Close



Results 1 to 8 of 8
  1. #1
    FEP Senior Member flyin5-o's Avatar
    Join Date
    Sep 2006
    Location
    Fond du Lac,Wisconsin
    Posts
    565

    Default Off season suspension change suggestions

    So while I was happy with the "out of the box" handling in my cars first outing I feel there is room for improvement. I am looking for some critique and suggestions. I am looking to stay somewhat low buck.

    Current setup:

    Front:
    Stock '88 k-member and arms
    '88 quick ratio rack
    SVO spindles with adapters
    Ground Pounder road race coil overs (400#/in)
    Ground Pounder camber caster plates
    MM spherical rack bushings
    MM STB
    '87-93 GT sway bar
    Motorsports Del a Lum control arm bushings
    '90 Gt tie rod ends

    Rear:
    PM3L
    Stock control arms/bushings
    Mathis anti squat brackets
    Panhard bar
    Stock '87-93 v8 springs
    Stock '87-93 v8 swaybar

    Alignment:
    3/4 degrees + caster
    1.5 degrees - camber
    0 Toe

    Tires/wheels:
    245/40r15 BFG Rival S-1.5
    15x8 4inch backspace rims

    On track impressions:
    The car seemed fairly balanced with a slight tendency to understeer. Rear end seemed to roll excessively especially compared to the front but it wasn't twitchy. Turn in was good. Like I said wasn't horrible but I feel it could be better.

    What I currently plan to do:

    Full Mathis mods to the front k-member with 99-04 arms-
    4cyl front sway bar
    Stiffer rear springs (MM tourque arm springs?) Need some type of height adjuster as lowering springs to short
    MM adjustable rear swaybar or no swaybar or a '80's Lincoln/Mercury something bar that mounted to the chassis and rear, bar is 9/16" diameter.

    Suggestions/ comments?
    Last edited by flyin5-o; 09-02-2018 at 11:02 AM. Reason: found front spring rate

  2. #2
    FEP Super Member erratic50's Avatar
    Join Date
    Dec 2016
    Location
    Nebraska
    Posts
    4,575

    Default

    Do you plan to drive it on the street or only the track?

    Track cars generally need more negative camber. -1.75 degrees minimum

    Lower K brace.
    Last edited by erratic50; 09-02-2018 at 01:25 AM.

  3. #3
    FEP Member
    Join Date
    Oct 2017
    Location
    south-central WY
    Posts
    251

    Default

    I didn't see subframe connectors on your list. Was that an oversight, or are they not used in this application ?

  4. #4
    FEP Senior Member flyin5-o's Avatar
    Join Date
    Sep 2006
    Location
    Fond du Lac,Wisconsin
    Posts
    565

    Default

    Quote Originally Posted by darkd0r View Post
    I didn't see subframe connectors on your list. Was that an oversight, or are they not used in this application ?
    Quote Originally Posted by erratic50 View Post
    Do you plan to drive it on the street or only the track?

    Track cars generally need more negative camber. -1.75 degrees minimum

    Lower K brace.
    Here is the link to my build thread so you can see the car in question. http://vb.foureyedpride.com/showthre...85-notch-build

    Subframe connectors are installed, just figured that was a given on these cars.

    Definitely track only. Only street it will ever see is loading onto the trailer in front of my house.
    As for the alignment 1.75 degrees was what I wanted to be at but could only get 1.5 degrees. Same with the caster, alignment tech aid he could only get .75 degrees due to the coilovers hitting the shock towers. As for the lower k brace I have one but can't put it on due to the long tube headers residing in the same place as it. I will add it to the list though just have to figure a way around the clearance issue.

    Forgot to add I have a bumpsteer kit I made that will be going on as well.

  5. #5
    FEP Super Member erratic50's Avatar
    Join Date
    Dec 2016
    Location
    Nebraska
    Posts
    4,575

    Default

    You should try some camber bolts or heavily loading the suspension at the end of the kingpin before torquing the strut bolts.

    camber bolts let you get your camber while keeping the struts centered in the opening but all the way back by the windshield.

    I was at +6 camber on my 86GT before camber bolts. Now I’m at -2 with my struts centered which allows for max caster

    Bumpsteer kits are a good idea. If you are lowered very much you may want to do rack offset bushings to keep your stack height down when setting up bumpsteer.

    At least you don’t have front coil springs to contend with when doing the bumpsteer stuff.

    Those find adjustments should cure the understeer except at the edge. WOT in lower gears can sometimes still get you some understeer. Firmer in back should help keep from planting the rear so hard that it pushes the front like that too

    one of my friends basically said you can’t turn when the front tires aren’t on the ground..... one of the problems with loads of power and a solid bite in the rear.

  6. #6
    FEP Senior Member flyin5-o's Avatar
    Join Date
    Sep 2006
    Location
    Fond du Lac,Wisconsin
    Posts
    565

    Default

    Dusting this thread off as I am going to get started on it in the next couple of weeks. Racing season will be upon us fast! Thanks for that camber bolt idea errtic50.
    Thinking about ordering a set of these https://www.maximummotorsports.com/M...2-12-P989.aspx. I wonder what makes them T-bird specific and what would need to change to make them fit? It would be nice to have the spring selection available. I would need to make them adjustable then for height so I wonder if these would be adaptable?https://www.maximummotorsports.com/M...014-P1467.aspx. I was hoping maybe Jack Hidley would chime in on this, and the rest of my set-up.

    As for the front, I would love to just throw a MM K-member at it. However being a Lemons car it is not in the budget. I got enough penalty laps at the last race. I don't know if adding the 99-04 arms are worth all the extra fab work? Do I just slide the k-member forward and do the requisite engine mount mod to get some more caster and better weight distribution?

    Thoughts?
    Last edited by flyin5-o; 01-06-2019 at 10:47 AM.

  7. #7
    Moderator wraithracing's Avatar
    Join Date
    Jun 2010
    Location
    Grand Junction, CO/RR TX
    Posts
    14,206

    Default

    Quote Originally Posted by flyin5-o View Post
    As for the front, I would love to just throw a MM K-member at it. However being a Lemons car it is not in the budget. I got enough penalty laps at the last race. I don't know if adding the 99-04 arms are worth all the extra fab work? Do I just slide the k-member forward and do the requisite engine mount mod to get some more caster and better weight distribution?

    Thoughts?
    The MM K member will move the ball joint center line along the center line of the car forward 3/4". The OEM stock 99-04 control arms don't really affect the ball joint position relative to the center line of the car. I believe there is a small difference, but relatively insignificant for this discussion. Running the 99-04 control arms will give you a better camber curve compared to the Fox length. There might be a small change to caster, but again relatively insignificant unless you have CC Plates that allow you to adjust the caster independently. The 94-04 arms are all the same basic geometry, the 99-04 have a different shape that allows for better tire clearance lock to lock, so worth getting if you don't already have a pair of the 94-98 arms.

    If you were to run the MM K member then you can run the Forward offset arms that will move the ball joint forward another 3/4" and lengthen your wheel base by moving the front tire forward @ 1.5". You can run the stock offset that will only be the 3/4" of the K member.

    In order to move the stock K member forward you will have to drill oversize or slot the 4 mounting holes at the frame rails IIRC. Depending on the year model of the K member I believe 3 of the 4 are oval or over sized, but one is standard size to help align the K member. Any movement forward should help increase the caster some.

    I reread the current setup. You might check your K member. There have been discussions as to when Ford introduced the last Fox K member version. Some say late 1987 and some say mid year 1988. I don't remember all the specs, etc. but if you don't have the last version might be worth picking one up. You already have the Mathis book, I assume so you have all the details and modifications. Good Luck!
    Last edited by wraithracing; 01-06-2019 at 01:06 PM. Reason: Corrections
    ​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

  8. #8

    Default

    Lots of stuff that could be done here to improve things.

    PHB looks quite good. The weak link will be the axle mount. Check it periodically for cracks.

    Good job with the fuel cell keeping it decoupled from any part of the rollcage.

    Add strut spacers between the upper thrust cone and c/c plate bearing. Add just enough of them so that the upper spring perch and thrust cone clear the bottom of the strut tower when the c/c plate is slid as far as possible towards the firewall for maximum positive caster.

    Throw away the c/c plates with the poly bushings and install something proper with a spherical bearing.

    Look at the upper spring perch on the k-member. If the perches are formed by punching through the k-member sheet metal, leaving a series of pie wedge pieces, then your car has a “narrow” 2.3l k-member. If the spring perches are welded on torroids, then you have the a wider late Fox V8 k-member. From the view in the engine compartment, you appear to have the later V8 k-member.

    Given how little camber the car has, I would definitely install SN95 FCAs. These will require SN95 inner and outer tie rods to be installed onto the steering rack, or if you install a bumpsteer kit, use the one below. If you already have a kit, we can sell you the longer tie rod sleeves that come in it. If at all possible try to keep the stock ball joints in the SN95 FCAs.

    https://www.maximummotorsports.com/B...yle-P1141.aspx

    If you do the Mathis mods to your k-member and use SN95 FCAs, you are going to need the bolt through style bumpsteer kit linked below. When you do the Mathis mods, I would not be concerned with moving the FCA pickup points inwards. Remove your front springs, install a 1” wheel spacer and cycle the front suspension to check for tire clearance with the fender arch. Since your car doesn’t have ABS, I would only add half of the antidive that Mathis talks about. When you do these mods it will be very challenging to make Delrin bushings work in the FCAs. The Delrin bushings require a perfectly flat, parallel thrust surface. When I did all of this work on one front end, I ended up having to custom sand the thrust surface of each Delrin washer that touched the k-member to that particular location. This is because after moving the FCA holes in the k-member, the 2” diameter area around each hole will not be flat. That effective locked each washer in place, forcing the aluminum insert in the FCA to pivot against the Delrin washer. No problem with this, but it made installing the FCAs into the k-member a puzzle. DO NOT try to do this on the car! Modify the k-member, put it on a table upside down and fit the FCA bushings to the k-member on the table.

    https://www.maximummotorsports.com/B...tyle-P452.aspx

    The longer SN95 FCAs will be much better than keeping the Fox FCAs and using camber bolts. Better camber curve, wider track, better bumpsteer curve, etc.

    The biggest problem with your car is the lack of rear roll stiffness and ride rate.

    The roll axis is defined by the location of the front and rear roll centers, NOT the amount of roll stiffness at either ends of the car. The front roll center is going to be quite low with a stock k-member. Your rear roll center is at the height of the PHB, which is much lower than stock, but still pretty high.

    Your front wheel rate is around 340lbs/in and the rear wheel rate is around 125lbs/in. The rear wheel rate should be about 10% lower than the front rate. (300lbs.in) If you install the stiffer MM TA springs (43TA7), it still won’t be high enough.

    The MMCA-1 that you linked in post #6 are not specific to the Thunderbird. They are listed for multiple chassis on the MM website.

    https://www.maximummotorsports.com/M...2-12-P989.aspx

    If you install them, you must have RLCAs with an adjustable spring perch. This combination will allow you to use much stiffer coilover springs in the rear to get the wheel rate up.

    I think that the Mm5RRHA-2 might be modified to fit a stock RLCA. We have never tried it. Lathe work would be required. The simplest solution is to install an RLCA with an adjustable spring perch and better bushings.

    If you keep the spring on the RLCA, you are going to need something in the range of 600lbs/in. Do you have corner weights for your car in race trim?

    Once that is done, your rear roll stiffness will still be too low. The car will need a larger rear swaybar. A 25mm bolt on rear swaybar would be a handicap fix. It will get the car closer, but the car will really need an adjustable MM rear swaybar to get enough rate.

    Currently the camber curve and static camber in the front is hurting front grip. In addition, the excessive body roll makes it difficult to move the car quickly through transitions, as the excess body roll tends to make the car loose from inertia. With less body roll, the car will be faster, but you will have more understeer. The camber and camber curve improvements will help this.
    Jack Hidley
    Maximum Motorsports Tech Support

Posting Permissions

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