8 replies to this topic

[Deathrow]

I enjoy knowing how things work, even more so when it comes to my car.

While putting together my front suspension today I came across something I couldn't quite understand which is how the lower suspension arm acts on its bushes.

So you've got the bushes metal sleeve on the pin and then you've got the camber arm on the rubber of the bush. When the arm moves up and down during suspension movement, what is the bush doing?

At first I thought it must be the metal sleeve of the bush pivoting on the shaft but surely that'd have awful wear rates and a needle bearing would have been used like on the top arm? As I assembled it all I found that as you tighten the bolt on the pin, it squashes the bushes between one of the flanges on the pin and the rear of the subframe which again would help to prevent the bush from rotating. I'm assuming it wouldn't be in the interest of the arm to pivot on the bush either since it's metal to rubber contact giving plenty of friction.

I can't quite work out how the suspension arm moves up and down in the assembley. Does anyone know of anything I can read with regards to this or can you educate me as to how it works?

[Dan]

It's a metalastic bush, the rubber flexes to allow the arm to move. Standard bushes don't have flanges at each end, it doesn't take much contact with the frame once compressed to hold them tight. That's why you don't tighten the arm until the car is sitting on its wheels, it's important that the rubber be in its most neutral and relaxed position at normal road height.

[MRA]

Unless you are using rose joints in which case you can tighten them in any position....

Which is the opposite to indespension commonly used on trailers...... which should demonstrate the point made by Dan above.

[Deathrow]

Ahh ok. I understand now.

Presumably, I want the engine and everything in before I tighten the pins then?

[MRA]

Yes, and ideally let it settle for a few weeks.... however it is a little overkill, most people will fit, tighten, drop on the wheels then drive off....

[Dan]

And then the bush fails in about 3 months (less if it's poly).

[Deathrow]

Does seem hardcore to leave it loose for a few weeks haha.

It'll be the last thing I do. All back together and ride height set then I'll torque it before going for the MOT.

Cheer guys and thanks for improving my understanding.

[MRA]

And then the bush fails in about 3 months (less if it's poly).

Absolutely.... hover experience is something that a lot of people want to work out for themselves.... usually the hard way.

Polyurethane bushes are even worse as they fail under load, which is what can make cheap and nasty poly bushes potentially dangerous..

[Deathrow]

I've used the Mini Spares fast road rubber bushes with the offset sleeves for corrected geometry.