Coil over suspension worth it?

[BlkBird]

Just got the car back from my favourite mechanic and he believes "our" next change on the car should be to switch the suspension to "coil over". Say $5K US.

Now I have heard some folks feel that if you switch out the Torsion bars to Coil Over you have made the car into a track car, ruined its resale value and made it a brute to drive on the street.

I'm wondering if anyone has made the switch to coil over on their street car, what you thought of the results and why you didn't choose a more conservative option of bigger torsion bars, Bilstein Sports and larger sway bars.

[Jack Olsen]

I can't see why you would go to coils if you didn't need stiffer spring rates than torsion bars can provide.

Generally speaking, a spring's a spring, and the chassis was designed for torsion bars.

[BlkBird]

so Jack, what torsion bars would you recommend for a 1989 930 (I know, I know - cab, ewwwww)?

[addictionMS]

well I agree a spring is a spring, but you can not make a progressive torsion bar, but you can make a progressive coil spring.

There is a reason most modern cars are on coil springs, and most if not all the top GT cars are on coil springs. Additionally it is generally much easier to change out a coil spring at a track. However I believe unless you have a full cage and tie it into the suspension mount points, Jack is correct your chassis will not take the additional forces put on it in the places a coil over suspension will create.

Jim

[dd74]

I've wondered about coil overs as well, but price definitely negates their value for a mostly street driven car. A race car's needs are much higher in this respect.

Yet there is the question: if one were to go to coil overs, are some coil overs less harsh than others, or are they all basically too harsh for street driving.

[addictionMS]

Coil overs are just like torsion bars, tune-able to your application. They are just shocks and springs, pick the combo that meets you needs.

remember "coil-over" simply means the coil (spring) is over the shock. Go check out just about any modern street car and they have coil overs on the front, not ajustable perch, adjustable shock, and stiff spring coil overs, but coil overs.

Jim

[Elombard]

Blacky give Weiner a call at Rennsport. He can sell you a custom valved shock T bar combo that will be perfect for what you want to do. I am thinking 30mm rears and 20/21 fronts with appropriately valved Bilsteins. Than add adjustable sway bars later. I think you can get very good suspension in a Tbar car that will work for all but the most rigorous track demands. You are not going to be interested in changing spring rates at a track day anyway, or even ride height for that matter. IF you want to go PCA racing build a purpose built car, not worth it for DEs IMHO.

[addictionMS]

just as a data point, my full out track car is still on torsion bars, so I agree with the advice to just get a well known combo and enjoy. Car set up is tough enough when all you have to change is camber/caster/toe/ride height/corner weight/sway bar settings with out adding spring rate/dual adjustable shocks

Jim

[Mr9146]

Jack, of all the people who responded to this thread, I would think that you would be the one to support a switch to coilovers ... after all, you did.

That aside, the coilovers vs. torsion bar argument is based around one thing and one thing only. A coilover setup provides you with infinite adjustability. That's the key ... infinite.

For most applications a coilover setup is overkill ... but then why did Porsche switch to the coilovers on the 964? Infinite adjustability offered by changing springs, and the inherent changes in ride quality that are inherent in a progressive rate spring design.

The torsion bar setup is, technically, an inferior design. But it's fine and worked well for decades ... in that respect Jack is correct is saying to leave it alone ... but if you want infinite adjustability - if you need infinite adjustability - then coilovers are the only way to go.

[island911]

Originally posted by Mr9146
. . For most applications a coilover setup is overkill ... but then why did Porsche switch to the coilovers on the 964?
. . .

ABS

The torsion bar setup is, technically, an inferior design

. . . thats why F1 cars use them.

[Mr9146]

PS: The 914 uses a standard torsion bar front end a coil over rear suspension ... the best of both worlds

[Mr9146]

Last time I checked, didn't F1 suspension use the motor and trans as stressed members in a multi-link, coilover design?

[Mike Feinstein]

Chris,

The only thing I'll add is that I think they are "over-selling" you. I think if Bob and company clearly understand that you are doing occasional DE's and mostly driving your family around with the top dropped and doing a few mountain runs on nice days, they might rethink their recommendation.

I'm not sure what size T-bars came on your Turbo, but 22's and 30's would probably work great. A new set of Koni yellows or Bilsteins, lower, align, and balance and I think you'd be ecstatic.....and have about $2500 left over.

You could then donate half of your savings to my Carrera upgrade fund. I'm not greedy....I didn't ask for all of it, did I?

[island911]

Originally posted by Mr9146
Last time I checked, didn't F1 suspension use the motor and trans as stressed members in a multi-link, coilover design?

Here is an enlightening link for ya.

[Randy Webb]

Another thing about coilovers -- you might be able to lose some wt. Jim Calzia's track car used F coilovers with the erp front end and save a lot of wt. No claim to cost-efficiency here...

[emcon5]

Originally posted by addictionMS
unless you have a full cage and tie it into the suspension mount points, Jack is correct your chassis will not take the additional forces put on it in the places a coil over suspension will create.

This bears repeating, especially in a cabriolet.

Tom

[ipapilot]

Would there be any benefit to doing coilovers only on the front? It would seem more suitable in terms of strength and it would also offer the ability to corner balance pretty easily. Somebody in Excellence has been offering a setup with adjustable perches and your choice of spring rates for relatively little money (under $500 if I rememeber right). I think it is agreed that to do the rears you would definitley have to strengthen that area.

[ZCAT3]

BlkBrd - I have a Bilstein RSR Coil Over suspension on my 930 and the general upgraded larger torsion bar, Bilstein gas shocks set up on my 87 Carrera (which is the car I usually use for DEs). I will say that on the 930, the coil overs not only handle better than the upgraded suspension on the 87 Carrera, but it is also a more comfortable ride for the street. Stephen Kaspar at Imagine Auto set me up with this suspension - it is the same suspension he used on his twin turbo 930 that was used extensively on the track, but also for street. He sold that car about a year ago, but it apparently has seen a lot of track use since then with good results. You may want to give him a call to at least get another opinion.

P.S. Stephen is the 911 National Tech Advisor for PCA, so someone thinks he knows his stuff.

[mm86911]

Chris,

It's your money and coil-over is certainly a nice setup. Definitely spend some time learning from other's experience here before you make that kind of investment. Also think about what you want to do with the car and how long you plan to keep it (more DE or just pimping? ). You've got a rocket and stops like hitting a brick wall.

In my case, I've slowed down on upgrades and have been spending more time driving (DE / AutoX). Toying with thought of 930 brake upgrade but desire hasn't overpowered logic - still learning how to drift through the esses and turn 12!

[Colby]

Somewhat off topic, but rarely discussed (as few ppl on here have cabs they are trying to get track worthy, even on a part time basis), but another mod worth considering is to switch your engine mount crossmember over to the coupe style, then go to solid mounts. The cabs came w/ a dampening system which allows too much flex and compromises chasis rigidity for comfort. I did this and can feel quite a difference after having had an opportunity to drive it for awhile. On my cab i went 21/27, but I'm not a turbo either.