Tire size
 

I was wondering if going from a tire size 255-40-19 to a 245-40-19 would make any difference (10mm is only about 1/2" in total tread width)

Car is a 2007 A8L and factory size is 255-40-19

it makes a little bit of difference
 

in that it is not only tread width that you're looking at
the ratio or percentage of the tread width is 40 per cent.
so it will be 40% of 245 as opposed to 40% of 255 so
overall the sidewall of the tire will be narrower or shorter
than the tire with the tread width of 255. ln other
words, the sidewall is a ratio or percentage of the tread
width. finally, the engine will spin a tincy bit faster
because the overall diameter of the tire is smaller.



I was wondering if going from a tire size 255-40-19 to a 245-40-19 would make any difference (10mm is only about 1/2" in total tread width)

Car is a 2007 A8L and factory size is 255-40-19