# 275/40-18 safe for 18x8 wheel?



## max13b2 (Jul 24, 2007)

If rubbing were not an issue, would a 275/40-18 be safe for spirited/daily driving mounted on a 18x8in wheel? TIA!


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## Marcus_Aurelius (Mar 1, 2012)

Safe --- Yes, Ideal --- No

It'll be much safer than the trendy agressive stretched tire thing going on, but there will be a bit of pinch and a rounded patch.


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## BoostedLTH (Mar 19, 2014)

I would think 225-235 would be a much better fit. Maximum contact patch, and not a lot of ballooning. 


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## Chickenman35 (Jul 28, 2006)

BoostedLTH said:


> I would think 225-235 would be a much better fit. Maximum contact patch, and not a lot of ballooning.
> 
> 
> Sent from my iPhone using Tapatalk


You could push that to a 245/45x18 with no issues...but I wouldn't go further. Tire Rack specifies 8 - 9.5" for most 245/40 x18's... so 8" is at the bottom of the recommended range. Tire Rack uses the Tire manufacturers specs so you can be sure it is accurate.

For a 275/40x 18 tire a 9" to 11" rim is recommended. An 8" rim would pinch the tire too much as Max mentioned.

Tire Rack is an excellent source for checking what size rim a certain tire requires. Every single tire has full specs including recommended rim widths.

BTW: Ideal rim width for a Radial Tire is usually calculated at around 90 % of section width. Allowed range is usually between 80 to 95%. You can go lower than that in a Pinch ( Pun intended ), say 75%. Depends on sidewall height. ... but you do not want to go higher than 95% because the sidewall needs to be pulled in slightly to allow it to flex properly to absorb load shocks from pot holes and bumps in the Road. If the sidewall is straight up and down or pulled outwards, this places a LOT more load stress on the tire carcass. 

Edit: A slightly " pinched tire " ( up to 1/2" too small a minimum spec rim ) is safer than a slightly ballooned tire ( 1/2" too large maximum spec rim ). Aspect ration affects this as well. A 50 series or 45 series Tire will accept more of a " pinch " than a 40 series or shorter . The shorter the Aspect ratio, the more critical the matching of the ideal rim width becomes. 

The popular " Stretched " look drives Tire engineers crazy!! It may look cool, but the tire was never designed to be installed on wheels that are wider than the section width. 


Edit: Frackin' Audio advertisements are happening again!!! :banghead:


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## 20v master (May 7, 2009)

Chickenman35 said:


> The popular " Stretched " look drives Tire engineers crazy!!


If only I was a tire engineer, then I'd fit in!


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## BoostedLTH (Mar 19, 2014)

I too am more about looking aggressive as opposed to looking like a fat girl wearing Uggs. I'd take 18x11 with 275's over 18.10.5 with 205's any day. Haha I guess my being 20 years old and feeling this way means there is still hope that stance will fade out? Haha


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## max13b2 (Jul 24, 2007)

Bringing this back from the dead. 
This is actually for a different car than the TT, but the wealth of knowledge here far exceeds the "other" forums. 
My Infiniti G35 coupe has staggered tires from the factory, a 225/45-18 front and 245/45-18 rear on 18x8 all the way around. I want to go wider for a performance improvement and the fact that I need new rears anyway just adds to the reason behind this decision. 
I was going to go 245/40-18 front and either:
255/45-18 or 
275/40-18 rears. 
Given these 2 choices on the factory 18x8 wheel, what say the guru's here? The 275 are actually a better match on paper to the 245/40s than the 255s. Many people have gone both directions (with the same 245/40-18 fronts), but I wanted another opinion. Thanks guys!


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