tire upsizing
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Joined: Mar 2001
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a few questions from a tire novice:
1) Why do people put different size tires on their stock rims? Example: I read about someone putting 245/40/17 tires on the stock 17" rims. What are the implications/benefits/fitting issues? The one part I can figure out myself is that you change the overall diameter by a third of an inch; that obviously screws with your speedo/odo. It seems you shouldn't be able to change tire sizes without changing rims, but I guess there's a little play in fitting on a given rim. I'm in need of new tires, and will get the stock 235/45/17 tires by default, unless the answer enlightens me.
2) What is this characterisic of tire performance known as "turn-in"?
thanks.
1) Why do people put different size tires on their stock rims? Example: I read about someone putting 245/40/17 tires on the stock 17" rims. What are the implications/benefits/fitting issues? The one part I can figure out myself is that you change the overall diameter by a third of an inch; that obviously screws with your speedo/odo. It seems you shouldn't be able to change tire sizes without changing rims, but I guess there's a little play in fitting on a given rim. I'm in need of new tires, and will get the stock 235/45/17 tires by default, unless the answer enlightens me.
2) What is this characterisic of tire performance known as "turn-in"?
thanks.
Sometimes you can put wider tires on the same rims, and the differences are in handling, and cosmetics.
Re: handling - generally wider rubber grips better.
Re: cosmetics - wider rubber can look better, and a bigger circumference can make the tire fill the wheel well better.
245/40/17 is actually 2.4% SMALLER in circumference than 235/45/17 according to my spreadsheet, so I'd say this will LOOK WORSE because of a bigger wheel gap.
Some people go for a bigger overall diameter, e.g., 245/45 because that fills the wheel a bit better. That size would be just 1.4% bigger circumference.
These percentages show what the speedo/odo would be off... and a 2% diff is just 1.2mph at 60, so it's nothing serious.
Hope that helps!
FYI, I got 235/40/18s on the front, and they're almost the same size as the stock 235/45/17s. I now wish I'd gotten 245/40/18s though so they'd fill out the wheel well a bit more. Nothing major though, I feel my wheels/tires definitely look better than stock, and with my much wider rims/tires on the back (265/35/18s on 9.5" wide rims) it fills the width of the wheel well really nicely.
Re: handling - generally wider rubber grips better.
Re: cosmetics - wider rubber can look better, and a bigger circumference can make the tire fill the wheel well better.
245/40/17 is actually 2.4% SMALLER in circumference than 235/45/17 according to my spreadsheet, so I'd say this will LOOK WORSE because of a bigger wheel gap.
Some people go for a bigger overall diameter, e.g., 245/45 because that fills the wheel a bit better. That size would be just 1.4% bigger circumference.
These percentages show what the speedo/odo would be off... and a 2% diff is just 1.2mph at 60, so it's nothing serious.
Hope that helps!
FYI, I got 235/40/18s on the front, and they're almost the same size as the stock 235/45/17s. I now wish I'd gotten 245/40/18s though so they'd fill out the wheel well a bit more. Nothing major though, I feel my wheels/tires definitely look better than stock, and with my much wider rims/tires on the back (265/35/18s on 9.5" wide rims) it fills the width of the wheel well really nicely.
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