Finally new tires

[Smokievol]

I have been going back and forth on what tires to put on the GT500 forged rims from 2010, which are 19x9.5. I have 2008 GT with a TVS.
So I can rotate side to side I went with the Nitto 555 G2. All around capable street tire.
285/35 on the rear, wanted the most tread width that will be the right fit for the wheels.

I am looking at either 275/35 on the front or 265/35.
The 275/35 keep the diameters closer together, fronts at 26.57 and rear at 26.89
The 265/35 would be 26.34 and rear at 26.89....

I guess the questions are, should I just go 275/35 squared, what's the real difference 285 VS 275 in width...not much. Or 275/40 squared?
Is the diameter matching that important?

I know I want more meat upfront compared to the original tire size of 255/40 and I wanted the largest for the wheels out back....don't want to use spacers.

Any feedback??

 

[Norm Peterson]

I suggest spending some time looking through the 'SPECS' pages for various tires over on the Tire Rack site. That's where you'll find actual tire section width, tread width, diameter, and revolutions per mile information.

A general guideline for diameter matching for cars that have ABS is to keep the difference between front and rear revs/mile within 3% of OE. IOW, if the OE setup is 'square' you could go with rear tires 3% taller than the front tires (or 3% fewer revs/mile). And if there was some OE tire size stagger going on, you could vary ±3% either way from that.


Norm

 

[JJ427R]

2010 Roush I have a bit larger 20" Roush wheels with the Mickey Thompson Street Comp 275/35 squared and I'm very happy with it. I wanted squared so I could rotate tires as well. Mine is also tracked at HPDE track days and that setup has worked well for me as I drive my car to the track.

My 2018 GT PP1 has the 19" factory wheel and Michelins with a 255 on front and 275 on rear. I ran that at Road America last July and was very impressed with that setup as well. The Michelins do have some great grip. They are directional tire so no rotating, plus up there in price.

 

[Smokievol]

The other question is why did Ford go with a staggered tires line up of 255 fronts and 285 rears. Checking out what they are selling today and from the 2010 GT500 launch, that's been their go to set up in most cases for their 19 inch wheel.

 

[Smokievol]

Doing the math Norm, either of my configurations will work then. The 18 inch original tire was a 235/50 at 27.28 inch diameter. TireSize.com has been my friend these past days. Some of this is outside of my league, don't want any rubbing and want a planted and controlled car for the street and once a year trip to VIR.

 

[Norm Peterson]

They are directional tire so no rotating

Nope.

Check the sidewalls for "OUTSIDE", which means that regardless of what the tread pattern looks like, the outside is the outside regardless of forward rotation direction.

This is as opposed to a directional arrow which specifically denotes the forward direction of rotation. Zoom in on this picture at just above the 9:00 position and you'll see it. Go check your own tires for your own verification.

Don't take it too personal, I used to get paid decent money to find errors like this in the reports people wrote, and it still comes naturally to go looking for proof.


Norm

 

[Norm Peterson]

Doing the math Norm, either of my configurations will work then. The 18 inch original tire was a 235/50 at 27.28 inch diameter. TireSize.com has been my friend these past days. Some of this is outside of my league, don't want any rubbing and want a planted and controlled car for the street and once a year trip to VIR.

Sounds good, then.

275/35-19's up front on 9.5" wide wheels shouldn't rub as long as the wheel offset is properly thought out - they're not all that much bigger than the 265/40-18's that I'm running as a "street setup" on 18x9.5, +45 offset GT500 wheels.

That's not the setup in my sig pic, which is 285/35's on 18x11's.


Norm

 

[Smokievol]

+ 45 for these wheels also, 275 are out for about a week, coming from Arizona.....prices should be coming down with the drop in oil prices....

 

[Gabe]

I'd just square it up with a nice 285/35/19 tire all around

 

[Norm Peterson]

285/35 is do-able on 9.5's, but 275/35's on 9.5's will likely "feel" better subjectively. In street driving, you're never up where the difference in 275 vs 285 grip (slip angles @ grip, actually) would matter.


Norm

 

[JJ427R]

Check the sidewalls for "OUTSIDE", which means that regardless of what the tread pattern looks like, the outside is the outside regardless of forward rotation direction.

My mistake on that, guess I was thinking of my ET Streets, could swear the Michelins were directional as well. I can admit you are right for once.

 

[Juice]

Now that I have mounted some of the so called ideal rims and tires, I have to say the official sizing guide is on the very conservartive side.
275/40/18 on 9" wheels is the perfect fit.
I mounted 275/675/19 slicks on 10" wheels. Tire is too small. The wheel lips are sticking out past the tire. Had a monted wheel fall on the finished side and scratched my brand new wheel before it was ever mounted on the car. 285s are going on these 10" wheels next. And.even those maybe too small.
My experience, your results may vary.

 

[Gabe]

Depending on the tire model (some run wider than others), anything from a 275 to a 295 can be a perfect fit on a 10"-wide wheel.
I've had a pair of 275/40/19 front tires on 19x10 wheels and the fitment was perfect. Sidewall completely square, no sign in sight of any bulging or stretching.

 

[MrAwesome987]

I have a 295 on my 10 in wheels and they look pretty good. This is the best picture I have right now. 295's square.

 

[Norm Peterson]

Now that I have mounted some of the so called ideal rims and tires, I have to say the official sizing guide is on the very conservartive side.
275/40/18 on 9" wheels is the perfect fit.
I mounted 275/675/19 slicks on 10" wheels. Tire is too small. The wheel lips are sticking out past the tire. Had a monted wheel fall on the finished side and scratched my brand new wheel before it was ever mounted on the car.

You do have to be somewhat more careful with wheels that are relatively wide for the tires fitted to them when either handling them "loose" or driving on them. After a while, it becomes second nature to be careful (full disclosure - I've been setting up my own seriously-intended tire to wheel sizings this way since the early 1970's, long before the term 'stretched' was ever applied to car tires).

As wheel width goes out toward "max recommended", there are some cornering performance benefits to be had . . . though you do have to get past conventional appearance preferences that don't understand the benefits coming from mild amounts of "stretch". I will say here that whatever constitutes a "perfect fit" for the average driver's street driving is not going to be the "perfect fit" for the same size tire being used by a track day enthusiast out on the track.


I have a little actual testing to support my opinion here. I have 265/40's on 18x9.5 wheels as a "street set" for my '08 GT, and a set of 285/35's on 18x11's nominally for its track time (though I do drive this setup on the street as well). In almost back-to-back test drives through the same unofficial "test loop", the mildly stretched 285's were more composed at a little over 0.9g cornering than the 265's were at only a little over 0.8g. That's with the same suspension tuning down to the shock settings, the same tire model (MPSS), and the two PSS sizes even share the same advertised tread width.

Max-recommended wins out over measuring width, and the min-recommended or "meaty" fitments are best left for the Cars & Coffee crowd.


Norm

 

[Juice]

I am not dealing with "careful handling" of lose wheels. I need to be able to stack lose wheels 4 high in my van for transport. Without worrying about wheel damage.
Plus it reminds me of the ricer "camber clan" look. Ewwwww.

 

[Norm Peterson]

Like I said, you have to get past any personal appearance issues. Once you do, it starts to look right because as "insider knowledge" you know they look right for what you're using them for. Doesn't matter what those who don't understand think, that's their problem.

I keep the square-ish or round cardboards that ship with new wheels specifically to separate wheels from touching each other whether the rims actually touch or don't quite. Even when they're stacked in the garage.


Norm

 

[Juice]

I also did not like how the 275 slicks on 10" wheels wore. Pressures were set with temp gun so inflation was correct for track use. And all 4 wore the same funky way, so it was not due to not enough camber. I have no idea or theory as to why. The nt01s wore just about perfect with the same suspension.

 

[Norm Peterson]

I also did not like how the 275 slicks on 10" wheels wore. Pressures were set with temp gun so inflation was correct for track use. And all 4 wore the same funky way, so it was not due to not enough camber. I have no idea or theory as to why. The nt01s wore just about perfect with the same suspension.

How were those slicks wearing? And whose slicks were they? There was one tire (I'm not trusting my memory which one it was) that there was considerable controversy over what the proper inflation pressures really were.

Here's my max-recommended 285's after more than a few track days (and a bunch of street miles). Around -1.9° camber when fitted up front.




Norm

 

[Juice]

They were Pirelli Ferrari Challenge used slicks with 3/4 or better tread when I got them. ($125 ea) DH compound IIRC
Let me try to explain without a picture. Basicall looking at the tires the kinda went egg shaped. Not like a belt shifted or broke. They still rode vibration free.
So these have 5 wear dots across the tire. Started with 4 and a half dots evenly across the tires.
Outside I had 2 dots left, next moving in, 3 and a half dot, further in, bearly 2 dots. And finally, inside edge had 4 dots left. Make sense? If not, I can get a pic.