Rubber Suspension Bushings: How do they work?

[TwelveVee]

Simply a question stemming from curiosity: how do the rubber suspension bushings in autos actually work? Which surface is the rubbing surface? I have looked at many, and it seems to me that they mostly stretch the rubber through the limited angles of motion they see in actual operation. They work well without lubrication, in all kinds of nasty dirt, and last a long time.

 

[GregLocock]

If they are going to last a long time they have no rubbing surface. The most reliable type is called double bonded, which means the rubber is glued to both the inner metal (where the bolt goes through) and the outer (which is a press fit in the housing). The rubber is compressed (one way or another) during the manufacturing process, so it starts off preloaded in compression, making it more difficult to load it in tension, which is the easy way to tear the rubber.



Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[Warpspeed]

Yes, the rubber compound is stiff in compression, but fairy flexible in shear. The rubber actually twists in shear, both the inner and outer metal sleeves being rigidly mounted to the car and suspension.

The suspension arms can therefore rotate fairly freely by allowing the rubber to twist, but the connection is stiff enough in compression to give fairly positive location.

The rubber can also absorb small amplitude high frequency noise and vibration, which is the main advantage. And there is nothing that can slowly wear out and then rattle, and no lubrication or maintenance is usually required.

 

[GregLocock]

... or indeed, possible!

Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.