Can I move to a lower load index tire?

[Torsion]

Hey guys,

I'm thinking of running 275/35/18 Super Sports on 18x10 (+43) wheels. The main reason being that they are $200 cheaper per set than the 285/35/18 tires.

I'll be using these tires for street use and for a few track days a year.

But the 275s have a load index of 99, and I *think* my Mustang GT is supposed to use 100.

Can anyone help me understand how to tell if a certain load index is safe to use for my car?

Thanks,

Torsion

 

[VoodooBoss]

You'll be fine. A word of caution running the shorter 18" wheels on the street especially if you lower your car and or install the trans cooling scoop. You'll just need to be very careful not to scrap the bottom on anything. I'm now driving my car to and from the track with 18's and it sits a lot lower which is great for the track but not so much if you're car is a DD.

 

[Torsion]

Thanks NFSBOSS... but does anyone know the math behind "you are fine"? I mean, can I run a 95 load index tire? A 93?

My GT with two adults is what, 4000 lbs? I don't understand the forces on the tires during a track session well enough to know how many pounds a tire needs to be able to carry. :-\

 

[VoodooBoss]

I don't know the math behind it but Tire Rack has a bunch of info.