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Discussion Starter · #1 ·
Need pros and cons from someone with 40 series sidewall on 20 inch wheels. Got myself some wiggle room with the coilovers. The car is my daily driver/back road auto-x. The wheels a razors from American muscle. 20x9/10. Offset is supposed to tuck wheels. Need opinions and pictures please. Considering front.265/40..rear. 295/40
 

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cons:
1) tire overall diameter will be larger and might not clear . . . you can check this on Tire Rack; look up a specific tire size, and check the "specs" tab for diameter. Do the same for your original tires. if the new size is more than about 1" larger outer diameter than your original tires, you might have a clearance problem
2) taller sidewall will have more flex, less crisp handling on the road track . . . yes it does make a difference, less sidewall is almost always "better" (up to the point where there is so little tire that the wheels are getting damaged all the time)

pros: taller sidewall will be more "comfortable" riding that shorter sidewall

be aware the 40 number is not an absolute height measurement, it is the "aspect ratio" which is the sidewall height as a percentage of the tread width. So a narrower 40 aspect ratio tire will be shorter (smaller overall diameter) than a wider tire with the same aspect ratio
 

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Discussion Starter · #4 · (Edited by Moderator)
cons:
1) tire overall diameter will be larger and might not clear . . . you can check this on Tire Rack; look up a specific tire size, and check the "specs" tab for diameter. Do the same for your original tires. if the new size is more than about 1" larger outer diameter than your original tires, you might have a clearance problem
2) taller sidewall will have more flex, less crisp handling on the road track . . . yes it does make a difference, less sidewall is almost always "better" (up to the point where there is so little tire that the wheels are getting damaged all the time)

pros: taller sidewall will be more "comfortable" riding that shorter sidewall

be aware the 40 number is not an absolute height measurement, it is the "aspect ratio" which is the sidewall height as a percentage of the tread width. So a narrower 40 aspect ratio tire will be shorter (smaller overall diameter) than a wider tire with the same aspect ratio

Alright. As for the front (20x9) I know it could hold a wide tire but how will a wide tire up front(265,275) translate to steering/handling?
 

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Lots of folks running anywhere from 275 to 305 fronts on these cars that feel the extra grip is worth any tramlining they get as a result. That said, IMO, a 275/40-20 is too tall for the front. A friend of mine has 275/35-20s on his 2014 and it fills the fenders nicely. A 255/40 might work but is a bit taller and I would definitely want to mount one up and check before buying. If that works, you could try the 275/40 on the back if you want the raked look. A 295/40 is more than 2" taller than stock and I wouldn't recommend it.
 

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Discussion Starter · #6 · (Edited by Moderator)
Lots of folks running anywhere from 275 to 305 fronts on these cars that feel the extra grip is worth any tramlining they get as a result. That said, IMO, a 275/40-20 is too tall for the front. A friend of mine has 275/35-20s on his 2014 and it fills the fenders nicely. A 255/40 might work but is a bit taller and I would definitely want to mount one up and check before buying. If that works, you could try the 275/40 on the back if you want the raked look. A 295/40 is more than 2" taller
How do u/others fill about (Courning wise) 275/35 on a 20x9 wheel. This set up would be for my s197.almost fully adjustable suspension. And it wont be raced. It's more a backroad auto-x/daily. I want the traction but also worried how a wide tire on front reacts to sharp fast turns
 

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You would have to check the manufacturer recommended wheel width for the specific tire you're looking at but I would bet most of them will have 9" as the minimum for a 275/35. You might sacrifice a bit of steering feel and turn in response vs. having the same tire on a wider wheel.
I have 275/35-19s on 9.5" wide wheels on my mostly street driven '05 GT. No notable weird handling traits at all. I wouldn't even consider running anything narrower. I'd actually like to step up to 295s on 10.5 or 11" wide wheels all around.
 

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I would not put 275 tire on 9" wheel. I am running 275 on 9.5 wheel which is the measuring width, and it seems OK to me but probably would be better on a 10" wheel. If you want to keep the 9" wheel on the front, I think 265 or 255 would be better.

If you check the tire specs on Tire Rack, look at the "recommended wheel rim width" ; for the best handling (like you want for road track) you want the wheel to be on the high end of that range, or at minimum the "measuring width".
 
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Discussion Starter · #9 ·
I've been using the tire calculator and I think I'm going with a 265/40 up front on the 20x9 and 295/35 on the rear 20x10. Keeps me in pretty close to the stock 245/55/18. Beside the new tires will have shorter side wall but keeping it almost same height/ect
 

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I've been using the tire calculator and I think I'm going with a 265/40 up front on the 20x9 and 295/35 on the rear 20x10. Keeps me in pretty close to the stock 245/55/18. Beside the new tires will have shorter side wall but keeping it almost same height/ect
Your stock tires were not 245/55-18s. That size was never used on the S197. Check the label in the driver's door jam for the size your car came with.
 

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^ I was wondering about that too, never heard of that size as a stock size. I haven't checked but I think the diameter on those would be a bit taller than the normal 27.2" and that might cause some confusion because you would be comparing diameters to a baseline that is wrong, meaning too big
 

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Discussion Starter · #12 ·
^ I was wondering about that too, never heard of that size as a stock size. I haven't checked but I think the diameter on those would be a bit taller than the normal 27.2" and that might cause some confusion because you would be comparing diameters to a baseline that is wrong, meaning too big
Okay then it was what was on the car when I bought it. Assuming stock. Glad yall caught that.
 
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