Close



Results 1 to 24 of 24
  1. #1

    Default Crazy Idea: 4-Lug IRS

    I'd like to install an IRS out of an 03-04 Cobra, anyone ever redrilled the hubs for 4-lug? I'm wondering if the hub bore has room for the 4-lug bolt pattern? I'm pretty sure I'm the only one who is silly enough to even think about this let alone go through with it. It looks like there's plenty of meat and that this could actually be fairly simple...

    Name:  m1109a_f72845e6.jpg
Views: 373
Size:  22.1 KB

    Name:  m1109a_f5a2d8a0.jpg
Views: 373
Size:  20.7 KB
    82 Mercury Capri - 11.99 @ 112, AFR headed Mountaineer motor
    86 Mustang LX Coupe - the original Coyote swap 4-eye. Gone but not forgotten!

  2. #2

    Default

    Christian,

    I went down this path a long, long time ago. It was a total disaster.

    The hubs from an MN12 Thunderbird will bolt right onto a Mustang Cobra IRS. They are still 5-lug, BUT they have a 4.25" bolt circle. This allows you to redrill three of the stud holes to make it work with Mustang 4-lug wheels. You will also have to open up the pilot hole in the wheel for the larger hub pilot.
    Jack Hidley
    Maximum Motorsports Tech Support

  3. #3

    Default

    Quote Originally Posted by Jack Hidley View Post
    Christian,

    I went down this path a long, long time ago. It was a total disaster.

    The hubs from an MN12 Thunderbird will bolt right onto a Mustang Cobra IRS. They are still 5-lug, BUT they have a 4.25" bolt circle. This allows you to redrill three of the stud holes to make it work with Mustang 4-lug wheels. You will also have to open up the pilot hole in the wheel for the larger hub pilot.
    Jack, could you possibly expand on what made it a disaster? Reason being I want to build a "period correct" looking fox body with 15" wheels. But having IRS is mandatory... Drilling rotors is extremely easy, obviously. We used to do it back in the day to run SVO rear discs with 4-lug wheels. So what makes the hubs any different? I know on the SN95 rear hubs, one of the holes partially overlaps so a hole would need to be welded up before the pattern is drilled.
    82 Mercury Capri - 11.99 @ 112, AFR headed Mountaineer motor
    86 Mustang LX Coupe - the original Coyote swap 4-eye. Gone but not forgotten!

  4. #4
    FEP Senior Member
    Join Date
    Dec 2016
    Location
    Grand Rapids, MI
    Posts
    721

    Default

    I think what he is saying is it will be easier to start with the MN12 hubs since they are 5x108 and the Mustang 4 lug is 4x108 so one of the holes will already be where you need it and you only need to drill three other holes. No welding required. You should be able to use the MN12 front wheel bearings as well. They assemble onto the spindle similar to the SN95 front wheel bearings. That is what MN12 guys used to use to swap to the Mustang lug pattern back in the day.

    EDIT: My comment on the fronts was assuming you would be swapping in SN95 front spindles.
    Last edited by KevinVarnes; 01-17-2020 at 01:22 PM.
    '89 XR-7 5 Speed
    '95 SC 5 Speed
    '91 Crown Vic P72 351W
    '97 Thunderbird
    '85 Ford LTD Squire

  5. #5

    Default

    What Kevin said.

    Back in the day, I tried to weld up one of the holes in an SN95 hub to redrill it. After welding, the hub was ruined because the bearing race is part of the hub. The welding deformed the hub. When I tried to drill out the welded hole, no normal bit would do this as the metal was so hard now. I tried a $40 solid carbide drill bit. That just cracked. If I had the hub fixture in a mill, instead of just a drill press maybe that wouldn't have happened. The bottom line was that the hub was far too hard. Even if you had managed to drill the hole, you wouldn't have been able to install a wheel stud and the hub would probably have cracked in use.

    Remember when installing the IRS, that it is 3" wider than the stock Fox axle assembly. You are going to need some wheels with a lot of back spacing to make this fit.
    Jack Hidley
    Maximum Motorsports Tech Support

  6. #6

    Default

    Quote Originally Posted by Jack Hidley View Post
    What Kevin said.

    Back in the day, I tried to weld up one of the holes in an SN95 hub to redrill it. After welding, the hub was ruined because the bearing race is part of the hub. The welding deformed the hub. When I tried to drill out the welded hole, no normal bit would do this as the metal was so hard now. I tried a $40 solid carbide drill bit. That just cracked. If I had the hub fixture in a mill, instead of just a drill press maybe that wouldn't have happened. The bottom line was that the hub was far too hard. Even if you had managed to drill the hole, you wouldn't have been able to install a wheel stud and the hub would probably have cracked in use.

    Remember when installing the IRS, that it is 3" wider than the stock Fox axle assembly. You are going to need some wheels with a lot of back spacing to make this fit.
    I'm aware of the 1.5" per side track increase. That being said, it sounds like the MN12 hubs are the way to go. Rotor wise is where things get complicated.
    The SN95 hub size I believe is larger (2.78" ID vs 2.51" ID) so I'd need to use a centering ring in order to use the SN95 rotors.
    82 Mercury Capri - 11.99 @ 112, AFR headed Mountaineer motor
    86 Mustang LX Coupe - the original Coyote swap 4-eye. Gone but not forgotten!

  7. #7

    Default

    Use a machined metal ring to center the rotor, not plastic. The rotors have too much mass to allow to be off center and the pad rubbing will create huge vibration issues. Since you will be redrilling the hubs and rotors, you really can't rely on the studs to accurately center things.
    Jack Hidley
    Maximum Motorsports Tech Support

  8. #8

    Default

    Quote Originally Posted by Jack Hidley View Post
    Use a machined metal ring to center the rotor, not plastic. The rotors have too much mass to allow to be off center and the pad rubbing will create huge vibration issues. Since you will be redrilling the hubs and rotors, you really can't rely on the studs to accurately center things.
    Yes I'd use a ring like this in this thread

    https://www.tccoa.com/threads/a-simp...rotors.168930/

    Name:  ring.jpg
Views: 333
Size:  34.8 KB
    82 Mercury Capri - 11.99 @ 112, AFR headed Mountaineer motor
    86 Mustang LX Coupe - the original Coyote swap 4-eye. Gone but not forgotten!

  9. #9
    Moderator wraithracing's Avatar
    Join Date
    Jun 2010
    Location
    Grand Junction, CO/RR TX
    Posts
    14,206

    Default

    This is unsolicited advice so feel free to ignore me . . . my Wife does it all the time.

    For all the headaches involved with stuff the IRS into a Fox combined with your desire to stay 4 lug, I would highly recommend considering spending the time and the money on installing the Full Torque Arm, Panhard bar, and rear lower control arms from Maximum Motorsports instead of the IRS.

    I have an 03/04 Cobra IRS installed in my 79 PC and I have another 2001 IRS sitting under a bench trying to decide what to do with it. My .02 is that unless you just want the stock IRS with none of the OEM flaws corrected, then fine. Problem is that at this point the newest version is 16 years old, so . . . You are most likely going to need to install all the bushings, the cross-axis joints, tie rods, etc. for a good all around unit. By the time you do all that, you will have spent just as much for those parts as the MM Torque arm setup and required parts. In my experience I will just save the headaches and do the full MM setup and not have the tire fitment issues and backspacing issues, etc. NOT to mention all the brake issues and machine work you have ahead of you. Oh don't forget you have to have IRS specific tail pipes too.

    The IRS is nice and it's a novelty item, but a well tuned Torque Arm will do just as well and be fewer headaches IMHO. Again just my .02 and I don't know how deep you are into the IRS at this point in time, so if you are dead set on the IRS, then just ignore me and my ramblings. Best of luck either way!
    ​Trey

    "I Don't build it hoping for your approval! I built it because it meets mine!"

    "I've spent most of my money on Mustangs, racing, and women... the rest I just wasted."

    Mustangs Past: Too many to remember!
    Current Mustangs:
    1969 Mach 1
    1979 Pace Car now 5.0/5 speed
    1982 GT Stalled RestoModification
    1984 SVO Still Waiting Restoration
    1986 GT Under going Wide Body Conversion Currently

    Current Capris:
    1981 Capri Roller
    1981 Capri Black Magic Roller Basket Case
    1982 Capri RS 5.0/4spd T-top Full Restoration Stalled in TX
    1984 Capri RS T-top Roller
    1983-84 Gloy Racing Trans Am/IMSA Body Parts

  10. #10

    Default

    Quote Originally Posted by wraithracing View Post
    This is unsolicited advice so feel free to ignore me . . . my Wife does it all the time.

    For all the headaches involved with stuff the IRS into a Fox combined with your desire to stay 4 lug, I would highly recommend considering spending the time and the money on installing the Full Torque Arm, Panhard bar, and rear lower control arms from Maximum Motorsports instead of the IRS.

    I have an 03/04 Cobra IRS installed in my 79 PC and I have another 2001 IRS sitting under a bench trying to decide what to do with it. My .02 is that unless you just want the stock IRS with none of the OEM flaws corrected, then fine. Problem is that at this point the newest version is 16 years old, so . . . You are most likely going to need to install all the bushings, the cross-axis joints, tie rods, etc. for a good all around unit. By the time you do all that, you will have spent just as much for those parts as the MM Torque arm setup and required parts. In my experience I will just save the headaches and do the full MM setup and not have the tire fitment issues and backspacing issues, etc. NOT to mention all the brake issues and machine work you have ahead of you. Oh don't forget you have to have IRS specific tail pipes too.

    The IRS is nice and it's a novelty item, but a well tuned Torque Arm will do just as well and be fewer headaches IMHO. Again just my .02 and I don't know how deep you are into the IRS at this point in time, so if you are dead set on the IRS, then just ignore me and my ramblings. Best of luck either way!
    I appreciate the insight! I've never done things easily, which is probably why the moment a car is sorted, I want it sold and out of my sight. Or maybe I just like building them more than driving them. My last fox that I sold 5 years ago had the complete MM catalog in it front to rear. TA, PHB, the works! On a smooth track, the TA/ PHB setup is fantastic. But on the street where my cars spend 99.99% of their time, the IRS is king. The ability for both rear wheels to absorb expansion joints and road ruts independently simply can't be beat. Nothing against the TA setup, but it has its own headaches. No factory exhaust will work with a TA and tailpipe clearance is a challenge with the PHB. My IRS setup would start with a bare cradle. I would do MM poly bushings, then I'd source a diff core and send it out for a TruTrac and new gears to match the tire height and gear ratios of the transmission I'll use (an automatic). I'm not 100% dead set on the 4-lug, but the IRS is mandatory simply due to the road compliance and ride quality benefits it provides.
    82 Mercury Capri - 11.99 @ 112, AFR headed Mountaineer motor
    86 Mustang LX Coupe - the original Coyote swap 4-eye. Gone but not forgotten!

  11. #11

    Default

    Instead of trying to make a production/stock piece work? Why not contact a aftermarket distributor of the hubs and request a blank set of hubs without any stud holes? I know my technical language sounds tacky here-but it might be worth a phone call. Blank slate might be your best bet then you can drill your own studs without working around what’s already there.
    86 Capri-84 LTD a wagon-85 notch-86 notch

  12. #12

    Default

    The manufacturer of the hubs is going to be making a couple hundred of them at a time, minimum. Even if you could get them to sell you a set with no stud holes, they would costs thousands of dollars.
    Jack Hidley
    Maximum Motorsports Tech Support

  13. #13

    Default

    Quote Originally Posted by Badsmurf View Post
    Instead of trying to make a production/stock piece work? Why not contact a aftermarket distributor of the hubs and request a blank set of hubs without any stud holes? I know my technical language sounds tacky here-but it might be worth a phone call. Blank slate might be your best bet then you can drill your own studs without working around what’s already there.
    Like Jack said, zero chance of calling Moog or Timken corporate and get them to sell me 2 blank hubs. Maybe in 1975, but with most things made overseas nowadays...

    I know the machinist I use can take care of this no problem. The MN12 hub idea was very helpful. Now if only I could find out where to get the hub rings?
    Last edited by lxcoupe86; 01-17-2020 at 11:57 PM.
    82 Mercury Capri - 11.99 @ 112, AFR headed Mountaineer motor
    86 Mustang LX Coupe - the original Coyote swap 4-eye. Gone but not forgotten!

  14. #14

    Default

    Double post
    82 Mercury Capri - 11.99 @ 112, AFR headed Mountaineer motor
    86 Mustang LX Coupe - the original Coyote swap 4-eye. Gone but not forgotten!

  15. #15
    FEP Super Member erratic50's Avatar
    Join Date
    Dec 2016
    Location
    Nebraska
    Posts
    4,575

    Default

    If you sort stuff - please add it to the 4 lug braking flug

  16. #16
    FEP Member svo84's Avatar
    Join Date
    Oct 2006
    Location
    York, Pennsylvania
    Posts
    167

    Default

    Merkur XR4TI IRS? Lots of work.

  17. #17
    FEP Super Member
    Join Date
    May 2003
    Location
    Roseburg Oregon
    Posts
    3,308

    Default

    5 lug , more wheel and tire choices .
    16" tires are the cheaper option over a 15"
    clowns to the left of me , Jokers to the right

  18. #18
    FEP Super Member erratic50's Avatar
    Join Date
    Dec 2016
    Location
    Nebraska
    Posts
    4,575

    Default

    It occurred to me the other day that there may be some usable parts to be had from some of the early 2000’s 4 lug Ford cars. I haven’t done any measurements or spent any time on it but when I was playing with my daughters 2002 Cougar it occurred to me how similar the rear brake rotors are to the SN95 rear brake rotors, only they are 4 lug.

    Since I have a complete parts car for hers I am hoping to get some time to do some mock-up while building my 86 8.8 with 3.90 gears - but we shall see. I barely see my wife and daughter or my house most weeks.

  19. #19

    Default

    Merkur stuff is, of course, hard to find but, it's also an open diff with few options for LSD and it won't take V8 power for long. Fitment, who knows? I don't know of anyone that ever tried it.

  20. #20
    FEP Super Member xctasy's Avatar
    Join Date
    Jun 2012
    Location
    Dunedin 9011, New Zealand, South Pacific
    Posts
    3,961

    Default

    Post #6 guys.

    The IFS and 4 on 108 mm Momo or BBS Ferrari Escort Colonge Capri style centre locks just use the MG and Volvo 240 hubs.


    This was devised by Mike Kanefuss before hus arrival ay SVO. Zakspeed in Colonge made the stock IFS cross member accept the ZakSpeed Escort BDA Turbo and Cologne Capri IFS.

    The Group A (International Group 1A Fisa formula from 1982 to 1991) system allowed stock pick up points to be used, and any gearbox or axle or IFS uprights to be integrated.

    Alfa Romeo for its Alfa 75 removed the simply awfull pidgeon toed Chrysler Á body style torsion bar IFS and converted it to strut adustale spring perch pure non Modified MacPherson Strut IFS as well

    See

    http://vb.foureyedpride.com/showthre...Upgrade-Thread

  21. #21
    FEP Super Member xctasy's Avatar
    Join Date
    Jun 2012
    Location
    Dunedin 9011, New Zealand, South Pacific
    Posts
    3,961

    Lightbulb

    For the IRS, the semi trailing arm Sierra and XR4Ti was the Cologne 7.5 inch axle center with Bob Lutz and Uwe Bahansen Granada Mark 1 & 2 based German system.

    The geometery and pickup points are different and inferior to the SN99 New Edge Mustang and MN12 system.

    Since the only issues are width, and since every proper early ETCC, Group A and Bathurst style Mustang used Ferrari style knock ons, then my suggestion is for you to investigate reworking something on a CNC mill to the required spec.

    The issue with the Ford Mustang IRS is just rear track width...my old Nissan Sykline GTR AWD Stagea had the same issue, a wider S15 240SX based multi link IRS which was too wide. You work around that with wheel offsets and repurposing the original frame mounts/pick up points.

    A great nachinist will make it all happen.

    Ill post the Kiwi rebuild of the No 18 Dick Johnson Mustang Group A axle. When the Pine Pac Mustang 32 broke its ring and pinion, the same guy remachined a Cologne Capri 3.09: 1 3.0 liter Essex V6 axle center from steel and sent it to Australia. The same guy did all of Fords 7.5 inch Cologne Sierra Turbo ring and pinion center stuff, shared with the rear drive Works RS 1800 and RS 2000 Escorts.

  22. #22
    FEP Super Member xctasy's Avatar
    Join Date
    Jun 2012
    Location
    Dunedin 9011, New Zealand, South Pacific
    Posts
    3,961

    Default

    Dick Johnson took his American “green machine” to eight podium finishes in the Australian Touring Car Championship and second outright in the 1985 Australian Touring Car Championship. He retired it when the turbocharged Ford Sierras were introduced.

    About 8 Group A Mustang cars raced at the 621 mile Mount Panorama and the 311 mile Wellington Water Front endurance events at 155 mph with four stud wheels, and they survived many bashes...





    The Kramer/Davison car
    The two Bo Seaton/David Smith Nu-Truck Spares cars,
    the two Palmer Tube Mills/ Dick Johnson Racing cars 17 or 71 and 18
    the three Pine Pack variants of the Black and Abe's Babe car (one a spare shell) ,
    plus the Capri Components Fox Mustang racer.

    Brakes: 1" thick 13.00" front rotors, 11.45" rear rotors with combination AP/Girling 4 pot callipers

    Ferrari 108 mm on four stud knock-on for Centrelock Momo 10 x 15” magnesium wheels...



    Guess what?

    Proof of the Ferrari 4 on 108 mm stud knock ons. Same as the factory Pinto/Mustang II/Fox 4 stud spacing.

    And look at the non standard front to back axle stagger....some serious alterations were going on underneath, with probably the "Baby Atlas" narrowed 53" rear axle on this speciman with later wider SVO IFS suspension width. It has clear, and very noticable stagger. :roll:


    Rudof Frieds wonderful Group A racing photos from Czechoslovakia's Brno circuit racing Mustang GT shows he final take on the heavily "swaged" Compomotive / Ronal magnesium turbo, this time with different sizes and hole arrangements, and Momo style hex nut, which used the Ferrari/MG 108 mm pitch center studs



    Ken Hopper used to machine the circuit racer Escort BDA/Cologne Capri and DJR/Pine Pac Mustang 7.5 inch Koln ZF Atlas axle parts.

    IIRC, the 4 stud Hex Nut AP 4 spot caliper circuit racing hubs.

    For a short spell, the Merkur XR4Ti and Sierra Cosworth Turbo circuit racing cars had the ZF Atlas Cologne axle, but it was soon replaced by a 9" Ford axle center on the RS500 Evolution Sierra...because 500 hp used to break axles rather a lot...

    See the Ken Hopper 7.5 inch axle.







    http://vb.foureyedpride.com/showthre...28#post1493228

    And some more info on the agonizing Australian compliance issues...The Mustang was hide-strung in Australian touring car racing because the scrutineers weren't liberal with the rules like the Europeans were.
    https://www.pressreader.com/australi...82333976804310

  23. #23
    FEP Super Member xctasy's Avatar
    Join Date
    Jun 2012
    Location
    Dunedin 9011, New Zealand, South Pacific
    Posts
    3,961

    Default

    Quote Originally Posted by svo84 View Post
    Merkur XR4TI IRS? Lots of work.
    Page 6 and 11 of the TCP catalog gives you the push rod articulated IRS weld in.

    #7793 and #5867 Rocker-Arm-Actuated Coil-Over Suspension respectively



    http://www.cachassisworks.com/Attach...alogs//TCP.pdf


    In Europe, the 7.5 inch XR4Ti IRS axle is often used as a push rod basis for a full multilink IRS in Lotus Seven replicas.

    Both the USA and UK/Europe do the same thing, Rocker Arm Actuated Coil-Over Suspension.



    The cost of putting in an IRS is related to perfecting it once mounted.

    Semi trailing arm IRS's were always combined with rear mounted steering gear, the Fox body platform is the exception. Bob Lutz's Sierra/XR4Ti/Scorpio platform is another.


    Due to that front mounted steering gear systems goodness, the Sierra/XR4Ti/Scorpiot Semi trailing arm doesn't need some kind of roll over steer mitigation strategy. An example of that is the old Porsches 928 Wiessach passive under-steer geometry or Nissans HICAS. I haven't driven the old Hyundai Nubira, but my engineer said even they used it on a front drive car since most front drives have a rear mount rack.

    Fords Mustang SN 99 system is well thought out, and is almost as good as a Mercedes Benz or Nissan multilink system, and it has front mounted steering gear which promotes under-steer on the limit.

    My last Nissan was an AWD Stagea. Having driven an 928S before, both vehicles have a rock solid steering feel, but there is a transient woolly feeling which even I noticed, and despite having gone to the Ford Advanced driving school in 2003, Im certainly no expert driver.

    The Nissan AWD and 928 both have a technically bad rear mounted steering rack, and its shared with the Ford Falcon EA26 to AU-BA-FB system. The Australian VB onwards 1978 to 2006 Commodore used it as well. Roll over steer in those cars had to be engineered out by having a very complicated IRS system.

    Fords MN12 and New Edge IRS were very simple, and free of that one vice.

    IRS is a complicated second step, but the Fox has few fish hooks.

    Unlike 1964 when the Mustang Jag and Cobra based IRS was nixed for cost reasons, the market place offers targeted IRS systems. I doubt they are much better than what Ford offered in the late 90's.

  24. #24

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •