Well it is that time to buy tires again, but this time i thinking of experimenting with different tire sizes...i am stuck on the Dunlop Direzza Z1 Star Spec, as these are the best tires ive ever driven on.

So the question is what size to choose? I daily these tires, autox and drag race on them. So i need the size that best suits me.

Choices are:

Stock
235/45/17

245/45/17
or
255/40/17

Which do u recommend and WHY?

 

255's are a tad wide for the oe wheels, the 245's are a little taller than normal. More common size is 245/40-17.

 

true but the 245/40/17 causes you to REV higher, and would make your speedometer read further off then a 245/45/17 tire would

ive actually owned a set of 255/40/17 before on an 8 wheel

Ive been told once to go with 245/45/17 but i wanted to know what ppl on here thought

 

I ran 245/45/17 for AX. They allow you to hold 2nd gear just a bit longer in fast tracks.

255/40 on the street is overkill, you will not use them to their fullest and they have more rotational mass.

245/40 is good, but will hurt you in AX.

 

yeah thats what ive heard that 245/45/17 is great when running on the track so you can hold a gear longer as u cross the finish line


any other opinions out there?

 

Im kinda in the same boat. I was originally trying to decide between a 245 and 255 mounted on an 8in wheel however I am leaning towards the 245. Im 99% sure the tire of choice will be star specs.

But now the topic of sidewall is brought to my attention. I understand a 45 sidewall will allow for a little more speed however how much sharper will a 40 series be?

 

I am also in the same boat on the tire choice which I am leaning tword the 245-45-17

 

245/40 series will have sharper response over the 245/45 series. But a 245/40 is also shorter than OE.

gain in one, lose in another.

 

I run 245/40-17 and am very happy with it. You also need to be careful and look at the specs of each tire very carefully, some 245/45's have LESS tread width than their 235/45 counterparts.

 

The stock tire has been fitted to the stock 8" rim. If you go from a 235 to a 245 you should theoretically get more grip from the additional width, but if you keep the same rim, won't you affect the integrity/performance of the sidewall? I would think that to maximize performance of a 245, you should go to an 8.5" rim.

 

true but check the dunlop direzza specs show the same tread depth

http://www.tirerack.com/tires/Spec.j...irePageLocQty=

 

And? Why are you bringing up tread depth? LOL

 

i think when u mentioned tread width u meant to say tread depth because when u go 235 to 245 u will always go wider especially when ur staying with the same brand and model tire

 

I'm in the exact same boat. Stock wheels and looking at 245 and 255 Star Specs. I've read a bajillion threads on it in the past week. There doesn't appear to be a common consensus other than 255s will fit, but like Smike said, there's tradeoffs at every step of the way from 235, 245, 255 and 40, 45 sidewalls.

My car is not a daily driver. I primarily autoX it but also do several track days a year. Still undecided on 245/40s (which I currently run; RE-01Rs from last year's firesale that will need to be replaced this year) and 255/40s.

 

Wrong. I meant what I typed. Tread width is not listed for the Z1 Star Specs, but for a good example check out the Sumitomo HTR Z III specs. The tire sizing is a very loose correlation to its actual size, it is not exact and widely varies from one tire to another (different model or brand).

Sumitomo HTR Z III
235/45-17: tread width = 8.5"
245/45-17: tread width = 8.3"
245/40-17: tread width = 8.8"

I think its pretty clear why I picked the 245/40.