I ran 245/45/17s on my 2000 maximas stock rims and I believe they were only 7.5in wide (might have only been 7in.) Made the tires break away a bit more progressively (slower). Definatly worth the increase in grip (especially on FWD) Didn't really notice a decrease in wear, if anthing it hellped them last longer due to less tire slip (again FWD). Going with a 255 width on the evos 8in wide rim should decrease this progressive effect comparitively since you are going up 10mm on the tire and the rim is going up by 12.5mm (0.5in).

What do you guys think? what othe issues are there with this up sizing (ie safety)??

 

hm. alright, fair enough. i'm usually not inclined to go against the factory specs on things like that, but i've never actually tried this. to each his own, i guess.

i do think think that you may see different results depending on use, though. i.e., what works for you on track with slicks may not work on the freeway with street tires.

i guess i'm just never inclined to believe trust the recommendations of guys in online car forums over those of the maufacturers, especially with something as critical as this. your life literally depends on your tires staying mounted properly...

 

hey, and i just noticed this-

NO the second number is NOT a simple measurement of sidewall height in mm- it is the sidewall height measured as a *percentage of width*- 45 means 45% of the section width, 35 means 35%, etc. it's called the Aspect ratio, and it is literally the ratio of sidewall to tire width.

therefore, a 255/40/17 has a *taller* sidewall than a 235/40/17, since 40% of 255 is greater than 40% of 235. it works out to about

255*.4=102mm
235*.4= 94mm

...in actual sidewall height.

now, check out the spec sheet for the tires i'm using, where those two sizes are listed right next to each other:

http://www.toyo.com/tires/tire_specsheet.cfm?id=1

...you'll notice that the overall diameter changes by 7/10ths of an inch between those two sizes. if that 40 number were a simple measurement in mm, those two 17 inch tires would have the same diameter. notice a couple lines above those two, and you'll also see our stock size, 235/45/17. it's diameter is slightly larger than both.

the size broeli is recommending is a 255/40/17, which is actually a smaller diameter that the stock 235/45/17's. goes along with my personal feelings for which sizes will work better for us, i just don't kow about his taste in wheel sizes.


what all this means is that an increase in width is not as simple as it looks. read up on the tech info at tire rack, and you'll catch on easy enough...

 

You said the exact thing I did. I explained that and broke down each measurement in an earlier post. IMO, a 235/40 is too big a difference from the stock diameter...maybe good for autox but not the street. A 255/40 is closer in sidewall height than a 245/45 is. Yes. a 255/40 is a tad shorter sidewall than the 235/45..that was stated earlier. ..a 235/40 is even shorter.
The RRE Eclipse uses Hoosier 245/40's on 8" rims....we all know that Hoosiers are actually a tad wider than their stated width. So if RRE gets the superb handling and is comfortable using that wide of a tire on an 8" rim for track days...everyone should be plenty comfortable running a similar width tire on the street...keep in mind a 245 series Hoosier is probably more like a 255 when compared to a normal tire.

 

I'll be running 245/40-17 V700's for autocross this year.

If you want to compare sizes, check out:

http://www.1010tires.com/tiresizecalculator.asp

or

http://www.miata.net/garage/tirecalc.html

 

I should be seeing you sometime this year. Maybe at the April event(s)? Are you also running ESP?

 

Here's a 245/40R17 Hoosier on a 8" rim. Superb grip and handling when dry -- makes the A046 look like a poser. Not so good in the rain.

 

right, ok. i've been behind in this thread since i first posted, one of the drawbacks to posting at work....

in any case, yeah, your breakdown was good, i wasn't contradicting it, i was just answering the guy asking the question. again.

... but i still wouldn't mount 255/40/17's on 8in rims for the street.

 

Yes, you'll more than likely see me a few times this year. I managed 1st year-end for the 2nd year in a row in the KYR.

I've moved to AS for the local events, but out of town events I'll probably run ESP.

 

My dad got his truck with 245's on a 6.5 in wide rim, he put 285's on it now, with no problem, the only noticable difference was the center wore out a bit more do to the tire squeezing in around bends, so im guessing 255/40 would be just fine for this rim. On my brabus 8.5 rims, people were running 265, 275's on it from the factory, my DSM buddies run 245's on their 7.5 in rims with no probs.. Im ordering 255/40 's for mine today