Bushings .. functions?

[dimlight]

Can someone please clarify what fucntion does a bushing have .. either on the transmission, suspension .. etc

[RacingManiac]

Isolate vibration and adds compliance.....in some cases I use them to double up on the bearing surface with a smaller fastener on a Aluminum bushing...

[dimlight]

by compliance.. you mean extension?

[RacingManiac]

no it gives a degree of play....its not necessarily desirable, more of a side effect of isolating vibration....

[baddabang]

It makes it so a joint can work without having metal to metal contact. It is usually some kind of rubber or plastic stuff depending on the situtation.

[dimlight]

Thanks, now I know.

[h00t_h00t]

Replacing rubber ones with plastic ones are supposed to improve handling (at the expense of comfort) though I can't see it making a MASSIVE difference.

[Matra et Alpine]

Replacing rubber ones with plastic ones are supposed to improve handling (at the expense of comfort) though I can't see it making a MASSIVE difference.

Obviously depends on the suspension as some setups rely on bush movement - ie Ford Fiesta XR2s have 1 degree of rear wheel steer provided by the movement in the bush as the outer rear wheel depresses.
Replacing the metalastic bush with a poly one removes that and for the XR2 may be detrimental -- but for the same suspension fittind in the longer Quantum is a BIG improvement.

For competition it makes a HUGE difference as it removes one more variability that affects the handling charactersitcs. Made a MASSIVE difference to the MGB GT and for Mini's saves the need to replace rose joints continuously

[RacingManiac]

Replacing rubber ones with plastic ones are supposed to improve handling (at the expense of comfort) though I can't see it making a MASSIVE difference.

Road car often uses whichever one satisfies their NVH requirement. As a result the softer bushing allows the components that mounted on them to not only pivots, also translate up and down/side to side as the material compresses. This obviously does quite a bit to your suspension kinematic and geometry, as well as transient response as you have to wait til your suspension takes set then start going about their business. Urathane replacement negates the NVH concern(harsher, noisier ride), but further restricts their movement compare to the rubber OEM counterpart, resulting less geometry changes, and more importantly better response, less complience.

There are metal bushings as well, it is often use where maybe a steel to steel contact(or Aluminum to aluminum, any same metal which give rises to galvanic corrosion), bronze, copper, aluminum are often used to take care of such issue, and sometimes even self lubricating, in the case of bronze and copper bushing...