Failed (bent) WEVO Spring Plate - cause?

[911pcars]

Does the torsion bar cover fit onto the chassis as shown in one of the above photos? If not, could be a spring plate bushing not fully seated or some other obstruction.

If the torsion bar cover is installed correctly, I'd say the spring plate and control arm should be fairly close. With the cover installed, the spring plate angle is fairly limited, so one usually uses a jack to raise the control arm to meet the spring plate.

Sherwood

[DW SD]

I'd inspect your ride height adjuster. If they are centered against their counterparts (looks like a ledge), I'd go with it.

Post mortem should be interesting on this thread.

Doug

[shbop]

Getting back to Jaydubya's problem, it's hard to imagine the control arm moving lateraly with the spring-plate, far enough to bend the height adjuster piece that much. It represents a great deal of force on the inner splines and torsion bar. Are todays tires that good?

[jaydubya]

Originally posted by shbop
Getting back to Jaydubya's problem, it's hard to imagine the control arm moving lateraly with the spring-plate, far enough to bend the height adjuster piece that much. It represents a great deal of force on the inner splines and torsion bar. Are todays tires that good?

Today's tires are truly amazing - I have great confidence in my tires and have no problem generating 1.5 Gs in corners

Regarding the movement - based on the very helpful discussion in this thread, I now suspect that some torsional (or torsional and bending) deformation of the main spring plate caused the top of the main spring plate to move toward the chassis, allowing the adjuster plate to slip down the side of the adjustment screw. Then the adjustment plate deformed plastically during cornering after that intial slip. So the amount of plastic deformation of the adjustment plate that is shown in the first photo may not have occurred during the initial slipping of the adjustment plate off of the screw.

I just spoke with Hayden at WEVO on the phone and he was extremely helpful. He is going to contact my shop to speak with the mechanics there directly. Between the folks at WEVO and the folks at my shop, I have no doubt that this problem will get diagnosed correctly and remedied. More as I know it.

Cheers,

Jeff

[Grady Clay]

Doug,

Jon’s new spring plates are for SWB (there isn’t an adjustable Factory part that directly replaces it).

I have considered using the LWB Factory spring plates and modifying them to fit a SWB. An advantage (other than having them clamped together) is I would be able to re-position the camber/toe adjusters to better work with a lowered car and the SWB trailing arm.

I think one issue with the WEVO/SaW spring plates might be patent issues with the Porsche design. Another surely is cost. The Porsche spring plates and hardware appear much more expensive to manufacture.

Can someone post a link to the WEVO spring plate. I can’t find it in their on-line catalog.

When assembling the spring plate to the trailing arm, there is an extreme rebound position where the plate and arm better align. This can only be done with the lower rear torsion bar cover support spacer, half-shaft, shock, and brake flex hose not yet installed. It is wise to get the camber and toe roughly set prior to tightening the bolts or adjusters. Of course it takes several iterations back and forth with the adjustments to get the corner balance, camber and toe correct.

Best,
Grady

[jaydubya]

Originally posted by Grady Clay
Can someone post a link to the WEVO spring plate. I can’t find it in their on-line catalog.

It's not on their web page, but the instruction manual with photos can be found on Smart Racing's web page:

http://www.smartracingproducts.com/pdfdocs/561300_wevospringplate.pdf

[Mahler9th]

Guys: Be very careful about jumping to conclusions. Let Wevo work with their customer. I know the owners of Wevo and they will take care of their customer. Like many of the businesses we buy from (including Smartracing Products), Wevo are professionals and it is always best to let them work with their customer before jumping to conclusions.

Be aware that in the case of these two companies, as with many others, truly solid engineering goes into the design of the products. These folks have pro racing experience at the top levels.

I hope that the original poster fills us in once all the information is available.

- Mike

[ZOA NOM]

Here are the closeups. It is apparent that my Weltmeister adjustables are indeed flexing in the same way, and logic would suggest that if I lighten the car, and increase grip, the problem will exacerbate. I also think that clamping the two plates will cause the overall droop to be limited, as evidenced by the gap between the adjuster screw and the stop in the relaxed position. It may be that the suspension travel never goes that far with the car on the ground however, so clamping may not be a problem.

[Chuck Moreland]

Originally posted by Elombard
I never realized the spring plate has to twist a bit...I thought all the movement was in the bannana pivot. Makes you realize what a "compromise" the whole set up is. I thought that with the ER Polybronze and monoball Bannana pivots everything would move smoothly with know bindingif the T bars were removed. Not the case at all. I wonder how much "rate" the twist adds.

As noted above the factory spring plate is designed to twist, and it takes surprising little force to twist it. Next time you have your factory spring plates off, clamp one end in a bench vise. Then twist the other end with your bare hands. You will easily cause visible deformation without added leverage.

Indeed everything does move smoothly with no binding with the Polybronze and Monoball setup. It works precisely as the factory intended.

Having now defended my honor I will offer that there is much speculation in this thread that shouldn't be taken as fact. Let wevo have a chance to evaluate and respond before finaling conclusions.

[DW SD]

Just to make it clear, my comments were pure speculation and only suggestive of possible faulty installation. I have the highest regard for WEVO's products and ability to properly support their customer.

As I mentioned, I look forward to the post mortem and analysis.

Doug

[analogmike]

Originally posted by Chuck Moreland

Having now defended my honor I will offer that there is much speculation in this thread that shouldn't be taken as fact. Let wevo have a chance to evaluate and respond before finaling conclusions.

THat's cool, but what do you think about improving the sway-away and WEVO plates by adding clamping screws?

I just remembered that I had that same problem on one side, the adjuster lever was bent outwards and it looked like it could eventually fail. I pulled it out, put it in a vice, and bent it INWARDS so there is a preload on it when assembled. I figured that might help it stay touching the main spring plate arm. It has not bent out again but I still think a clamping bolt would be a good idea.

If I had a welder I would just put a tack weld there and chisel it off if I needed to adjust the ride height.

How about looking into it and offering a simple DIY kit for this on your website, Chuck?

[911pcars]

There are several methods to keep the two pieces in contact. A nut and bolt is one, but there would have to be provisions for later ride height adjustments, as in a slotted hole. A problem might be in the limited space behind the spring plate for a bolt head, even a recessed, countersunk head.

Another method would be to create a bored seat instead of a flat surface for the adjuster screw as shown.

I borrowed Zoanas' photo to illustrate:


Sherwood

[analogmike]

Sherwood, you are the guy who could make up a nice kit for this. The idea above is not a good one, I can see the adjustment bolt still getting jammed and hung-up. Also does nothing to limit droop/loosening which is a problem. I think we need to clamp the arm together like the factory did. I still like drilling a hole, tapping the plate, and just installing a screw.

[Grady Clay]

Mike & Chuck,

I agree about jumping to conclusions.

I also think this is a healthy discussion about the dynamics of the rear suspension and the degrees of suitability of various products, including Porsche. In an open forum like this shortcomings in one design lead to a manufacturer marketing a product that better fills the need. This is why we have so many great aftermarket suppliers for Porsche parts.

I think it is essential to critique every design, including Porsche. Every car and part is an engineering compromise. Recognizing that allows for skewing the requirements to better fit a particular need or situation.

Not everyone here is familiar with the process of assessing the market, design, manufacturing, marketing, servicing, warranty, etc. Companies in this field take a great risk at every turn. Clearly the successful ones should be rewarded both financially and with reputation.

I haven’t seen anything in this thread that would even slightly impugn WEVO. Just the opposite.

Can the WEVO adjustable spring plate be better? Of course. Is it necessary? Perhaps not.

We would be missing the whole point of a Technical Forum if we didn’t discuss this in detail.

Chuck, I think one of the great features of the Pelican Forum is our ability to correct errors and clarify issues. I make at least one mistake per month. I am grateful for the corrections or requests for clarification. If you see things in this thread that are “ …speculation in this thread that shouldn't be taken as fact.”
please be specific so it can be corrected.

If I offer opinion, I am generally clear that it is exactly that. When clearly subjective opinion I include “In my opinion….” When less clear cut, I use the key words; “I think….” or “It seems….” Most of the time include my argument for; sometimes I even include an argument against (with my rebuttal).

Sorry for getting off topic.


Looking at this issue, it strikes me that the height adjusting screw must traverse a slight arc at its point of contact as the spring plate twists. I think that is about ˝ the arc of the wheel camber change. What is the camber change from full bump (on the stop hard) to full rebound (limited by the shock or spring plate)? Yet another consideration.

Best,
Grady

[randywebb]

I agree - and what Grady does is what a scientist would do in a peer reviewed publication. Totally appropriate.

I'm interested in seeing Wevo's response and agree that a lot of engineering goes into their products.

We all need to remember that the factory made mistakes too -- as did the engineers who designed the Tacoma Narrows bridge... this doesn't mean I think there is a design failure here (as vs., say, an installation failure), but no company is going to be perfect.

[Cory M]

We would be missing the whole point of a Technical Forum if we didn’t discuss this in detail.

+1

[lateapex911]

Interesting. I have the SPS on my car, and run it on the street with R-comound tires. As a matter of fact, I just took it out yesterday and ran it very hard...they were warm and sticky when done. Lots of hard corners and dips and bumps.

When I installed my set, (I think I was probably the third set shipped), Hayden and I talked a lot. He was curious about the install, the directions, and so on.. One item he stressed, both in the (very thorough) directions, and on the phone, was the correct alignment of the springplate relative to the adjuster. He actually called me post install and asked me to look and see if things were properly lined up with the adjuster bolt after a few miles.

So he was aware that the problem could exist, which is, of course, very obvious when you look at the basic design. Porsche didn't make the plates as thin as they did for no good reason.

Whats interesting to me about this issue is that the forces occurred when the corner was loaded as the inside wheel. In other words, it was more lightly loaded by far, than the outside wheel which would load the plate inboard.

Of course, with R-compound tires, momentary loading over berms and such can be very high.

I thought, when buying the setup, that it was just common sense to get the inner T arm (banana) monoballs, as to lock the movement into the designed planes.

I am surprised to see that much deflection.

Tonight I will look under my car for similar issues.

Finally, Hayden (and Tyson) are top notch, both in terms of engineering expertise, and the level of care they take in their parts and their customers. I expect that this will be resolved properly. I'd bet a ton on it, actually.

[Grady Clay]

Guys,

In the middle of all this, does someone have a new WEVO spring plate set of pieces you can photo? How about Sway-a-Way (SaW) and the Factory parts? Are there others?

Who has some well worn used parts?

One thing not discussed (yet) is the angular attachment of the spring plate to the torsion bar arm. On the original (non-adjustable) spring plate it is firmly welded. On all the adjustable ones the spring plate has to be free to rotate (with the adjustment) on the torsion bar arm cylindrical piece.

The Factory part bolts the spring plate to the torsion bar arm. This increases the angular twist resistance (spring rate) of the assembly (compared to the non-adjustable spring plate). It also means that the connection between the spring plate and the torsion bar arm is not (all) at the cylindrical piece.

Both the WEVO and SaW require the spring plate twist to be taken by the thin connection to the torsion bar arm cylindrical piece and spacers between the spring plate and the other components. Without a bolted connection, is any twist taken by the torsion bar arm?

Could we have a situation where the spring plate can twist at its attachment around the torsion bar arm cylindrical piece?

Reading the WEVO instructions, clearly careful attention is needed to the spacers locating the outboard housing. One feature of that is to properly clamp the spring plate axially around the torsion bar arm cylindrical piece. Any extra clearance there would allow more twist and possibly this problem.

I agree; Hayden and Tyson are some of the best in the Porsche world. Our goal should be to help them be even better. This feedback (while public) is very important to them.

Best,
Grady

[jaydubya]

Originally posted by 911pcars
Another method would be to create a bored seat instead of a flat surface for the adjuster screw as shown.

Seems like a good idea, would certainly keep things in place when the corner was loaded.

Maybe combine that with a second screw that came down through the upper seat and threaded into the center of the adjustment screw? Not sure I've described that well... basically drill and tap a hole along the axis of the current adjustment screw, put another bolt through from the top of the platform that is welded on the end of the adjustment plate.

[jaydubya]

Wait - even better! Drill a hole though the adjustment screw transverse to its long axis at the top end. Then drill a hole through the platform (after the bored seat is put in). Put a pin through the two sets of holes. Could only adjust in 180 deg increments - perhaps enough flexibility for corner balancing?