Cutting late dual spring plates down to single?

[Piledriver]

OK, I'm stuffing bigger rubber under the rear of my Squareback partially in preparation for an upcoming somewhat stouter 2L or 2.5L T4 engine and perhaps a Vanagon auto trans that could deal with said engines under boost.

That and it was time for a new set of tires anyway so these cost ~about the same as just replacing, at least for the tires. Discounttireonline had them for a good price with free shipping AND $40 off a set sale.
(I had them in 2 days, shipped from Dallas)
.
Tires/Wheels:
Cooper Zeon RS-A 245-50-16 on 944T 8" Et52.5 manhole covers, possibly the only forged aluminum rims anyone is ever going to get in nice shape for $200/set of 4.

The rears are ~stock height, or close at 25.5".

The fronts are 6" ET53.5s with matching tires in 205/55-16s, looks like no fit/offset issues there at all.
(other than swapping to 5x205 and installing studs)
May put the 1" spacers up front to fill out the fender well better.
Maybe.

Using 1" spacer. I have about 10mm to the OUTER blade of the dual T3 springplate, and that's the closest rub point by miles due to previous trimming.
I have already started rolling the fender lip a bit and it looks ~OK with suspension compressed to desired height.
I plan on pulling the bars to test with full travel weather allowing.

BUT:

If I drop to a 15mm hubcentric spacer, tire now just barely rubs on the outer of the dual springplate.

Can I (reasonably safely)
A) cut off the outer spring plate blade like a T1,
B) give the front end of the trailing arm to spring plate bracket a slight shave, and
C) only run the rear 3 trailing arm<>springplate bolts? (front one reversed so head is outside)

This would give me the same or slightly more springplate clearance as the 1" spacer, and give me more "headroom" and less needed fender work.
(15mm may have fitted with no fender work, but getting rid of the sharp edge is good anyway)

Each of the dual spring plate blades appears to be ~the same thickness as the singles.
(Don't have one to measure to be certain)

Pic is with the 1" spacers (long studs on modded (now) Porsche hubcentric T3 rear hubs) and ~10mm to the stock dual springplate. Hubs also modded to center 5x205 drilled Wilwood stamped steel brake hats...

May need to mod inner fender a bit for full "up" travel, but that will be outwardly invisible.
The cut down spring plate/15mm spacer may allow me to skip that mod.
At least the fenders come off in 3 minutes.

[Ol'fogasaurus]

Pile, measure not only the thickness of the arms but the spacing of leaves on the arms. Since I am not at home I can't help here but not only is the fastener pattern to the trailing arm different (pictures at home) but I think the single arm is more centered in-between the locations for the two arms (not sure but the one time I was playing with both spring plates I think this is what I found out but that was many years ago) spring plates.

I also don't know if the material spec is different. Sometimes they can get by with making changes like this with just a material change (math involved here) to meet the spec required.

After straightening out several single arm spring plates I still think that for rough treatment the dual arms are stronger and that is for many reasons. They are getting fewer and fewer so that is a consideration also.

Also, I think a lot of the aftermarket spring plates are a bit thicker than the stock one.

Food for thought and it is time for breakfast for me.

Lee

[Bruce2]

I'd be more inclined to swap your TAs, spring plates, and torsion covers for Beetle singles.

The strength of the spring plate is irrelevant. The single spring plates never bend or break. When Porsche adopted Beetle TAs, they used single spring plates. Much heavier car with more hp. Never a problem.

For added clearance at the forward M12 bolt at the spring plate tab, countersink the hole and put a flat head in. I did that mod to well over 100 TAs for use with big tires.

One guy I know did not install the 3rd bolt, using only two. Even when torqued to spec, the TA moved relative to the spring plate, causing positive camber. You must have 3 minimum.

[Ol'fogasaurus]

Bruce2, they do bend, maybe not often but they do bend. I think I even remember seeing one tear but I don't know if I knew what or why. People can be pretty tuff on things. Off-camber landing, bouncing off stuff, etc. is part of where I ride and part of racing (why do they drive over the curbs and sidewalks on the race courses ) Also remember: Mr. Porsche and his group I don't think even considered his cars to be used the way some of us now use them.

Any, what I posted was just for consideration.

Lee

[Piledriver]

The front bolt threads (of the 3 rear bolts) just catches the wheel weight with the 15mm spacers, flipping it around with the nut on the inside would solve that, but with the 1" spacer no inside clearance issues at all, at least as much clearance as the 5.5" et38 914 Mahles I was running... The most fwd 4th bolt was the issue, bad location, will look for some countersunk hex bolts, even the Mahles with 205s were pretty close to the 4th bolt head, I might be able to use a button head from the inside.

No off-roading abuse for this one, I'd love some adjustable plates but they usually have the adjuster bit in exactly the worst place for squeezing big fat tires in.

I'll probably just leave the 1" spacer in for now.
I still haven't found an old baseball bat yet to roll the lip etc, but it required little work for clearance...Plus with the 4-way springs on there it doesn't compress very easy, she gets pretty stiff in a hurry away from static ride height.

I may drop her one outer spline F&R, but that's about my limit with the great roads around here.

[Marc]

I don't have any single springplates "loose" so I'd have to drag out a jack and roll in the mud to measure one, but if memory serves they are thicker than the dual ones.
One "dual" plate should be plenty strong enough to serve as the radius arm, what I'd be concerned about is whether it'd be sufficient for support if torsion bars are retained as the spring medium - if it's thinner as I suspect, the area proximate to the weld might be a weak point. I guess the worst case, if it did fracture there, would mean driving home on the rubber snubber

[Piledriver]

My sons 71 super may have single spring plates out back, should be able to measure if that's the case, its parked in a dry barn and the fenders are off, can check tomorrow.
If so, may work out a parts swap.

[Ol'fogasaurus]

The front bolt threads (of the 3 rear bolts) just catches the wheel weight with the 15mm spacers, flipping it around with the nut on the inside would solve that, but with the 1" spacer no inside clearance issues at all, at least as much clearance as the 5.5" et38 914 Mahles I was running... The most fwd 4th bolt was the issue, bad location, will look for some countersunk hex bolts, even the Mahles with 205s were pretty close to the 4th bolt head, I might be able to use a button head from the inside.

No off-roading abuse for this one, I'd love some adjustable plates but they usually have the adjuster bit in exactly the worst place for squeezing big fat tires in.

I always thought that the horizontal spring plate to trailing nuts were supposed to be located on the inside; at least that is what I have always done. The proper thread lengths coming through the nut were then out of the way. It is something that I was told to do almost my first day when designing; that and the nut on the bottom when the fastener is vertical. I think my boss, when I was a young mechanic, said pretty much the same thing. That way, on a vertical installation, if the fastener loosens up the nut can drop out but you will still have the bolt doing some work. I have notice when watching some of the "build shows" that they break that rule quite a bit. Showing an end built should be complete and correct not just showing the assembly.

On the dual arm spring plate here is one bolt that goes into the threaded hole of the trailing arm then is "nutted" on the inside. One of the forward bolts is a bit harder to get into the hole from the outside but not that hard. It is interesting that it us a fully threaded bolt; e.g., no shank so it must be for "clamping" only and there must be no shear load on it (you don't put shear loads on threads).

I am not sure what "spacer" you are talking about but if it is a wheel spacer ....

I didn't expect you to go off-road. I have been on the fringe of a lot of forms of racing but never could afford or had spousal support to get into it but I did see and hear a lot from friends who were able to do it. "Stuff happens" so I always try to accommodate for it/go to the "worse possible case".

Lee

[Bruce2]

Bruce2, they do bend, maybe not often but they do bend. ....... Off-camber landing, bouncing off stuff,

Sure, in a collision things bend. But in normal street use, spring plates never bend.

I always thought that the horizontal spring plate to trailing nuts were supposed to be located on the inside; at least that is what I have always done. The proper thread lengths coming through the nut were then out of the way. It is something that I was told to do almost my first day when designing; that and the nut on the bottom when the fastener is vertical. I think my boss, when I was a young mechanic, said pretty much the same thing. That way, on a vertical installation, if the fastener loosens up the nut can drop out but you will still have the bolt doing some work. I have notice when watching some of the "build shows" that they break that rule quite a bit. Showing an end built should be complete and correct not just showing the assembly.

There's no such "rule" about how to orient a bolt. VW installed the bolts from the backside so the nuts were easy to access from the outside. Probably an ease of manufacturing thing.

On the dual arm spring plate here is one bolt that goes into the threaded hole of the trailing arm then is "nutted" on the inside.

VW never added an extra nut on the bolt that's threaded into the early TA. The bolt isn't long enough for it.

[Marc]

I always thought that the horizontal spring plate to trailing nuts were supposed to be located on the inside; at least that is what I have always done. The proper thread lengths coming through the nut were then out of the way. It is something that I was told to do almost my first day when designing; that and the nut on the bottom when the fastener is vertical. I think my boss, when I was a young mechanic, said pretty much the same thing. That way, on a vertical installation, if the fastener loosens up the nut can drop out but you will still have the bolt doing some work. I have notice when watching some of the "build shows" that they break that rule quite a bit. Showing an end built should be complete and correct not just showing the assembly.

There's no such "rule" about how to orient a bolt. VW installed the bolts from the backside so the nuts were easy to access from the outside. Probably an ease of manufacturing thing.

I believe he was only using that term as shorthand for "best practice, if you're the type who likes to think things ahead to their worst-case scenarios to decide which is the best arrangement"

[Ol'fogasaurus]

My dual spring plate did come with the nut to that threaded hole in the trailing arm and to the inside. If not there then you are only holding the one side of the spring plate to the trailing arm in that area.

In engineering the rule of thumb is the nut goes on the hidden side/far side (the callout is on the side the bolt head otherwise you have to identify the head side). There are things like riveted in nut plates or nut gangs to accommodate the inability to put the nut there. There are times you have to go the other way but that is an individual design requirement, probably not the norm.

The same for vertical fasteners; the nut goes on the bottom unless otherwise stated. Again, it is in case the fastener assy. comes undone the bolt is still there vs the bolt falling out if the heavy head of the bolt is on the bottom.

The three thread minimum rule is there (unless class/assn. rules call for 2 1/2 diameters [or more] showing) because of the "easy-on taper at the bottom of the bolt (machine screws don't always have the easy-on accommodation). The threads on the taper are not full on the taper so roughly three full thread gets the nut past not having a full grip on the bolt.

Bruce2, people bounce off curbs, turtles, lane dividers and stuff all the time on the street so I guess you could technically call it a collision or an AW $#it. I have seen bent spring plates before so I am assuming it can happen.

When I took out my trailing arm when kissing a tree that was too close to the trail (it is now gone), the dual spring plate was in a bent condition but did go back into shape w/o much work.

Lee

What Pile said about the word "complete" (below) is true. One of the things you do when teaching or mentoring... do/show it correct then you can cover exceptions if necessary. I was taught that and it is the way I did it when teaching or mentoring.

Correction: I did replace the spring plate at the advice of the shop where I got the replacement arm. I was very new to VWs at the time.

Made some wording corrections and added a sentence below my sig.

[Piledriver]

Got the rears on with the 1" spacers, I need to track down a longer set of studs so I can use "just" 1" spacers rather than the adapter style.
Setup is still with the same 914 rotor/Mk4 Passat-ish calipers out back for the moment, but the Wilwood steel hats etc fit fine.

With the 914 rotor the wheel sits another ~4mm out vs the Wilwood steel hats.

If I had single spring plates I could have easily gone 255/45, maybe even 265/40s on 9s but 245s are the "correct" width for the 8s, and it already looks like a pretty serious shoehorn job..

The T3 dual spring plate setup has some standoffs to allow the wider spring plate setup, not sure if the welded on spacers are part of the cover or torsion, cant remember, and not motivated enough to take them off to find out right now.

Have driven about 60 miles this afternoon, city/highway and bombed out roads.
I can definitely feel the taller effective gearing and reduced rear braking from the ~stock dia rear tire.

No rubbing at all despite thrashing it some, do need to drop the rear pressure from 35 and perhaps raise front pressure to match.

It kind of has a way too much of "Hot Wheels" look right now so I'm going to have to get the front done ASAP and drop F&R a spline or so, this will require inner fender mods but its not too hard.

I'll weld a patch on those trimmed spots the coming weekend weather allowing, it was sunny today, felt like 50-55F.
It didn't really need that much cut off the bump stop. but I'm still assuming I'll be swapping for single spring plates at some point.

The angle of this photo doesn't really do it justice: The rears are 10" wide on 8" rims...
Still haven't decided on polished or flat black...
(one of them is painted, the other 3 have the factory anodization in ~OK shape, I rather doubt they painted anodized wheels .)

[Marc]

I'm running bolt-on spacers on my Beetle. Good enough for Porsche to use as OEM equipment, no worries that they'll do on a street ride...having 40 lugnuts to deal with is somewhat vexing, but I'm confident of their integrity. Quite-likely better than pass-through spacers with gangly studs, especially on redrilled rotors.

[Piledriver]

I should have taken a pic of the modded T3 hubs alone, they are fully hubcentric for the wheels/adapters and the Wilwood hats.
The studs have ~no effect on axle/rotor/wheel centering...
(although they were setup on a manual Bridgeport using the CNC adapters as jigs, they came out nice)

The OG T3 hubs are some nice, tough, and hard iron, still ~8mm thick under the new stud locations.
They sheared the knurling OFF the EMPI studs I installed at first with absolutely zero effect to the holes... made sure to put a little countersink/break the edge on the second try with the larger/longer Dorman studs.

The studs I finally used have an extended shoulder that is actually a slip fit in the (one) original 914 rotor hole, and the 914 rotor centered perfectly---shockingly considering the 4 new holes were 3/4"--- the bolt on spacers also save me having to drill/tap/use hold downs for the rotors/hats.

The Wilwood hats have about .0015 clearance on the hub, and will probably self-secure with rust when in use.

[Bruce2]

The T3 dual spring plate setup has some standoffs to allow the wider spring plate setup, not sure if the welded on spacers are part of the cover or torsion,

They're part of the cover. If you swap to single spring plates you need the covers without the spacers.

It looks like your tire was rubbing on the outer spring plate ahead of the missing bolt. Is that from before? If not, I think you'll need to go to singles.

When I used the max tire possible in a 50 series, I found that with 3mm of clearance the tire didn't deflect enough to touch the spring plate. Since the short tire altered the gearing too much, I now use a narrower tire that is 60 series. With more clearance, it rubs slightly more due to the flexyier sidewalls of the taller tire.