"bad quality" of rubber bushes due to torsion?

[Jinx]

All over the german kadett B forum, there is the opinion that reproduction rubber bushes are very bad and get worn out really quickly.
A dutch collegue found a passage in an old service manual about how to bolt down the bushes. It stated that the lower A arms should almost be horizontal before you properly torque up the bolts.

I'm redoing my front suspension so i made a little video of the bushes that are coming out that nicely shows how much rubber should flex and why that passage in the FSM 'might' be so important...

YouTube - Kadett B draagarm rubbers

what is you guys' opinion. If the guideline is not obeyed, do you think the new rubber will go bad quickly?
(as a comparison: PU bushes are lubricated to stop 'squeeking' so i assume they arent 1 solid structure but 2 metal liners and a seperate PU bush)

[heimue]

It looks to me that you are right. the rotating motion from a rubber bushing comes from within the rubber, while a PU bushing actually rotates on the shaft or inside the housing. A rubber bushing that gets rotated out of place will fail immediately.

Dieter

[MantAscona]

Not saying that this is the cause, but it's worth mentioning. When using PU bushings, you can completely assemble and torque the whole suspension unit on a bench and then install it in the car. This is due to the fact that the bushings rotate on the inner sleeve like a hinge just as Dieter mentioned. However, when using stock type rubber bushings, you can assemble it loosely on the bench, but everything must be torqued with the full weight of the car sitting on the suspension. This is because the rubber bushings are actually bonded to the inner sleeve and they work on deflection. That's why the inner sleeves have the serrated teeth on the ends. The bushings find their neutral position when weighted and then you tighten everything which will cause the serrated teeth to bite into the mountings. If you tighten everything unloaded then the rubber will already be deflected when you lower the car down. Now, any suspension compression as you drive will over rotate the rubber and it will fail.

Duane

[DennisGardiner]

Having been a mechanic since '83 and having passed the ASE equivalent certifications, I can answer this one.
When installing rubber bushings you have to torque them down with the vehicle at ride-height. This mean the car must be sitting on the ground when you tighten the rubber bushings ensuring the bushings are free of any bind.

NOW, if the bushings are torque down with the cars suspension drooping, (such as it is on jack stands) then when the car is lowered to the ground, the control arms will twist the rubber in the bushing/s.

So over time, the permanent twist in the rubber bushings will unduly stress the rubber causing it to prematurely fail.

BTW, doing this procedure right, IS-A-Pain, and believe me I've had to crawl under to many Fords and GMs, in my day, doing just that.

Note: Poly Bushings, acting more like a bearing, can be torque with the car on jack stands or ride height. Just lube the snot out of every inch of the poly bushing and metal contact areas.

[neuropel]

Having recently rebuilt a Manta front suspension I recall lowering the car to the ground before applying torque to the swaybar-to-control arm bushings for this same issue - it WAS a pain. They were the only new rubber bushings I had replaced as all others I installed were PU. By the way, how soon after the car is back on the road is it recommended to check and re-torque all the bushings, and is it the same for rubber and PU?

TK

[Jinx]

thanks for the replies; I'll make sure to properly install my fresh rubber (i'm legally not allowed to use PU bushes)