Mustang GT 99-04 vs 05-09 painted aluminum wheels?

RED09GT

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I'd pick none of the above and get the GT500 wheels and run a 275/40 square setup.

Matching tires in the correct GT500 stagger are limited and the benefit of running a staggered setup in rear traction is not significant enough to me. I'd rather run a 255/45 all around on the GT500 wheels with a better tire than deal with the limited pairs in correct sizes.

Option #2 would certainly be my least favorite-I would always know that my fronts and rears don't match-okay for drag wheels that serve a purpose but not cool in this case.
Option 3 needs more info-how wide are the wheels?
 

Enfield

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Based on dimensions of replicas, I assume 17x9 front and 17x10.5 rear for the FR500's. As far as different width rims go, there are lots of cars that have run them; I'd be more concerned about vertical stagger than width. In my road racing days, most pure race cars ran wider rears regardless of horsepower; cars in classes that were more production-based ran square setups because that's the way they came from the factory. When it came time to fine-tune the handling, raising both rears was an easy cure for oversteer: put more weight on the front. That's why I'm focused on getting the same diameter front-to-rear more than width. Anyway, that's from my road-racing experience, but none of it was in 3-link Mustangs. There were lots of ways to tune the handling; I favored spring rates, shock rates, and sway bar torsion rates. None of those are very adjustable when running a car without coilovers or adjustable shocks/sway bars.
Not racing now - just trying to get a setup that turns and stops predictably. And yes, I think S197's look better with wider rear wheels/tires. YMMV, but give me reasons.
 

Norm Peterson

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S197 Mustangs are front-heavy, you need front grip just to get your cornering started, and MacStrut geometry is inherently geometry-challenged. All three represent understeer effects, so all three call for more front tire rather than less. After all, the best way to fix excessive understeer is by adding front grip - reducing front slip angles to be more precise - rather than throwing away rear grip (increasing rear slip angles). Improve the end of the car with the greater weakness first.

You have to remember that you're not working with a Porsche 911 (weight very heavily biased to the rear) or a Viper (big power/big torque and still with a more rearward-biased weight distribution than a S197 GT). Not even a S197 GT500 (meets the big power/big torque criterion).

Using the throttle to crutch insufficient front grip by loosining the tail is not the fast way through most corners.

Adding rake by increasing rear ride height does not change the car's front to rear weight distribution very much. The larger effect probably comes from dragging the rear geometric roll center upward, which does a couple of things (increases the rear percent of total lateral load transfer, and in particular increases how fast this load transfer happens (transient handling on turn-in/corner entry).

What I could find for the FR500 cars (from the 2009 FRPP catalog) was that the FR500S came with 18x9.5" wheels all around, and that the FR500C came with 18x10" wheels front and rear.


I've done a little datalogging with my '08 GT, mostly on road courses but a little on the street. These pics were taken with 18x11 wheels and 285/35-18 MPSS tires on all four corners. The readings are peak g's, which run 15% - 20% higher than the sustained g's through the same and similar corners. I'm pretty sure the car was good for more than I was. Koni yellows, Strano sta-bars, aftermarket LCAs (not poly/poly), and about -2° camber rounds out the mods. Stock springs. Car turned in very nicely on lift-throttle.

1.30g.jpg

15-2-4 T'bolt T12.jpg

And a brief clip from a track session. It really felt like a brisk but relaxing drive out in the country (minus the risk of official-capacity roadside interviews).



I ran comparative tests on one of my unofficial "test loops", running the above wheel & tire combination against 265/40-18 MPSS on 18x9.5" wheels all around. Tire tread widths were listed as identical at (IIRC) 10.2". The car was noticeably more composed and less slide-y with the 285/11" combination at 0.9x lat-g than the 265/9.5 combination did at nearly a whole tenth of a g less.

It's not that the 265 setup was bad, just that the 285 setup was that much better. A 265 front / 285 rear combo would have understeered enough more to clearly feel.


Norm
 
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Enfield

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Well, that's a lot of reasons to go square. Budget suggests just getting two more AM 18x10 Bullitts, but AM says "rear only" for those. Pretty sure I remember reading that 3mm spacers make it possible to use the AM deep-dish Bullitt up front. Any confirmation on that?
Been able to take brisk but relaxing drives through the country [we live in the country] the past few days. With new orange Koni's and half-poly bushings, the ride is very well planted and right on the verge of jiggly. Any suggestions on which 40 or 45 tires might have the softest ride? Again, no track days ahead, and no need for all-season tires, either. Default would be General UHP summer RS in 275.
Thanks to all,
Enfield
 

Norm Peterson

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AM and most other wheel suppliers are going to err on the side of conservatism, at least partly because they can't control what tire sizes somebody might choose to use.

I see five possible answers.

18x9.5 GT500 wheels (ET+45) with 275/40 tires (spacers possibly needed)
18x10 AM wheels (ET+45) with 275/40 tires (spacers likely required)
18x9.5 GT500 wheels (ET+45) with 265/40 tires
18x10 AM wheels (ET+45) with 265/40 tires
18x9.5 GT500 wheels (ET+45) with 255/45 tires (OE GT500 front setup, total no-brainer)

The combinations with 275/40 tires may or may not need thin spacers, which may or may not then require longer wheel studs. Note that it is possible to make your own spacers from material thinner than any of the commercially available spacers. I'm not sure if anybody's OE wheel studs can use 3 mm spacers and still get one full diameter's worth of thread engagement.

The 265/40 combinations won't need spacers but are a little shorter than the 275/40 combinations.


If it matters, I've run GT500 wheels with both 255/45-18 and 265/40-18 tires.


Norm
 

Pentalab

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Well, that's a lot of reasons to go square. Budget suggests just getting two more AM 18x10 Bullitts, but AM says "rear only" for those. Pretty sure I remember reading that 3mm spacers make it possible to use the AM deep-dish Bullitt up front. Any confirmation on that?
Been able to take brisk but relaxing drives through the country [we live in the country] the past few days. With new orange Koni's and half-poly bushings, the ride is very well planted and right on the verge of jiggly. Any suggestions on which 40 or 45 tires might have the softest ride? Again, no track days ahead, and no need for all-season tires, either. Default would be General UHP summer RS in 275.
Thanks to all,
Enfield

I would get 2 x more AM 18 x 10 Bullitts. (45mm ET) Install 3mm spacers for the fronts. On oem front studs, WITH the 3mm spacer, there is bucket loads of thread left over. The oem front studs are slightly longer than the oem rear studs. Even with 3mm spacers on the front of my 2010, the amount of excess thread on the front studs is still more than the oem rear studs.... with no rear spacer. With the 3mm front spacers used, the effective ET is now 42mm.

Then use either 275-40-18's on all 4 x corners.... or 285-40-18's on all 4 x corners. The difference in actual tread width is exactly 1/4" wider with the 285's.
 

Enfield

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American Muscle no longer carries the 18x10 Bullitt in Gloss Black w/machined lip; in fact, their 18x9 version is on back order. However, the American Racing Torq-Thrust A105 #322-AR105M8166B seems to be a dead ringer, and it can be had with 45mm offset. 275/40 looks to be the right choice here.
Anyone have experience with this wheel? I doubt there would ever be a need to go with Brembos, as the stock brakes will chirp the fronts now - probably due to diameter mismatch of 27.2 vs 28.5.
Will be nice to get rid of the rake and find some front grip:IMG_1489.JPG
 

dark steed

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I’m running the AM 18x10 GT4 (caught them on sale for $89/ea) wheels square with no spacers. It said “rear only” but they cleared fine, close but no rub.
Also running 275/40 tires.
09567bf1aab27fdf647c3861f76f520f.jpg



Sent from my iPhone using Tapatalk
 

Norm Peterson

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I doubt there would ever be a need to go with Brembos
With appropriate pads and brake fluid, Base-level GT brakes can handle entry-level track driving, maybe a bit higher depending on how hard the track is on brakes. But base front brakes will go through pads faster than with Brembos.


Norm
 

Enfield

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Managed to score a couple of GT 500 rims in decent shape off CL. Anyone know if the rim offered by various aftermarket vendors is also forged? My two are stamped 7R3V-1007-AC; the aftermarket ones are listed as "SKU : M-1007-S1895". Same?
tia, Enfield
 

Norm Peterson

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M-1007-S1895 is a Ford Performance number, if that helps any.

2009 FRPP Catalog said:
M-1007-S1895* ➀
Fits 2005-09 Mustang GT and
the 2007-09 SVT Mustang
5-lug, 4.5" bolt circle
7.125" backspacing
45 mm offset
18" x 9.5" wide
Includes SVT center cap
Same as production 2007-08 SVT Mustang
Fits M-2300-S brake kit

I've had a set of those 1007-1895 wheels for at least 10 years. They've seen year-round use and some track time (as seen in my avatar pic), but they've since been bumped out of normal track duty by a set of 18x11 wheels.


Norm
 
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