Options for replacing rear struts needed.

[Ronnie]

12 hours ago, 2seater said:

I hope the experiment is still going well but this seems to have died??

Seems like about everything Reatta related has died.

[Padgett]

Suspect the larger rod may be for sway bar loads. Allante does not have one. What is the Monroe diameter, is replacement for both ?

 

[Ronnie]

I've said this several times before in this thread but I'm going to say it again.

 

In the photo below you see a shock on the left. We keep referrring to as a strut but it's not. Look it up on RockAuto and you will see they list it as a shock. It has an eye mount on the bottom that allows it to pivot in the lower control arm on an Allante. A shocks sole purpose is to control the up and down motion of the wheel. The fact that it can pivot on the mounting bolt eliminates any side load so a smaller rod can be used.

 

The STRUT on the right is clamped tightly in the knuckle. The knuckle pivots on the one (1) bolt that connects it to the lower control arm. The strut is what maintains the knuckle at the proper angle (camber). The knuckle trying to pivot in the lower control arm by the weight of the car is what puts a side load on the strut rod. A strut controls the up and down movement of the wheel as well as maintaining the correct camber of the knuckle and the bearing and  wheel bolted to it. The side load is why the strut needs a larger diameter rod than the shock.

 

I'm not saying the smaller rod of the shock won't be adequate when used as a strut. I'm just trying to explain the reason the shock has a smaller rod than the strut.

 

[Ronnie]

Just to add to what I said above... The Allantes that used the shock had an upper control arm to control the camber of the knuckle.

 

[Padgett]

And just a note but 1987-1992 Allante uses the same rear thingie as the Reatta (but no rear sway bar). 1993 just looks similar to earlier ones but the chassis & powertrain is very different.

IMNSHO too much of the Allante was Japanese (but does not admit it).

[2seater]

I see it illustrated above and have thought of this before: we need an upper link to take the side load. Essentially a double "A" arm vs a strut type suspension but I don't see there is enough room to do so. Kind of reinventing the wheel, even more than finding a substitute for the strut. We would probably have better luck with a group buy of the original strut to get a run of them made, essentially a zero chance as the OP has explored that ground. We have been trying to find something that fits the original pattern without a lot of success except for the present substitute which does appear to work. Another option is of course adapting the stock suspension parts to accept a completely different type of strut design, probably a front strut from something, but that would be an equally large challenge.

[Padgett]

Group buy could include 1987-1992 Allante folk.

[DAVES89]

Don't want to be a downer but never gonna happen. Padgett  if you were to do this my guess is you would have to commit to Monroe for at least 2500 units. Let's say they need a deposit of $100,000.00 [$40.00 times 2500] are you up for it? It would take you 10 years to sell them at 250 a year. 

I'm 66 and I believe you are in your 70s, not enough time left in my life for this...

[Padgett]

Just saying, Allante folk are having enough trouble replacing failing LCDs.

[DPS.01]

On 12/16/2022 at 2:05 PM, Ronnie said:

I'm not saying the smaller rod of the shock won't be adequate when used as a strut.

Another point to consider:

 

The piston rod of the Allante shock and the Reatta strut are 20mm and 25mm respectively.

 

The piston is a smaller diameter where the upper attachment is made on the vehicle.  I don’t recall the diameter, but they are the same (and use the same upper mounting hardware). 
 

Would the upper mount have the most force applied to it during vehicle operation?  If so that smaller diameter would be the weakest point, and they are the same. 

 

I am pleased with the Allante shock modification, but ultimately the strut insert will likely be my final solution.   
 

As previously stated, the stroke is similar and the piston diameter is the same, and it would use the existing strut housing so mounting to the vehicle remains the same. 

[Ronnie]

5 hours ago, DPS.01 said:

Would the upper mount have the most force applied to it during vehicle operation?  If so that smaller diameter would be the weakest point, and they are the same. 

I'm not an engineer, just a machinist, so take what I say with a grain of salt. In relation to force being applied to the Allante shock rod, I view it as a lever that controls the knuckle's ability to pivot in the control arm. The longer the lever the less force would be exerted on the end farthest away from fulcrum (pivot point of the knuckle). Although the rod in the shock is about 20 percent smaller than the rod in the strut, I personally would feel OK with normally driving my Reatta with the Allante shock installed, as long it is strongly secured in the knuckle. As you said, the end of the shock and strut rods where they attach to the top mount are equal in diameter.  However, I wouldn't feel comfortable pushing my Reatta really hard through sharp curves like I often do when running a section of curvy road like the Tail of The Dragon with the Allante shocks installed. Side force that is applied to the wheel in a curve is transferred to the smaller shock rod and I wouldn't want to push my luck. 

 

[Padgett]

Interesting, Monroe shows the same rear shock for both

[DAVES89]

18 minutes ago, Ronnie said:

I'm not an engineer, just a machinist, so take what I say with a grain of salt. In relation to force being applied to the Allante shock rod, I view it as a lever that controls the knuckle's ability to pivot in the control arm. The longer the lever the less force would be exerted on the end farthest away from fulcrum (pivot point of the knuckle). Although the rod in the shock is about 20 percent smaller than the rod in the strut, I personally would feel OK with normally driving my Reatta with the Allante shock installed, as long it is strongly secured in the knuckle. As you said, the end of the shock and strut rods where they attach to the top mount are equal in diameter.  However, I wouldn't feel comfortable pushing my Reatta really hard through sharp curves like I often do when running a section of curvy road like the Tail of The Dragon with the Allante shocks installed. Side force that is applied to the wheel in a curve is transferred to the smaller shock rod and I wouldn't want to push my luck. 

 

I certainly am nether an engineer or mechanic, but actually Ronnie when you are taking sharp turns the weight shift to that side actually pushes the strut rod in, so the rod is inside the cylinder getting extra support. It is the non weight bearing side that is extended. I also believe [unfounded certainly] that car makers overbuild parts to handle additional stress. A good example is ladders. Ever look at the rating and see how much extra weight of the person/equipment is on them?

[Ronnie]

1 hour ago, DAVES89 said:

actually Ronnie when you are taking sharp turns the weight shift to that side actually pushes the strut rod in, so the rod is inside the cylinder getting extra support.

Good point Dave that I hadn't thought of. Right now the Allante shocks and associated parts to install are about the only over-the-counter option available as far as I know. It's certainly with a try.

[jon L]

I would be worried about the base coming out of the knuckle under hard maneuvers. If a hole was drilled  across the knuckle and a bolt was inserted thru the knuckle and the shock, thru the bushing it would hold it secure.

[DAVES89]

On 11/20/2022 at 3:13 PM, DPS.01 said:

 

The Allante would not need the extra clamp.  In this application, it is only used as an attachment point for the sway bar. 
 

I will put together a parts list and post once the installation is finalized. 

 

Yes, the upper portion of the piston is extended using an 18-8 stainless steel coupler, and 12.9 grade threaded rod, ~100mm long. 
 

 

Do we have this list somewhere? Or did I miss it?

[ErnieR]

On 12/24/2022 at 1:59 PM, DAVES89 said:

Do we have this list somewhere? Or did I miss it?

When I thought of this for my Allante and then proposed it here, the clamp was going to be a way to further secure the shock in the control arm.  My concern was that the arm would move up on the strut.  I was going to fab something that tied control arm to the clamp, my original thought was drilling a hole in the arm and fastening a heim joint to the clamp and the control arm.  I think under normal collector car driving a visible check once in a while would verify if there was unwanted movement.  On the Reatta, I would periodically check the clamps for movement side to side, also becuse of the sway bar connection.

[vlib]

After reading all 16 pages of this thread...I am wondering why more attention has not been focused on the Koni inserts. The dimentions look like they will work and the insert can be locked into the original strut housing using the bottom attachment bolt. Additionally they would be adjustable. Is it the price or some other reason I have missed?I am looking to buy an 89 with rear strut problems.

[Padgett]

Cutting and welding is part of the issue. Looks like a 93 Allante just needs bushing removal, a bit of filing, an extension, and a clamp.

Just waiting for the parts/source list.

[vlib]

Thank you for the reply. From what I have seen of the installation requirements of the KONI insert, no welding would be necessary. There would be some cutting, filing and drilling that could be done by anyone with standard tools. I am certainly no expert and I applaud the ingenuity  of the Allante shock install, but I personally would be conserned about the limited amount of clamping surface where the shock and knuckle attach. I guess I'm looking for some reasonable assurance that the Koni could work before I buy a car with bad struts.  Further input would be greatly appreciated.