Rear Shock Absorber Inserts

[david.g.chapman]

I have just fitted new rear shock inserts to my +2, but have noticed a knock in the suspension when grabbing hold of the top of the rear wheel, and shaking the car.

After some diagnostic work, I have traced the knock to one of the new inserts. The inner steel shaft seems to be moving slightly with respect to the body of the insert. We are only talking about a mm or less. The road wheel hardly moves at all.

If the load is taking off the suspension and the shock fully extends, the play disappears when the suspension is reloaded. The play returns after a few road miles.

I have made sure that the body of the insert is properly clamped in the suspension tube.

The shocks work OK, and the road handling is fine. The suspension is quiet in normal use.

My question is - is this situation typical, or have I got a bad shock absorber?

What about the MOT?

Dave Chapman

[Hamish Coutts]

David,

Sounds like you've got a suspect insert. I had the same problem but it made the back end of the car feel a bit loose. There was also a very annoying 'clunk' when going over a bump or pothole.
If as you say, the insert is properly clamped inside the strut I would go back to the supplier and see what they say. Sounds like you need a replacement.

Regards,

Hamish.

[david.g.chapman]

I have had a chat with the suppliers, and they have suggested a few things to check. The most likely cause could be the spring cap at the top of the road spring moving about with respect to the shock absorber shaft.
The D hole in the middle of the cap tends to strip, giving some clearance. I know my caps are in that state.
The knocking noise soungs quite sharp, so they could be right. I will have a look.

Dave Chapman.

[nebogipfel]

Dave, What make insert did you fit?

[david.g.chapman]

They are Monroes - the standard non-adjustable type. Apparently the last two in stock!

Dave.

[nebogipfel]

OK, I asked because I was not happy with the fit of Spax Inserts. The shaft is a very poor fit in the "D" hole and will actually pass through the Lotocone. It looked like they are designed to have some kind of circlip (there is a groove at the top of the shaft beneath the thread) but nothing was supplied nor mentioned in the useless instructions.

Even if the top plate "D" hole failed on OE units the shaft still cannot pass through the lotocone

I decided to use OE replacements and have also decided when possible to do so throughout the rest of the rebuild.

John

[type26owner]

It makes a tremendous thumping noise doesn't it? Been there, done that. The insert is still loose inside the housing possibly. Just tighten it up again. I made a tool out of steel barstock to engage the hex end of the nut and snug it up in situ with hammer blows. The coil spring spreads out enough at full suspension droop to allow you to do this no problem. For whatever reason gettting the insert fully seated while it's out of the car is not all that easy to accomplish.

I've also had the D-shaped threaded end of the insert not fully tighten up onto new lotocones. It makes a similiar alarming noise. IIRC, for some reason the threads bottomed out or the insert sleeve was too long before the connection was cinched up. I had to make up some spacers to get that sorted.
-Keith

[pereirac]

I seem to remember dropping a couple of washers under my strut inserts to lift them up before clamping them down because I thought they were a bit loose. It seemed to solve the problem as the only time I had knocking from the rear of my Elan was when I lost a dougnut bolt and the doughnut started hitting the chassis!!

[david.g.chapman]

Thanks for all of your replies.

I have found the "problem". As I shake the suspension by rocking the top of the rear wheel, the rear discs make contact with the rear brake pads. This gives a knocking noise - not that loud, but you can feel it through the wheel.

I found this out by removing the pads. The knocking disappears! My bushes and shocker must have enough compliance to allow this to happen, but there is no free movement anywhere I can see. Also with the handbrake on and the pads replaced, there is again no knocking.

I now think this is normal, and may confuse someone else out there. Any opinions?

Dave Chapman.

[rgh0]

You have to much free play in the rear hub bearings. Time to replace them

Rohan

[david.g.chapman]

Rohan,

I replaced them about 2 years (10,000) miles ago, so I would not normally suspect them. However, it is a likely cause. The other possibility is that the rear stub axle is slipping on the bearings and has worn down to produce the play. I checked for that briefly before, but will now take a closer look.

Dave Chapman.

[rgh0]

Dave

I have had the circlip that locates the inner bearing on the stub axle and provides the lateral location for the shaft come out of its groove and then had the shaft move. So if the bearings are relatively new and not making any other noises than this knocking, then this could be the problem.

Rohan

[type26owner]

Checking for play in the hub carrier/strut bearings is tricky if you have the rubber donuts still attached. At full suspension droop the donuts are applying a rather large torque to the axle preloading it to oneside making the diagnosis of extra play very difficult and nearly impossible for one person to do alone. Suggest you leave the wheel in place and have a strong assistant apply an out-of-plane torque while you peer around the backside looking of movement where there should not be any. Making that amount of noise the play will be easy to spot I'm afraid.

The interference fit of the outboard bearing onto the axle is a critical one and a small deviation form the optimal fit can lead to a rapid failure. It's extremely prone to fretting corrosion and soon followed by creep failure. Dodgy bearing engineering at best even for that time period.
-Keith

[lotusanglia1965]

:ph34r: Anyone tried loctite bearing fit to stop driveshaft fretting in bearing? Martin

[rgh0]

Martin

I have used loctite on both the shaft to bearing fit and on the bearing to housing fit.

I had a shaft that was slighly undersize that allowed the inner bearing to move and push the circlip off. When I refitted I used loctite until I could get a new shaft with the right interference fit, it lasted Ok for 12 months and was fine when I dismantled it.

I have also had a bearing spin in the alloy carrier. I refitted using loctite "quickmetal" as the clearance was excessive for the normal bearing mounting compound. This again was Ok until I could get the time for a proper repair by welding and remachining the hub back to the correct clerances about 6 months later.

I normally fit all bearings in aluminium alloy housings using loctite to minimise the risk of the bearing fretting and damaging the relatively soft alloy. Not so critical to use on a steel shaft unless unusual loadings or the bearing fit not correct.

Rohan