bobbyt01nc

Since I've never bought aftermarket rims and always kept factory size. Please explain the difference and benefits...

ex.
245/40/18

compared to

245/45/18

is the middle number the difference from the rim to outer edge of tire?
any benefits to a lower number

Say I bought new 18 inch rims - non staggered, am I better off with say 235's compared to 245's? 40 or 45? I know the price goes up, but does the life of the tire also go down as well the wider the tire is? life of tire would need to be important to me since this is my main vehicle

thanks!

NoS

I am no tire pro but I did have 19' for a few months with 245/40/35 tires instead of the usual 245/35/35. This was called Fat Setup. With a fat setup you get more tire which means better ride, more rim protection if you hit a pot hole, etc. As for life of tire I dont really know...

GQD_GS4

ok here's what the sizes mean. we'll use the example size of 245/40/18, which is the OEM size of the sc430's tires.

245 is how wide the tire is. this is the width of the contact patch on the ground. i think this is measured in mm.

40 is called the aspect ratio. this is the measurement of the inner edge of the tire to the outer edge of the tire, AKA the sidewall. the 40 is a percentage value. to find the size of the sidewall in mm, you use the tire width, which is 245 in this case and multiply by 0.40.... 245 x 0.40 = 98mm side wall height

last, the 18 is the size of the rim.

as a general rule, the bigger your rims get, the worse your ride quality becomes. its either looks or comfort, you must pick hehe. this is so because as the rim size increases, the sidewall size must decrease. otherwise, the tire would not fit on the car. for example, a 16 inch rim would use, say 225/60/16...while an 18 inch rim would use 245/40/18. because the sidewall on the 16 inch rim is taller, the ride quality is improved due to the fact that there's more rubber to absorb bumps and impacts on the road.

last, every tire has a certain tire wear value. this is regardless of tire width. if you look at a tire's sidewall, you will see a tire wear rating. 100 is the base score of this rating. if a tire's rating is 340, that means it lasted 3.4 times longer than the base tire.

everyone, please correct me if i'm wrong.

rominl

iTrader: (4)

that's correct. the 45series will have more sidewall compared to the 40 and the ride quality will be better (if the brand and model of tire stays the same).

but the 45 will be "overspec" meaning the overall diameter of the wheel will be larger than stock. there are certain downside like potential rubbing, etc...