Lets say an STi runs consistant 12.0 at 114 on 225/45/17 ES100s. Would it do better or worse with 235/40/17 ES100s?

Specs:
225/45/17: dia=25.1, wieght=24.36, circum=78.85, thread width=8.7
235/40/17: dia=24.5, wieght=24.79, circum=76.97, thread width=9.1

Facts:
1) The 235 has more rolling resistance.
2) The larger dia of the 225 is a resistance to acceleration, intrinsically.
3) The smaller dia of the 235 makes for higher acceleration gearing.
4) The 225 requires 5 less full rotations to complete the quarter

Post away.

Same time different speed?

Assuming your making enough power to need the traction, go with the 235/40/17, better gearing and more tread width for the launch will trump the slightly heavier weight.

If your not traction limited on launch, the 225/45/17 may give the same numbers.

Larry

I'm thinking all things will be equal in the 60 and the differences will come over the last 1260 feet. I think the smaller dia of the 235 is great for accel, but I think the car has enough power that the larger dia of the 225 will be more benificial, giving a better trap and ET. I'm open to being told I'm wrong though.

I don't think you would save much time going to the 235. IF you could get a tire that was big enough to keep you from having to go into 5th you may save time assuming you have enough torque to get off the line and not slow down accel by having the larger tires.

Tire weights are almost identical too (the 235 is slightly heavier though).

225/45-17 = 24.36
235/40-17 = 24.79

Is this on pump gas?..or race gas? :devil:

My vote is for the smaller rolling diameter tire.....but I think they're close enough that you may have difficulty "proving" that one tire was better than the other based simply on ET/trap. Unless you're consistently running between 12.000 and 12.050, I think you'll have a hard time convincing me that it was ONLY due to tire size.
All that being said.....I vote for the 235

Is this on pump gas?..or race gas? :devil:

My vote is for the smaller rolling diameter tire.....but I think they're close enough that you may have difficulty "proving" that one tire was better than the other based simply on ET/trap. Unless you're consistently running between 12.000 and 12.050, I think you'll have a hard time convincing me that it was ONLY due to tire size.
All that being said.....I vote for the 235


If it were me, it would be pump only (since you asked).

The scenerio is based on one setup with the driver being very consistant. The question is, how would wider, heavier, smaller dia tire effect things.

IF you could get a tire that was big enough to keep you from having to go into 5th......

That would be one BIG tire on an STi with that power. You'll be into fifth way before the end of the quarter. An STi on stock gears and tires will not hit 100 in 4th before 7000rpm.