Need 2nd Gen suspension to carry extra 1200 lbs
 

Before you ask, "What the heck?" I'm building an electric version of my 1986 GXL. I need to find struts/shocks that can carry an extra 1200-1500 lbs due to battery weight. Anyone know the most economical option to upgrade my suspension? I do have the sport suspension, but I expect it's worn out.

Thanks,
Dave

Just about any shock and strut (hereafter reffered to as dampers) should be capable, but for the springs you'll basically need coilovers, otherwise you'll be riding quite low. To deal with the extra spring rate that goes with getting coilovers (Ground Control makes sleeve over adapters for conventional damper and will sell the kit with many different spring rates) you'll need stiffer dampers, which basically means adjustables. The choices are basically just the Tokico Illuminas, the KYB AGX or the Koni Yellow. The AGX is probably the best value, but the Konis are the best performers. If you maintain the ride height at near stock levels you won't have to worry about alignment issues.

GC's and AGX's should run you about $800. Not a bad deal all things considered.

Thanks, I really appreciate it. Dave

1200lbs of batteries??? What is the range of this car going to be? Also, how will the load be distributed? Are you going to remove the gas tank and make that entire area battery packs? What will the weight be in front? In order for the car to drive anywhere close to stock you need to keep the corner weights at the same percentage.

Are you going to use a factory transmission and differntial? I am very interested in what you are doing because I have thougth about it myself.

Look on the drivers side door panel. It will tell you the Maximum gross vehicle weight for a factory car. Even with stiffer springs and better struts I don't know how much above those weights is safe to go.

Like was previously stated, I would do everything possible to even the weight out on the car. If that requires you to remove the gas tank and then put half the batteries in the rear of the car and half in the front engine bay, that sounds like it would be ideal. Putting all that weight up front will ruin all driving dynamics no matter how much you stiffen up the front end.

Personally, I would reccomend calling a company such as H&R or Tokico or another reputable suspension company and explaining to them that you have an FC3S which weights XXXXlbs from the factory and uses XXXlb front spring rates and dampening and XXXlb rear rates and dampening... Tell them you plan on adding XXXlbs to the front of the car, and XXXlbs to the rear of the car, and are wondering what THEY would suggest increasing the rates of spring and dampening force to in order to keep the car off the bump stops.

For a project like this, I would not reccomend you using an aftermarket coilover system that is already available, because although they are stiffer than stock suspension, I doubt they are stiff enough or set up to take the weight of the car plus 1200lbs...

Ummm, for any coilover suspension out there you can get alternate rates, and the rates range from less than twice as stiff to 4-5x as stiff, so there's one out there that's stiff enough. Now the problem you'd run into is not being able to raise it high enough, but you can also get alternate length springs. Ground Controls can be bought in nearly any number of stiffnesses and lenghts.

As a guess I'd say you'd want to go 1.5-2x as stiff. GC uses essentially the same setup on a 2200lb Miata as on a 3800lb Mustang or whatever that's seriously heavy. It's probably a good idea to talk to them about it, but I don't see it being a big problem. A 2600lb S4 with 1200lb is the same weight as that 3800lb Mustang, and then you can save weight from removing the engine, gas tank and a whole lot of other stuff.

It's probably not a good idea to jump it or anything, but I don't see that with normal use it'll be an issue.

Thanks everyone, good advice. I am planning on keeping the weight 50/50 front to back by putting batteries up front, behind the seats, and where the gas tank is. I'll be about 400lbs under the max weight on the door jam.

Luckily, I'm not the first to convert an RX-7. For a kick, see:

http://www.austinev.org/evalbum/047.html
http://www.austinev.org/evalbum/120.html
http://www.austinev.org/evalbum/179
http://www.austinev.org/evalbum/260.html

If you ever want to take the discussion of conversion to electric off-line, contact me at toolmanca1@yahoo.com.

Appreciate the advice.

Dave