Bench testing front shock absorbers

[millerman]

I've just taken the front lever arm shock absorbers off a 68 2-door which I'm scrapping.

In view of the earlier discussion on the merits of various shock absorber oils etc I drained the units which included removing the bottom valve and topped up 1 damper with a 15/50 engine oil, clamped the damper in the vice and it proved to be quite difficult to move the arm. The other damper was topped up with the correct lever arm shock absorber oil, this time only slightly easier to move the arm! In both cases easier to move the arm upwards rather than down.
To make sure sure that there was no dirt in the valve I washed them with petrol, took the top off the unit and swilled out with petrol. I was surprised at how much sludge was in the damper! re-assembled everything and topped up with oil and it still took the same amount of effort to move the arms.
So the question (at last) how muh effort does it take to move the arm by hand when the the front shocks are in good condition? It has always seemed easy when I've changed trunions and what are the views on taking the top off the damper and giving them a good clean out?

Discuss further at the Website Rally??

[Cam]

PERSONALLY I would not clean them out with anything other than a 'flush through' with oil. No real scientific reason, I just don't like the idea of it.

It should be hard but possible to move the arm with the units in your hand. In the vice it's a lot easier but as long as there are no leaks, no front to back movement and resistance to 'fast' change is felt then they should be fine.

The damper should be easier to move when moving the arm slowly than when trying to move it quickly.

My old one that I took off Gracie had about 2" of play (that you could wobble about with your little finger). That was quite obviously knackered.

Bring them/one to the website rally and we'll have a play.

[newagetraveller]

It sounds as if these shock absorbers are perfectly serviceable.

When a shock absorber has failed there is usually either no resistance at all or the resistance that you feel when moving the arms is jerky rather than smooth.

[bmcecosse]

Try filling then uip with EP 90 - now you have some REAL damping !!
Yes - there will now follow a stream of posts decrying this - I used it for years on my Rally Minor - no problems at all. For normal road use - I use 20w50 - it's fine. The cleaning out with petrol is not a good idea - may damage the seals - but a good flush through with oil is highly recommended. It's also possible to fiddle with the little valve you took out - but the effects are minimal - far better to adjust the oil viscosity!

[minor_hickup]

I know I preffer the ride with the thicker oil. You can really tell the difference in ride between my, and my brother's car.

[millerman]

Thanks for comments.
BMC..... I will give your idea a go and report back in a few weeks

[Pyoor_Kate]

Yes - there will now follow a stream of posts decrying this

Well yes, some of us think that the guys who designed these parts had a good idea of how they worked and what they'd withstand. Hence mine being filled with shock absorber oil (it's not like it's expensive - nearly all bike shops sell fork oil which is shock absorber oil - in a variety of thicknesses)

[bmcecosse]

But they work so much better with more viscous oil. Remember - it was some 50 years ago they 'designed ' these - road conditions and traffic conditions - and peeps expectations of vehicle performance have moved on a tad!

[Cam]

Remember - it was some 50 years ago they 'designed ' these - road conditions and traffic conditions - and peeps expectations of vehicle performance have moved on a tad!

But we are still using the same hardware! So the same design specs apply regardless of how well you'd 'expect' it to perform nowadays.

[bmcecosse]

Ah but we want and expect the car to behave so much better these days - so we make improvements where we can !

[Pyoor_Kate]

But you're not actually improving the components; you're pushing a 35+ year old component far harder than it was originally intended - you're going beyond it's design specs when it's already worn. If you want better shock absorbers then you should change the design you're using, for example telescopic shocks...

Anyway, we're aware that we disagree, and I should probably shut up...

[millerman]

Kate

I agree with your comments but if the damper gives up so what? they are so easy to replace and I'm interested to see if there is any improvement in handling

[Cam]

I agree with your comments but if the damper gives up so what? they are so easy to replace and I'm interested to see if there is any improvement in handling

Well, the issue is that we have had reports from people who have had sheared mounting bolts due to the 'out of design spec' larger loads being passed through the damper body and to the mountings. Putting thicker oil in does increase the damping but it also increases the stress on the mountings. If the mountings then expire, you loose your steering as the shocker is also your top suspension arm!

You might 'get away' with it for years and never have a problem, but it's an issue that people need to be aware of before proceeding down this road. Pushing things past their design specs is bad engineering practice, especially if the failure could result in a loss of steering control.

[bigginger]

Hear Hear.

[millerman]

Cam

Fair comment

Colin

[Onne]

But you could still bring them along to the www. rally saturday!