As I posted before, I recently bought a bone stock '86 930. I find the suspension to be too soft, the car has too much squat for my taste, and it's roll rate is unacceptable to me.

I've done searches here and on Pelican about suspension upgrades and I see both sides of the coin.

Upgrading the torsion bars and dampers is "purer" to the original design of the car and it saves a bit of weight compared to the coilovers (seems negligible), but the setup does not allow for any adjustability.

The coilovers add a range of adjustability that the torsion setup cannot and allow for easier corner weighting/setting up.

What other considerations do I need to take into account for this decision on which way to go? I'm trying to tackle the suspension of the car first before jumping into engine mods (plus I'm just aching to order some goods for the car).

I've read that the coilover setup is looked down upon for some reason- why?

The car will see spirited street use, about 4 DE's/track days per year. I like a firm riding car. I find my stock Elise to be just fine on trips, but it has more roll than I would like, but I'm looking for that type of ride.

Edit- let me also add that I would'nt be doing away with the torsion bars w/ the coilover setup- it would be to augment the torsion bars per Nathan K's suggestion.

TIA.

 

Jim,
You can stiffen up the car PLENTY via torsion bars without having to go through the superfluous expense of coilovers. You don't really *need* coilovers until you've got a dedicated track car with over 500 hp. Ask Geoffrey.

The coilovers are the *hip* way to go, but it's like putting big red brakes on a street car. It does nothing for you but look good and add to your bench racing capacity.

I don't know how much track driving experience you have, but you may want to upgrade slowly. A stiffer suspension isn't always a good thing.

The 930 is very, very fast with a stock suspension with some minor tweaks to get it to rotate a little more (stiffen the rear roll resistance), but there will be other opinions...

-dc

 

They are both springs and work the same. You might note that 934's and 935's used both torsion and coilovers. They would adjust the coilovers for individual tracks.

 

A consideration for coilovers on a 930 is that the upper shock mounts were not designed to carry the full load of the car. For driving on a track use of coilover helpers should include reinforcement of the upper shock mounts.

 

S_Craig said it - you'll want to reinforce how the shock/spring is mounted before going that route. Done properly, other than cost, I don't think its bad. Done wrong, you'll start to crack the paint then the chassis potentially.

 

If you drive the car on the street and DE you will be fine. We have installed tons of these kits and the warnings have all been unfounded. Yes, if you run the 24 Le Man then you will have serious issues. If lightly used for DE then you will not have an issue. Monster after spending a year on the track, dragged and driven on the street and sent to Australia never suffered a single issue.

I even have them on my wife's 76 Targa.

Coilovers are a more mature feel and rebound and dampening and coil rebound is far superior than that of torsion bars. The system also is easily corner balanced now by the home wrench and ride height is nothing more than adjusting the collars. Don't like the ride, swap the springs in an hour verses half a day to index the bars.

I honestly find the ride a lot more accommodating and mature than HDs and Torsion bars.

 

I installed coil overs I my 89 930 and am running 733rwhp. My car has less squat rides much better does not bounce on bumpy turns and handles better plus all the other positives. I also installed big reds and am happy I did. If you remove your torsion bars and run the coilovers you will save weight.

David

 

So you got rid of the front and rear bars? What other modifications did you have to do to only run the coilovers besides reinforcing the front perches?

 

Yes, you get rid of all the bars.

You have to do no modifications unless you are on the track as a dedicated track car. Also if anything is going to be done, which it doesn't need to be it is the rear, not the front

 

And if you find the cost of the coil over route is too expensive, consider a matched set of torsion bars and custom valved shocks. What I mean by matched is to your car's weight and driving style. For example, I have 29mm hollow bars in the back with RSR custom valved shocks, and 100lb helper springs to eliminate the squat under full accel. The fronts have (I think) 20mm hollow bars with RSR custom valved shocks. It corner balances easily and is a completely different car than stock. The only adjustments I've had to do at the track are sway bar adjustments.

 

I think if you look at sway bars, good torsion bars and shocks the cost difference is very minimal. I guess it depends on what people are charging but the cost is not that far off. By the time I looked at bars and all the goodies for my wife’s 76 the cost was only a few hundred off. So coilovers it was.

 

Metal fatigue is cummulative. If 24 consecutive hours of hard driving will cause a problem, 24 cummulative hours of hard driving will have the same effect. Porsche did not carry forward the same shock mount configuaration when they switched to coilover.

 

While it may be cumulative the chicken little syndrome of the shock towers falling out of a DE/Street car is unfounded. I have used and installed more sets than I can count and suspect that if the issue was as problematic as presented I would have 10 years of very angry people after me. The issue is spring rates and use. A simple DE is no where near a true SCCA or club race nor would you typically run the same rates. A 3/400 mildly valved shock and strut is not going to create an issue. Again, this I what I personally use and have used for some time without failure. I typically don’t make liberal suggestions when it comes to peoples cars and make sure that they will be safe for years to come.

If one wants to reinforce the area the procedure is to weld a triangular supports along the mount and the upper support in the rear.

 

Dumb question, but how about running Autocrosses with coil overs? A car really gets thrown around alot in 60 seconds.

 

One additional thing to consider is effective rates available. IMHO you can't get a Tbar setup near stiff enough for serious track use. I run 700#/900# in my C2 Turbo.