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I’m a new member here on Rennlist, and I apologize for introducing myself with a question.
I recently got a set of 18" wheels from a friend and plan to install them on my 718 T. However, I’m struggling with the tire selection.
The factory sizes are 235/45-18 and 265/45-18, but I’ve noticed that many people seem to run 245/40-18 and 275/40-18 on this car. I’m curious—do they choose this setup simply for a wider selection of tires, or is there an actual benefit to using a 40 aspect ratio?
Some people say that a 40-series tire provides a more appropriate sidewall height for performance driving.
Right now, I’m deciding between these two options:
1. Bridgestone Potenza Sport – F: 235/45-18 & R: 265/45-18. $1,020.
2. Continental ExtremeContact Sport 02 – F: 245/40-18 & R: 275/40-18. $1,010.
I’d really appreciate your insights on this. Thanks in advance!
40 is a meaningless number for performance. It is the percentage measurement of the width of the tire and used to determine the sidewall height. You could have a 35 profile that is a taller sidewall than a 45 profile.
What matters is width and diameter. 245/40/18 is shorter than a 245/40/18, but it also wider. If you ran a 245/45/18 it would be taller and potentially rub, which is why someone would pick the 245/40/18 over it.
40 is a meaningless number for performance. It is the percentage measurement of the width of the tire and used to determine the sidewall height.
What I really want to ask is, the sidewall height of the 18" OEM tires (235/45-18 & 265/45-18) is noticeably taller compared to the 19" or 20" OEM sizes, right?
So, do people go with 245/40-18 and 275/40-18 specifically for a more responsive steering feel, or is it simply for cost-effectiveness and a wider tire selection? If it were you, which size would you prefer?
This fitment guide is one of the holy grails and should give you an idea of what options you have… both OEM and track focused.
I recently went down to 18s and wanted forged specifically… and decided on the VS-5RS in 235/45-18 and 265/45-18 to match as closely to OEM rolling diameter. This is how they look with the SPASM 20mm drop.
To answer your questions… yeah there’s absolutely more rubber on the sidewalls compared to 20” OEM. Wheels are lighter, ride comfort is improved, much less concerned with potholes or other nastiness… I run Michelin All Seasons cause I drive this daily, and even those can handle 1.4Gs in the turns and 150+MPH, and even with the added rubber she feels as sharp and agile as ever.
I wanted the smallest, lightest wheels I could get over my calipers and the most rubber possible. I considered 19s but I figured might as well go as far as I could.
And yes, I absolutely noticed an immediate difference in overall feel. Quicker to accelerate, esp out of corners… quicker to brake, just over feels like a noticeably lighter car, even if that much weight wasn’t shaved, it was all unsprung.
What I really want to ask is, the sidewall height of the 18" OEM tires (235/45-18 & 265/45-18) is noticeably taller compared to the 19" or 20" OEM sizes, right?
So, do people go with 245/40-18 and 275/40-18 specifically for a more responsive steering feel, or is it simply for cost-effectiveness and a wider tire selection? If it were you, which size would you prefer?
40 or 45, you're not feeling that. I'd pick the size that makes me fastest if the car is seeing track.
That generally means wider but not too wide for the rim width. A 245 I'd probably want on a 9in rim; 8.5 at skinniest. a 245 on a 8 wide rim is going to probably be much slower than even a 225 with the same compound. I also wouldn't want to mess up gear shifts on the track. Shrinking or increasing the diameter is going to change shift points on a track, and sometimes that'll create awkward spots to shift, which slows you down.
Price factors in. If i'm spending $200 more for another 10mm that's bad value imo. Certain sizes are common, and end up being easier to get and potentially cheaper.
For a tire for street use, OE sizing is good enough. Street doesn't need anything crazy as you're not utilizing the limits of the tire anyway (or at least you should not be). I'd be shopping on what fits, what is a good price, and what is easy to get.
This fitment guide is one of the holy grails and should give you an idea of what options you have… both OEM and track focused.
I recently went down to 18s and wanted forged specifically… and decided on the VS-5RS in 235/45-18 and 265/45-18 to match as closely to OEM rolling diameter. This is how they look with the SPASM 20mm drop.
To answer your questions… yeah there’s absolutely more rubber on the sidewalls compared to 20” OEM. Wheels are lighter, ride comfort is improved, much less concerned with potholes or other nastiness… I run Michelin All Seasons cause I drive this daily, and even those can handle 1.4Gs in the turns and 150+MPH, and even with the added rubber she feels as sharp and agile as ever.
I wanted the smallest, lightest wheels I could get over my calipers and the most rubber possible. I considered 19s but I figured might as well go as far as I could.
And yes, I absolutely noticed an immediate difference in overall feel. Quicker to accelerate, esp out of corners… quicker to brake, just over feels like a noticeably lighter car, even if that much weight wasn’t shaved, it was all unsprung.
Looks cool! Thanks for sharing your experience. I recently installed 18" wheels as well, and I’m really happy with the improved responsiveness.
40 or 45, you're not feeling that. I'd pick the size that makes me fastest if the car is seeing track.
That generally means wider but not too wide for the rim width. A 245 I'd probably want on a 9in rim; 8.5 at skinniest. a 245 on a 8 wide rim is going to probably be much slower than even a 225 with the same compound. I also wouldn't want to mess up gear shifts on the track. Shrinking or increasing the diameter is going to change shift points on a track, and sometimes that'll create awkward spots to shift, which slows you down.
Price factors in. If i'm spending $200 more for another 10mm that's bad value imo. Certain sizes are common, and end up being easier to get and potentially cheaper.
For a tire for street use, OE sizing is good enough. Street doesn't need anything crazy as you're not utilizing the limits of the tire anyway (or at least you should not be). I'd be shopping on what fits, what is a good price, and what is easy to get.
Thanks for your reply! I was away on a long trip to pick up the wheels from my friend, so my response is a bit late.
245/275 does feel slightly wide on the original 8J & 9J rims, so next time, I’ll try to get the factory 235/265 size next time if possible. That said, I’m still quite happy with the setup.
I’ll be heading to Streets of Willow soon to test it out as well. haha
This fitment guide is one of the holy grails and should give you an idea of what options you have… both OEM and track focused.
I recently went down to 18s and wanted forged specifically… and decided on the VS-5RS in 235/45-18 and 265/45-18 to match as closely to OEM rolling diameter. This is how they look with the SPASM 20mm drop.
To answer your questions… yeah there’s absolutely more rubber on the sidewalls compared to 20” OEM. Wheels are lighter, ride comfort is improved, much less concerned with potholes or other nastiness… I run Michelin All Seasons cause I drive this daily, and even those can handle 1.4Gs in the turns and 150+MPH, and even with the added rubber she feels as sharp and agile as ever.
I wanted the smallest, lightest wheels I could get over my calipers and the most rubber possible. I considered 19s but I figured might as well go as far as I could.
And yes, I absolutely noticed an immediate difference in overall feel. Quicker to accelerate, esp out of corners… quicker to brake, just over feels like a noticeably lighter car, even if that much weight wasn’t shaved, it was all unsprung.
I've been going back and forth on this...
can't decide between..
1. factory size + all seasons on the 18" tire
2. 245/40 and 275/40 on 18" with summer tires
3. buy 19"
I am not pulling 1.4g...more like 1g.....so i am leaning towards option 1 ..especially since the other poster said 8" might be too narrow for 245..
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18" Tires: 40 vs. 45 Aspect Ratio?
