FR500 Wheels and my Gen III Coupe

[Dave Tabor]

Following Logan's most excellent post on wheel/tire fitments on the Gen III Coupe, here is some info on what I've been running for the last 3 years and 12,000 miles.

FR500 'style' front: https://www.americanmuscle.com/fr500wheels.html
FR500 'style' rear: https://www.americanmuscle.com/musta...nly-28099.html

The backspacing on these is listed as 6.2"- no good on the Coupe. My brain only works in backspacing and this is key to avoid the 'usual' rear tire/frame rub issue.

I ran 2" hubcentric spacers in the rear and occasionally 1" spacers in the front. The attached pics are with 2" rear spacers only.

Tires are Nitto NT01 275-35-18 front and 305-35-18 rear- no rubbing and no issues.

I'm running 700lb front and 500lb rear springs, 4" ride height all around.
Front sway bar one hole away from full stiff (can't get to the last hole) and no rear sway bar.

I really do/did not like running the rear spacer, so I've just retired this wheelset (more on that later).

This was a good set of wheels that have had the tires changed 3x all around- each wheel is cheaper than a single tire and are consumable/disposable at their price.

Dave
Gen III Coupe #17

[Logan]

Are you planning to keep this set as a backup, or sell? Or keep using this set for racing, and save the new Rocket wheels for the street?

I'm similarly setup right now, spring rates are 850/500, front swaybar in hole 3 of 4 (cannot use the 4th and stiffest hole due to awful design), no rear swaybar...it is there but disconnected. My new wheels and tires should be here in January. I'm currently engineering a custom splined front swaybar that will be much stiffer than the 7/8" Miata bar, and hopefully more adjustable too.

I'll add this FR500/NT01 setup of yours to the repository also. I have already added your Rocket/R888R setup.

[Dave Tabor]

Are you planning to keep this set as a backup, or sell? Or keep using this set for racing, and save the new Rocket wheels for the street?

I'm similarly setup right now, spring rates are 850/500, front swaybar in hole 3 of 4 (cannot use the 4th and stiffest hole due to awful design), no rear swaybar...it is there but disconnected. My new wheels and tires should be here in January. I'm currently engineering a custom splined front swaybar that will be much stiffer than the 7/8" Miata bar, and hopefully more adjustable too.

Logan, if you get a workable front swaybar engineered would you consider getting a few made? I've never been able to get my car to understeer, except on the throttle going up hill at Sonoma Raceway.

I'll try to sell/give this set of wheels tire away- good maybe for a Mustang person or a FFR builder looking for a set to get rolling. I have another FR500 set for drifting - a whole other set of 4. I'm sure that these FR500 'style' are not for racing either- whatever that means to Rocket Racing.

I'll write up my track experiences soon- I've got maybe 10 track days and 3 autocrosses on the car- and 12,000+ miles. I'm happy with it.

Dave
Gen III #17

[Logan]

I will make a swaybar thread, or post my solution in my build thread once I complete it (probably both). I have all the parts on my bench, and will be working on it this weekend. Thankfully, everything is available piecemeal off the shelf... So no custom machine shop small volume runs needed. With a much stiffer front bar, you will be able to induce understeer, then adjust the bar down until you are neutral or slight oversteer (whatever the driver's preference is). In fact, you could set the splined front bar stiff enough such that you can then hook the rear swaybar back up too, for more tuneability. Most guys find it's easier to lay on the ground with two wrenches in hand and make a rear swaybar adjustment, than to jack up the car and mess with the front swaybar when at a track event.

Giving the FR500s away?! Wish I were closer, that's an unbeatable price. I'd say they have value, you might sell the complete set of wheels/tires for $400 or something, but I can also see helping out another builder if you're feeling philanthropic.

As is usually the case, it's just legalese (lawyer-speak) when companies slap warnings on their products. Rocket Racing (it's in the name for crying out loud!) is likely doing the same thing here, putting a warning statement on them stating "Not for racing" but doesn't mean the wheels are incapable of lapping and autocross events. Plus I know fellow racers using them HARD on their much heavier racecars, so I would absolutely run them on my own car.

Eager to see your track experience writeup!

[GT_Rich]

Hey guys, I have a Coupe R on order and I'm currently putting together a driveline. Just about have the engine wrapped up and ready to start building an 8.8 rear. I have foxbody length 31 spline axles to go in it. Rear wheels are 18x10.5 +23 offset (6.7 BS). Should I be getting the longer 94-98 Mustang axles? They are 0.75" longer per side.

Also, interested in the front swaybar solution. The FFR setup looks hokey. I ordered my kit without shocks, springs, or bars.
Thanks,
Rich

[Logan]

Welcome GT-Rich, and congrats on the Coupe-R purchase!

If you're doing a solid rear axle, you absolutely want to go with the widest axle option you can. From what I understand, that is the later years of Mustang. The rear of the Daytona Coupe body is really wide, relative to the axle options, so regardless if you do SRA or IRS....you'll probably still be searching for the lowest offset wheel you can find, and/or running spacers to push them out further.

It's one of the more....challenging...aspects of this chassis design, and makes me want to build custom longer control arms and halfshafts for my IRS. The goal is to make the hubs wider, to allow you to use the more common/popular high offset wheels without spacers. I think the FFR design really had vintage looks in mind as a primary design goal, rather than performance.

As for the sway bar, I have a splined front bar in my car now. Working on endlink geometry now, should have a finished solution in the next 3 weeks or so. I'll make a post when it's complete and tested.

What shocks and springs (and engine/trans) do you have in mind? You may want to start your own Introduction or build thread, so we don't run away with Dave's thread here.

[GT_Rich]

Thanks, Logan. I'll start an intro/build thread and include the details your asking about. I've followed your build thread and we're similar minded guys with similar goals, so I think you'll approve.

One question related to this thread - is the hub to hub width on the IRS the same as a foxbody rear axle? Just making sure I can directly compare wheel/tire fitment data between both platforms.

[Logan]

One question related to this thread - is the hub to hub width on the IRS the same as a foxbody rear axle? Just making sure I can directly compare wheel/tire fitment data between both platforms.

I do not know which SRA hub width is closest to the IRS width. My wheel and tire fitment thread (link below) has a lot of data in it, but I think 98% of the cars on that list are IRS. Not many Gen3 Coupe builds running solid axles, from what I've seen.

The Daytona Wheel and Tire Repository:
https://thefactoryfiveforum.com/show...ire-Repository

[GT_Rich]

You should measure, then we'd know.

[racingandfishing]

Like GT_Rich I would be interested to know the width of the IRS.

On the SRA I found the info along with a lot of other great information. Also wondering if there is a reason the 99-04 wouldn't work. Guessing the mounting points may be different, but not sure.

https://lmr.com/products/Mustang-7-5...-End-Axle-Info

FOX LENGTH AXLES VS. SN95 LENGTH AXLES
79-93 Mustangs - 29 3/16" long rear axle.
94-98 Mustangs - 29 31/32" long rear axle.
99-04 Mustangs - 30 11/16" long rear axle.

[Jim1855]

I'm interested in options/concepts/engineering that will work with the MK4. I'm looking at a shaft in a tube design, Speedway parts.
I have a local friend with a Gen 3 at a chassis build stage but access is difficult.
I have SolidWorks CAD but certainly not an expert.
Also have access to a full machine shop. These guys are experts and capable of low volume production.
I'm trying to learn, long ways to go.
Jim