widest tire possible for 2011 gt

moneymike6991 · Sep 21, 2010

I have a 2011 gt with the brembo brake package and I want to know what the widest tire I can put safely onto it. The stock tires are 255/40-19 and I won't be changing the rims. I'm hoping to get nitto nt555s or nt05s at 275/40-19.

JJs89lx · Sep 21, 2010

275 would be the best bet, but others have managed to put bigger. I have a 2010 and plan on going with a 19 x 10.5 in the rear for a 315 or so.

Rickmaan1 · Sep 21, 2010

You need to keep in mind that changing tire size the way you are considering will throw your speedo calibration off. Changing the tire diameter has the same effect as changing the rear end gears.

In order to put a wider tire on and keep the same overall diameter you have to go with a shorter aspect ratio. In your case that means going from a 40 to a 35, and the size closest to your stock diameter is 295/35. If your stock rims are 19x8.5" a 295 width tire won't work very well. A 285/35 is the next closest size, and still close enough that it shouldn't put the speedo off by too much, but a 285 is still just a bit more than a 8.5" rim can handle. You can physically mount it on the rim, but it probably won't look right with so much tire extending past the rim with such a short sidewall, and it certainly isn't ideal for tire performance or tread wear either.

You could get away with going to a 275/40 on that rim width (even that size has a minimum recommended rim width of 9"), but you'd need to have your pcm reflashed to correct the speedo.

I need to ask what your goals are in changing tire size, because going from a 255 to a 275 isn't going to make a huge difference, either in grip or visually, so it seems like a lot of trouble and $$ without much pay off.

moneymike6991 · Sep 21, 2010

Rickmaan1 said:
You need to keep in mind that changing tire size the way you are considering will throw your speedo calibration off. Changing the tire diameter has the same effect as changing the rear end gears.

In order to put a wider tire on and keep the same overall diameter you have to go with a shorter aspect ratio. In your case that means going from a 40 to a 35, and the size closest to your stock diameter is 295/35. If your stock rims are 19x8.5" a 295 width tire won't work very well. A 285/35 is the next closest size, and still close enough that it shouldn't put the speedo off by too much, but a 285 is still just a bit more than a 8.5" rim can handle. You can physically mount it on the rim, but it probably won't look right with so much tire extending past the rim with such a short sidewall, and it certainly isn't ideal for tire performance or tread wear either.

You could get away with going to a 275/40 on that rim width (even that size has a minimum recommended rim width of 9"), but you'd need to have your pcm reflashed to correct the speedo.

I need to ask what your goals are in changing tire size, because going from a 255 to a 275 isn't going to make a huge difference, either in grip or visually, so it seems like a lot of trouble and $$ without much pay off.

Thanks for both your comments. Rickmaan, changing my speedo isn't a big deal, I have a tuner. The brembo rims are 19"x9.0" and I read on some forums and JJs reply that the rims can take the 275s (and even 315s with the nitto nt555). The stock Pirelli's were good tires untill i put the bama race tune on it, now it spins tires through first and second and supposedly these tires only last around 6,000-8,000 miles (I have around 3700 miles now) and I think I'm going to need new summer tires by May or June and since I heard Nittos are good I'm going to get them. The Nittos I want dont come in 255s so I looked up the 275/40(and 35)-19s and there actually $100 less a tire then my stock Pirellis so I might as well get the best I can. I just wanted to know the widest tire that can fit on those rims so if I can get wider tires with out consequences I will.

Ltngdrvr · Sep 21, 2010

The wider tires will not help much as far as starting line traction unless you go with a drag radial on the rear and then they won't last much longer than the pirelli's.

moneymike6991 · Sep 21, 2010

Ltngdrvr said:
The wider tires will not help much as far as starting line traction unless you go with a drag radial on the rear and then they won't last much longer than the pirelli's.

I don't think I'm going to get a drag radial. Basically if the wider and way cheaper nitto nt05s get even a slight bit more traction and last around the same length of time as the pirellis it's worth it to me. I guess my new question is are the stock pirelli p zeros better then nitto nt05s and if the nittos are better can the 275s fit my rims.

Ltngdrvr · Sep 22, 2010

The 275's will fit very well, no problem on a 9" rim, you will be looking at a little bit of difference in height and will have a little bit of error in the speedo.

Both tires in question are very good.

moneymike6991 · Sep 22, 2010

Ltngdrvr said:
The 275's will fit very well, no problem on a 9" rim, you will be looking at a little bit of difference in height and will have a little bit of error in the speedo.

Both tires in question are very good.

The speedo is no problem seeing I can just retune it. I did like the Pirellis when I got the car but I think the bama race tune pushed them past their limits, I never spun tires through first and second with the stock tune. I just have a feeling that the nt05s will have alot more grip. I'm only 19 so seeing that i could have a way better performing tire for around $100 less a tire seems way too good to be true which is why I'm trying to get as many opinions on both tires as i can.

Rickmaan1 · Sep 22, 2010

The best thing you can do is check out tirerack.com. They list all the specs for the tires like revs per mile, diameter, traction rating, rim width requirements, even all available sizes for a particular brand and model of tire. You can also read reviews and check tireracks own ratings of each tire. IMO it's about the best research tool available for deciding what tire you want.

Having said that, street tires just aren't made for great drag launch traction on a street car, there are simply too many compromises in both the tire and car for that in order to make acceptable performance in other areas like cornering and ride. That's just a fact of life you'll have to learn to live with. Putting over 400 hp to a street tire (any street tire) will require restraint in the right foot, or you will drastically shorten the tread life, although that can be fun to do I have no doubt that Fords stock tune takes into account the available traction of the stock tires and probably limits lower rpm power to help the situation some. Your tuner took that out of the picture so you have to learn to compensate for it on your own with how you drive.

Maybe you could also try out a tune a little less aggressive than the race tune. A street performance tune may not spin the tires as easily as a race tune, since by definition a race tune is intended to maximize power for the best race times, leaving traction as the drivers problem to deal with.

moneymike6991 · Sep 22, 2010

I looked up reviews for the nt05 and almost all of them are great. I know that I'm limited by street tires but I want a street tire that will limit me less. I really don't care about noise and ride comfort so that's why I'm going to go with the nt05s. I understand that the street tune will help out with traction because its not anywhere near as aggressive as the race tune but I'm addicted to that tune and I don't think I could go back lol.

eas9898 · Sep 22, 2010

You will be going 20-30mm over spec for the 9" rim. I did that once on an older mustang, and did not like the feel of the handling afterward. I would check with someone who has actually done it before committing that kind of money to the experiment.

moneymike6991 · Sep 22, 2010

eas9898 said:
You will be going 20-30mm over spec for the 9" rim. I did that once on an older mustang, and did not like the feel of the handling afterward. I would check with someone who has actually done it before committing that kind of money to the experiment.

Thanks for the input, when I go to the tire shop I'll ask them about it. On Nittos site they say the approved rim for the 275s is 9-(9.5)-11, which I assume is width of the rim. Also Nittos supposedly run a little thinner so that may help. How did it change the handling of your car?

Five Oh Brian · Sep 23, 2010

275's will fit and work well on a 9" wide rim. Consider that all 2003-4 SVT Cobras came from the factory on 17x9 rims with 275/40/17 tires and the handling was excellent.

moneymike6991 · Sep 23, 2010

Really good point lol, thanks.

DougNuts · Sep 23, 2010

I ran 275/40/17 Nitto drag radials on an 8" wide rim. They looked, handled and wore normally, you'll be fine!

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