Hypothetical rear shock/coilover question

[Zandoz]

To be up front for those that are unfamiliar with my situation, my build was cut short by health issues...almost certainly permanently. I still play around with the plans and what-if ideas just to have something to do.

One of several unconventional aspects of the plan was to be the use of many of the components and the geometry from a Fox body Mustang racing triangulated 4 link rear suspension...but with air bags and shocks instead of the stock separate coils & shocks or the racing coilovers. One aspect of the plan I'd not worked out was the frame mounting points for the shocks...or if I skipped the air bags, coilovers.

The typical Fox rear shocks mounted vertically, with the lower loop axis parallel to the axle, and a threaded shaft on the upper end. I'd hoped to keep the stock axle mount...but the upper mounting was going to require custom fabrication no matter what. The shocks I have and intended to use are PRO SM600s with loops on both ends. The questions come from the orientation of the shock loops. In my mind, with both loops parallel to the axle, given the articulation of a triangulated 4 link, that orientation would introduce a lot of binding. To me, turning the shock shaft and upper loop so that the axis is around 90 degrees from the lower may help the binding during articulation and is the best compromise. Yes? No? Seriously No!?

How about if double loop coilovers are used instead of conventional shocks?

Just one of the multitude of things that make me go hmmmmm.

 

[choppedtop]

No answer here from me, so I will hmmmm with you. Bet Jim will know.

 

[2old2fast]

As usual , that depends , plot your expected arc travel & find out how compliant the bushings are , that should give you the answer....if Ford setup those bushings , obviously it worked for them ...

 

[Zandoz]

As usual , that depends , plot your expected arc travel & find out how compliant the bushings are , that should give you the answer....if Ford setup those bushings , obviously it worked for them ...

No Ford bushings in this scenario...just the ones from the Pro shocks...probably stiffer than the factory ones.

 

[old round fart]

Get the shocks with heim joints on them.

 

[Zandoz]

Get the shocks with heim joints on them.

Yes, that would have been the probable ideal solution...but I suspect (and may well be wrong) a pricy one, based on the near non existent budget I was working with. The Pro SM600s that I have are new old stock, 6" stroke chrome monotube units...no slouches. A quick search of Speedway & Summit yielded only 2 bearing end monotube shocks of comparable dimensions, both over $150 each, neither chrome. <shrug>

 

[AusBucket]

G'Day Bill,
Have this scenario all the time with the Clubman builds using live axles. Answer is to place the pivots on the axle parallel to the centreline of the car, the top ones can be placed parallel to the axle centreline without problems. I proved early in our builds that pretty much all of the twist takes place at the axle end of the shock, and the same thing happens with trailing arms. The other thing we learned was not to use Urethane bushings, because when they heat up (with the constant suspension movement) they start to bind up. The other thing that happens with Urethane is if it's too soft the urethane migrates round to the unloaded side of the joint removing any cushioning effect on the loaded side. It's interesting to see how far the nose of the diff moves between loaded and unloaded when the bushes soften up.
Hope this is helpful.
Regards,
Mike.

 

[Zandoz]

G'Day Bill,
Have this scenario all the time with the Clubman builds using live axles. Answer is to place the pivots on the axle parallel to the centreline of the car, the top ones can be placed parallel to the axle centreline without problems. I proved early in our builds that pretty much all of the twist takes place at the axle end of the shock, and the same thing happens with trailing arms. The other thing we learned was not to use Urethane bushings, because when they heat up (with the constant suspension movement) they start to bind up. The other thing that happens with Urethane is if it's too soft the urethane migrates round to the unloaded side of the joint removing any cushioning effect on the loaded side. It's interesting to see how far the nose of the diff moves between loaded and unloaded when the bushes soften up.
Hope this is helpful.
Regards,
Mike.

What you're saying makes sense, but unfortunately without reengineering the axle bracketry I would have been stuck with the lower pivot being parallel to the axil.

The urethane bushing issue would have been a mixed bag. Johnny Joints or spherical bearings on all but the lower control arm axle ends...those would be bushings. Those bushings were an odd size, and the only ones I could find were from an off-road vehicle supplier....and urethane.