Wheel & Tire Specifications - Roadsters and Type 65 Coupes

Wheel & Tire Specifications - Roadster

Optimum Backspace Calculation Chart
Vehicle Position On Vehicle Backspace Equation Maximum Width Pin-Drive Backspace Equation
Roadster Front (width/2)+1.25"=B.S.* 9" (width/2)-0.375"=B.S.
79’-93’ Rear Axle or IRS (width/2)+1.25"=B.S. 10" (width/2)-1.25"=B.S. [IRS only]
94’-98’ Rear Axle (width/2)+2.00"=B.S. 10" N/A
99’-present Rear Axle (width/2)+2.875"=B.S. 10” N/A

Coupe & Spyder Front (width/2)+0.75"=B.S. 10" no change
79’-93’ Rear Axle or IRS (width/2)+0.25"=B.S. 12" (width/2)-2.25"=B.S. [IRS only]
94’-98’ Rear Axle (width/2)+1.00"=B.S. 12" N/A
99’-present Rear axle (width/2)+1.875"=B.S. 12” N/A

* 9" wheel would be desirable to have a 6" B.S.
79’-93’ 4-lug Rear Axle is 59.25" hub to hub (4.25” 4-lug bolt pattern)
94’-98’ 5-lug Rear Axle is 61.125” hub to hub (4.5” 5-lug bolt pattern)
99’-present Rear Axle is 62.52” hub to hub (4.5” 5-lug bolt pattern)

To run 315/35R-17 tires on an MKIII Roadster it would be desirable to have the 59.25” width rear axle. 10.5” wide wheels with a 6.85” B.S. fit well with the 315’s, and are easily attainable in the aftermarket from several of the OEM reproduction wheel suppliers. With custom wheels, use the same backspace, or with an 11” wide wheel, run a 7.1” B.S.

Pin-drive IFS hubs are 1.625” further in per side and the IRS is 2.5” further in per side
Pin-drive adaptors are 0.375” thick

Maximum Tire Sizes
Wheel Diameter Front Tire Sizes Rear Tire Sizes
Roadsters 15" 235/60R-15 275/50R-15
16" 255/50R-16 255/50R-16
17" 245/45R-17 or 255/40R-17 275/40R-17 *

18" 245/40R-18 275/35R-18

Coupe & Spyder 15" 255/60R-15 295/50R-15
16" 255/50R-16 255/50R-16
17" 275/40R-17 335/35R-17
18" 275/35R-18 295/35R-18



*For a Mk3/Mk4 Roadster you can run a 315/35R-17


Alignment Specifications Suppliers of Cobra R’s and Modern style wheels
Alignment Spec Value Unit
Front For All Vehicles Caster 3 degrees
Camber - 1/2 degrees
Toe 1/16 inch

IRS All Camber -1 degrees
Toe 1/16 inch
Tire Rack 888-541-1777 tirerack.com
Diviersified 734-459-0130 buyfordmotorsport.com
Discount Tire Direct 800-589-6789 tires.com
*Performance Wheel Outlet 909-825-5242 performancewheeloutlet.com
*AFS 818-340-6181 afswheels.com
*Performance Tire 832-567-5265 wheelreplicas.com *(OEM reproduction wheels)

Thanks. This is way helpful!

So help me get this right.......

For the MK-IV the rear axle is 59.25" inches. A rim 17" x 10 1/2" with a backspace of 6.85 will fit a tire 315/35/R17.

For the front end what's the backspace and a recommended tire for a front rim of 17" x 9" , obviously to look good with the rear above?

Quote:

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Originally Posted by DavidW

So help me get this right.......

For the MK-IV the rear axle is 59.25" inches. A rim 17" x 10 1/2" with a backspace of 6.85 will fit a tire 315/35/R17.

For the front end what's the backspace and a recommended tire for a front rim of 17" x 9" , obviously to look good with the rear above?

---

I was given the info, thanks again.

Technical Specifications:

Wheel Set Part Number: 14865

Front Wheel Size (Diameter x width): 17"x 9"

Rear Wheel Size (Diameter x width): 17"x 10.5"

Front Wheel Backspace: 6.00" (24mm Offset)

Rear Wheel Backspace: 6.7" (27mm

Offset Wheel Lug Pattern: Ford style 5 lug x 4.5" bolt circle

Material: Cast Aluminum

Color: Gun Metal



Weight with adapter, spinner and lug cover
17"x 9": 20.36 lb 17"x 10.5": 22.66 lb



FFR Fitment Applications:

Mk3 and Mk4 Roadster

65 Coupe



Axle Applications:
1979-1993 width Ford 8.8" solid axle FFR standard width IRS



Front Brake Fitment
11" 1999-2002 Mustang GT Calipers and Rotors

11" 87-93 Mustang GT Calipers and Rotors

13" Mustang Performance Calipers and Rotors

These will not fit 2003-04 GT Calipers



Rear Brake Fitment:

10.5" Rear disc brake kit
11.65" Rear disc brake kit
13.00" Rear disc brake kit



Recommended Tire Sizes:
Front: 245/45 R17
Rear: 315/35 R17

Quote:

---

Originally Posted by DavidW

I was given the info, thanks again.

Technical Specifications:

Wheel Set Part Number: 14865

Front Wheel Size (Diameter x width): 17"x 9"

Rear Wheel Size (Diameter x width): 17"x 10.5"

Front Wheel Backspace: 6.00" (24mm Offset)

Rear Wheel Backspace: 6.7" (27mm

Offset Wheel Lug Pattern: Ford style 5 lug x 4.5" bolt circle

Material: Cast Aluminum

Color: Gun Metal



Weight with adapter, spinner and lug cover
17"x 9": 20.36 lb 17"x 10.5": 22.66 lb



FFR Fitment Applications:

Mk3 and Mk4 Roadster

65 Coupe



Axle Applications:
1979-1993 width Ford 8.8" solid axle FFR standard width IRS



Front Brake Fitment
11" 1999-2002 Mustang GT Calipers and Rotors

11" 87-93 Mustang GT Calipers and Rotors

13" Mustang Performance Calipers and Rotors

These will not fit 2003-04 GT Calipers



Rear Brake Fitment:

10.5" Rear disc brake kit
11.65" Rear disc brake kit
13.00" Rear disc brake kit



Recommended Tire Sizes:
Front: 245/45 R17
Rear: 315/35 R17

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this is great information . could we get the same for the FF5 33 Hot Rod wheels Please
I am thinking of running the 17" Halibrand wheels on a 33 HR and want to check compare the back space dimensions
Thanks
Kevin

Over 5 years now since the last post on this thread, and nearly 8 years since the original post by Mad Dog! Wow!

Any updates on wheel specs with the new Gen 3 Type 65 Coupe, which is well under way in production now? Specifically, I'd like to know what the widest wheel fitment achievable in both front and rear of the new Coupe. I daily drive a 2017 Mustang (S550) with 19x11" +50ET wheels at all four corners, with 20mm spacers on the front. This is a reasonable width for the rear and an aggressive width in front. However, having the offset the same on all four wheels allows easy rotation, thus extending the life of the tires and making track spares simple.

I'd love to be able to use a set of my existing wheels on the Gen 3 Coupe R. I think the rear will be pretty straightforward, with the 2015+ Mustang IRS. The front hubs will be drilled out and 14mm studs pressed in to match the rear (maintaining S550 Mustang spec). I am just not sure how much wheel the chassis is capable of fitting up front.

Once the maximum "Race Spec" wheel fitment is known, we can easily see what is a more comfortable "Street Spec" fitment, too.

i got the 17 wheels with my gen 3 kit the front rims dont fit the hit upper ball joint and i will have to space out at least 1/8 maybe little more
any body had this issue ? im using 95 stang spindle

2020 Specs for the new body mold would be helpful too!

Quote:

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Originally Posted by toadster

2020 Specs for the new body mold would be helpful too!

---

I've got a couple years old Mk4 body sitting next to a 25th Anniversary body right no so just took some measurements:

Front to back the rear wheel opening is one inch smaller on the 2020 body. In the front the 2020 body is and 1/2 inch larger.

Measuring across the width is exactly the same on both front and rear.

So, I'd say that the minor difference would not result in a change to the specs.

Jeff

Thanks for the update. What are the tire size recommendations for the 18” wheels that come with the 25th Anniversary Roadster? Can I put 275s on the front or stick with 255s?

Hey Maven:
I have the Gen 3 type 65 Coupe. Ordered the Mustang IRS and the wheels (17") from FFR. Fronts are fine, but the rears are at least 2" too far inboard...looks ridiculous. Prefer not to go with extenders on the rear so I am looking at new wheels. What did you end up sorting out? Thanks!

Quote:

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Originally Posted by Broncobra

Hey Maven:
I have the Gen 3 type 65 Coupe. Ordered the Mustang IRS and the wheels (17") from FFR. Fronts are fine, but the rears are at least 2" too far inboard...looks ridiculous. Prefer not to go with extenders on the rear so I am looking at new wheels. What did you end up sorting out? Thanks!

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Here is a link to the Coupe wheel + tire repository. https://thefactoryfiveforum.com/show...ire-Repository

Logan very kindly put together a spreadsheet that shows the wheels and tires that posters actually used on their Coupes, with backspacing used, and whether spacers were needed

It hasn't been updated in a few years, but much more info than found here

Much Obliged!