Chassis Stiffening, should I? Options

[Woody]

So I bought the 10 piece chassis kit and the trailing arm box kit and the car is prepped for install. My car has never had any rust issues and looking at the bare metal everything looks great. I can't find any cracks or any other irregularities. The car is autocrossed at least monthly and I am attempting to stiffen it up. I will fab up a inner ear brace as well and rollbar is in the works too. Well I started browsing and I guess some of you guys don't like the 10 piece kit. Should I just leave it off and stitch weld all the body seams instead? What about the trailing arm box kit? Am I going to be adding weight that isn't going to benefit anything?

[SirAndy]

What about the trailing arm box kit?

Ditch it.

I think boxed trailing arms are overkill for anything but the most hardcore AX car with huge sticky tires.

Plus, there are better ways (read: lighter) to get the same or more stiffness.
Like adding one or two hollow tubes horizontally and vertically.

Also, IMHO, the piece that goes on the inner read fender wall is useless as that is a double wall and you're not stiffening anything with it.

(IMG:style_emoticons/default/popcorn[1].gif)

[Racing916]

What about the trailing arm box kit?

Ditch it.

I think boxed trailing arms are overkill for anything but the most hardcore AX car with huge sticky tires.

Plus, there are better ways (read: lighter) to get the same or more stiffness.
Like adding one or two hollow tubes horizontally and vertically.

Also, IMHO, the piece that goes on the inner read fender wall is useless as that is a double wall and you're not stiffening anything with it.

(IMG:style_emoticons/default/popcorn[1].gif)

I Agree!! Overkill!

[neilca]

I do not run it in road racing, too heavy. I also do not have enough talent to feel flex in my trailing arms.

The 914 has a spot weld about every 1/4 inch on the body seams. I know cause I had to drill them out. I do not think welding the seams will get you anything and the foam in between the panels will catch on fire.

Cage is the best way to stiffen the chassis and it protects the driver too.

Good luck,

[J P Stein]

I do not think......

Just about the only part of the prior post with which I agree.

[Woody]

I do not think......

Just about the only part of the prior post with which I agree.

Hey J P, how are ya? Do you have anything constructive to add to my thread? I understand you're quite the authority on everything 914 related.

Thanks, your friend Jon.

[Woody]

I do not run it in road racing, too heavy. I also do not have enough talent to feel flex in my trailing arms.

The 914 has a spot weld about every 1/4 inch on the body seams. I know cause I had to drill them out. I do not think welding the seams will get you anything and the foam in between the panels will catch on fire.

Cage is the best way to stiffen the chassis and it protects the driver too.

Good luck,

I was unaware that there is foam in between the panels. I was looking at it last night and I think I would be more inclined to stitch weld the trailing arm mounts and leave the rest alone. Thanks.

[J P Stein]

I do not think......

Just about the only part of the prior post with which I agree.

Hey J P, how are ya? Do you have anything constructive to add to my thread? I understand you're quite the authority on everything 914 related.

Thanks, your friend Jon.

Sure, I'm a legend in my own mind.

I ran my 914 for 6-8 years at AX with big stickey tires with seam welding only....no "reinforcement kits" here. I did have a cage but is made stiffness from door jamb to door jamb only.

Seam welding is no small chore. The most important seams on the 914 to prevent cracking are where most cracks occur/propagate from....duh. (IMG:style_emoticons/default/biggrin.gif) Around the outside of the inner ear and the pinch seam over the rear wheel arch. After welding these points must be smoothed out with a grinder....to a nice radius on the weld....to prevent a stress riser....a kerf or notch which concentrates stress.
Both of these areas often have a spot weld that "breaks out" (overlap) of the seam metal....a large stress riser. Without a rotisserie this welding is a bitch....you get to light your self on fire a bunch....even with protective leathers...BTDT.

That said, when I welded down tubes from the cage to the shock towers it was a revelation....wow, the car moved as a unit rather than an independent front & rear.
Stiffness is relative depending on how much TM&E you want to spend. (IMG:style_emoticons/default/biggrin.gif)
Some is good but a lot is better. Making them shocks & springs & things actually do their job is a good thing for consistent handling.

The only cracking I ever had was at the bottom front of the rear shock towers (pre down tubes). These come with stiffer (over 200lb ) springs. The connections, longs to shock towers, really sucks.......but hay, the car was never designed to cope these spring rates.

BTW, no swing arm bracing.....they are more fishing lures IMO.

Your friend JP. (IMG:style_emoticons/default/biggrin.gif)

[Woody]

Thanks J P, I wasn't accounting for adding stress risers. How did you tie the cage into the rear struts? Do you have a back window? I still drive mine on the street from time to time.

[SirAndy]

Thanks J P, I wasn't accounting for adding stress risers. How did you tie the cage into the rear struts? Do you have a back window? I still drive mine on the street from time to time.

You can go lower than the window, through the firewall (or even sandwich at the firewall). Not the ideal angle, but it will work.

(IMG:style_emoticons/default/smash.gif)

[moggy]

Thanks J P, I wasn't accounting for adding stress risers. How did you tie the cage into the rear struts? Do you have a back window? I still drive mine on the street from time to time.

You can go lower than the window, through the firewall (or even sandwich at the firewall). Not the ideal angle, but it will work.

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I did mine like this:

(IMG:http://i31.photobucket.com/albums/c395/odg743g/IMAGE_028.jpg)

(IMG:http://i31.photobucket.com/albums/c395/odg743g/IMAGE_027.jpg)

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cut a new perpex/lexan back window.... job done.

First thing I would recommend is a decent cage like mine that attaches to the body in at least 6 places (mine attaches in 10 places). I also went for inner long strengthening as there was already cracks forming by the handbrake before I fitted the cage so as I was rallying the car I didnt want to take any chances so I went for belt and braces with a cage and inner long strengthing.

(IMG:http://i31.photobucket.com/albums/c395/odg743g/IMAGE_032.jpg)

(IMG:http://i31.photobucket.com/albums/c395/odg743g/IMAGE_038.jpg)

I also bought a rear pickup point strengthening kit from CFR, including inner ear strengthening as I was conscious this was a weak point in our cars and I was going to be stressing it out more than most (IMG:style_emoticons/default/happy11.gif)

(IMG:http://i31.photobucket.com/albums/c395/odg743g/IMAGE_034.jpg)

(IMG:http://i31.photobucket.com/albums/c395/odg743g/IMAGE_043.jpg)

(IMG:http://i31.photobucket.com/albums/c395/odg743g/IMAGE_044.jpg)

(IMG:http://i31.photobucket.com/albums/c395/odg743g/IMAGE_039.jpg)

(IMG:http://i31.photobucket.com/albums/c395/odg743g/IMAGE_040.jpg)

(IMG:http://i31.photobucket.com/albums/c395/odg743g/IMAGE_041.jpg)

on the rear arms I can only talk about my own direct experience (I have NOT AX'd with this car) I only rally it (IMG:style_emoticons/default/driving.gif) on tarmac and gravel. I have bent 1 arm, twisted another and completely folded in another (hit a rock on a side slide at about 50mph - the rock won (IMG:style_emoticons/default/blink.gif) ) Since I've fitted some of the arms with the tubes welded through from PMB Performance - Eric Shea if I remember rightly (someone correct me please if I've got myself mixed up and it's someone else that makes these.... it was some time ago I bought them and fitted them) But the main point I'm trying to make is.... since I fitted them a few years ago I have not had them bend or fail on me in ANY way. They are ROCK solid and believe me... I've been trying my hardest to bend them (IMG:style_emoticons/default/biggrin.gif)

Hope this helps (IMG:style_emoticons/default/beerchug.gif)

[Woody]

Moggy that is awesome. Thanks.

[J P Stein]

IMO, you want to go right to the towers, front & rear.
As Andy says, going below the window will do the trick (no rear window here) IF you run another from the tube down to the long top. Too much vertical displacement without this support, methinks.
I don't have a real good pic of the connection but I did take care of the lousy connection (long to tower) with a scab plate that I needed anyway. The down tube lands on it as far back as it would go.

[J P Stein]

Humm, forgot the front.

[SirAndy]

I did take care of the lousy connection (long to tower) with a scab plate that I needed anyway.

JP is correct, one of the real weak spots is the (almost non-existent) connection between the rear shock tower and the long.
It's basically just a thin layer of sheet-metal to cover the gap.
They aren't even touching each other directly (!).

I have seen more than one high HP 914 where the shock tower has separated from the long completely.
(IMG:style_emoticons/default/icon8.gif)

[Joe Ricard]

I did what JP did to the rear shock tower and long connection. Whe I remeoves the factory putty from that area you could see it wasn't actually connected.

Full cage tied to front and rear shock towers were good but when i put a diagonal top right cage to cross bar on dash and then continue to left front shock tower THEN the car got stiff. then X braced the front torision bar pick up to nthe shock tower the car turned in like I was handling a scapel.

Shocks HAVE to go metal to metal, Anything else is just a waste of time.

[Britain Smith]

This is what the back of the frame rail looks like where the shock tower mount is.

(IMG:http://a4.sphotos.ak.fbcdn.net/hphotos-ak-ash4/s720x720/386146_2225265277708_1430063084_31762344_830209375_n.jpg)

Here is what the back of JP's old car looks like now:

(IMG:http://a1.sphotos.ak.fbcdn.net/hphotos-ak-snc7/s720x720/381802_2225265157705_1430063084_31762343_756234827_n.jpg)

Any with some tubing put back into place:

(IMG:http://a4.sphotos.ak.fbcdn.net/hphotos-ak-ash4/s720x720/377776_2264975630442_1430063084_31774257_127900001_n.jpg)

-Britain

[0396]

JP,

Your engineering skills never cease to amaze me....hopefully with in the next month; I will be able to stop by the ‘shop’ to admire your ride.

[J P Stein]

JP,

Your engineering skills never cease to amaze me....hopefully with in the next month; I will be able to stop by the ‘shop’ to admire your ride.

That is now Brit's car, not mine. He's doing the conversion to double A-arm suspenders, F & R. Just to be clear, Brit is lead engineer on this project.

I was a steelworker. We can make things strong but it takes an engineer to make it light. By my eyeball "Brit the engineer" needs to get on the strong bandwagon.....but he's got Brad so he don't need me. (IMG:style_emoticons/default/confused24.gif)

BTW, the car is down in SoCal where the work is taking place.

[Britain Smith]

Ah come on JP!

I will be down there this weekend making it stronger...just for JP.

-Britain