Tire size question

[89lxsport50]

I'm looking at buying a set of Nitto 555's for my 02 GT. The wheels are the stock Bullitts, and I'm running 373 gears. I want to step up from the stock 245 width to 255. I'm leaning towards 255/45/17 because I think the 255/40/17 would look too short. My question is, will the difference in tire diameter and revolutions per mile affect the performance of the car? I want to get the most out of the 373s I can. How much will my speedometer be off?

Here are the specs on the tires:

245/45/17 - 25.67 in. - 821 revs per mile
255/40/17 - 25.08 in. - 829 revs per mile
255/45/17 - 25.95 in. - 800 revs per mile

 

[sneaky98gt]

I'm running the 255/40-17 and I don't like the shorter height. I'd go with the taller tire (255/45-17) just for the better looks.

Will you notice difference in performance? No, not anything recognizable. As per this calculator, going from a 245/45-17 to a 255/40-17 with 3.73s will result in a 3.83:1 equivalent gear ratio. Going from 245/45-17 to a 255/45-17 will result in a 3.68:1 equivalent gear ratio.

The speedo with my tires is off just a bit. When it shows 80, I'm actually doing about 76.

 

[89lxsport50]

Good info. Do you have any pics of your 255/40/17s on the car?

 

[sneaky98gt]

Good info. Do you have any pics of your 255/40/17s on the car?

Sorry, I somehow missed this.

I do, but I'll have to go through my pictures and find some good ones. I'll get it up later tonight.

 

[AlbertaEthan]

hugely helpful tire size resource: 1010 Tires

 

[007]

If I were you I would by new rear wheels and wider meats. The rims are usually cheaper than tires after all.

 

[89lxsport50]

If I were you I would by new rear wheels and wider meats. The rims are usually cheaper than tires after all.

I would do that if this wasn't my daily driver, but I need to be able to rotate them.

 

[Shiroelex]

I ran some Sumitomo 275/40s on my old stock Bullitts, and it looked great.

 

[89lxsport50]

Well, I went ahead and got the 255/45/17s. They look great, and fill in the wheel well better than the stock 245/45s. They are quite a bit softer/cushier feeling than the BFGs I had before. I may play around with the air pressure a little to see if I can firm them up a little. They sure do grip well on dry pavement. I haven't tried them in the rain yet.