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[Norm Peterson]

Depends on the tracks you'll be running and your car's gearing . . . you probably aren't going to want to have to use 6th gear. I'm assuming your car has a manual transmission here.

Shorter tires will lower your car's CG without adversely affecting suspension geometry, and if some of the "shortness" comes from a little less sidewall height, you can make gains in things like turn-in response and general steering precision.

I'm running 25.9" tall tires, where OE was 27", maybe 27.2". I wish I had another thousand rpm to play with (I've only got the 4.6L 3-valve motor), but I won't be going back to 27" even for the street driving part.


Norm

 

[Zerobar78]

I haven't run my S500 on the RT615-K but had run them on my new edge for numerous events. They are a solid tire that handled the heat and abuse well in my opinion, they remained sticky until they ran completely out of tread. They're nowhere near the fastest tire anymore but they do everything well.

I had a short run with the Star Specs and really liked them, found them quite noisy as they wore down but they also withstood the abuse well for the 2 events I ran them.

 

[SteveW]

I can understand the desire try to maintain close to stock diameter but a 295 street tire is too much tire for a 10" wheel, IMO. I think you'd be better off with a 275 or 285 for track use.

Nitto NT05 and Bridgestone RE-11A both come on a 275/40/18 which isn't too far off stock diameter. Another good option for 18 and HPDE is Dunlop Direzza ZII SS but it is in a 275/35/18.

19s have a few more options and much closer to stock diameters.

 

[Zerobar78]

I can understand the desire try to maintain close to stock diameter but a 295 street tire is too much tire for a 10" wheel, IMO. I think you'd be better off with a 275 or 285 for track use.

Nitto NT05 and Bridgestone RE-11A both come on a 275/40/18 which isn't too far off stock diameter. Another good option for 18 and HPDE is Dunlop Direzza ZII SS but it is in a 275/35/18.

19s have a few more options and much closer to stock diameters.

I spent a season in an S2000, we squeezed a 245 on a 7in front rim and a 275 on the rear 8.5in rim and it worked quite well. This was a track only setup of course.

 

[apex15stangPP]

The grip level of the 615K and NT-05 is pretty low compared to most other tires in the UHP market, they do last awhile but you will be scarficing speed. The Hankook RS-3 and RE-71R and Z-2 are prolly the best.

 

[c_reber]

I agree with Zerobar78, a 295 on a 10" should be fine. I have 295/30/20 Michelin PSS on 20x10 wheels. No bulge at all. Near perfect fit.

Granted, some of these extreme performance tires might be a little be wider (even at the same 295 size) than the MPSS.

I can comment on the NT05's on my old car and they were just ok, wear was good, but ultimate grip was not up there. But for trackdays, that might be what you're looking for.

 

[Norm Peterson]

I agree with Zerobar78, a 295 on a 10" should be fine. I have 295/30/20 Michelin PSS on 20x10 wheels. No bulge at all. Near perfect fit.

It'll work . . .

But it won't be optimal, not by a long shot if you're going to be doing the track thing more than rarely/occasionally. It's a minimum-width fitment even for street duty.

Visual appearance is for car shows and such, and is a terrible way to evaluate tire to wheel fitments for track duty.


Norm

 

[SteveW]

It'll work . . .

But it won't be optimal, not by a long shot if you're going to be doing the track thing more than rarely/occasionally. It's a minimum-width fitment even for street duty.

Visual appearance is for car shows and such, and is a terrible way to evaluate tire to wheel fitments for track duty.


Norm

Try to get a setup where rim width = tread width or round up half in. The Falkens in this thread have a 10.9" tread width and would be much better on an 11" wheel.

 

[c_reber]

It'll work . . .

But it won't be optimal, not by a long shot if you're going to be doing the track thing more than rarely/occasionally. It's a minimum-width fitment even for street duty.

Visual appearance is for car shows and such, and is a terrible way to evaluate tire to wheel fitments for track duty.


Norm

Sorry, I didn't mean to "steer" the OP in the wrong direction. :frusty::frusty: I guess I will head off to a car show now

Norm, I'm sure you probably have a lot more track experience than me (especially with this car, I haven't even had my 2016 out on track yet), and I respect your knowledge on the subject. I'd be interested in more info on the setup you're running both wheel/tire and suspension also.

Do you think the factory 275/40/19 that comes on the 9.5" wide GTPP wheels is too wide? Since 275mm = 10.8 inches.

 

[SteveW]

Do you think the factory 275/40/19 that comes on the 9.5" wide GTPP wheels is too wide? Since 275mm = 10.8 inches.

You can't go by just the idea that it's a 275 so therefore that equates to 10.8" for all tires. The tread width for the Pirelli PZero in 275/40/19 is 7.7" so if anything, it is stretched out on the rim. You have to look up the actual specs for the tire you are considering and how it will fit on the wheel you're planning to mount it on.

 

[Norm Peterson]

Sorry, I didn't mean to "steer" the OP in the wrong direction. :frusty::frusty: I guess I will head off to a car show now

Norm, I'm sure you probably have a lot more track experience than me (especially with this car, I haven't even had my 2016 out on track yet), and I respect your knowledge on the subject. I'd be interested in more info on the setup you're running both wheel/tire and suspension also.

Let's just say I never met a non-residential corner I didn't like, or at least none that I didn't feel a challenge from . . . and having a wife all these years who doesn't mind a slightly firm ride has never hurt either.


My track tires are MPSS in 285/35-18 on max-recommended width wheels (18x11). On all four corners. My street set is currently 265/40-18's on 18x9.5 GT500 wheels. Used to be 255/45-18's. In 2008, Ford put 235/50's on 18x8.5" wheels - a max-recommended-width fitment as OE (imagine that!).

Strano's sta-bars (35mm front/middle hole, 22mm rear/full firm), Koni yellows (adjusted to suit whichever of about three different situations). UMI (rod-ended) front endlinks. Steeda HD strut mounts.

Currie rear LCAs (nonmetal spherical/DIY-modified poly ends), a DIY-stiffened OE PHB, and about -2° camber up front.

I'm partway through some suspension and brake upgrades at the moment.

Do you think the factory 275/40/19 that comes on the 9.5" wide GTPP wheels is too wide? Since 275mm = 10.8 inches.

A 9.5" wide wheel is the "measuring width" for 275/40 (I think in any diameter). Meaning that it favors neither handling nor ride quality over the other making it a good choice for most street driving situations and up to occasional track use. Visually, you'd be comparing that 10.8" tire section width against about 9.5" plus two wheel flange thicknesses (about 1" total), which leaves less than 3/16" of the tire peeking outside the extreme width of the wheel (that's on both the inside and the outside). That won't look like much, but if you put that same 275/40 tire on a 10.5" wide wheel (a legit fitment), the tire could be a quarter inch or so narrower than the overall width of the wheel (11.2" vs 11.5"). There are noticeable differences in response and softness over rough pavement when the sidewall shape looks more like |_______| or like a mild version of \_______/ than (_______). Best I can do with ASCII extended character sets.

FWIW, 9.5" is still a little narrower than I'd prefer for 275/40's on my car, and I think I'd prefer 10" for the 265/40's that I do have. Just not badly enough to buy yet another set of wheels for the tires that aren't expected to see any track time.


Norm

 

[Brent Dalton]

I think a 295/40/18 tire is a good choice for a 10in wide rim in generally. As SteveW said, not all tires are created equal. Hoosier tire recommends a 9.5-11in rim for their 295/40/18's for example(and that's what I run on the track). If you are running HPDE's, going to a smaller OD tire is probably fine. You run out of gear at around 140mph with a 25.5 OD tire if you have the 3.73 rearend. That may be fine. I run time trials in my car. To be competitive, I generally need to the car to be able to reach 150mph or pretty close to. You may not need that top speed at smaller tracks though(and if you are running the car competitively). Will less sidewall give you a crisper turn in? Sure. I've never noticed enough of a change for it to be significant, one way or the other though going from a 30 to a 40 or vice versa(and I've done it several times in other cars)

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