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-   -   ideal tire size for 17X9 +42 offset wheels on '12 WRX? (http://www.wrxtuners.com/forums/f139/ideal-tire-size-17x9-42-offset-wheels-12-wrx-50961/)

Pakal13 07-07-2014 08:08 PM

ideal tire size for 17X9 +42 offset wheels on '12 WRX?
 
Newb question on ideal tire size, hoping to get it together to track this year.

I have '12 WRX, stage 2ish, suspension modes are Koni dampers, RCE "regular guy" black springs, sways & endlinks and whiteline anti-lift kit.

I'm pretty sold on getting some [URL="http://www.fastwrx.com/collections/wheels/products/mach-v-17x9-awesome-wheel"]MACH V "Awesome" wheelsl[/URL] with 17X9 +42 offset. I've seen and heard of folks running tire sizes from 245/40x17, 245/45x17 and 255/40x17. 255/40x17 seems to be the closest circumference to stock and shouldn't stick out too far; willing to do some fender rolling if need be. But what size would be best for handling? Which I'd rather go performance over looks.

I've heard that 255/40 is good on these wheels since the gears are tall but curious if that'd really be the best way to go... esp. as this is my daily more than it is a track car.

Realize this is just advice I'm looking for, but if anyone has any experience with this size wheel & offset, I'd appreciate hearing what tire size(s) you like best.

Thanks,
- Steve

arcticscythe 07-08-2014 12:43 PM

Heads up, incoming tire fire. Those are hard to put out : ) Because you want sizes not brands ill stick with the question and hope that everyone else does the same.

Assuming your wheels can properly mount all three sizes the biggest difference will be sidewall tension, Sidewall flex and contact patch. A bigger contact patch will Increases traction (not the same as friction but close) and decrease fuel economy , A shorter sidewall means less to flex during cornering and less forgiving road feel ( louder and less confortable ride), and a wider tire on a slimmer rim will preload tension on the sdiewall which can in extreme cases cause unwanted thread patern deformation and abnormal tire wear.

For most drivers a sidewall of 40mm gives them a nice cornering without too much harsh road-feel or too much noise. 40 seems to be the magic number for most drivers and lots of guys swap their factory 235/45s for 240 or 245/40s

As for the width the only limitation is the ability of your sidewall to carry the width of the tire in your rims. If you go really wide , like 255/40 you might be putting additional stress on your sidewalls unless your wheel can support the extra width. that means you could be bending the thread pattern and reducing your contact patch.

Personally I would go with the 245/40x17s in something with a nice soft thread compound and stiff sidewall. Itll be a bit rougher than stock but it should corner well without sacrificing daily driving handling.

brfatal 07-08-2014 12:58 PM

245/40/17 or 255/40/17

[quote=arcticscythe;460609]Heads up, incoming tire fire. Those are hard to put out : ) Because you want sizes not brands ill stick with the question and hope that everyone else does the same.

Assuming your wheels can properly mount all three sizes the biggest difference will be sidewall tension, Sidewall flex and contact patch. A bigger contact patch will Increases traction (not the same as friction but close) and decrease fuel economy , A shorter sidewall means less to flex during cornering and less forgiving road feel ( louder and less confortable ride), and a wider tire on a slimmer rim will preload tension on the sdiewall which can in extreme cases cause unwanted thread patern deformation and abnormal tire wear.

For most drivers a sidewall of 40mm gives them a nice cornering without too much harsh road-feel or too much noise. 40 seems to be the magic number for most drivers and lots of guys swap their factory 235/45s for 240 or 245/40s

As for the width the only limitation is the ability of your sidewall to carry the width of the tire in your rims. If you go really wide , like 255/40 you might be putting additional stress on your sidewalls unless your wheel can support the extra width. that means you could be bending the thread pattern and reducing your contact patch.

Personally I would go with the 245/40x17s in something with a nice soft thread compound and stiff sidewall. Itll be a bit rougher than stock but it should corner well without sacrificing daily driving handling.[/quote]

The middle number in tire sizing is not sidewall in a measurement in millimeters, it's a ratio of the tire width. A 40 sidewall means the sidewall is 40% as tall as the tire is wide. I don't think any wheel would fair well with 40 mm of sidewall. That's 1.5 inch. That pretty much voids everything you said. :-/

There is no problem running a 245/40 or 255/40/17 on those wheels. 245s would be a quicker tire due to less weight and a slight gearing advantage due to smaller circumference. But 255/40s would offer better peak grip and heat resistance in hard driving.

Pakal13 07-08-2014 01:24 PM

Thanks arcticscythe & brfatal for the explanations helps a lot to understand why some go 1 way or the other.

And, yeah, should've realized that I was asking for info about stuff folks might have strong opinions about :) Just wish tires somewhat more affordable so I wouldn't be worrying about making the wrong choice.

It's appreciated -

- Steve

arcticscythe 07-08-2014 01:27 PM

[quote=brfatal;460617]245/40/17 or 255/40/17



The middle number in tire sizing is not sidewall in a measurement in millimeters, it's a ratio of the tire width. A 40 sidewall means the sidewall is 40% as tall as the tire is wide. I don't think any wheel would fair well with 40 mm of sidewall. That's 1.5 inch. That pretty much voids everything you said. :-/

There is no problem running a 245/40 or 255/40/17 on those wheels. 245s would be a quicker tire due to less weight and a slight gearing advantage due to smaller circumference. But 255/40s would offer better peak grip and heat resistance in hard driving.[/quote]

Thats what I get for working on too many things at the same time. Your absolutely right about it being 40 Percent of 245, 255. I was running some renders for work and transfered units.

Statement still stand that most guys like 245/40s on 17x9 rims. bigger and the sidewall starts getting squishy and smaller and the road starts getting rough.

brfatal 07-08-2014 05:45 PM

[quote=Pakal13;460649]Thanks arcticscythe & brfatal for the explanations helps a lot to understand why some go 1 way or the other.

And, yeah, should've realized that I was asking for info about stuff folks might have strong opinions about :) Just wish tires somewhat more affordable so I wouldn't be worrying about making the wrong choice.

It's appreciated -

- Steve[/quote]

2 things to note.

1. Tire compound has more to do with level of grip than tire width. A 225/45/17 R-Compound (see racing tires) will man handle a set of 255/40/17 budget summer tires. What you are expecting out of the tire should be the most important factor that goes into what decides what you get.

2. Feeding into the above, your tires will last you years (in most cases), don't be afraid to spend a little more on something better. An extra $10 per year of use for a good tire is well worth it over a lesser tire that's $30-40 cheaper.

Pakal13 07-08-2014 06:22 PM

[quote=brfatal;460729]2 things to note.

1. Tire compound has more to do with level of grip than tire width. A 225/45/17 R-Compound (see racing tires) will man handle a set of 255/40/17 budget summer tires. What you are expecting out of the tire should be the most important factor that goes into what decides what you get.

2. Feeding into the above, your tires will last you years (in most cases), don't be afraid to spend a little more on something better. An extra $10 per year of use for a good tire is well worth it over a lesser tire that's $30-40 cheaper.[/quote]

Makes good sense - yeah, deciding on which tires is the next step to worry over. Going with 245/40/17's, thinking of Michelin Pilot Super Sports or similar, since these will also be my summer daily's as well.

I appreciate the help & info - thanks!

man show 07-13-2014 10:02 AM

1 Attachment(s)
I have 17x9 +42 wheels on my 07 WRX and I went with 245/40/17 Dunlop Direzza ZIIs. I would have gone with 255s, but my fenders won't allow it.


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