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Discussion Starter #1
Bought a stiffener about one month ago from Mark Ereminas in Oregon City. Just now starting to install and so far the main problem is it's too short by about 1/8 to 1/4 inch. My thought process tells me to install from the rear first because of the need to install the rear shims without the worry of horizontal alignment under stress if the front is already attached (i.e the need to adjust the shims to accomodate the rear cross bar). So far I tried to jack the car at left center body but made no difference. One thought is the front flat iron plate that attaches to the sterring box bolts bottoms out against the rear of the wheel well which may be the reason why its too short. Just some thoughts begging an experienced response. I have read most all the posts on this issue and I'll keep you posted with my (lack of) progress and pictures.
 

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It's been an awful long time (7 years) since I installed mine but the one thing I remember was that it was pretty much impossible to do it according to the instruction sheet - mount front then rear. I ended up doing it opposite by mounting the rear first and then using a tapered alignment drift in one of the mounting holes in the forward plate, forcing it into a position where I could get a bolt through one of the other mounting holes.

An eighth of an inch doesn't sound like much. Have you tried doing this yet?
 

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1966-2013
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Yup, back to front would be the way.

Tapered drift, or you can use the left over set of throughbolts and grind points on them, drift them in from the outside to align the plate, then drift them out out from the inside using the bolts that are to replace them.
(new bolts that came with the stiffener in drivers side, old drivers side bolts in passenger side, old passenger side bolts as tools IIRC)

Don't hog the holes out in a fit of frustration. as it kinda defeates the purpose a bit, and can make for possible problems down the road as the bigger holes allow shuckage which in turn will beat up the sides of the throughbolts, potentially to the point of loosening up or outright failure.

Oh, and as a side note:
If you are gonna try to jack the chassis to flex it, you gotta have both of the doors open, otherwise they act as structural stiffeners and won't allow as much flex.
(not that bending the car is a good plan, but if one had to, that would be the way to go about it)
 

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+++ on the drift. I have a three foot prybar with a rattail on one end.
Don't know what I would have done without it.

Drivers side was a ***** but the passenger side was easy?
 

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Discussion Starter #5
After my first attempt I kinda figured I would have to go from rear to front. Excellent advice as usual and never thought about the doors needing to be open! What about aligning the rail widths in the rear to accomodate the rear cross bar length? Seems that after installing the shims on the outside of the front trailing arm (drivers side) and then bolting to steering box, one would have to install (temporarily) the rear cross bar to measure the right width for installation of the passenger side shims.

Going to again try, as IAP suggests, to jack up the left side center, this time with the doors open (duh), just to see if there is a difference. If not I'll get the pry bar and/or tapered drift (and trusty wife) to work. Thanks all.
 

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If you measure C to C on the trailing arms and then layout the same on the stiffener long bars, you can get a fair idea how many shims need to be where.

ie: if the rear crossbar bolts line up with the long bars set at = center width as the trailing arm ends, then there should be equal #'s of shims on both sides of each trailing arm yoke.

In the grander scheme, you'll likely find = #'s of shims on both trailing arm ends, and that split evenly between both sides of the given yokes is just fine in around 98% of the installs.

Really about the only reason you'd have to shim differently is if the cross bar didn't bolt up (unlikely unless something is way messed up) or the long bars bumped up against the chassis in such a way that it/they couldn't be tightened up true to the trailing arm yoke w/o deflection/bending of the bar or undue stress on the yoke. (which could result in the proverbial 'bad thing')
 

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Discussion Starter #7
So as I re-read the instructions and your advice the cross bar should fit if an equal (as possible) number of shims are added on each side of each trailing arm. In other words the long bar "U's are centered on the the trailing arms. I will measure first and see if this is reasonable and adjust as necessary. Thanks.
 

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That is correct.

Oh, and from someone else's (sorry I don't recall specifically who) fine suggestion regarding installing the shims: superglue them together so you don't have to fight them as a loose stack that won't want to stay lined up.
 

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I'm starting to take my Duetto apart to fix some rusted floor pans and other bits; after that the body will be stripped for a major repaint. The chassis will also be getting a set of the commonly used stiffeners in all the well known places, and seam welding on all the others ( i've found som stress cracks at the steering and idler mounts, and especially at the front sway bar bolts. I also plan to add a chassis stiffener before the paint job.

The stiffener is just two long square torque tubes, and is known to do good things to these spiders. Has anyone considered welding it into place in addition to the mounting bolts? Potentially you could weld the steering box/idler ends and make great stiffeners at this known weak spot in the front sheet metal.

It may even be possible to seam weld along the length of the chassis frame and the stiffener's tubes; Has anyone ever tried this?

Robert
 

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Welding to the seams around the mount plates sounds like it might be a viable option, but there would be the concern over the temper/hardness change that might come with it (too brittle and things ouywld just shred at that weld joint)

It's been discussed before IIRC in regard to affixing the length of the bars to the lengthwise seams of the chassis.
(suspension subsection mabe?)
Something to the effect that the stiffener works better as it hangs below the chassis rather than being 'part' of it.
Being seperate it acts in tension and has more strength than it would in flex if welded full length.
EG: the difference between trying to pull a pipe apart by stretching it lengthwise vs bending it over the corner of a bench.

Simular to the effect of a strut or cable type brace being more effective than an extra slab of framing.
 

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Discussion Starter #11
Success almost!!

Just finished the installation and even drove it a few blocks (no insurance at the moment) and all is well. Feels great and I don't notice any obvious alignment problems. So here's my thoughts.

Unless you have a perfect fit install from back to front. I had to grind away at the fender wall drivers side (see photo) where the plate rests. Otherwise the plate would not reach the bolt holes. Used a bungie to suspend the front plate while installing the rear shims - used 4 on each side driver and 3 on each side on the passenger side. Installed shims tied with sewing thread. Had to install the lower front plate bolt, left side, in reverse. It simply would not go through the plate from the inside.

Other side was relatively easy once I figured out placing a small wood block on the bar a foot or so from the trailing arm and then a jack under the plate would bend the bar enough to line up the 3 bolt holes (see photo). Worked perfectly! Brilliant!! Yes, the wood block has been removed.

Front cross bar installed without issue. Rear bar bolts (all 8) lined up well but tail pipe was too low to install. Is this bar real necessary??

Anyway, once I get insurance (when the weather turns) I'll test some serious bumps and report on the results. Thanks all for the sage advice.
 

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Had to install the lower front plate bolt, left side, in reverse. It simply would not go through the plate from the inside.
Use an old bolt to go from outside to in like you did, then using the correct bolt from the inside, drive the old bolt out.
No harm, no foul, it'll be OK the way you've got it going if you don't fancy changing it around, though you may get a DPO rating from a buyer or shop in ther future if they ever need to mess with steering box.

Rear bar bolts (all 8) lined up well but tail pipe was too low to install. Is this bar real necessary??
In the grander scheme of things, no, it's not super neccisary.
The very vast majority of the stiffening is done by the long bars.

That being said, the pix of your exhaust indicate that it's not the stiffener cross bar thats at odds, its the funny way your system hangs in the center section (obvious droop between the joint and middle can pipe)
and you may be able to correct it by fitting that section better. It's either on the hangers wrong, or the joint is out of clock.
(without even seeing it, I'd hazard your tailpipe is off center in the hole of the rear pan too. Probably to the left. This would be a result of that center section front joint)

Did you remember to adjust the turnstop bolts to account for the added thickness of the stiffener plates?

EDIT

You gonna sign up on team darkside anytime soon with that shiny black machine?
(you ain't gotta race it, 'cause everyone already knows the black ones are fastest)
 

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Discussion Starter #13
Yep, adjusted the steering stops. So far as I can tell the stiffener does indeed make a significant difference.
 

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Congrats on the install and thanks for sharing.

I always find finishing the projects that give the most "trouble" to be the most satisfying.

Are those original shocks I see? :eek:

Changing the shocks is an easy and inexpensive way to give a great improvement to your ride.

Congrats again. I will be saving this post for future reference. ;)

Vin
 

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I installed my stiffener during a major restoration that included new floorpans, engine and tranny rebuild, upholstery and just about everything you could think of - well, not everything. When I got it all together I took it down the road for a test run and as I was making a u-turn to head back my old Burman steering box busted into about 3 pieces, literally exploded. I replaced it with a ZF out of a later model from APE and at the same time I made a steel plate for the inside of the fender that matches the one on the chassis stiffener and lays between the steering box and fender. The idea was to cut down on the flex in what is a known weak area. It seems to have worked well.

BTW - despite what some people say, I couldn't tell any difference between Burman and ZF boxes as far as drivability and feel goes. Of course I didn't get to switch back and forth and do active comparison but overall I really can't say that there is anything I noticed and I've owned the car for a long time.

As far as welding the chassis stiffener members to the bodywork, I don't see that as a good solution. The stresses have to be distributed and welding the plates is simply going to force it to concentrate along those welds. The plate and welds will survive but the body sheetmetal will probably begin to crack along those seams. Also, the physics of the stiffener are really pretty simple. In order for the chassis to flex or bend at the center where the doors are the two points at which the chassis stiffener rails are bolted must move closer together. They can't do it with that parallel square tube installed between them - or at least not as easily.
 

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... welding the plates is simply going to force it to concentrate along those welds. The plate and welds will survive but the body sheetmetal will probably begin to crack along those seams.
This is not at all obvious. Reinforcement plate are commonly welded in here (and several other places) on many of the 105 racers because of the known weaknesses. There are several threads showing these; I've added a few of the pics from them. Pinch friction between the stiffener plate and the body with just three bolts will not be as stiff as a full seam weld as is commonly done.

Also, the physics of the stiffener are really pretty simple. In order for the chassis to flex or bend at the center where the doors are the two points at which the chassis stiffener rails are bolted must move closer together. They can't do it with that parallel square tube installed between them - or at least not as easily.
Seems like its a simple shear I-Beam. For these, the major load is carried by the top and bottom member, but the shear membrane between them adds a factor of 5 in stiffness in its plane*. (In this case the top and bottom members are the body and the stiffener tube); the membrane would be a welded seam along the length of the body tieing the stiffener box to the body).

* more or less depending on the depth of the membrane and its ultimate shear load.
 

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It's true what you are saying but what you are showing is something that is ridiculously overbuilt. I'm an aircraft guy so we are always striving to make things as strong and light as possible. It's not as critical in an automobile but really, if you are aiming to build a racer I think the last thing you want are boilerplates of iron here and there.
 

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This is not at all obvious. Reinforcement plate are commonly welded in here (and several other places) on many of the 105 racers because of the known weaknesses.... Pinch friction between the stiffener plate and the body with just three bolts will not be as stiff as a full seam weld as is commonly done.
One thing to consider regarding fish plates vs the stiffener mount plates that I think is being missed here:

While the addition of fish plates (that's what I call them so deal with it :)), do reinforce that area, and seam welding them helps that process along, thier primary job is to help prevent the steering and idler boxes from transmitting flex and torsional stress to the chassis proper when the boxes get 'shoved around' during high load situations along with trying to reduce any inherant flex of the front 'arms' of the chassis that go around the sides of the engine bay out to the front crossmember.

What they aren't designed to do is also deal with the shearing force stress placed upon it by that (basically) 5 foot long lever arm thats tied to the rear suspension and that works directly against one single edge of the plates.

Putting on fish plates works in the immediate area and is effective because the plates rather large yet the stress applied to them (the boxes + comparatively short lever arms the front arms present) are pretty well centered in its anchorage points, but as soon as that lever arm comes into play, shear stresses go up proportionate to the length of the lever and amount of deflection that bar is given. (chassis stress over X bump or roll transition)

Granted that movement is minimal given the amount that the chassis can flex over is length, but it doesn't take a yard of reptetative movements in shear direction to put huge deflection type stresses on a welded seam or the materials in the immediate vicinity of that weld.


Really basic over simplified comparative:

Take a tea saucer and tape it very well to a table around the plate's edges.
Put a plunger on the plate and try to pick it straight up.

That is the stress of just fish plates with welded seams.

Take the same plate taped the same way and affix a 4 foot broom handle to it parallel to the tabletop surface, plop on the plunger and then move the far end of the lever in a clock~like motion in an effort to try to get the plate to rotate on the tabletop while also pulling upward on the plunger as before.

It should take very little effort at all to get the tape holding the plate to the table to start to deform or outright come loose.

That it the stress induced by the arm that goes from the front mount plate to the rear suspension by the stiffener.


It's just a matter of time before a seam welded stiffener mount plate will being to tear up the sheet metal its welded to.
Not an 'if' mind you, strictly a 'how long before'.


Now if one were to weld on thin fish plates in the accepted fashion, then mount the stiffener over top of that without any welding at all you could in theory benifit from both seperate systems and allow them to work individually at thier strongest rather than radically comprimising either to make it more like the other.
 

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.....Now if one were to weld on thin fish plates in the accepted fashion, then mount the stiffener over top of that without any welding at all you could in theory benifit from both seperate systems and allow them to work individually at thier strongest rather than radically comprimising either to make it more like the other.
The only difference seems to be whether the stiffener plates are welded or bolted. They should work just the same. Or are you saying that the bolts allow some slip, so it's mechanically connected differently from the welded "fish" plates? Wouldn't that just enlarge the bolt holes and fail too?

It sounds like you are arguing that the stiffener makes the chassis stronger but will damage the front structure almost immediately.

All I've been looking for is someone with some actual experience. I know several threads that support the value of reinforcement plates in the front structure; they are often used by the best racers here, especially for the early 105 chassis (e.g. the 2-bolt crossmember - these are made from lighter gauge sheet metal than the later cars with a 4-bolt crossmember).

And many here espouse the virtue of the chassis stiffener.

What I'd like to find is some experience with BOTH. Also, since reinforcements would be welded in, I am curious about welding in the chassis stiffener - IN ADDITION to bolting it to the steering and idler boxes.

As always, an interesting discussion.

Robert
 

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I think the only place you could weld the stiffener is at the forward plates because the tubes do not actually contact the structure underneath. Also, I think the stiffener works as advertised the way it is. The physics of it seem pretty simple to me. If the chassis flexes in the middle it's just like pulling on the center of a straight piece of string, the two ends must move closer together and the stiffener is just a longitudinal steel tube that tries to prevent that.

My thoughts on the steering box mounting - I'm thinking that the greatest forces and stresses on it are exerted in low speed or stationary turning of the wheels such as in parallel parking, especially if you happen to have low pressure in one or both of your front tires.
 
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