15 replies to this topic

[Remylebleu]

My car is jacked up, took the wheels off and i want to remove the dampers....what will happen when i do this?

Will the car drop? Or will it stay the same height? As i dont want the car dropping onto me

Thanks

[Mini Mad Drakeley]

it wont drop so it wont, i put my front subframe back on and built it up so its on its front 2 wheels, i didnt put the dampers on and its fine

[Remylebleu]

Ok thanks, ive still got my training wheels on you see im new to this

[andydclements]

it wont drop so it wont, i put my front subframe back on and built it up so its on its front 2 wheels, i didnt put the dampers on and its fine

Assuming it's jacked up in a suitable place (I have seen cars jacked up under the trailing arms/ wishbones of other cars).

[Mini Mad Drakeley]

it wont drop so it wont, i put my front subframe back on and built it up so its on its front 2 wheels, i didnt put the dampers on and its fine

Assuming it's jacked up in a suitable place (I have seen cars jacked up under the trailing arms/ wishbones of other cars).

nope, its on ramps now and i can say putting the subfame on is a 2 man job, sat for hours trying to get both sides right so i could bolt it up

[Ethel]

Just be careful that the rear suspension if properly seated in the subframe when you're putting the dampers back on.

[bmcecosse]

Rear suspension drops when dampers are removed. Front may drop too if the rebound stops are missing. Whya re you taking the dampers off??

Edited by bmcecosse, 27 February 2011 - 03:51 PM.

[Remylebleu]

Taking the dampers off to see if there knackered.

When i compress a damper in my hands, should expand back to normal size afterwards?
Because mine just stay the size i compressed them too and i have to pull it either end to get it back to the length it was.

The car is completely off the floor so there is no weight on the rear suspension

[Ethel]

It depends on the type of damper, even if they're gas pressurised it's not the gas that does the damping so they can still be serviceable. A push on that corner of the car, with all wheels on a hard level surface, will tell you more.

Changing dampers is easy & uncomplicated, just watch that the rubber cones are sat in the subframe properly before you put the weight of the car back on them, or they may damage their seats.

If the suspension fully unloads itself when you lift the wheels off the floor (with dampers fitted), it really needs attention as it could happen while you're driving.

[Remylebleu]

They only seem to squash not expand....surely this isnt right?

What do you mean by "unload" ?

[ibrooks]

Gas shocks will expand on their own but conventional oil shocks won't. So long as the movement in and out is smooth with no stiff spots then they are working fine.

Iain

[ibrooks]

What do you mean by "unload" ?

He means that all the weight is off the suspension.

At the front even with the dampers off the bottom arm should not drop far enough to release the cone when the weight is off the car. At the rear the dampers provide the limit so with the car jacked up the suspension will hang on the shock - again at this point there should still be some tension in the cone.

If stuff comes free at either end then it's possible when braking/cornering/going over bumps that the weight comes off the wheel completely and the cones can un-seat themselves. When the weight goes back onto the wheels the cones might not drop back into their correct position.

Quite common when people lower a car by chopping springs. The rears of many fwd cars especially can end up with the springs dropping out under heavy braking (when all the weight transfers to the front). When the brakes then come off there's no spring to hold the car up and the wheel comes into contact with the body with a fairly predictable dramatic and unexpected off-road experience.

Iain

Edited by ibrooks, 27 February 2011 - 03:28 PM.

[Remylebleu]

Ok, so when there on the car and i go down a pot hole the oil shock wont expand?

[andydclements]

Not quite.
As others have said, gas ones (gas and oil) expand themselves, oil (only oil) ones don't. Both are normally used in conjunction with the springs, so when you take the load of the wheel (pot-hole, jack car up etc) the spring forces the wheel down and the damper (technically the spring absorbs the hock, but the damper is what so many of us refer to as the shock absorber) put resistance in to the movement, so it's slower to move.


If the damper is in good condition you'll know by the bounce test. Press down on the corner of the car with all your weight, the car should go down, up and then down to it's resting position. If it goes down a second time (or worse) then it's either worn out or nut suitable (some units damp more than others).

If the dampers are off the car. Press them in (close them up), it should be possible but not easy, now pull them back out, that should be just as hard to do. If they go weak near the end of the travel then the damper has failed. Similarly you may hear the oil moving, if you start to hear air moving (bubbles in the oil) then you've probably got a leak in the damper somewhere, so time to get rid of it.

[ibrooks]

Ok, so when there on the car and i go down a pot hole the oil shock wont expand?

You don't seem to be understanding the fundamentals of what a shock absorber is supposed to do. Shock absorber is a misnomer and just what people tend to call them they are actually a damper and that's what they do - they damp the motion.

The rubber cone/doughnut is a spring. On most cars it's a conventional metal coil spring but on the Mini Mr Moulton came up with a rubber doughnut shaped thing to do the job instead. When the car runs over a bump that spring compresses and expands to allow the wheel to move up and down more than the body.

If the story ended there you would tend to find that when the wheel hit a bump it would go up and keep going after it hit the top of the bump due to it's momentum (inertia). The wheel woud briefly leave the ground and only come back down when the spring's compression matched the wheel's inertia at which point it would uncompress and the wheel would come back down with a thump. Problem is that there is nothing to damp the motion and so when it gets to the bottom it has compressef the tyre a bit which then gives it's energy back to the spring and the whole lot starts again.

Car goes bouncy bouncy down the road and apart from the occupants getting seasick the thing is near undriveable as the wheels spend a fair amount of time in the air.

The function of the damper is to give a bit of resistance to the movement and convert some of that energy into heat. So when you go over a bump the wheel rises in the arch but the damper slows the rate at which it can rise and adds a portion of the car's mass to the wheel by attaching the body the the wheel. This means that over a smaller bump the wheel stays on the ground when it reaches the top of the bump. The same happens whe they wheel goes back down.

The shock absorber does not support the car - the springs do that. The shock absorber simply applies a bit of control to the rate at which the spring can expand and compress. The shock won't have any effect on the ride height of the car.

So when you go over a bump the shock will compress along with the spring and then it will expand again as the spring forces it back down.

Iain