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914World.com _ 914World Garage _ Should I reinforce my rear strut towers?

Posted by: chad newton Jul 24 2013, 01:02 AM

My plans for my 914 are to run as a track car more then on the street. If I wanted one for the street I probably would get another that at least had interior and paint. I will be installing a cage, already have the 911 front suspension, will have the sway bar installed shortly, around 250hp 2.7, what else needs to be looked at? I have seen a lot of guys running a bar welded to the rear strut towers and was thinking about doing that to mine. I will not at this time connect it to a cage because I was thinking of starting with a six point then maybe later going all out. Isn't it a good idea to stiffen the rear towers before I tweak them out? I tried the search engine but again I couldn't find any threads pertaining to this perticular mod.

Posted by: wildman Jul 24 2013, 06:08 AM

Someone with a little more experience may correct me on this but I dont think re-enforcing the rear shock pickup points is a major issue. They are not truly struts as the suspension console sees the load from lateral acceleration, the shock tops only handle vertical loads so a bar between them is just extra weight with no benefit. If you are concerned with "tweaking" parts in corners I would consider the suspension console and trailing arm pickup ears to be a much greater stiffness per pound modification. I would guess that the bars you refer to in other's cages running to the rear shock towers are from the rear hoop of the cage down, which provides torsional rigidity for the chassis and takes out twist around the hell hole area, something a simple side to side bar couldn't do. Hope this helps and I haven't miss-led you.

Posted by: Racer Chris Jul 24 2013, 06:39 AM

Merely welding a bar between the towers is a poor use of reinforcement material.
The weight is up high and the shocks carry no side loads, only vertical.
As part of a sophisticated roll cage design a properly installed bar in that area can allow for removal of other sheet metal, making for easier engine compartment access while adding overall stiffness to the chassis at the same time.

Posted by: carr914 Jul 24 2013, 07:41 AM

I agree with the others - justing putting a Bar there is worthless. And takes away from otherwise good storage (Battery, 2nd Spare Tire, etc)

Go to RacerChris's Site and buy the Suspension Ear with a Bar that goes to the Firewall

This is the only Bar that I like as it ties into the Area that the Trannie Mounts are under

Attached Image

Posted by: sean_v8_914 Jul 24 2013, 09:10 AM

no.
the only cars that show signs of movement in this area are EXTREMELY modified with huge sticky meats.

the factory bulkhead between teh towers is a double wall box and teh trunk floor is a sheer panel.

Posted by: chad newton Jul 24 2013, 09:36 AM

Thanks guys, I'm not touching it for now.

Posted by: FourBlades Jul 24 2013, 10:56 AM

Like others have said, I would reinforce the points where the rear trailing arms attach to the body. The inner ears rust from the inside out. All the thrust from the engine is pushing on them breaking them off eventually.

Look at Tangerine Racings home page for a lot of good stuff.

John

Posted by: sean_v8_914 Jul 24 2013, 11:38 AM

yes, what four blades said!!!

Posted by: Dave_Darling Jul 24 2013, 03:49 PM

There have been cases where the factory welds between the shock top "pod" and the surrounding structure have failed. It appeared that there were just too few and not very good welds in those cases--probably a "Friday afternoon car", or built by someone with a hangover.

It can be worthwhile to clean all the stuff away from the seams and do some stitches along them, but a bar across between them is almost exclusively excess weight.

--DD