Rear chassis flex. What do you think?, Discovery prepping for Road America next week Options

[vintage914racer]

Paranoia has set in as I'm nut and bolting the 914 before Road America next week. I'm hoping I can some second opinions.

A little background. My 914 has been a track car for nearly the entirely of it's life. She's been used and abused, but generally has been a reliable steed. Over the years chassis reinforcement and modifications have been made. Notably, the RR (pass) rear suspension console was replaced after the original tore (which is seemingly pretty normal).

What I'm noticing. After getting my car up on stands and prepping/inspecting for the next event I noticed a small amount of tire wear on my inner driver's left fender. I initially attributed it to bumping up to wider tires last Fall (225 Hoosiers vs. 205 Kumhos), but started investigating further to make sure there wasn't something else upstream.

When I have the car on jack stands and put pressure on the LR wheel, there's what I consider quite a bit of flex at the outer A-arm mount and forward into the rear long. You can see it in the attached video. As a point of comparison, when I do the same on the RR/passenger rear wheel there is some flex, but not as much. It should be noted that I had the inner suspension console replaced on the passenger side a few years ago after the old one tore, so in theory it should be stronger. 

The LR doesn't show any signs of tearing. It's also reinforced with stress bars on the outside and inside. 

Left Rear Flex Video (the side I'm worried about): https://youtu.be/NZDbDg22dFI

https://www.youtube.com/watch?v=NZDbDg22dFI


Right Rear Flex Video (the "control" if you will): https://youtu.be/bQMBecKZ6Yc

https://www.youtube.com/watch?v=bQMBecKZ6Yc



My questions are as follows:

1) How much flex is normal? Is this outside what is normal?

2) My flex test doesn't necessarily translate to how torsion is applied to the chassis when the car is on the ground, so am I worrying about something that isn't relevant? Wouldn't the applicable stress while driving get suppressed in part by the rear shock?

3) Would you be concerned about running the car?

Mid-term I'm going to get the LR console replaced for peace of mind, get the reinforcements cleaned up and tidy. The question is, should I forego my race and get it repaired before running.

[rick 918-S]

It was a nice day. When I arrived the suspension was off so it wasn't real easy to see what happened. Ben made up a quick lever out of some square tubing and bolted it to the three point mount. With a little pressure it was clear what was moving. The upper spot welds had completely unzipped from the bottom to the top of the inner rail.

I went over and checked the right side and the same thing had occurred. The right side was not as obvious as the suspension console had been replaced and it was tied into the roll bar.

The easies fix was to use Drill Screws to pull the flange back in place. As I removed one screw at a time I used a 1/4 drill to flare the hole and expose the inner flange. I just plug welded both sides. Should be good to go.

If you race or AX alot you may want to check to see if this is happening. Just stick a screw driver or pry bar between the panel and the flang and see if moves. My 6 is stitch welded from the engine bay side along the top edge of the inner flange as it used to be a race/AX car. Even with this method and a poor welding job I can see some of the welds did not hold like a spot weld thru the flange would.




It was nice to see Ben again. It has been a few years. Time flies..

[infraredcalvin]

It was a nice day. When I arrived the suspension was off so it wasn't real easy to see what happened. Ben made up a quick lever out of some square tubing and bolted it to the three point mount. With a little pressure it was clear what was moving. The upper spot welds had completely unzipped from the bottom to the top of the inner rail.

I went over and checked the right side and the same thing had occurred. The right side was not as obvious as the suspension console had been replaced and it was tied into the roll bar.

The easies fix was to use Drill Screws to pull the flange back in place. As I removed one screw at a time I used a 1/4 drill to flare the hole and expose the inner flange. I just plug welded both sides. Should be good to go.

If you race or AX alot you may want to check to see if this is happening. Just stick a screw driver or pry bar between the panel and the flang and see if moves. My 6 is stitch welded from the engine bay side along the top edge of the inner flange as it used to be a race/AX car. Even with this method and a poor welding job I can see some of the welds did not hold like a spot weld thru the flange would.




It was nice to see Ben again. It has been a few years. Time flies..

Seems like this fix might be good preemptive measure when installing gt reinforcement kit in wheel wells if planning on heavy tracking or autox…