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Thread: Wheel & Tire Specifications - Roadsters and Type 65 Coupes

  1. #1
    Webmaster, FFR
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    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)
    Dave Lindsey
    FFR's Mad Dog

  2. #2
    Member Glory Bound's Avatar
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    Thanks. This is way helpful!
    God is good - all the time!

  3. #3
    Senior Member DavidW's Avatar
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    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?

  4. #4
    Senior Member DavidW's Avatar
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    Quote Originally Posted by DavidW View Post
    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

  5. #5
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    Quote Originally Posted by DavidW View Post
    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

    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

  6. #6
    FFR Maven Logan's Avatar
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    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.
    Logan's Gen 3 Coupe-R Build
    Ordered 4/23/19 | Delivered 6/29/19 | First Start 8/1/20 | First Drive 9/20/20

  7. #7
    Senior Member jwhit's Avatar
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    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

  8. #8
    25th Anniversary #9772 toadster's Avatar
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    2020 Specs for the new body mold would be helpful too!
    Todd
    25th Anniversary MkIV | #20 of 25 | Build #9772
    https://cobradreams.com/ <- my build!

  9. #9
    Not a waxer Jeff Kleiner's Avatar
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    Quote Originally Posted by toadster View Post
    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

  10. #10
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    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?
    Proud owner of #4 - 25th Anniversary Roadster delivered Sept 2019. Coyote Gen 3 with TKO 600 from Mike Forte delivered Jan 2020.

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