I have been thinking about trying a staggered setup on the autocross car. 255/40/13 on 13x10 for the fronts and 275/35/15 on 15x10.5 for the rear.

The theory is that it will
a) let me put more heat in the front tires
b) reduce unsprung weight by 6 lbs a side

it will make the car a couple of inches wider in the front (5 inch backspace on the 13s) but that is both good and bad.

Pictures for comparison. I really don't think I am going to give up much tire and hopefully the warmer temps will offset the reduced width.

225 on 13x8 versus 255 on 13x10


275s on 15x10 on the left, 255 on 13x10 on the right

 

I would say no. I drove my old turbo car with staggerd size before and it felt dangerously unstable up front. Too much oversteer

 

Oversteer? Smaller fronts would tend to make the car understeer...

Chris, there's some merit to the idea as we have a number of older F1 cars at the shop that ran 13" front/15" rear combos... whether it will work on a Miata or not is another story. Looks like you have the tires to try out, I'd see how you like it.

 

+1. Try it and see.

 

Nope, never work. I've got some tires that I guarantee will work, I'll bring to Lincoln in Sept. Secret stock, just for you! You just have to promise to use them all week.

Until then, I'm really surprised at the look of the 275 15s vs the 255 13s, they are a lot closer in width than I would have thought. I think there some merit to this staggered setup with respect to the tire temp argument. I've heard a story from a few different people about a very very fast guy in my division who opted out of the widest fitment in favor for maintaining temp, this in an r-comp class. He had success with it.

I keep wondering if on the short (30-40 second) courses where I am, if I would be better off with a 225/45-15 fitment on a 9" wheel. I will test 225 NT01 vs 275 A6 in a couple weeks if my car is ready. I'll have some temp data to report then.

BTW Chris, can you document the installed diameter of those 13s on the 10" wide wheels vs the 15s in case other guys here want to calculate rollout?

 

Now that I think of this on a clear head, wouldn't the front ride so much lower than the rear?

 

Only if I don't adjust it 8^)

 

Adjusted, but it does look "different"

 

I am assuming that you'll have to realign your car from the new ride height adjustment?

 

I have to take the rear suspension apart when I change the rear diff (Boy do I need to get those two piece axles rebuilt) so it was going in for an alignment anyway. But I would suspect that I lost some front camber when I adjusted things. Although, with my higher spring rates and now slightly wider track, I was considering using a little less in the front anyway.