June 3, 2009 at 8:09 pm #232640
My 1988 FiberFab is looking a little droupy in the rear with it’s 1974 Mustang leaf springs so I thought it’s time for a lift. With 450 lbs in the car it’s definately a low rider. I’ll take some measurements to see what I gain. May have them installed this weekend if not definitely within a couple of weeks. The old springs seem to be installed correctly so I’m guessing they are just sagging from age.
RobBaker 39967.8427777778June 4, 2009 at 10:02 am #239014
Aren’t your car’s springs quarter elliptical? If so, then these need to be cut as they are semi-elliptical.
I had Eaton-Detroit Spring make a set of quarter elliptical springs for the Ford based CMC kit I built. Just cutting the stock springs ended up riding like a brick. The springs they made me allowed for leaf removal. I ended up with the main leaf and one auxillary leaf.
Did you think of trying coil over “load leveler” shocks?June 4, 2009 at 11:01 am #239015Rich BellefeuilleParticipant
I have the same quarter elliptical set up on my 88 FiberFab, and I don’t find the ride to be too harsh at all. Not sure what my builder did different. It does have shocks with coil springs in the back, but I’m not sure that’s what you are talking about. I’m assuming you mean to go away from the leaf springs completely? Just wondering what kind of work and cost would be involved. I’m happy with mine the way it is, but I like to keep a list of possible improvement projects for those cold, boring winter days.
RichJune 4, 2009 at 2:04 pm #239016
Yes these springs will need to be cut per the build instructions. The car doesn’t sit right the rear drivers side is actually lower then the passenger side, without the driver in the car. I’ll put the new springs in which should get everything realigned and then troubleshoot if things still aren’t right. With two of us in the car we can bottom out and the muffler is lower then what I would like. Perhaps coilover shocks would help but I think I’ve got to get things level first.
These springs are stock 74 mustang springs from jc witney.
Your ideas are appreciated, thanks, more to follow.June 4, 2009 at 4:36 pm #239017
No Rich…the quarter elliptical springs work fine once you find the right rate.
I was asking Rob Baker if he thought of using those coil over “helper” shocks before replacing the springs. Monroe used to call them “Load Levelers”.
To put a coil over set up in these cars requires the fabrication of a 4 link rear suspension. Depending on the design of the 4 link, a panhard bar or Jacob’s Ladder would also be required (using a parallel 4 link).
I use an aftermarket Torque (Maximum Motorsports) arm set-up on my ’85 Mustang Road Racer. It uses a panhard bar and just the two lower control arms. The front of the torque arm pivots at the back of the transmission and the rear of it attaches to the axle tubes. Talk about traction!!! No tire spin under acceleration or wheel hop under hard braking. A set up like this would work great in the CMC Ford based TD’s.June 4, 2009 at 6:49 pm #239018Steve CritesParticipant
Mark and Gang;
What you describe on your ’85 ‘stang is pretty much what I have on my Duchess. Ford engine and tranny, but theres a torque tube from the tranny to the rear end, 2 lower control arms, panhard bar and coils. The interesting thing is, it’s a stock chevette rear! And it most certainly works great in a Ford powered car. No bounce, no give, no problems. And since it’s stock, easy to get parts so far.
About a year ago I met a fella that had worked in the Fargo plant who told me the factory built cars had that setup unless they were specifically ordered with all Ford running gear. He said the torque tube eliminated the fitment problems with cutting and welding the elliptical springs.
Too bad I can’t really test the traction with “just” a 4 banger.June 5, 2009 at 7:45 am #239019
I may delay cocktail hour tonight and spend some quality garage time in NH. Think I got all the tools together and have printed out the Monroe catalogue as I’m prepared to order some coil over shocks or as Monroe calls them today “load adjusting shock”. I’ll have to study what’s there as I didn’t build this car. I’ll report back on Monday as to the progress.June 5, 2009 at 11:36 am #239020
Do you think that the Chevette rear suspension was designed to eliminate wheel-hop under their “stuck to seat back” acceleration and “bug on the inside of the windshield” braking?
My Mustang stil has the open aluminum driveshaft. I had to install frame connectors and a special crossmember that goes between them. The front of the torque arm connects to that crossmember located about 1″ behind the end of the Tremec TKO 500 tailshaft.
The rear of the torque arm mounts on the rear axle tubes with U-bolts just where the tubes exit the differential thrid member. It’s a simple and effective set up.
The GM “F” body cars (Camaro/Firebird) had a similar set up from the factory. The Fox body Mustang’s rear stock rear suspension is an aboration. In the SCCA American Sedan and NASA American Iron classes the Mustang’s don’t handle as well under braking and acceleration as the “F” bodies did. This aftermarket set up makes them handle better than the OEM set up GM cars.June 6, 2009 at 8:23 am #239021Rich BellefeuilleParticipant
For those of you who, like me, have no clue what Mark is talking about with “Panhards” and “4 Link suspensions” the reference link below has a very good explanation of these terms.
Thanks Mark for challenging us to be bettter car “Techies”. Now if I can just figure out what a “Tremec TKO 500 tailshaft” is
http://www.popularhotrodding.com/tech/0604_rear_suspension_g uide/index.htmlJune 7, 2009 at 7:09 pm #239022Montie HendersonParticipant
I’m glad I’m not the only one that was lost. Thanks Rich for the link, at least I kinda know what the problem is.. My CMC Ford TD has the same sag on the drivers side. I replaced the shocks, only thing available was the stock style shock for a Pinto. I looked for air shocks or load levelers and was told nothing is avaliable. Any one know of a shop around Dayton Ohio that can help.
Thanks MontieJune 8, 2009 at 8:27 am #239023
Replaced my rear leaf springs this weekend and I would say it was a partial success. Before I started I measured from the ground to the top of the arch the rear fenders drivers side was 26, passenger side was 26 ?, so I?m leaning left and low. After I cut the new springs the installation was pretty straight forward. Not necessary easy but pretty straight forward. I got them on and bounced the suspension went for a short ride and measured again, now getting 27 ? and 27 ? so I gained an inch. This is good but not enough in my opinion. I looked at the standard shock attachment points and they are only 12 ? from bracket to bracket with no weight in the car. My shocks are not spring loaded, they are only dampening shocks so they are not contributing to ride height. Rear ride height on my car is a factor of the leaf springs only. I believe this some how needs to change with an adjustable coil over shock. I will have some PRO shocks off my Cobra in a couple of weeks that I will be able to play with. Finding a short coil over adjustable shock may be a challenge so I think a bracket will need to be created to allow for a longer shock to be installed in which the ride height could be adjusted or tuned for spring age and vehicle load. Obviously with me driving at 200 lbs and my wife in the passenger side at 115 lbs having a car that is already leaning left is not ideal and should be corrected.
After the new spring installation project I measured the frame height on the passenger side, the front was 8 inches from the ground to the bottom of the frame and the rear frame was 7 1/8 so I?m still probably a little lower in the rear then I would like. More to follow on a new tread as I work up something for the rear adjustable coil over installation until then I?ll be enjoying another inch of rear ride height.
Ps when cutting leaf springs you need a large grinding tool, leaf springs are really tuff steel to cut.June 8, 2009 at 9:55 am #239024
As Rob noted, Sagging or drooping suspensions are NEVER caused by a standard style shock absorber. The shock is there to dampen spring oscillation and keep the tire glued to the pavement (or dirt).
If a car’s frame or uni-body is straight and square and all the suspension components (a-arms, links etc.) are straight as well, then only the spring rate affects the “droop”, sagging and ride height. Replacing standard shocks will do absolutely nothing to revive a dead spring.
The quarter elliptical design of the CMC Ford based TD’s have several problems. One is that the spring is ancient and from a donor car that in some cases were worn out before they were used on the TD in the first place.
Another is that most builders used a torch to cut the spring (heat kills it’s rate). They should be cut with a cold saw. Ambient temperature actually affects a leaf spring’s rate.
Another is that the design of these springs make it so they don’t last very long anyway.
Adding a “load leveling” or “air shock” will affect the ride height, but a standard shock will not.
Converting a CMC ford based kit to a 4 link/coil over set-up would be the bee’s knees!
Pink MG39972.4189930556September 3, 2009 at 3:33 pm #239025CoffeyDParticipant
I own a CMC ford MGTD with a V6 automatic set up. I am runing oversized tires on 80 spoke wire wheels. The MGTD now has air shocks to lift the rear and clear the tires.
I am getting ready to convert to coil over shocks and add the mounting plates needed . Does any one have a specific referance for the recomended coil shock unit?
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