Hinojosa

Last week one of my front tires died so i had to replace it, replaced both fron tires with what it had before, 245/45/18 and started checking my tires.
I bought my mustang used 6 months ago and i just realized that im running 245/45/18(toyo proxes 4) in the front and 235/55/18 bfgoodrich gforceTA in the back, isnt this wrong? shouldn't the wider tires be in the back? should i rotate them? the rear end slips a lot but i tough it was normal in a mustang, plus i go hard on the gas in the corners on purpose to drift a little.

Rylay

Well...you should rotate them whenever they start to "cheesegrade" (where the treads are smooth one way on the fronts but not the other way, like a cheesegrader) which is every 7-10k miles for me but I would definitely put the wider ones on the back. And maybe look for a matching set so you can rotate them regularly to avoid uneven tread wear.

Tygr1

Your best pair of tires should go on the rear.

SpartaPerformance

Being you have narrower tires on the rear I'd rotate them so the 235's are on front or if they're in bad condition just replace them if budget permits. Tygr1 is correct, best tires always go on rear even on FWD cars.

WildAzCat

Ditto!

Hinojosa

all of the tires are in their last hours, so i plan on keeping the 245s in the front but im not sure if i should go 245 55, 255 45 or 255 55 in the back, since the rear tires i have right now are a bit taller than the front ones

Art161

The bigger tires should be on the rear. As was previously stated, though, the tires with more tread should be on the rear. So you really need to make both happen if you can afford it.

The reason you want equal or more tread on the rear is if you encounter slippery conditions, you don't want the rear tires to break loose first. You might wind up doing a 180. If the front tires lose traction, you have a more controllable skid.

Nuke

Definitely wider in the back.