08 Coupe S here....replacing OEM 19" Tires with new ones.

I see all over the board these sizes posted for OEM replacement:
Front: 245/40/19 OR 245/35/19
Rear: 275/35/19

Seems the consensus on the rear is 275/35/19.
On the fronts, I see lots of postings about either of the different sizes, but no discussion of why you would go with a 40 or 35.

So - which is better and why?

Note my car is on BC Coilovers and dropped about 2". Is the drop what makes the difference for people? Does one size look better/perform better than another?

I admit fully I don't know crap about tires.

Thanks

 

For the fronts:

40 means you'll have a tire sidewall of 0.4*245 = 98 mm's
35 means you'll have a tire sidewall of 0.35*245 = 85.75 mm's

OEM (225/45/19) sidewall is 0.45*225 = 101.25 mm's

You want to try and stay as close to the OEM sidewall height as possible, that's why everyone runs 245/40/19

Another thing to keep in mind is, going with a shorter sidewall means your ride will be sitting even lower.

 

While Sam is technically correct, it is easier just to look at or calculate the total height of the tire. Here is a link that should help. Note there is an attachment you can download and stare at: Tire Size Table.

 

245/40-19 front 275/35-19 rear most common fit.