installing coilovers, reinforcement really needed?
 

I've noticed some people welding in some reinforced sheet metal on their rear shock towers.

Is this REALLY needed? I mean... has anyone ever seen a coilover being ripped from the rear shock towers or pushed through completely?


If you have, or have some pics that show the damage done, I'd be curious to see.

The short answer is that photos have been posted with such failures. The question for me is do you need this an a street car.

Those shock towers were not designed to support the car.

I've looked, and googled, and still couldn't find anything... at least not on a G-body 911.

In that case, a pair of really stiff shocks could cause damage then?

Reinforcement pieces to tub are welded in to spread the load properly

and some even add a complete length tube piece between both towers for more rigidity

They can and do. It's why they reinforced the shock towers for the 911 race versions.

The torsion bars support the suspension. Take the shocks out and the car still sits there. Coil overs, all of the load is at the upper shock mount.

Exactly. Huge difference in the force applied to the shock mounts.

yes you really need to

Unless you’re racing the car, the coil overs are probably overkill. The chassis wasn’t designed to carry the loads through coil overs without support.

Absolutely reinforce them Trakrat. I have seen the complete crossmember break loose at the welds. Car came in bouncy bouncy, like the shocks were gone, opened the rear and the whole cross member was moving up and down with the motion of the car. Gusset, Gusset, Gusset!

Better still, perhaps reconsider. Why do you want coilovers? There is no difference in suspension geometry between T bars and coilovers - both are just springs (assuming you aren't going to use taper ground titanium springs to get a progressive effect, as Porsche did on some race cars).

You can get a torsion bar which literally is as large as will fit the various holes, and is even larger than the inner spline diameter. I've got that on my track car. Pretty stiff for the street.

On a track car, the benefit of coilovers is the ease with which you can change them (not expensive, either, considering) to tune the car for this or that track or just overall. Do you plan to experiment on your car?

Of course if it is to be a track car, fine. Just reinforce. You can get away without it for a while. But just a while.

almost everyone does. Both TRE and Elephant Racing sell reinforcement kits ready to weld in.

pictures of what happens when you don't - and a great explanation as to why you need to are both in this thread.

http://forums.pelicanparts.com/porsche-911-technical-forum/739625-rear-crossmember-tower-damage-pics-coliovers.html

this is a case if you had to ask, you really already knew...

Here's a pic of a tower failure.
http://forums.pelicanparts.com/uploa...1567923890.jpg

Not my car, so I don't know the failure conditions, etc.

Point of reference, 1979, with 3.6, 935 setup, street compliant springs, JRZ's. Rear tower plates, some front reinforcement, increased space for springs, welded in half cage.

I put a crack in tub after a day at the track last year, didn't know it was there until I got home and swapped wheels.

Seems like an odd place for a crack but there it is.

Coilovers are a blast, car feels like a go-cart now, night and day, Doing a coilover conversion over here in New Zealand was a nightmare to get done due to the certification process....cad drawings required/suspension x-rays, all OEM parts, bump steer must remain unchanged over stock etc etc.


Crack at top:
http://forums.pelicanparts.com/uploa...1567929397.jpg

Welded up:
http://forums.pelicanparts.com/uploa...1567929647.jpg

Tower:
http://forums.pelicanparts.com/uploa...1567929921.jpg

Rear:
http://forums.pelicanparts.com/uploa...1567930180.jpg