GAZZ

I've read how many people are struggling with putting on 18" or 19" rims.
Currently Im trying to get 18" rims on so I can run some super softs. Have found a few things out so far which I thought I would share...


I tried some Yokohama 18" Advan rims with large barrel intended for 991s'. These do fit over the calipers, but hit the rear suspension toe arms.
These 991 rims are a special shape.


I tried some other regular Yokohama 18" rims with spacers (19 or 21mm)and they clear the toe arms, yay. But don't fit over the calipers properly.


So looking to try the 991 rims with spacers next. Or maybe different offset rims but with the big barrel this may be a big ask.
Not sure if the spacers will have issues with the guards yet.

s2ktaxi

let me know what you find out...

mooty

18" on GT4 is trickly
19" fits. question is what tires

s2ktaxi

I'm looking for something for the street so that I don't have to use the Cup Sports in the cold/wet or even use them up on the street.

STLPCA

I mounted MPSS to the oem wheels and now need to find track wheels for the Cup 2. It looks like TireRack's reasonably priced and lightweight 20" OZ Leggera HLT should work. Same widths as oem. The 55 front offset will move the wheel out 6mm and the rear is the oem 50. I plan to test fit an oem front with a 5mm spacer to check clearances, unless someone here has already done that.

STLPCA

At this point I've decided to stay on 20s due to a dearth of alternative tire diameters and no desire to reduce the already low ride height. Given the low demand for GT4 sizes, I think it'll be at least a few years before we have more choices.

fishing

Here are Tire Racks current options. http://www.tirerack.com/wheels/resul...s&package=true It Looks like the OZ wheels are 10 inch wide instead of 11, and Tire rack is recommending 285/35-19 rear tires if you go with OZ 19 inch by 10 wheels.

ExMB

At present OZ doesn't make a 19 x 11 with an offset that doesn't hit the rear toe link. If you go to 20 x 11 you need to look at fitment for a C4S.

The other thing I noticed that some 19" wheel recommendations by tirerack have an offset that push out the fronts by almost 1/2".

verstraete

I am no expert, but I think that probably the 10 inch wide wheels are intended by the Tire Rack for winter/snow use, where narrower wheels and tires are normally better, not for track use.

s2ktaxi

maybe narrower rears on the track would dial out some of the understeer

RocketGuy3

I'd love to switch to 19s (wish it came with those from the factory) if I get a hold of a GT4, but I'd very much want to keep the same overall tire diameter if possible. Partly because I don't want to mess with the gearing, and partly because I don't want the car to ride any lower.

verstraete

A reduction in wheel diameter does not lead to a reduction in tire rolling radius if the tire profile is changed correctly. I have 20 inch S wheels with summer tires on my base 991 and 19 inch Tire Rack wheels with winter tires. The 19 winter tires are higher profile and give the same ride height and effective gearing as the 20s. They are also less vulnerable to winter pothole damage. A similar situation applies for base 991's ordered with either standard base 19 or optional S 20 inch wheels, same ride height, same effective gear ratio.

Mvez

Here's the deal guys, 18's can fit, but they require specific offsets and widths.

For example, Finspeed's F14 wheel will fit. He has already confirmed the 18" front wheel clears the 991 GT3 brakes, so they will clear ours.

The rear will fit easily, but requires a 18x10.5" wheel, ET44, if you want to avoid using alot of rear camber to clear the toe-link. The problem is tire sizes, there are currently not any 18" tires with more ideal sizes, which need to be:

245-45-18 and 295-40-18 (or 285-40-18).....these will keep rolling diameters the similar and keep your TC/PSM happy if you keep it on.

I would start asking Nitto and/or Hoosier to make these sizes. It will likely take a year or so, but would be well worth the effort.

For anybody who thinks its too tall of a tire, or the "sidewall is too big"...that's total hogwash. I run 245-40-18 and 275-40-18's on my 987, and they are perfect. I never get any "ice mode" or ABS problems, compared to the fairly regular complaints of those running the 275-35-18 rear. Those sizes provide a much better load rating as well.

285/295-40-18 on the GT4 would be great.

orthojoe

Thanks for sharing this info. I'd love to be able to run nt01 in 18" size on a gt4. It would push use of my gt3 to the sideline

Gofishracing

Did you see what new GT4 wheels cost at Suncoast? OMG