Suspension advice for 80 wide body hot rod

[chucksmith]

I recently bought a 1980 wide body 911 with no engine or transmission and plan a 3.6 swap with a built 915 with LSD. I am starting to consider suspension choices and would appreciate advice from members that have gone through such a task. My first thought and plan is for coilovers front and rear, but upgrading stock suspension geometry may also be a good option. I will not be tracking the car and do value a decent ride quality. Any advice o experience is much appreciated. chuck

[Bill Verburg]

Originally Posted by chucksmith

I recently bought a 1980 wide body 911 with no engine or transmission and plan a 3.6 swap with a built 915 with LSD. I am starting to consider suspension choices and would appreciate advice from members that have gone through such a task. My first thought and plan is for coilovers front and rear, but upgrading stock suspension geometry may also be a good option. I will not be tracking the car and do value a decent ride quality. Any advice o experience is much appreciated. chuck

I use 20/26 w/ Bilstein hd/sport, 8-225/45 & 9.5-255/40 x17, stock sways on mine

street use only

[Walt Fricke]

Coilovers are easy to change and relatively inexpensive, so a decent choice for getting the ride you want by experiment. However, a torsion bar is just a spring, no magic in coilovers, and Porsche designed about as good a street ride as one could expect, balancing handling with comfort. You could up the size of the rear T bar some to compensate for the extra weight of the engine, and the wider track you probably have with the wide body has the effect of softening the rear. And to compensate for the extra torque, to reduce squat under hard acceleration and reduce understeer.

Coilovers require significant reinforcing of the shock perch up top, and often welding and other sheet metal work to increase the fenderwell space for the springs. You can add coilovers to about any shock (you can slip over a threaded cylinder for adjusting the lower perch), but it is more straight forward to purchase shocks/struts set up for coilovers.

It is a lot of work to change suspension geometry. With coilovers you can weld in camber boxes to hold the inner banana arm mounts so the pivot can be adjusted upward. You can also move the pivot for the spring plate up some.

Now, if you really want a helpful change, consider switching to the 993 rear suspension. Can be done, but look into the cost.

In front, you can move the end of the steering arm effectively down a bit with spacers on the rack, or in other ways.

However, most of this suspension geometry stuff is for racing/track, or if you want to make your car lower. Lower has consequences for street use, and doesn't help the driving experience. You aren't driving 10/10ths or anything close to it on the streets and highways, so why fuss with the geometry beyond alignment settings?

And for ride, you wouldn't want to replace rubber bushings with metal. Replacing old, worn out bushings with new pliable bushings, yes. You can get used to stiff bushings and higher spring rates (I did), but at a cost for comfort. Do you really want to try to take those 45 MPH curves at 90?

When my SC was dual use, I found the best street ride improvement was to change my track tires to street tires. Softer sidewalls (taller tires) made a huge difference in ride. A seat with good bolsters for legs and torso helps on the street as well as the track, but one which is adjustable and has springs or is otherwise softer makes driving on the street more comfortable as opposed to the thin padding on a fiberglass or carbon fiber one piece race seat. With that motor you have no need to reduce weight.

So that last is my little bit of actual experience as opposed to theory. It boils down to the fact that we shade tree mechanics can't really expect to do better than Porsche's engineers from the 1970s for a sporty street car. It started life handling much better than big Detroit boats.

I suppose you could see if there was a way to switch to shocks like my 07 Turbo has - a dash switch to change their characteristics - ride comfort vs stiffness? Be a fun project, but sounds expensive?

[PeteKz]

I don't have coil-overs (yet), but the thing about them that is making me consider swapping (after putting fair coin into Koni shocks and stiffer T-bars) is that the KW's have more adjustments, including "divergent" valving. That allows quick short movements to be damped softly (e.g., hitting a pothole), and larger longer suspension movements to be damped more strongly (e.g., road heaves). I have Ohlins shocks with those adjustments on another car (not Porsche) and I really like the suspension compliance on the road. For the occasional track jaunts, I crank up the rebound and compression adjustment knobs.

[Walt Fricke]

You can get adjustable shocks for torsion bar suspensions, though in this owner's case he doesn't see track driving in his future. You can also custom valve shocks, though you'd need someone with a lot of rather esoteric knowledge or experience to hit any particular sweet spot for a particular car and driver right out of the box. Or just take the advice of someone like Bill V.

[chucksmith]

I appreciate the advice. There are so many choices out there now it is hard to figure out what works best. It is also easy to over think it.