Tire Size question
 

What width should I go with

Rim Size (decided): 18 x 7.5

Tire size: 235x40-18 OR 245x40-18?

I'm leaning towards Falken Azenis ST115 in 235x40-18.

Well, keep in mind that the 2nd number is a ratio... so a 235/40 is going to be a lower profile tire than a 245/40... Also, a 245 on a 7.5" wide rim is pushing it... in fact I think on my roommate's 235/XX-17 ST-115 have a warning printed right on 'em "do not install on a 7.5" rim".

I'd check tirerack and see how man rev-per-mile each size tire has and what's closest to stock... if they're both pretty close, go with the wider tire as long as you know there's no rubbing.

The handful of 245s I checked recommend at least an 8" wheel.

Assuming you don't want to mess up your speedo, neither is a great choice.

225/40-18 is closest to your stock circumference, and probably the best size for a 7.5" rim.

There is a great tire size calculator here:
http://www.miata.net/garage/tirecalc.html

You would want to be within 1%, and could live with 2%.

Sorry, no Azenis Sports in 18 at all...

What are you looking for in a tire, and I can help you narrow it down.

The spedo reading at both of those isn't too bad. I just checked an online calculator and at 75mph, the 245/40/18 at ~72.3mph and 235/40/18 at ~73.3mph.

But, the STi spedo is about 5mph high.

Oh, and the 235s I spot checked also reccomend 8"+ rims...

There are a handful of 235 and 245 tires that will work on a 7.5" wide rim, but they're all "reinforced sidewall" models that cost more IIRC.

Matt just get a 18x8 rim?

Re: Tire Size question
 

Doh... Didn't even see the ST115 .. Why these tires? Are you looking for a UTQG over 350, or becaue they are a step down from the RT-215s?

Re: Tire Size question
 

The ST-115's are dead quiet compared to most tires with their performance. I have them on my P1's. I think they're a great street tire since they'll last a while, have decent (but not great) dry traction, have very decent wet traction, don't cost too much, and of course the aformentioned quite ride.

Good daily driver tires.

BTW: What tire is the RT-215? Is that the Azenis Sport?

Re: Tire Size question
 

Yes. I guess the full name is Axenis Sport RT-215 Pure sports, and the 115 is the Azenis ST-115 D1 Sports. Confused yet? I am...
http://www.falkentire.com/tires/tuner_choose.htm
If I had to choose a daily driver for those rims, I'd go with a 225/40/17, and probably a Kumho ECSTA Supra 712 for $25 less a tire... Unfortunately, I can't find any test data on the Falken

Re: Tire Size question
 

I had some 712's (225/40-18's even), and while they're good tires, I think the ST115 beats them in just about every aspect. The 712 might have just a nudge better dry performance, but they're *much* louder and their wet performance can't compare to the ST115s. But I guess that's why the Falkens cost $100 more.

255/35ZR18, you know you want to.

Re: Tire Size question
 

What size are your 115s? Is it a fair comparison since I think yours are on 17s now? Not saying you aren't right, just making sure we have apples to apples...

Get some cool 17X8s. The tires will be cheaper, and you can go offroading with Art and Josh... :-)

Re: Tire Size question
 

My ST115's are 225/45R17's. So I'm not apples to apples... more like McIntosh's to Fugi's. :P However, the 17 vs. 18 difference shouldn't make much difference in the noise level on smooth tarmac, and that's where the Falkens are far superior. For a daily driven street tire I still recommend them over the 712's... you just have to be willing to give up some performance, or have a set of Azenis Sports hanging on the wall. :disco:

Oh, and Matt: if you're going with 7.5" wide rims just get the 225's... These are your street tires after all, you'll get better fuel mileage on the skinnier tire, and you shouldn't be driving around at the traction limits on city streets anyway. :P :lol:

Re: Tire Size question
 

I guess it depends on if it was air through the tire coming through the window noise, or vibration base coming through the shorter stiffer sidewall and larger rim?

Hey, at least we agree on the 225s... :D

Re: Tire Size question
 

Most the noise from the 712's is just due to the wide arrow tread pattern on the road IMO. The ST115's have a less perpendicular pattern... and their marking literature states they're made with some sort of micro bubbles in the rubber itself designed to absorb noise. The really are very quiet.

Oh and the ST115's have dual rain channels as opposed to the 712's single center channel.

Re: Tire Size question
 

Oooohhh Micro bubbles... I want...

Have you ever thought that sometimes you and I are the only ones reading a thread anymore? I bet Matt gave up on us 5 or 6 posts ago.. Can you say... Losers... or just :alien: :alien:

I have been reading it. I just don't have much to contribute to the thread.

But...Knowlegde is Power... :lol:

:lol: I've also been reading...........Matt still hasent anwsered my question :lol:

I'm also keeping up on this one. I need new tires for the new rims I am wishing for for father's day!

Franz

The rims I want are in 7.5 only

OK, so if Scott and I have convinced you to go with 225/40/18s...

Your inexpensive spring-Fall tire choices are. (edited from TireRack and Discount)

Kumho ECSTA Supra 712 $96ea UTOG 280, 10/32 TR
Kumho Ecsta MX $126ea. UTOG 220, 9/32 TR
Falken Azenis ST115 $131 UTOG 360 10/32 DT
Yokohama AVS ES100 $138 UTOG 280, 10/32 TR

Ok, there are others, but these are the serious contenders IMHO on the <$140/tire budget I picked. Tough call. All good tires in their own right. I'd love to see some tire tests on some of the lesser known tires on Discount Tire's site. Both Nittos look interesting...

You can't beat under $100 for an 18" UHP tire...
Even though Falken tends to pad their UTOG, the Falkens may last the longest and be the quietiest. The MXs followed closely by the AVS 100s probably have the best performance.

I don't think I can help any more than that. I wouldn't buy 18x7.5s, so I wouldn't know how to narrow it down much more... I guess if somebody gave me a set of rims and said you have to use them for a daily driver, I'd probably go with the AVS 100s. If they forced me to pay for the rims as well, I'd probably go with the 712s and see if I liked them.

nah...... Matt you need the BFGoodrich Scorcher T/A Red (High Performance Summer) they be the shizzy :shock:

Those are the exact 712's I had on my 18" subzeros.

I'm surprised the ST115's are so expensive in 225/40R18... I got my 225/45R17's for like $85/tire IIRC. But that was with the Kragen hookup via Discount Tire Direct.

Kragen hookup still applies at Discount Tire. Azenis ST-115 in 225/40/18 are $112, P-Zero Nero M+S $118, Kumho 712 $89, Hankook Sport K104 $103 (A not so well known tire that seems to get good reviews), Yokohama AVS ES100 $125, Kumho MX $146. Not all of these are in stock currently though.

Khail