Help:  What Size Tires Do I Buy?

Kinja'd!!! "marshknute" (marshknute)
07/29/2015 at 08:42 • Filed to: None

Kinja'd!!!0 Kinja'd!!! 18

So I want to buy a set of aftermarket wheels for my new WRX, but I’ve never actually bought tires before, so I don’t know what size is appropriate.

The only car I’ve owned long enough to replace the tires was my 1995 Miata, and my dad was the one to actually take it to Town Fair Tire. Plus, that car had stock wheels, so the replacement tires were the same size as the old ones.

Kinja'd!!!

The wheels I’m looking at are these: !!!error: Indecipherable SUB-paragraph formatting!!!

The stock wheels are 17x8 and use 235/45/17 tires, but the gold XXR’s are larger and wider.

Does anyone know what size tires I need for the XXR wheels? Or know a handy trick/website to determining what size tires go with which size wheels?


DISCUSSION (18)


Kinja'd!!! Snuze: Needs another Swede > marshknute
07/29/2015 at 08:47

Kinja'd!!!2

Tirerack. You can select your car and then it will give you the option to show OEM sizes, “+1” sizes, “+2” sizes, etc.


Kinja'd!!! Smallbear wants a modern Syclone, local Maple Leafs spammer > marshknute
07/29/2015 at 08:48

Kinja'd!!!0

www.tirerack.com should have the info


Kinja'd!!! Tohru > marshknute
07/29/2015 at 08:50

Kinja'd!!!2

Instead of that, buy a lift kit so you can rock 235/75/17’s and dominate winter.


Kinja'd!!! marshknute > Snuze: Needs another Swede
07/29/2015 at 08:55

Kinja'd!!!0

I’m more concerned with the 3/4” increase in width. I know that a 235/ 45 / 17 and a 235/ 40 / 18 have a near-identical circumference, but Tirerack doesn’t let you specify how wide your wheels are.

Not sure if I need to go from a 235 to a 245 to account for the extra width.


Kinja'd!!! macanamera > marshknute
07/29/2015 at 08:57

Kinja'd!!!0

22 x 13.5


Kinja'd!!! Tareim - V8 powered > marshknute
07/29/2015 at 08:58

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there is only a 0.4% difference from 235/45/17 to 235/40/18 so you’re best with that option


Kinja'd!!! Short-throw Granny Shifter is 2 #blessed 2b stressed > marshknute
07/29/2015 at 09:00

Kinja'd!!!0

https://www.tacomaworld.com/tirecalc

That’s a handy little tool for quickly comparing the diameters of you old and new tires. A good rule of thumb is to aim for within 3% for traction control purposes. You should email the company who makes the wheel to see what widths they recommend. I would guess no less than 245 mm and up to 275 mm or so. Shoot for the most common width/aspect combo within that range while trying to stay as close to the original overall diameter as possible.


Kinja'd!!! Echo51 > marshknute
07/29/2015 at 09:00

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Look at http://tyrestretch.com/

It’s mostly for stancers and stretch fitments, but there’s typically a “normal” sidewall pic or so for most size rims too.


Kinja'd!!! marshknute > Tareim - V8 powered
07/29/2015 at 09:01

Kinja'd!!!0

But can a 235 wide tire fit on an 8.75” wide wheel? Or is it being stretched too much and really deserves wider tires?


Kinja'd!!! LongbowMkII > marshknute
07/29/2015 at 09:08

Kinja'd!!!1

255s or go home.


Kinja'd!!! marshknute > LongbowMkII
07/29/2015 at 09:12

Kinja'd!!!0

THANK YOU!!!


Kinja'd!!! Tareim - V8 powered > marshknute
07/29/2015 at 09:16

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using http://www.frsproject.com/tire_size.php it appears that it would be a square setup, little or no stretch


Kinja'd!!! Snuze: Needs another Swede > marshknute
07/29/2015 at 09:27

Kinja'd!!!1

Sorry, I think I misunderstood your question. You’re right, with the extra .75” width, you can, and probably should go wider.

Your stock tire gives a diameter of 25.3” and section width of 9.3” and tread width of 8.4” as measured on a 17x8” rim.

I’d suggest going up 245 or even 255 series tire to take advantage of your extra wheel width, unless you’re into that stretched look.

For 245 your options are (as measured on an 18x8.5” wheel):

245/35R18 which gives you 25” diameter, 9.8” section width, 8.7” tread width

245/40/R18 which gives you a 25.7” diameter, 9.7” section width, 8.9” tread width

For 255 your options are (as measured on an 18x9” wheel):

255/35R18 which gives you 25.1” diameter, 10.2” section width, 9.5” tread width

255/40R18 which gives you 26.1” diameter, 10” section width, 9.1” tread width

I think any of these would be a decent choice, though I’d lean towards the 245/40 or 255/35 as they are very close to the OEM diameter, which will ensure your speedo is relatively accurate, and won’t mess with your ABS, traction control, etc.

Also keep in mind these measurements came from Tire Rack on a Bridgestone RE050 Potenza tire (first one that popped up in my search). So there might me some inconsistency or variability.

Lastly, I would advise looking around, maybe checking some forums, see what other people are running with similar wheel setups. It would be pretty bad to buy 255’s only to find out they rub.


Kinja'd!!! Milky > marshknute
07/29/2015 at 09:32

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Forums seriously, someone has already done and documented whatever you’re thinking about.

Esp. with how big modding subbies is there are probably 9001 threads on tire fitment. The forums told me going wider +10 front would only rub reversing to the right and going wider +20 rear would be no problem … and thats exactly what happened.


Kinja'd!!! Will Race For Food > marshknute
07/29/2015 at 09:45

Kinja'd!!!0

Here’s a handy guide for tire width in relation to wheel width: http://www.brick-yard.co.uk/forum/tyre-siz…

As for wheel height, it is up to you to see what you like more, a higher sidewall tire will be more comfortable on the street but, arguably, look worse than a lower sidewall one. When it comes to fitment in regards to tire total height, it looks to me like you’ve got the maths down and will be able to understand whether a tire will physically fit in the wheel arches without rubbing


Kinja'd!!! marshknute > Snuze: Needs another Swede
07/29/2015 at 09:59

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Super helpful. Thanks.

I’ve seen dozens of forums where Subi owners post/brag about their aftermarket wheels, but they only listed the size of the wheels/tires, not WHY they chose those widths/aspects for those specific wheels.

It seems that 255/ 35 /18 is the most common, but people have used 255/ 40 /18 and didn’t seem to experience any problems. I’ll probably go with the latter (larger aspect ratio) since I’ll be dealing with snow-ravaged New England back roads and could use the extra air cushion.


Kinja'd!!! SummerFun > marshknute
07/29/2015 at 10:28

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A 235 on a 8.75” wheel is fine. You’d be surprised how much you can stretch tires.


Kinja'd!!! You can tell a Finn but you can't tell him much > marshknute
07/29/2015 at 13:54

Kinja'd!!!0

Keep the stock / original wheels and put winter tires on them. As for ride, you’re right that a taller sidewall will help with comfort.