I am really satisfied with the aggressive, deep tread pattern. Works well with the rocky trails here in Colorado. Acceptable noise level. Fantastic busting snow drifts too.

 

yes i know the 275/45r20 is not a good off road size,
it is just a small step up from the 21" i thought.

actually stock is a 275/40r20, but i went up to the 45 percent for height, now i think they are about 30" total height.

the cooper zeon has good tread i must say.

i have my stock 18" wheels, those would be great.

 

acoveart - will be in Holland week of Aug 10 visiting family. Was born & raised in GR & Holland; and have deep roots there. Would have PM'd this to you, but my post count is too low to allow. (Strange rule!)

 

Sorry for the long wait to reply. But I have some news after a LOT of research:

Mounted 255/55-18 Nitto Terra Grapplers onto Victor Zehn matte black wheels. See the pics for result. Personally I am thrilled. There was some question, for some reason, if 18" wheels would work on the Cayenne GTS. The unequivocal answer- without a doubt.

The only Cayenne's this 18" wheel won't fit on are those with PCCB.

These wheels clear the caliper with plenty of room! They do not require the use of a hub spacer as Victors are specifically designed and pre-machined to fit the Cayenne.

The stock wheel studs are reused as well.

As I wanted to straight-up swap out my stock 21" tires/wheels, Discount Tire obtained and installed four new TPMS sensors. After a few miles the computer asked (via center dash display) if I changed tires, I ticked the check box for "All-Weather" then ticked the next pop-up box for "18"" wheel size and it was good to go.

The TPMS sensors were recognized and working within minutes with no other programming needed.

So...so...easy.

First pic suspension at full height. Second pic suspension in "Sport".

Handling as you would expect is softer and more compliant.

Many thanks to the guys at Discount Tire in Reno NV (Carson, Steve and manager Mike McFarlane). **Superb service and excellent value**

The Victor Zehn wheels carry a lifetime structural warranty and a 1 year warranty on the finish.

If you seek all-weather functionality this will fill the bill nicely.

 

Why not larger rubber, like 265/60-18? The bigger the profile, the more rubber between the rocks and your rims.

 

sweet!
yes, i love this area, i have lived here for a little over 10 years.

 

Completely agree.

But- the 265/60 is 5.1% (4.7") bigger in circumference than the 255/55 and I was afraid I would be unhappy with the numerically lower gear ratio that would result (slower 0-60 but probably better MPG). And it is not possible to compensate for the bigger diameter in the vehicle computer therefore the NAV and speedo would read incorrect.

And I "knew" the 255/55 would physically fit with no rubbing. I was pretty sure up to a 265/65 would physically fit, however I was unwilling to be the fitment tester

Here is a link to a great interactive tire size calculator which helps you visualize different sizing: http://www.miata.net/garage/tirecalc.html