Tire Aspect ratio vs. Width

[fulanititoo8198]

I'm wondering what is going to provide more straight line traction assuming the same tire is used for both. A 245/45/17 or a 255/40/17? Is there a "rule" for when aspect ratio overcomes width or vice versa?

 

[DirtyBirdRacing]

Hi,

For straight line traction I would think that the 245/45/17 tire would provide better straight line traction. This is becasue it would have a taller sidewall then the other tire that you listed. For straight line traction I think you want a taller softer sidewall but for better traction at say an auto x you would want the thinner stiffer sidewall. If I'm wrong please someone correct me.

Bill

 

[jtmcinder]

For a given tire width, the taller sidewall will provide more longitudinal grip. However, if what you are really after is better acceleration, then, with a 14-second car, the shorter tire would probably be better, since you'd have better gearing. I would only switch to a taller tire when you are over 100 and want to avoid the shift the fourth.

In summary, for your car, I'd get neither of the tires you listed. I'd get 245/40/17s or, if you are getting lots of slip at the launch, 245/45/16s.

And please don't be offended. I'm not a whole lot faster or quicker, even with AWD, which is why I use 245/40/17s (or my snow-tires) for drag-racing.

- Jtoby

 

[fulanititoo8198]

For a given tire width, the taller sidewall will provide more longitudinal grip. However, if what you are really after is better acceleration, then, with a 14-second car, the shorter tire would probably be better, since you'd have better gearing. I would only switch to a taller tire when you are over 100 and want to avoid the shift the fourth.

In summary, for your car, I'd get neither of the tires you listed. I'd get 245/40/17s or, if you are getting lots of slip at the launch, 245/45/16s.

And please don't be offended. I'm not a whole lot faster or quicker, even with AWD, which is why I use 245/40/17s (or my snow-tires) for drag-racing.

- Jtoby

Thanks for your reply and no offense taken at all. The time listed was when the car was stock. Haven't been to the track, but my logs show that I should be trapping in the 107-112 area. I'm getting a lot of wheel spin in 2nd at 17psi and I will be turning it up to 22 shortly. That is why I'm looking for a new wheel setup. I'm also interested in doing auto x thus the the smaller sidewall appeals to me.

I guess what I meant to ask is will the 255/40/17 have equal/more/less traction then the 245/45/17? Although the 255 loses some sidewall will the extra 10mm make up for it?

 

[95blackGsTurbo]

For the power being made, the extra width isn't going to be enough to make a difference over a taller sidewall. You are looking at probably hundredths of a second difference.

 

[jtmcinder]

+1

10mm of tread won't make up for the loss of sidewall.

You know: many autocrossers are in the process of moving from 245/45/16 to 285/30/18, so a bunch of light 16s might be available, some with Victoracers on them. Maybe give this a try. Yeah, I know that Victoracers aren't great for drag-racing, but if you've done the mods to deal with wheel-hop, they would still be an easy experiment. Do not try drag-racing on Hoosier autocross tires; at least, be very careful if you do.

- Jtoby