New To Stangnet! Got Some ??'s

Michael Rush

New Member
Jan 11, 2017
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Sorry this is going to sound confusing and round about. So I recently acquired rims with tires on them. They are 17x9s for the front and 18x9s for the back. unfortunately the 17x9s have the wrong size tire and are dry rotted but the 18s are good to go. So I was planning on just putting the tires I have on. The hard part is, they are 245/45r17s. The 18x9s I have for the back have 245/40r18s. Will having a bigger side will (45 in front 40 in back) make a difference. I lowered about 2 inches.
 
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Sorry this is going to sound confusing and round about. So I recently acquired rims with tires on them. They are 17x9s for the front and 18x9s for the back. unfortunately the 17x9s have the wrong size tire and are dry rotted but the 18s are good to go. So I was planning on just putting the tires I have on. The hard part is, they are 245/45r17s. The 18x9s I have for the back have 245/40r18s. Will having a bigger side will (45 in front 40 in back) make a difference. I lowered about 2 inches.
I'll post a more detailed answer in a few hours after I've had some sleep (just got home from an 11-hour shift with an hour commute on each end of it), but the short answer is "no, it won't hurt anything".
 
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Alright, more detailed answer time!
Modern radial tire sizes are read as such:
Tire type, tread width, aspect ratio, speed rating (optional), and then rim size.

Aspect ratio is the distance from the rim of the wheel to the outside of the tread, expressed as a percentage of the tread width (which is measured in millimeters).

This means on your 245/40/18s, there is 98mm between the ground and the rim, and on your 245/45/17, there is 110mm between the rim and the ground. 12mm is less than a half inch, meaning your front tires will be just under an inch taller between the rim and the tread overall, but with the wheel being an inch smaller, they're actually going to be fairly equal in outside diameter. It might look a little odd, but it's not going to hurt anything.
 
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Alright, more detailed answer time!
Modern radial tire sizes are read as such:
Tire type, tread width, aspect ratio, speed rating (optional), and then rim size.

Aspect ratio is the distance from the rim of the wheel to the outside of the tread, expressed as a percentage of the tread width (which is measured in millimeters).

This means on your 245/40/18s, there is 98mm between the ground and the rim, and on your 245/45/17, there is 110mm between the rim and the ground. 12mm is less than a half inch, meaning your front tires will be just under an inch taller between the rim and the tread overall, but with the wheel being an inch smaller, they're actually going to be fairly equal in outside diameter. It might look a little odd, but it's not going to hurt anything.

That's what I was thinking. The look may bug me, so I'll just get proper new front tires . Thanks!