Can you really test a Shock without removing it ??

JoeySully

So i've changed shock absorbers on 3 cars that i have owned in the past. when i removed each of them i pushed the piston or bar in and they never come back out ie completly gone!!!

now driving around with them its not really that noticeable - well the rear ones anyway. But after replacing them you really feel the difference.

i did have a one front shock gone once and yes i did notice this going around bumpy turns - scary in fact!

so is it possible to test a shock when its on a car ?? the NCT does not check them correctly it just checks the difference in them and the force required to shake them is not taken into account.

im pretty light so my guide is if the car goes down when i sit in the back then there is something wrong!!

How long should the last ?? i think its about 60K mls.

-Chris-

I'm not sure if you're testing the right thing Joey when you push the piston in - a shock piston won't return under it's own steam, it needs to be pulled back out. The friction you feel as you push/pull the piston is what dictates if the shock is gone.

Your springs provide the bounce and shock absorbtion on your car, your shocks stop the car from continuing to bounce - they dampen the bounce and return the car to level asap.

Without shocks on your car (or with worn shocks) you'll find that you go over a bump and your car continues bouncing for several more oscillations. With shocks, you should get one bounce and then the car is settled again.

Shocks can be tested on or off the car - testing for damping properties and testing for leaks can both be done in sitiu.

JoeySully

AudiChris wrote: »

a shock piston won't return under it's own steam, it needs to be pulled back out.

i would disagree with this as ever new shock i have ever fitted always returned out after pushing it in.

pred racer

what Audichris said +1

Also you can bounce the corner of the car you think is gone. if you bounce it 2 or 3 times when you stop it should pretty much return to is normal rest place straight away. if it doesnt your shock is knackered. its not a definitive test though and it can be hard to tell.

JoeySully

well do they gradually get softer over their lifetime ? or just one day they expire and begin to leak.

one thing that i really do notice is that after applying the handbrake on a hill the rear of the car no longer moves when it released.

Anan1

JoeySully wrote: »

well do they gradually get softer over their lifetime ? or just one day they expire and begin to leak.

one thing that i really do notice is that after applying the handbrake on a hill the rear of the car no longer moves when it released.

As AudiChris says, they provide friction, not springing. As they wear, they provide less and less friction - ie the piston moves more freely in the shock.

RobAMerc

Well put Chris -

Shocks can also be called Dampers which imo is a better name for the function they are designed for - the damp the recoil action of the spring.

Anyway - doesn't bouncing the corners give you a good indication on the car if its any good ?

Slig

RobAMerc wrote: »

Well put Chris -

Shocks can also be called Dampers which imo is a better name for the function they are designed for - the damp the recoil action of the spring.

Anyway - doesn't bouncing the corners give you a good indication on the car if its any good ?

A common misconseption it is in fact by kicking the tyres that you can verify the build quality, reliability and top speed of a car. Bouncing the corner should only be carried out during negociations on the final asking price:D

blackbox

JoeySully wrote: »

well do they gradually get softer over their lifetime ? or just one day they expire and begin to leak.

one thing that i really do notice is that after applying the handbrake on a hill the rear of the car no longer moves when it released.

Mostly the dampers gradually deteriorate over their lifetime, but sometimes they will fail suddenly, often associated with a yump.

I don't see how the movement of the car when the handbrake is released is related to the shock absorbers/dampers. This is more a function of the suspension geometry and the angle of pull of the brake cable and will vary from model to model.

BTW AudiChris is correct - the shock absorber doesn't have a springing function - it is purely there to dampen oscillations. Without them the wheels would bounce and only make occassional contact with the road. In many cars they locate the wheels as part of the suspension structure (e.g. McPherson strut).

Provided there are no leaks and the car does not bounce when any corner is released your shocks are in reasonable condition. However if you replace them after 60k miles you probably will notice an improvement in handling.

-Chris-

JoeySully wrote: »

one thing that i really do notice is that after applying the handbrake on a hill the rear of the car no longer moves when it released.

Does anyone think this could be the rear brake shoes sticking?

Engage handbrake, car rolls back slightly (against the normal grain of the wear on the disks), breaks jam.
Release handbrake, handbrake cable goes slack, shoes stay engaged/stuck, by driving forward you "unstick" the shoes.

Is that a case of replacing the drum or shoes or what?

JoeySully

AudiChris wrote: »

Does anyone think this could be the rear brake shoes sticking?

Engage handbrake, car rolls back slightly (against the normal grain of the wear on the disks), breaks jam.
Release handbrake, handbrake cable goes slack, shoes stay engaged/stuck, by driving forward you "unstick" the shoes.

Is that a case of replacing the drum or shoes or what?

No they are not sitcking it was just that the shock were so bad that when i applied the handbrake on a hill the rear of the car would go up and when released to drive off the car would go down. Like an old Peugeot. it didnt happen on the flat so not sticking.

Slig

JoeySully wrote: »

No they are not sitcking it was just that the shock were so bad that when i applied the handbrake on a hill the rear of the car would go up and when released to drive off the car would go down. Like an old Peugeot. it didnt happen on the flat so not sticking.

Do you drive a citroen?

JoeySully

Slig wrote: »

Do you drive a citroen?

no its a e36 318

Slig

JoeySully wrote: »

no its a e36 318

I just dont see how the shocks are affecting the brakes, maybe its just me. If you are changing them though do both sides.