Lateral front end steering wheel/pedal shudder

[grantw]

I understood that the suspension spring offered resistance to the compression and the damper controlled the undesirable effects of the spring recovery.

I admit this is only a fundamental approach and technology has taken suspension to several new levels over the years, but a damper fighting the compression action of the spring seems pointless to me, as a matter of principle.

Don't get me wrong, I'm not arguing with anyone on this, just trying to get a better understanding....

That's how I understand it too ... if you have enough load/force to fully compress your springs I think something has gone horribly wrong.

 

[ByronJ]

Shock absorbers dampen the kinetic energy of a spring.

A shock absorber can be thought of as a kind of oil pump.

This is a pretty good explaination I just found:

'Shock absorbers work in two cycles -- the compression cycle and the extension cycle. The compression cycle occurs as the piston moves downward, compressing the hydraulic fluid in the chamber below the piston. The extension cycle occurs as the piston moves toward the top of the pressure tube, compressing the fluid in the chamber above the piston. A typical car or light truck will have more resistance during its extension cycle than its compression cycle. With that in mind, the compression cycle controls the motion of the vehicle's unsprung weight, while extension controls the heavier, sprung weight.'

The piston has small holes in it that allow the fluid to pass through it at high pressure. This creates heat so the kinetic energy of the spring is converted into heat. Once fluid is able to pass around the piston (worn seals etc.) then its effectiveness is lost.

 

[frank rabbets]

You have the spring taking the weight of the car and the shock absorber takes any upward shock. If you just had a spring on upward movement the axle would fly up and hit the bump stop all the time. Also the wheel might leave the road and affect steering if it flew up with no damping. The resistance on the 80 shocks feel about the same up or down.

Just doing my tracking with my string box Clive. It's parallel at the moment but I am having to take the track rod off as the ends are seized. I greased them a few years ago when in bits. I hope 1/2* toe out will stop it wandering.

 

[clivehorridge]

You have the spring taking the weight of the car and the shock absorber takes any upward shock. If you just had a spring on upward movement the axle would fly up and hit the bump stop all the time. Also the wheel might leave the road and affect steering if it flew up with no damping. The resistance on the 80 shocks feel about the same up or down.

Just doing my tracking with my string box Clive. It's parallel at the moment but I am having to take the track rod off as the ends are seized. I greased them a few years ago when in bits. I hope 1/2* toe out will stop it wandering.

So, I conclude that I was say 80% right, as there is some benefit from damping in the compression phase, as opposed to none as I had suggested.

As for the steering track alignment, I noted from the "recommended" setting, it had a wide range, from 0 to 1 degree toe-out, but I don't see that anywhere in Mr. T literature, maybe I'm just not looking in the right place. 1/2 degree toe-out did it for me, just right! Good luck with the string box Frank

 

[mark lang]

Just a quick update , just undone top bolt off each shock , upon downward compression the offside immediately returned back up however the nearside stayed compressed momentarily and then after a few seconds started to rise very slowly , at last I think I've found the problem with the front end wobble .

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