This spring I'm wrapping up completely rebuilding my suspension. Right now I'm working on the rear end.

First off, what do ya'll think about the weld on trailing arm reinforcing plates (like PP and a number of other places sell for ~$100). The reinforcing plates seem like a reasonable thing to do, right? All these kits look like the same stuff to me. Is there a mo-better way to do the job, allowing that I can fabricate anything I need?

Secondly, I'd like to go ahead and reinforce the suspension consoles while I'm at it. The problem I've got is that I've never had a good look at the underside of a teener (laying on my back on my creeper in the garage doesn't count). I've looked at the PCA GGR picture for the reinforcment setup. Is the GGR setup state of the art OR is something else the hot ticket? Any recommendations for SoCal shops to do this for me - ones you've used in LA/Orange/San Diego county area?

Have fun,
Kevin

Here is my take on the control arms reinforcement:

1. If it doesnt bend in a off course excursion..where does the energy go ?? (The control arm mounts on the tub)

2. Do I really need to ad weight to a unsprung component ??

3. Control arms are cheap.. if I bend one (without the stiff kit on it) replacement can be made in about 2 hours and 50$.

4. I know of many many club racers that dont run the stiff kit (guy's that race on 10inch wide slicks... and win) Guy's who have been racing for 12-15 years.

I do suggest you stiffen the control arm pickup points. About 4 pieces out of the chassis stiff kit actually do anything when installed on the tub. The rest are worthless and just ad weight. I'm not the only one to share this view... The 914 IMSA racers of the early eighties figured this out way back when running 12+24 hour events in 914's.

TonyC is the fabricator here.. let him show you what he came up with on one of our 914's for the control arm pickup points. It involves a few tubes all tied to the main hoop.

B

Brad wrote: "...About 4 pieces out of the chassis stiff kit actually do anything when installed on the tub. The rest are worthless and just ad weight..."

Ok, so which four pieces would that be? Saving weight is cheap hp

Any pics from Tony would be great as well
I've got a fairly good idea of what to do, and have seen some, but more "btdt" info and pics is always good!

Cheers,

Jeroen

Here are some pics of the re-enforcement of the rear control arm pick-up points. I don't have any of the innear pick up, but it was done very similar.

TC Design outer pick-up point

TC Design 914-6 Project

-Tony

Thanks Tony. I was just looking at those pics yesterday. I need to have a closer look when I'm not a work. I may have some questions.

Mike

kdfoust; If you try to box your trailing arms yourself be aware that you can warp them with too much heat. I believe the good shops use a jig to keep them true while welding. I didn't want to take a chance and ordered rebuilt ones through Patrick Motorsports. They exchange new for old. I also would like to know which parts of the stiffening kit should be used and which trashed. I have a kit here waiting to go on my car when I have time.

I need a pic of the kit laid out. I'll circle the ones you can use. If you have a cage that passes through the rear window or ties the rear shock towers together.. you wont need it at all. The chassis cracks on the tub right where the centerline of the shock goes up (draw a virtual picture inside the fenderwell following the shock) The only reason the chassis' crack is when you add more spring (225 and up will start the process within a few months of TT or RR) The problem is: the tops of the shock towers are not strong. They are only held in place on 2 sides (both of which are weak) The actual frame rail ends in front of the shock tower....leaving the sides vulnerable to cracking.

The outside mount normally wont crack until the inside one lets go.

B

Here's a pic of the kit
Call the numbers, just like bingo

Cheers,

Jeroen

5,2,4,3

B

2+4+3 are questionable.

4+3 dont do anything. Several old school racers figured out that the chassis will still crack even under number 5. Number 5 helps support that increase in spring rate that I spoke of above.2 right above 5 (when mounted on the car) really doesnt do anything. The piece below it is whats left of the frame rail.

I think people install these pieces (because the factory did) (because so and so has it) (they think it increases the value)

After seeing factory race cars from that era (they where designed in the early 70's) Porsche hacked together whatever they could to get the cars on the tracks. They where the factory.. they didnt expect this stiff kit to last..they would throw the chassis away and build a new race car. I even doubt that the factory designed this kit. I'm finidng more and more that they listened to racers and adjusted accordingly.

B

here's a pic of how the frame-rail is actually attached to the rear shock tower
(or better, how it is NOT attached)

Cheers,

Jeroen

Correct. Its more like 1.5 sides of support. Run a tube to that spot... and stiff kit pieces numbers 2+5 become 100% worthless. The fram rail ends right there.

B

Jeroen,
Can you take or post another pic of that area with the camera 1/2 a meter or so back from that same area?

Like this?

Cheers,

Jeroen

Great shot. This really shows how the frame rail ends in front of the shock tower.

The idea from here would be to triangulate to the front side of the shock tower (if your rules permit) Think of the frame rail as one side of the triangle and the main hoop of the cage as another "side" of the triangle. Then from the top of the main hoop go down to the front of the shock tower to complete the triangle. Several of our classes dont allow us to pass through the back window (or bulkheads) This is when we have to get creative with a tube that runs forward to the firewall and ends... doesnt exactly work as well as the tube running from the main hoop.. but it works well.

B

Brad, Jeroen, et. all.....

Dang....
great shots, great explanation.
I heard brad talk about not using the full kit in the past... but those shots are great...

I want to truly thank you for the info...
sometimes you see something like this at the perfect time (right when you need it)...

Thanks for the site... and the expertise...

brant

Jeroen; thanks for the good pics.
Brad; thanks for the good info. Since I just reinforced my trailing arms and console ear and installed 250# springs I now know what area of the car to keep a close eye on.

Perfect Jeroen. Thanks!

Hey Brant (and anyone else interested),

Take a look at the first shot on this page (thanks Jeroen). See that rust hole at the bottom of the long just after where it curves up ad before it reaches the console? The hole on my right long I was telling you about last night is about 2" directly above the hole in that picture.

Mike,

perfect... timing wise...
and great shots...
so what is the group consensus...
Mike, I think you could cut out, or cut back to good metal and then weld in a patch... or piece of the silver car....

it depends upon how far you would have to cut back.
but in an ideal world, you may not have to remove the entire floor pan (as Jeroen did)... if you don't mind it being less than concours.......

Using heavier than stock gauge metal... you should be able to make a patch that would restore the original strength...

yep.. I agree that the motor would need to come out.. but with that fancy lift of yours... and the chassis supported correctly.... it should be doable...

what's the group consensus...
and how do we talk mike into firing up that fancy new welder he bought and jumping in with both feet...

brant

troublemaker...

Actually the lift rails are too narrow to allow a motor drop. I may find some way to modify it, dunno yet.

As for motivation, well, I guess I could use some. But that's not the *only* rust I have to repair. You need to come over and have a good look to fully understand.

crap I nuked my response...

Mike,
I'd like to come see it
maybe next weekend..
worse case senario.. you could always pull the motor and then roll it onto the lift.. utilize the lift to get that chassis up and weld while standing on 2 feet instead of your back..

You'll do as good of a work as others.. just because of your attention to detail.

its doable..
I'd like to see it some time...

brant

Hey Ginter,

Musta missed your earlier posts on your rust issues
Have you got any pics to post?

Personally, I think the area between the rear susp.pickups and the firewall is the most complex of the 914. There are places where 4 or 5 different pieces of sheetmetal overlap

Did you also see the pic on the bottom of my "body" page.
You'll see there is a reinforcement on the inside of the frame-rails
If you just start cutting out sheetmetal there without good caution, you may do more damage than good (you might cut into the reinforcements).

I'd suggest you (carefully) grind away as much rust as you can
Use Ospo (or likewise product) to treat the surrounding surface and Por15 or what ever anything you can reach while you're in there
Clean the surrouding surface of the part you need to weld and spray on layer of zinc-primer (the weld-through kind)
Also do this with the backside of the sheetmetal patch before you weld it.
I'd suggest you weld a patch over the damaged area instead of in it.
May not be as clean, but if you nicely grind your welds after you're done it would be hard to notice.
If the covered area is a bit bigger, you could drill some holes in the sheetmetal patch so you can do some spotwelds closer to the center of the patch.

Just take some time to do it right.
Don't be too eager to fire up your weldingmachine.
Look, poke around, sit back, think and look again before you decide on anything definate...

Cheers,

Jeroen

I just get tired of seeing people install shit on their cars...and they dont really know why. I personally dont want anything on my car that doesnt help in some form or fashion...and if you can prove that it helps.. I'm all for it and will shut up. Ask my wife about the plates that hang on our walls here at the house.. LOSE THEM. I cant eat off of them... worthless.

My favorite write up is the stress analysis tests done by true to god stress testing engineers for General Dynamics. They tested the 914 control arm with and without that stiff kit installed (on the arm)..It took the guy almost 6 months to complete all the testing and metalurgy tests. In a nutshell.. he said that the side we weld the kit is not the week side. The side with the exposed pivot arm is what tweaked first in side load testing. They could not get it to twist without completely breaking. Again.. Porsche slapping a band-aid on a problem.

I wish I could find the test. I sold the guy a 914 that him and his son built.

B

Likin' this thread. Content is very good, too. I don't plan on having these problems but want to know what not to do and where to look every year under the belly. Right now I've got very minimal rust problems on the former jackposts which will be repaired by spring.
Mark S.
'70 914-6

Jeroen,

I didn't ever post about my rust issue. I had been talking to Brant on the phone Thursday night trying to describe my rusty area on the right long. I took the opportunity to use your pic to describe the area to him. I'll get some pics this weekend. Believe me, I'm in no rush to start melting metal on an original /6. It would probably be a different story if it were a rusty beater 4 cylinder car. I'm kinda afraid of that welder at the moment.

Did you mean this pic?
I saw it. I need to print it and take it out to the car with me to get a better orientation.

I'll start a new thread tomorrow with pics.

That's the kind of info I'm looking for! I had this gut feeling that the tailing arm reinforcement plates were a bogus 'improvement." Scratch that one off the list...

Kevin

Hey Ginter,

"...I didn't ever post about my rust issue. I had been talking to Brant on the phone ..."
That's why I couldn't find it

"...Did you mean this pic?
I saw it. I need to print it and take it out to the car with me to get a better orientation..."

Yep, that's the pic I meant.
About the orientation: this is the inside of the passenger side frame rail
Your looking up from the firewall to the rear shocktower
The "donuts" on the left is where the outside pickups for the trailing arm are

Cheers,

Jeroen

I have that pic too of my rust bucket, mine is worst off.
Geoff

Someone sent an email about the brace for the inner mount arm. Here is the body of the email telling how to do it. I have a picture I will try to find it and post later:

>>>>>>>>>>
The brace runs from the suspension swing-arm inner mounting point towards the center of the car. I clears the exhaust and runs below the corner of the engine sheetmetal. Thus to remove the engine the brace has to be removed, and it would not work to weld in a piece of tubing for this reason. Additionally the brace I have is threaded so that it can be put into place and tightened.

The repair is straighforward. I purchased a new suspension console from ? (Stoddard), and then had it welded in in the location of the torn one.

After it is welded in, you attach a means for the brace to mount. We used a piece of heavey stock (1/4 inch ?) with two holes drilled in it. Our piece was approximately 4 inches rectangle. One of the holes was the same size as the swingarm bolt, The other was the same size as the brace bolt. These mounting points pieces are then welded in with the swingarm bolt hold lined up, and the new piece pointing down to the ground.

On the firewall, A heavy U shapped tab is welded on, to provide a mounting point for the other end of the brace.

When completed this keeps the swingarm from flexing towards the center of the car, thus relieving the G-forces from the stock suspension console.

A lot of people used this setup. We figured out how to weld them in and keep them out of the way of the valve covers.

Hey guys, looking at the discussion about flex, will this device support the flex by triangulating the rear shock towers?

Thanks,
Sean Lee

Hey Sean,

IMHO that is complete overkill
I've cut the firewall between the rear shocktowers out or my car and I can tell you that is one sturdy piece
I think it's very unlikely that it's gonna flex THERE

What you could do is make braces that run from the rear shocktowers to the dogbone, right above the trannymounts

Cheers,

Jeroen

So, the problem is not the shock towers flexing it is the different flexing between where the frame ends and the shock towers?

(sorry if this sounds dumb, I just haven't seen one cracked)

thanks,
sean

hey sean,

take another look at the closeup pic of the rearshock tower on the previous page
You can still see where the firewall used to be
(or go have another look at your own car for comparison)

You'll see how poorly the end of the framerail is connected to the rear shock tower

Cheers,

Jeroen

Cool. A Indy Guy.

Sean. No 914 needs a rear brace. The shock towers have NO side load on them. If I could..I would brace the shock towers straight down from the top.. cant exactly do that soo... We brace the front of them and the back of them. The load is from the ground up (spring and shock)

I'll see if I can dig up pics of a cracked tub.. I'm normally repairing them fairly quickly (at the track)

B

Hi,

Thought some might like to see why not to box trailing arms. The picture is my 914 that had a dance with another 914 on the track. Broke the 901 tranny left mount, shattered the inner and outer CVs, ripped the fender off, and bent the trailing arm. But because the arm bent and was not reinforced, the inner trailing arm mount had minor damage and the outer had none. I feel that by take the impact and bending the trailing arm was sacreficed and saved the body to trailing arm mounts. Can't find the picture of the armby itself.

As they say on FOX...I reported...you decide.


John

HOLY COW.

John I recognize your name, where do you normally race ?? I try and try to tell these guys that the tub is more important than stiff arms. Thanks for backing me up with real world experience. Now, my question is: will the car be ready for this season ?? Is it back together ??

Thanks for posting.


B

Hi..

Yep...not a pretty sight...quick turn in for autox though..

I race mainly in the Mid-West.

That happened about 2 years ago and I ran the car for a season just fine until in pre-season shake down I found lots of metal fatigue in the front pan at suspension points. The metal had just cracked. No rust problems...just flexing. Like taking a piece of metal and bending it back and forth and it will break. I was really shocked as to how it looked. Sorry now I did not take any pictures.

I decided to scrap that body since I had another one that was from AZ and very rust free.
That of course is another story about starting with a good body. When I first started racing I always wondered why so many people used such nice bodies to race. Now I know...start with only the best body for the track car. The street car can live with flex and bondo. And the extra weight.


John

All,
I have been thinking about doing something like creating a triangle between the shock tower, the rear top of the firewall (where the seat belt bracket is) and the lower "frame" member.
Then another in front of the firewall to the rocker.

I have enclosed a drawing that looks like my kid did, but it is the best I could do right now.

The black is the existing car, the red is the new tubes I am thinking about...

In front of the firewall I have also considered a 6" inch high ladder truss going along the rocker to pick up the load from the tail.

Rich

The conventional wisdom for stiffening either (or both )
ends of the car is to start with a roll cage.
Once this box section is installed (no small chore), it is relativly easy to run tube sections to the suspension mounts. Also, these sections should be as straight as possible due to their loadings being in compression and tension. Curved runs will tend to bend more or straighten, depending on load.

None of this is really necessary unless one plans to compete with the car. One also has to look at the rule book to see what effect doing the stiffening has on your class structure.

This prolly should be another thread.

This will help out (a lot). You have the right idea.

Now.. here is the problem:

The weekest point of the whole car is straight down from the top of the windshield. Basically drop a plumb from the windshield hoop to the frame rails. This is where the cars start to crack with big HP and AutoX. I dont talk about it much, because most of my guy's run cages, but this is where the BradMayeur kit works very well. I actually (in the past) have welded what would be a chassis stiff kit plate along the inside of the frame rails. I can hide this with carpet.

The piece starts around the bottom of the speaker area and runs all the way around the firewall to the to the other speaker area. Lots of welding... but MAN does it stiffen the car. I think this combined with your thinking on the rear support would work great.

B

Brad,
It seems to me that a weaker link in the car is where some dumb ass drilled a 2.5 inch hole into the "frame" right below the firewall for the heat pipe.
This still amazes me that they would do it right where that section turns to horizontal and put the stress on the outer rocker. (this is a simple reason that the apprenticeship engineers should never be let near a car until they have raced)

In the days this car was built, outer rockers where almost sacrificial parts that we all knew would rust.
To put that much stress on that part of the "frame" is insane IMHO.

This is where the car bends when jacking (both my complete cars) and this is what I am trying to fix with less than a cage...

I was thinking that a piece of 1/8 or 1/4 in steel, basically a triangle in front of the firewall maybe 12" by 12" would help, then tie that in with the inner longitudinal fix that you propose (BTW I love that idea, easy to do, less work than the meyers kit IMHO)

Then connect the rear suspension to the firewall, right behind the top or the plate...steel going through the hole/cup to the suspension might work...

Also considered running a pipe like a harness bar, but inside the engine compartment to tie the two bars running to the suspension together...little 45 degree 3 by 3 corners welded in...

Basically I am trying to NOT put in a full cage...
But rather a lower cage front to back...

I would propose to tie in the front to the sections near the speaker...although outside the front "firewall"

Thoughts and advice needed and gratefully absorbed...
This will run in both a 2.0 liter AutoX car as well as a special project 914/928 that I am going to do, although the 914/928 one will be a true convertible...
This one I may ship over to you and have you do all the metal/custom lower cage work to ensure good welding..

Rich

Rich,

what I have found: The outside frame rail is thicker than the inside. I do agree 100% that the heater duct opening at the base of the firewall needs to be addressed. Once I found out the inside sheet metal of the frame rail appeared to be thinner.. we came up with the idea to stregthen it. Brad's kit was truelly designed for rust prevention. The BITCH of his system is the jack post and what has to be done to make it work.

Last night a 914 racer and I went over a accident in his race car where he was hit in the side at more than 100mph.. the firewall collasped over 4 inches behind his seat. He now runs a a 2inch by 1 inch thick steel "bar" from one side of the engine bay to the other side of the engine bay. This sits right below the engine lid and cannot be detected when the lid is in place. It mounts just below the hinges for the engine lid. He commented on how much stiffer the new car was with that cross bar welded in.

B

This thread is Grade "A" prime. Don't stop now. Toss it out there.



BTW - How 'bout "Brasshole"

Hey Rich,

No offense, and all IM(very)HO, but I think this way, you're aiming all the stress to one point (the point where the frontbars meet the framerails in the passenger compartment).

Basically, as with any cabriolet, that would be the weekest point of the car.

I think the only way to get the flex out of it is to compensate for the absence of the roofstructure (by ways of a full rollcage).

You can try to reinforce the rockers all you want, but it would still be the only area that got all the stressloads.

Any reason why you don't want a full cage?

Cheers,

Jeroen
(not dissing your ideas, just brainstorming along)

PS here are my "cage plans" for other to shoot at

Sorry for not re-visiting this one, life got in the way.

I am still trying to get a grip on several issues here.

I understand the benefits of a full cage.

It seems to me that if you build the lower part of the chassis the right way, you could reduce (not eliminate) quite a bit of the flex.

Another thought I had was why not remove the outer rocker...(kinda have to due to rust anyways) then make a ladder bar or a solid piece of plate that welds into the inner longitudinal on the vertical plane, paint that and put on the new outer rocker...
Seems, aside from the heater hole, that would add the strength enough for autocross and aggressive street driving.

Brad, I love that thought about the bar under the engine lid, kinda what I was looking for with the bar from side to side tying the bars together.

but now I will put a triangle from the middle down to the lower firewall on both sides.
So a tube goes from the shock tower to the seatbelt mount on the rear of the firewall.
A tube will go from each of those tubes, across the engine compartment,,,and in the middle of that tube would be tubes going down at 45 degrees to the lower firewall.

Now, what size tube would you use???
I would prefer lots of lightweight triangles versus several heavier ones...
I an willing to break the triangles down to smaller ones to reduce the tube size...

Need help on this question...

Rich

Use legal .095 Inch and half. This is good for cars up too 2200 lbs. We have to use .125 wall on cars that weigh over 2200lbs.

B

I little addition/correction to Brad's post: You have to use 1.5" X.095 DOM steel up to 2200lbs and 1.5 X.120 DOM steel up to 2500lbs. You MUST use DOM steel not HREW office chair material or the tubing sizes/thickness' change.
-Tony

Oh yeah.. DOM all the way. The first inspection for the new cage would go something like this: Um.. ha ha ha... oh ha ha ha.. You used... office chair tubeing..LOL

Sorry.


B