Falken FK452's

Fronts - 255/35ZR20 (20x8.5)
Rear - 275/35ZR20 (20x10)

Thanks

 

Great, so nobody knows...too funny!

 

The front tire carries the same load index as the 235/50-18, so 32 would be adequate in terms of load capacity. However, you've got a much shorter sidewall, so you might want slightly more (2 or 3 psi more?) to provide a little more resistance to getting pinch flats or rim damage on sharp edged potholes and such.

The rear tire has about the same load index as the 285/40-18 as used on the 2008 GT500 (I think it differs by one). So I'd start with whatever inflation pressure that Ford spec'ed for that tire, and again add a little.




Warning: long way of asking for a little patience . . . . . 7:00 AM is about as early as it gets for me to look at any new stuff, and I'm sorry to report that I can't surf the net, read stuff, and reply to it while I'm sleeping. Hell, I refuse to "multi-task" when I'm awake.


Norm

 

IMO I would think that 32-34 PSI all around would be just fine..!!

 

If you'll post the offsets of those wheels, I can provide cross section plots that compare those wheels/tires against the 18" wheels/tires for either the GT or the GT500 (it's a little Excel app I'm mostly done putting together).


Norm

 

Correct in what respect? Norm has given you the technical info but you also need to balance that with what's correct for YOU and your driving needs/style. With the 20's, you've limited yourself somewhat in regards to having to maintain a slightly higher pressure to protect the rims IF that's an issue for YOU. Depending on the roads in your area, you may not want kidney damage from riding at too high a pressure.

 

Excellent info guys, thanks Norm. The only reason I'm posting at that crackhead hour of the night is because my 2 month old has no concept of time???

20x8.5 - 35mm
20x10 - 38mm

I drive 80mph most of the time and go around corners fast.

PS. I just had this staggered setup installed and I'm not sure what the pressure is now, but it looks like 1/2 inch on either side of the rear tire is not touching the road, even under hard cornering???

 

I'm running 20x9's upfront with 255/35/20's and 20x10's outback with 275/35/20's and I found that 35psi works well for me.

 

It's kind of a personal preference to some degree. Norm for non track/daily driving would be 30-35psi on most tires. I run 35psi hot in the spring/summer and 32psi in the winter.

 

32 to 34 psi would be fine.