MASCOT January - February 2007

Ask Aunty - Shock Absorbers

Bill Haverly

Dear Aunty. Can you please help me - I've made a `shocking' mistakes! The rear Armstrong DAS-8 lever-arm shock absorbers on my Roadster were not soaking up the bumps like they used to, so when I found a pair in good condition for £40 at the recent Beaulieu autojumble, I was well pleased. Until I got them home, that is, when I realised that what I thought were a pair were in fact two of a kind, with both arms pointing in the same direction. Shock-Horror!! It is my spirits that are now well damped. However, the bodies all these shockers appear identical, so I wondered if there is any way of repositioning one of the arms to create a proper pair?

Yours beseechingly, Deirdre Damper.

Dear Deirdre. I haven't heard of anyone doing this, so I put your question to our Roadster expert, Bill Haverly, and the good news is that it should be possible to remove the arms from their shafts and replace them at whatever angle you desire,

But you will need a stout puller, as well as a vice, an angle grinder and preferably a source of heat. You will also need to be in a 'Have-a-go' frame of mind!

Bill worked out a procedure and used an old shocker on which to try it out. He found that a Sykes-Pickavant Ball Joint Puller 081800 was ideal for the job, as it has wide enough jaws to go over the end of the arm and thin enough lips to slide between the arm and damper body. Bill suggests that before you start, you turn the arms on both dampers to the end of their travel and in the same direction so that you know where the shaft is when you come to reposition the lever. Grip the arm, NOT the damper body, firmly in the vice, then grind off the swaging carefully from the end of the shaft until you can see the full ring of splines between shaft and arm. Slide the puller onto the end of the arm until the screw is concentric with the shaft. The shaft will almost certainly be very tight on the splines - it may be worth trying a pull cold, although some heat applied to the end of the arm should make removal easier. When applying heat, take care not to heat the shaft or damper body directly.

Offer the arm to the shaft in the desired new position and mark both accordingly. By heating the end of the arm you should find it will press back on a bit easier than it came off. Use the vice to press the arm back flush with the end of the shaft - do NOT try to hammer it back on. The arm is unlikely to come off again of its own accord, but to be on the safe side you should peen the shaft around the splines with a centre-punch in a few places or add a few spots of weld.

Good luck, and please let me know how you get on, Aunty.


Comment by Richard from New Zealand

A bit late in the day, but I've just come across your article "Ask Aunty - Shock Absorbers" by Bill Haverly and feel that an important issue has been overlooked.

While the procedure outlined seems perfectly sound, the principle of turning the arm through 180° to convert it into an opposite-side unit is not, because it will then be operating in the reverse sense, ie. when the suspension rises (bump) the damper will be operating on rebound, and vice versa.

Put another way, the piston intended to operate on the bump stroke will actually be operating on the rebound stroke, and vice versa. Rebound damping is usually set to a much lower resistance than bump damping.

Best wishes,

RF