Failed (bent) WEVO Spring Plate - cause?

[jaydubya]

You should probably check with Hayden - I talked to him last week and they were still deciding whether a re-design was needed or not.

My new ones are installed and came with shorter adjusting screws and a trick anodized clamping system that holds the two plates together while still allowing you to adjust the height. I asked him if this was an interim or permanent fix, and he said "if you don't hear from us, it's permanent".

Cheers,

Jeff

[Vintage911Racer]

Is it just me or does this gap look to far apart? It is like that on both sides. Look at the pictures. Maybe it is supposed to be like that, But I know on my car with Adjustable Spring plates the gap is not nearly that far apart.

Just a thought.

[lateapex911]

One thing that does look odd is the amount of extention of the adjuster screw. To my eye, thats a bit much...maybe a re indexx to expose less thread and bring the adjuster to a more square relationship with the contact point is in order. Or maybe this pic is of the set up in some non loaded state, and I just can't tell from the angle.

As an aside, I called Hayden a few weeks ago, as I was one of the first two or three to install the SPS, to report my findings. So far, so good, both sides look very much in alignment. (Wish I could say the same for the odd ball body my 911 came with, LOL)

He seemed to indicate that my experience was typical.
Hopefully this is a one off.

[randywebb]

"if you don't hear from us, it's permanent".

That's great! I'm going to use that phrase.

[frankc]

Jeff,
Do you have any pictures of what the replacement plates and clamping mechanism look like? I didn't see an updated picture on WEVO's site.

I will try to call WEVO on Monday to see if they are shipping the newer style kits. I would like to install their SPS kit this winter.

[jaydubya]

Hi Frank - here's a picture; not a very good one but hopefully you get the idea.

This was apparently a piece that they used to include with an earlier version of the SPS, but after revision they decided that it was no longer necessary.

It may be that if you just keep the adjuster screws at a reasonable height the problems that I encountered will not occur.

Cheers,

Jeff

[frankc]

Jeff

Thanks for the picture - that certainly seems like it should do the trick.

For my rear suspension, I am trying to decide if I would be better off going with the ER poly-bronze and my stock adj spring plates, or go with the WEVO SPS. If I were considering ER & WM adj plates, then the choice of going the WEVO route would be simple. However, since I don't plan on changing the ride height of the car that often (probably once & then leave it), I'm not sure if the added expense for WEVO is worth it (although I usually opt for the over-engineered solution if available).

Frank

[jaydubya]

If you have a track/race car, the ease and range of height adjustment with the Wevo SPS design in comparison to the stock design is a huge plus.

As Hayden described them to me, and supported by the experiences of people in this thread, the manufacture and finish quality of the Welmeister/Sway Away adjustable spring plates are "rather agricultural".

I think the Wevo SPS has an advantage over the ER Poly Bronze bushings in terms of ease of installation, although the latter are a great design too. However, if you don't need to adjust the rear height regularly, I would suggest using the ER parts with the factory spring plates since they are substantially less money.

Cheers,

Jeff

[beepbeep]

How does 935 uniball/coilover setup behave regarding this problem?

[Walt Fricke]

The 935 setup doesn't need to handle this problem. As the camber changes, the spherical bearing at the end of the now vestigal torsion tube simply rotates along a fore and aft axis. We are only talking a few degrees here, so there is plenty of room in that plane for this rotation at the spherical bearing.

And with coilovers you don't need no stinkin spring plate ride height adjusters (see Grady's post earlier in this discussion) - it is just done with a threaded collar on whatever the springs are mounted on - typically threads cut into the shock tube.

I wonder if Jaydubya didn't have this problem because he asked his shop to dial in as much negative camber as it could back there. Think of it: A radial plane normal to the torsion bars is (pre-G50) at zero camber and zero toe, and (relative to the chassis) never changes. The way the vertical surfaces of the ends of the banana arms are configured, they fall into this plane only (per Grady) at below normal maximum droop. Just how much droop would depend on the camber setting. To adjust camber you have to "bend" the banana arm mounting surface in at the top/out at the bottom as you rotate the banana arm end with the eccentric bolt. Because it is not cut to be zero camber at static ride height, it has to bend the spring plate in a "top inward" direction (the twist everyone mentions). And the more camber, the more twist. Without this skewing you could not adjust the rear camber.

Walt Fricke

(wondering if the "don't need no stinkin" line of expression came from Treasure of the Sierra Madre, which was just on the tube)

[jaydubya]

Hi Walt - thanks for your comments. Your description of how camber affects the plate twist sounds reasonable to me. Camber was around -2.25 in the rear when this happened (I believe there is more adjustment available). Not sure if that's enough to cause a problem, but it's what the tires want...

(I drive the brown "G" 911SC with no spoiler and Utah plates that was in the MMP club race)

Cheers,

Jeff

[Mysterytrain]

I'm not a mechanical engineer so I had read thru this thread twice because something really jumped out at me on the first read. If you look at the way the factory springplate is designed you can see it is superior stucturely to both aftermarket versions. Those two adjustment bolts nearest the t-bar 'sister' the two pieces of steel together making the plate very strong from the t-bar tube welds to the far, height adjustment bolt. The bolts shorten [for lack of a better term] the 'flex distance' of the steel to half of the aftermark versions. The factory plate design only leaves a couple of inches of steel that is single thickness and unsupported. The aftermark plates ignore that part of the original design and move the pivot from the height bolt position back to the t-bar!
Simple example is if you grab a pencil from both ends it doesn't take much force to bend of snap the pencil...if you move your hands closer together the bending requires alot more force.
Again, I'm not a mechanical engineer but it appears that with the current advances in tire stick and stiffer non-rubber bushings we have exposed a basic design flaw in the aftermark product. Makes you really think about how robust the original design was and still is.

[jaydubya]

Just wanted to follow up - I now have three track days (including two qualifying sessions and two races) on the new spring plates. They are working perfectly, no evidence of separation or bending between the plates.

Although the additional retainer clips might be helping, I'm fairly confident at this point that my initial problem was due to running the adjustment screw too high, so that the plates were not overlapping as much as they should.

I had a need/opportunity to adjust the rear ride height yesterday. Here is what it took:

Measure initial ride height on both sides.
Jack up rear of car on jack plate/tow hook (leaving wheels on).
Loosen set screw.
Turn adjusting screw two full rotations (Hayden said 1 rotation was 1/4" ride height).
Tighten set screw.
Repeat for other side.
Lower car, roll back and forth, bounce on bumper, check new ride height.
New ride heights were exactly 1/2" higher on each side

And the best part - this all took less than 10 minutes

Cheers,

Jeff

[Jandrews]

Glad to hear everything is working well jaydubya. That rear adjustment flexibility sounds really nice. Any idea what that 1/2 inch adjustment does to your alignment settings, i.e. camber?


Thanks,

JA

[lateapex911]

Originally posted by Jandrews
Glad to hear everything is working well jaydubya. That rear adjustment flexibility sounds really nice. Any idea what that 1/2 inch adjustment does to your alignment settings, i.e. camber?


Thanks,

JA

Or to your corner weights??

[jaydubya]

As far as alignment, I'm no expert but in Ray Scrugg's book, "Home Alignment of Porsche 911", the last paragraph says:

"It should not be necessary to realign the rear [after changing rear ride height] because the toe does not change significantly when raised or lowered 1" or less. Rear camber changes to more negative when lowered, less negative when raised."

So you lose a little camber when you raise it but I'm at 3+ degrees in the rear so no big deal.

As far as corner weights, my understanding is that if you raise both sides the same amount the cross weight percentages shouldn't change much.

Cheers,

Jeff