Tyre size for front GTO rims

If you want the exact same diameter, the alternative is 245/35R20.

If you're asking what will fit a 9.5"x20" rim, the list is long.

What's your goal?

 

I would run an entire F12 setup with MPSS tyres. It seems to be a very popular combo for the 599.

The F12 set is:
255/35R20 K2
315/35R20 K2

You can run your 245's, but that will make the car understeer more depending on your rears, especially if they are GTO rears.

Alternatively, you can just run the GTO MPSS setup.

The GTO set is:
285/30R20 K1
315/35R20 K1

Be aware that the GTO set is softer and has a more shallow tread. It's a more track oriented set of tyres, and due to the shallow tread and different compound, they are not as wet/cold weather friendly as the other MPSS tyres.

 

Those superwide fronts were accompanied by quite a few changes to the suspension on the 599 GTO. One problem you could run into with the 285/30 20s up front is a pretty good dose of oversteer caused by all that bite up front.

The 255/35 20 K2s (accept rim width 8.5-10") and 315/35 20 K2s should make for a really good combination, have full tread depth (K1s are shallower), and will probably work in a wider set of weather conditions with oversteer under control.

So I agree with AB's first choice.

 

Olivier- What makes you say 245/35s will not fit? Recommended rim size is 8-9.5" from Michelin for the 245/35 20s and 8.5-10" for the 255/35/20s. GTO rims are 9.5". Sounds like someone is blowing smoke up your rear end.

Be ready for a squirrely oversteer with those big fronts and no other changes. Such a big problem on the F12 TdF, they went to 4 wheel steering to counteract it.

 

Olivier- Your tire shop is probably just not used to working with wheels and tires that wide. The 255s are good for wheels up to 10" wide. I have seen shops use a belt around the center of tires to get the beads to match the rims on really wide wheels.

 

The 255/35R20 K2 is mounted on the 9.5" F12 rims all the time, without issues - and so are 245 section tyres on other 9.5" rims. Not sure what your shop is doing wrong, but I like Terry, find that it does not make a lot of sense that they can't mount them. And the idea of the sensors going bad? NEVER heard that one before.

If you get a puncture, you'll have the exact same issues which ever tyre you run as long as it fits the rim, no matter the size. The 245 won't act much different than the others.

Which rears do you currently have?

 

I just bought a set of GTO rims for my 612-

Taz & DK308 are right on target and have given perfect info

The 255 is the tire I'm using as well and it fits no problem- It is also the standard tire size as mentioned on the F12 which also has same width 9.5" front rims as GTO.
The sizes and set up they recommended are the ideal for your car

As Terry states, Michelin also quotes the recommended rim width for the 255's at 8.5 to 10 inches

You should have no problems- Someone isn't doing something correctly or doesn't have the proper equipment to install these performance tires. Without wasting any further time, and before they try leveraging every pry bar they have against your wheel lips trying to pull on the tire beads, I'd grab my car and tires and go to the nearest authorized dealer. Tire installation is basic and at least you know any dealer can do it capably...

 

I think the known authorities around this forum gave you straight up best advice above.

Sounds like they're getting the tire on the rim, but have an inflation issue and can't properly seat the tire bead- Perhaps their equipment isn't capable or user error. Regardless I think you will be better if you go anywhere more experienced with performance tire install. Tire install isn't rocket science and I'm surprised your chosen shop isn't being more forthright with you.

Also I think based on the width of the rim, 245 works, but the 255 is a better choice. I know for my own sake I wanted a little more footprint on my car & that's one of the reasons why I bought GTO rims, but that's up to you.

 

Interesting...

Have you ordered the MPSS 255/35R20 K2 Ferrari tyre specifically? Also, is your rears the Ferrari K1 or K2 model?
As for the Ferrari recommendation? Not useful at all. They see a GTO rim, so they say GTO tyre. If it was an F12 rim, they would say F12 Tyre. Good grief...

Did you find a different performance shop for your tyre install? If they can't get the 255's on, they are not worth supporting.

 

Yes- K2

 

255's on 9.5" rims will feel stiffer than your 245's on 8.5" rims, as the more stretched tyre will "float" around less on the wider rim. Also, your new tyres have a load rating of 97 vs. 95 for your old ones, that makes a difference too. You now run a tyre with more volume on a wider rim and larger tread patch as well, so you might want to try running 1-3 psi less than what you had in your 245's on 8.5"'s and see how that feels, and how they wear.

 

Olivier- I'm Glad you're back up & running- Good for you

DK- Good advice, I may give that a try myself just to see how it feels- Thanks for the suggestion