Snapped front shock - HELP

[CycleSi]

I'm having a bad day !

The offside front shock has snapped (again) on my AK.

Some background - my AK was factory built by Ken 9 1/2 years ago and originally fitted with AVO shocks all round. Over the years I had a few problems with them leaking oil and the adjuster knobs seizing up, etc. so approx. 4 years ago replaced them all with GAZ units.

Around April this year I was driving the Cobra home late at night and heard/felt a "thud". Upon examination I saw the offside shock had snapped and the coil spring was banana shaped but 'holding' the shock in place luckily. Thinking it was defective l returned it to Dampertech along with the nearside shock as a warranty issue. They then informed me that the inner shaft in the nearside one was also bent and said the suspension was clearly "stressed" and suggested I had an alignment problem as the shocks were suffering some kind of 'loading'.

The car has never had an impact - frontal or otherwise - or any heavy landings. lt has been driven hard at times and taken to the Nurburgring last year but nothing to explain what is causing the problem.

Anyway, after only a few months the offside one has snapped again leaving me fed up and confused that after almost 10 years I'm having a major (potentially very dangerous) problem.

The only other thing worth mentioning is AK fitted one of their front anti-roll bars just over a year ago.

Nothing looks wrong and I've had it checked by a very experienced Motor Engineer who looks after my Cobra.

I really need some help on this one especially as l was looking forward to driving to Donington next week and also because AK have asked me to drive at Brands Hatch next month.

Thanks in advance for any advice.....

[dave]

Before you fit the spring put the shock on the car disconnect the anti roll bar and work the suspension up and down and check for twisting of the shock mount. Might reveal nothing as the rubber bushing should take up slight deviation from true but you never know.
HTH.
Good luck.

[CycleSi]

l've spoken to AK and they don't see how their anti-roll bar could cause this. They have suggested that maybe the top of the shock is hitting the chassis under full compression and that a slight 'sculpting' of the chassis plate maybe necessary?

It's also been mentioned that GAZ shocks are made to tighter tolerances than the old AVO's and are therefore less 'forgiving'?

[dave]

The only reasson I mention disconnecting the anti roll bar is so that each side of the car can be worked through its asuspension range without having to deal with the weight of the other side. (Hope you didn't think that I meant the anti roll bar could be the cause).:thumb:

[wilf]

The bolts running through the top and bottom shock mounts must be able to turn within the rubber bushes in the "eyes" of the shock mounts, or a twisting action is forced onto the shock, which could well result in the failures you describe. They should not be tightened up - they should be relatively loose, and a locking type nut used.

As Dave suggests, disconnect the anti roll bar, take the springs off completely, and work the suspension through its entire mpovement range and see what is happening.

If you back the shock adjusment (if the are the adjustable type) right off, there should be little resistance to movement.

[colinb]

This may or not be relevant but we experienced on a track car that if the angle of the shock from the verticle plane was too horizontal the bending of the shaft ocoured and leaking of the seals, this obviously happens more at full travel yours may be bordering on the limit , Just a thought?

Colinb:thumb:

[CycleSi]

Dave and Wilf - So what you're saying is that (possibly) the shock mount bolts are too tight and not allowing the shocks to 'move' under their range of suspension travel?

That makes sense to me except why should this suddenly become a problem when for 8 1/2 years they were fine.

Am l using the 'wrong' shock mount nuts & bolts, what are the correct one's to use?

Apparently AK have only ever had one other car, to their knowledge, snap shocks so it is obviously extremely rare.

[dave]

The bolt should pinch tight onto the ferrule in the centre of the shock and the rubber should be able to take up any small deflection in the angle of the shock in use. If the outer ring of the mount comes into conflict with the shock support on the chassis then you do run the risk of the deflection being passed onto the steelwork of the shock and this will cause fatigue and something will eventually give. Look for marks on the chassis where the outer ring has maybe rubbed.

[CycleSi]

Again, that all makes sense Dave. What bolts do you use? Is there a recommended torque figure to tighten them?

I'll have to check the chassis to look for damage.

Hope to make it to Donington in the Cobra assuming we get this sorted.