Converting to coil over, what are the options?

[FirstGen]

Thinking about converting to coil overs and was wondeing what my options are and what is the best bang for the buck?

Car is a '77 911S with a widebody and 18x8.5 and 18x10.5

[HarryD]

First,

Why are you converting to Coilovers? Can you not get a big enough spring with torsion bars?

Going to coilovers entails a huge cost to modify the car to accept them since the mounting points to bear the loads do not exist in your car.

[FirstGen]

Originally Posted by HarryD

First,

Why are you converting to Coilovers? Can you not get a big enough spring with torsion bars?

Going to coilovers entails a huge cost to modify the car to accept them since the mounting points to bear the loads do not exist in your car.

It's my personal car and I do chassis work for a living. I had planned on building a cage for it, and prep it for the coil overs while the engine is out of the car.

[RWebb]

I cannot answer your question but for numerous examples, just do a search.

As to what is best - that would take a lot of hands on driving & testing - or some very serious finite element modeling...

Generally, the factory's last 964 based race cars (rallys?) should be expected to be pretty good.

[HarryD]

Originally Posted by FirstGen

It's my personal car and I do chassis work for a living. I had planned on building a cage for it, and prep it for the coil overs while the engine is out of the car.

No offense intended. Your car, your money, your time, your choice.

IMHO, it is my understanding that the only reason to go to coilovers is to get greater spring rates than you can with torsion bars.

What is your intended use? Why do you need such a stout spring? Have ou spent some quality time with a qualified speed shop to verify the plan and get some pointers?

As Randy notes, do a search and you will find numerous examples of coil over conversions.

[scottbooth]

Check out this link:

http://www.rebelracingproducts.com/Suspension/Steering.html

I did a lot of research on this and ended up talking myself off the ledge, because I realized that just because I'm working on a stripped chassis and welding stuff here and there, doesn't mean that I am good enough on the track to out-drive big torsion bars. No offense intended, hell I might change my mind tomorrow (probably after I've painted the tub ).

Anyway, this looked like the best bang for the buck option for a coil over conversion, and is the path I would take if I were going to do one.

Some of the necessary chassis reinforcements are covered in this thread:

RSR Rear Shock Reinforcements

Basically you need to gusset and brace the shock tower mounts to handle the added load. If you are doing a cage that ties to these points then part of that is probably already taken care of.

Good luck

Scott

[Jack Olsen]

Unless you need stiffer spring rates than torsion bars can provide, then you get worse unsprung weight, a higher center of gravity, and the hassle of welding in gussets and reinforcements in the rear. And adding more weight back there, where you generally want to cut as much as you can.

I got rid of mine in the front, since they reduce the width of tire and wheel you can fit. I run 600# springs in the back.

Here's a thread that shows some of the work you do.

This picture shows the gussets for the rear shock towers. You also weld pieces in where the rear crossmember meets the chassis.

[FirstGen]

I appreciate all of the feedback everyone. I do not want to give up wheel or tire clearance in the front.

I am running a 245 on a 18x8.5, would this be out of the question? I will eyeball the clearance a little later.

My hopes for the coil overs were, easy spring rate changes, better ride quality with more adjust ability. Maybe I am off base here.

If nothing else, it sounds like sticking to my 22mm front torsions and converting only in the rear might not be a bad idea.

Thoughts?

[RWebb]

How many different tracks do you run at?

[lateapex911]

I'd be VERY leery....the car wasn't designed for coilovers, and while I know people love to do it, I just don't see the need if the car sees the street at all.

One major advantage is that in racing you need to change settings quickly, and coil overs with adjustable perches are the cats meow when it's time to corner weight it.

In the front of an old 911 that adjustment is a piece of cake, in the rear, it's more difficult, but...there are great rear solutions like Chuck Morelands Elephant Racing parts and the WEVO SPS system, that can make corner weighting a breeze. Both systems improve location and precision, and Chucks improves geometry as well.

I'd do some real soul searching and lok at alternatives before I jumped into a system thats so invasive.

[barney911rs]

If you decide to make the leap, +1 on Scott's recommendation of Rebel Racing Products. That is where I got my coil overs from. I'm a full GT race car running slicks and I needed more spring rate. I did have to weld up the rear suspension mounts like Jack said. There is a whole thread showing lots of different methods of doing that. RSR Rear Shock Reinforcements

[rusnak]

I think raised spindles are a good starting point. If you get the Bilstein RSR struts, then you will have the benefits of a raised and reinforced spindle, and you can decide whether to go with coil overs, or you can keep your torsion bars and not install the coils at all. I think Smart Racing makes some interesting looking coil over struts, but I have not tried them so I can't comment.

Also, 18x8.5....why such a TALL and narrow wheel?

[FirstGen]

Originally Posted by rusnak

I think raised spindles are a good starting point. If you get the Bilstein RSR struts, then you will have the benefits of a raised and reinforced spindle, and you can decide whether to go with coil overs, or you can keep your torsion bars and not install the coils at all. I think Smart Racing makes some interesting looking coil over struts, but I have not tried them so I can't comment.

Also, 18x8.5....why such a TALL and narrow wheel?

I didn't think 18x8.5 was an odd size? What is more common 17x9?