Suspension bushings – does torque matter?

[My Nameis]

Ok so I’m curious about something. When it comes to replacing suspension components involving bushings is it absolutely necessary to torque to specs?

I ask because I skateboard and if anyone is familiar with the trucks of a skateboard they consist of two bushings using a kingpin that bolts through them.

[IMG]http://uploads.tapatalk-cdn.com/20160220/20c45046da41c4906861d1df6135db49.jpg[/IMG]

Now with a skateboard altering the tightness of the kingpin nut gives either a firmer or looser feel to ride quality aka preference of the skater to board feel.

This got me curious as if the same “feel” can be altered in a car and if so you should always torque to factory specs to maintain original feel or if it doesn’t matter just tighten till tight.

Topic

[college man]

Factory torque specs are always the best procedure to follow. You can ruin a bushing by over tightening it.

[Mike]

I don’t think you can alter the handling characteristics of a vehicle by manipulating torque values, except in the case where everything is so loose that things are ready to fall off, which isn’t what you want.

The bushing material is the deciding factor when it comes to road feel. Many cars have a variety of suspension bushings available, from many different sources, that will give the vehicle certain ride characteristics, from luxury cruiser smooth to tooth-loosening race firmness. It was, and still is, common practice to upgrade the suspension bushings on 60s-70s era muscle cars to firmer stuff than what came from the factory. It helped to get rid of some the wallowing that heavy old Detroit iron is known for.

[Mike]

The only kinds of suspension parts that attach like a kingpin/truck bushing setup are some designs of sway bar end links, radius rods, and some designs of upper shock/strut mounts. Neither of those are intended to be ‘tuned’ in the way your thinking. I have never seen or heard of any type of control arm or suspension link that is meant to be tuned is such a way.

On a side note, it does matter what height the suspension is at when links and arms with bushings are tightened down. If they are tightened while the suspension is as full droop as is normal when the car is jacked up with a wheel removed, the bushing will be twisted when you let the car back down to it’s loaded rest position. The bushings are designed to be straight when the car is sitting at rest and to twist only during suspension travel. If you tighten them down with the suspension at full droop, the lifespan and performance of the bushing is affected.

Another thing I’m thinking of is that bushings pressed into a suspension arm frequently don’t have rubber all the way around connecting the center sleeve (where the bolt goes thru) to the outer sleeve (the metal ring actually pressed into the arm) If you replace bushings like that, you can orient the openings in the connecting rubber a ‘right’ way and ‘wrong’ way typically. If you know what you’re doing, you can firm up or loosen control arm movement by changing the orientation of such bushings.

Just to clarify, an example:

Note how the bushing can be turned 90° and how it might change the way the control arm is allowed to move around under load.

[EricTheCarGuy]

Yes, torque specs are the best practices with suspension parts. WHEN you tighten may also be important. Many compliance bushings you want to tighten with the vehicle weight on the ground. If not, you could tighten the bushing in a position where it gets stressed when it’s placed on the ground.

That said, I mostly run suspension parts down with my impact, usually my 3/8″, but I try and make sure with the above mentioned bushings I tighten them when the vehicle is on the ground.

[My Nameis]

Thanks guys. I’m now wondering how tightening a suspension part with the vehicle on jack stands causes the bushing to be twisted and affect longevity.

I mean aren’t the bushings going to be moving during normal use anyway? How’s it any different the position they’re in during installation if they’re meant to move?

[Mike]

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