Spring cleaning this week!
New serrated bushes and bolts were made for the front end of the springs, both out of En24T, over-size on diameter to suit the now reamed holes in the chassis bracket and the 14.3mm bore of the metalastic bushes. I hardened the serrated bushes - red hot then quench in 50/50 engine oil and kerosene, polish then warm until straw/ blue and cool slowly. They are hard enough to be pretty resistant to filing.
I replaced the bearings at the rear (shackle) end of the springs. These look like metalastic bushes but include small rollers in place of the rubber in metalastic bushes. I replaced them with a steel inner sleeve clamped by the original 9mm through bolt, surrounded with a bush made of nylon which is a press fit into the eye of the spring and a running fit on the inner sleeve. I thought that the nylon bushes would end up with a smaller bore after pressing into the spring eye so bored them first and then made the inner sleeve to fit. In fact the reduction in bore was very slight but I’d still do it the same way. Googly research suggested that Vaseline (petroleum jelly) is the best lubricant for nylon so the medicine cupboard was raided. The lower bearings on the shackles were replaced but I left the top ones undisturbed as they turned smoothly and had little detectable play.
Next job was to clean the spring leaves, grease and re-assemble them, taking care not to mix the leaves, and to put the springs back on the correct sides of the car, which a previous fettler had failed to do so that the serrated bushes were not engaged. Castrol advised that a molybdenum disulphide grease was appropriate between the leaves, readily available as it is used for CV joints. Assembly of the springs involves a pair of large “G” clamps to compress the two top rebound leaves which are of the opposite curvature to the main leaves, and a length of 6mm rod to align the holes for the centre clamping bolt. Once the leaves are fully compressed the clamping bolt can be tapped in, displacing the 6mm rod and holding the spring together so the clamps can be removed. A slightly fraught process as the greasy leaves are very slippery but trivial compared with the frightening task of fitting an Aprilia spring.
I then wrapped the springs with Denso waterproof tape which keeps the mud and wet out and refitted them to the car, nor forgetting the red fibre pads between spring and axle and between spring and U bolt plate. The U bolts were slightly spread and needed squeezing in a vice to match the holes in the plate. They are a very hard grade of steel and I found that I had to re-tighten them several times, presumably as the red fibre pads get compressed. There is no means of locking them on our car, although I see from Karl’s photo that a second locking nut could be fitted if there were enough thread projecting. Ours would need to be a half nut.
All back together for a test run this afternoon. All seems fine and the car improves each time and goes really well. There is still a small vibration of unidentified origin but I am becoming more and more sure that it is not engine related as it continues even if the clutch is disengaged and the revs allowed to drop. I thought I had found a cause as two of the (Michelin rim) wheels are a bit out of shape so although the whole is balanced, the tyres run slightly eccentric, but swapping them with the spares which do run true had no effect. I wondered if the fabric U/J at the rear of the propshaft might be off centre but it does not seem to be. My only idea now is that the fabric may distort under load as that disc does look a bit skinny compared with the front one and the bolt holes are a fairly free fit.
Mike
