Coilover regrets?

[donbecker1234]

Doing my research on a full suspension rebuild on a 1987 930 (clone).

For those that have done a conversion from torsion bars to coilovers:

1. What were your reasons?

2. Would you do it differently if you could choose again?

3. Rear shock tower reinforcement...do you feel it's absolutely required going to ANY coilover setup, or only for racing/autocross?

4. Any opinions on brands manufacturers greatly appreciated.

My use case would be frequent/daily driver, occasional spirited canyon. No track or autocross.

Thanks in advance!

[David]

I did it last year on my '79 930. I did not find it drastically different or better than torsion bars. The main difference is easier ride height changes and corner balancing. Springs can be changed cheaper and faster than torsion bars too. I have not done shock tower reinforcement yet, but I plan to in the next couple months.

BTW, I started with 300/450 springs and softened to 250/375 which I like better.

[donbecker1234]

Originally Posted by David

I did it last year on my '79 930. I did not find it drastically different or better than torsion bars. The main difference is easier ride height changes and corner balancing. Springs can be changed cheaper and faster than torsion bars too. I have not done shock tower reinforcement yet, but I plan to in the next couple months.

BTW, I started with 300/450 springs and softened to 250/375 which I like better.

Thanks David. Did you document it here on the forum, or could you tell me more about your setup?

Are you using helper springs?

Did you change your shocks at the same time? I'm considering changing shocks, keeping stock torsion, then converting over to coilovers later.

[3rd_gear_Ted]

Front T-bars and JRZ strut inserts
Rear T-bars and two way adjustable JRZ shocks with coil over spring helpers.
Purchased from Jae @ Mirage in San Diego.
Ride height, shock settings, alignment and corner balance by Steve @ Johnson Alignment in Torrance.

[wayner]

Aside from the fact that multi-way adjustable damping is more common with coil overs
(and adjustable spring perches make ride height adjustments easy as mentioned)

The main reason for coil overs is that that take up less space.
A coil-over spring and a torsion rod are the same thing (a spring)

When the 1973 factory race team needed to go to even larger torsion bars, they found space an issue so fitted coil overs.

With the spiders that Pensky and others used in American lemans etc. just a few years ago, they employed torsion bars and not coil overs.

There is nothing inherently better about a coil over spring than a torsion bar unless you are changing the size of the spring at the same time.

Some people even say that since the torsion bar is mounted lower on teh chassis it is better since it doesn't transmit the load up high on the chasis.

If you are looking for better handling, if it were me I'd look at what characteristics you want to change.

If you aren't looking at changing the shocks or spring sizes, then i'd just go for whatever adjustments and improvements you need. If your are changing shock valving, getting more adjustability or bigger bars dont fit then getting the coil over may be a good choice for future tuning even if you keep the same spring size, but not because the springs are better than the bars.

When most people say the coil overs handle better, its because along with those simple bolt on parts, they received a lot of other improvements that came as part of the package. It wasn't from the coil part of the coil-over shock unless we are also talking heavier springs.

[donbecker1234]

Originally Posted by wayner

Aside from the fact that multi-way adjustable damping is more common with coil overs
(and adjustable spring perches make ride height adjustments easy as mentioned)

The main reason for coil overs is that that take up less space.
A coil-over spring and a torsion rod are the same thing (a spring)

When the factory race team needed to go to even larger torsion bars, they found space an issue so fitted coil overs.

With the spiders that Pensky and others used in American lemans etc. just a few years ago, they employed torsion bars and not coil overs.

There is nothing inherently better about a coil over spring than a torsion bar unless you are changing the size of the spring at the same time.

Some people even say that since the torsion bar is mounted lower on teh chassis it is better since it doesn't transmit the load up high on the chasis.

If you are looking for better handling, if it were me I'd look at what characteristics you want to change.

If you aren't looking at changing the shocks or spring sizes, then i'd just go for whatever adjustments and improvements you need. If your are changing shock valving, getting more adjustability or bigger bars dont fit then getting the coil over may be a good choice for future tuning even if you keep the same spring size, but not because the springs are better than the bars.

When most people say the coil overs handle better, its because along with those simple bolt on parts, they received a lot of other improvements that came as part of the package. It wasn't from the coil part of the coil-over shock unless we are also talking heavier springs.

Thanks Wayne, that makes a lot of sense, especially:

Originally Posted by wayner

When most people say the coil overs handle better, its because along with those simple bolt on parts, they received a lot of other improvements that came as part of the package. It wasn't from the coil part of the coil-over shock unless we are also talking heavier springs.

Reading about others' changes to suspensions on the forums and it is rarely one part being swapped out.

[wayner]

Originally Posted by donbecker1234

Thanks Wayne, that makes a lot of sense, especially:



Reading about others' changes to suspensions on the forums and it is rarely one part being swapped out.

The beauty of coil overs is that by swapping out just that one part, the old shocks for new coil overs, those coil overs are nice neat little packages of many new things all in one


Take a look at the post above but 3rd_gear_Ted
where its not even necessary to replace the torsion bar but to supplement it. Thats even a simpler but still effective change

If you are into efficiecy how do you want to measure it?

1. If efficiency is Labour involved and cost (leave the torsion bars in place and supplement)

OR

2. Remove the torsion bars and spec heavier coils and brace the shock towers(if you believe efficiency is having fewer parts)

Having said all of that, modern shocks with all of the cool new digressive internal valving methods are absolute magic

[David]

Originally Posted by donbecker1234

Thanks David. Did you document it here on the forum, or could you tell me more about your setup?

Are you using helper springs?

Did you change your shocks at the same time? I'm considering changing shocks, keeping stock torsion, then converting over to coilovers later.

I do have helper springs. I used my existing Bilstein front sport and custom (stiffer than sport) rear shocks with Rebel Racing kit. I also lowered (oops,) i meant raised the spindles.

I think I posted the mods on the turbo forum.

Going with KW or other adjustable shocks or coilovers would be awesome but cost is substantially more.

[Flojo]

Originally Posted by donbecker1234

3. Rear shock tower reinforcement...do you feel it's absolutely required going to ANY coilover setup, or only for racing/autocross?

at least reweld the seam of the cap!
keep in mind that shock tower is 40 year old and suddenly gets more spring pressure.

regarding the swap in general, David sead it all. It's the common and modern.

I'd swap right away, if I could afford.

[jpnovak]

Agree with everything said so far. There are a few missing thoughts to the process.

IMO the biggest advantage of coil overs is the ability to use progressive wound springs. However, most suppliers ship linear rate springs. You could be missing the gains related to ride quality AND lateral load handling.

The second is damping. if you are not changing the damping of your shocks when you add stiffer coil over springs then you have harmonics that are not matched. Stiffer springs require reduced compression (jounce) damping and increased rebound damping. Think of it. It takes more force to compress a stiffer spring. If you add additional damping force on top the ride can be harsh and jittery because of limited travel. Then the spring can be bouncy on return because it wants to return back to its original state faster than the damper can keep up. Ever watch a lowered car bounce down the road? Not good for handling and not confidence inspiring behind the wheel. Make sure your suspension system is well matched and properly balanced to the car and its weights. This is all true whether coil over or torsion bars.

[ADDvanced]

Originally Posted by donbecker1234

Doing my research on a full suspension rebuild on a 1987 930 (clone).

For those that have done a conversion from torsion bars to coilovers:

1. What were your reasons?

2. Would you do it differently if you could choose again?

3. Rear shock tower reinforcement...do you feel it's absolutely required going to ANY coilover setup, or only for racing/autocross?

4. Any opinions on brands manufacturers greatly appreciated.

My use case would be frequent/daily driver, occasional spirited canyon. No track or autocross.

Thanks in advance!

If it's just a sporty daily, why bother with all the hassle? You aren't competing for half seconds on lap times, so don't cut up the car and just run torsions.

[Duc Hunter]

I went to coilers from Rebel Racing only Rat Rod. Clint set me up with the same street coil weights he runs on his personal car. It rides beautifully, and better than my 89 Carrera does on its new Bilstein shocks. On bigger bumpers I find the coil overs are smoother, and the Rat Rod rides almost as smooth as my 996TT. I could not be happier. That said my Carrera rides good too, and would ride even better at its lower ride height when I have the spindles raised.

[Flojo]

Originally Posted by jpnovak

The second is damping. if you are not changing the damping of your shocks when you add stiffer coil over springs then you have harmonics that are not matched.

as far as I know, the coil-over shocks are adapted to that.
I'd wonder anyway if a premium manufacturer (e.g. like Bilstein) would not respect that.

[Cory M]

Originally Posted by ADDvanced

If it's just a sporty daily, why bother with all the hassle? You aren't competing for half seconds on lap times, so don't cut up the car and just run torsions.

I agree.

I have coilovers on the racecar and torsions on the street car. On the racecar I'm running springs that are stiffer than the biggest torsion bars and adjustable shocks. A potential downside to coilovers that hasn't been mentioned is that they can reduce the amount of room available for wide tires. For street driving and the occasional canyon run I'm not convinced the cost and work to properly convert to coilovers is worth it.

[glerbone]

Call:

Steve Weiner
Rennsport Systems
Portland, Oregon
503.244.0990
E-mail: porsche@rennsportsystems.

He is one of the Nicest guys you will ever speak to and is an encyclopedia of knowledge.
He is a MCS distributor. He can have set of remote reservoir shocks which will have enough adjustments that will allow you to from touring - sport to track if you want.

[glerbone]

Pic of my for my 1972 ST build

[Cory M]

MCS are great dampers, at over $6k plus the cost of springs or bars they are overkill for "occasional spirited canyon" driving but as Ferris Bueller said, "if you have the means, I highly recommend..."

[wayner]

Here is what I did when building my 73RSR replica, and it is very counter intuitive to some

1) I got the body done, painted and running

2) I got the engine in and mounted the suspension that I had.
(the shocks were still good adn the T-bars had been upgraded already by the previous owner)

3) I drove it on the street, and worked out the bugs.

4) I took it to the tack (just DE events) and kept a log book of what I liked and didn't like (including on the street)

5) I talked to a tech expert about suspension and rather than give me this opinion on what I thought I wanted, his first question was "what problems are you trying to solve?"

Since then I have enjoyed solving one "problem" and then seeing what pops up next on my list of tweaks.
I don't ever "need" new suspension parts, instead I "need" to go faster, or tune out some undesirable quality, or get more of something else that I enjoy (which may require new shocks).

I am taking it in steps and enjoying the process, perhaps aligning and corner weighting the car and adjusting ride height and then driving it for a few months before deciding that I need better tires, which then leads to teh next step (cranking in more weight into my adjustable rear sway bar, which has now lead to me wanting to replace the front one with an adjustable one.

Someone asked me why I didn't weld up the shock towers while I was in their during the restoration.
Quite simply because I didn't need to. Im not running coil overs.

But, what if you decide to go to coil overs?

Well, I've fine tuned my wiring harness and mounts to that I can drop my engine in under an hour using only to tools in my on board tool roll. I can always do the mod over the winter.

I've spanned it out over years, enjoying being the development driver rather than just throwing some paint by numbers solution at it and missing all the fun of knowing why the next setup is better.

I don't drive the car the way I want Instead I let the car tell me how it wants to be driven. I enjoy that process, and then once it tells me what it needs next, I go out and solve that problem by talking to the tech experts and asking others for advice.

I'm running 275/17 tires on the back and the biggest T-bar that will fit, so at some point I may need to go to bigger springs by way of coil overs or helpers, but I haven't gotten there yet. Maybe when I start running R-compound tires at the track I'll need to do that.

With my big heavy larger than stock wheels and tires, adn the biggest torsion bar, my car actually rides quite comfortably on the street though, and takes the corners flat. Its perfect! On track though it has a bit more body roll that I would like, so, I'll explore that one day. I'm enjoying the engineering process.

Right now it tells me it needs me to get rid of the poly bushings in the back that make it sound like squeaky old boat trailer, and introduce more decibels into the cockpit than the noisy exhaust does. (I've measured that and I wouldn't have guessed that when catalogue shopping for parts)

[jpnovak]

Originally Posted by Flojo

as far as I know, the coil-over shocks are adapted to that.
I'd wonder anyway if a premium manufacturer (e.g. like Bilstein) would not respect that.

If you buy a complete coil over system including dampers and springs you should get a matched system. There are examples from Bilstein, KW, etc that fit this category. If you are using a conversion kit you may or may not have a matched system.

The point is to make sure to work with the vendor and get these questions asked along with satisfactory answers.

[jpnovak]

Wayne has it correct.

What suspension/handling problem are you trying to solve?