SILENTBLOC RUBBER BUSHES USED ON THE ISETTA
by Vic Locke (published in the Isetta GazetteAugust 1979)
There are two types of steering bush, both fulfilling the same purpose. The only difference is the length of the bush. The short one, about 18mm long, was fitted to earlier Isetta', the longer bush, which is more durable, was fitted to later built Isetta's, and is 28mm long. Naturally, it is possible for various components to have been changed around later, so, in reality, it may be that any Isetta could be fitted with either size bush. The longer bush uses longer track rod and drag link bolts, and the drag link has a wider fork end. You can change your car from short to long if you get a set, plus four of the longer bolts and a drag link with the wider forks each end, or, of course, vice versa. The diameter of the long and short bush is the same in both cases.
INSPECTION OF BUSHES FOR DETERIORATION
Movement, back and forth in bush and connection, ragged ends of rubber sticking out of the bush, both indicate the necessity to change the bush. It will be necessary to remove the bolt and pull the track rod clear to make a closer inspection. If the centre of the bush is out of centre and the rubber breaking up, REPLACE IMMEDIATELY.
REMOVAL OF OLD BUSH
Sometimes the whole interior of the bush falls out when you remove the bolt, sometimes the interior remains stuck in. If this is the case, heat up with a blowlamp until the rubber melts away, and the centre pushes out. You are then left with the outer ring of the old bush still stuck in the track rod end eyes. Take a Paddy Saw, or Hacksaw blade and saw through the bush casing. DO NOT SAW THROUGH THE EYE. Gently does it, and then collapse the bush shell inwards with a small chisel or punch. Clean out the interior surface of the eyes before fitting new bushes.
To remove the old bush from the drop arm and steering knuckle alloy arm, remove the drop arm from the end of the steering shaft by removing the bolt completely from the drop arm, and mark with a centre punch the position of the arm on the shaft. Then pull the arm clear of the shaft.
FITTING NEW BUSHES
This can be done in a medium size vice, pressed into place using two pieces of tubing, one piece slightly larger than the eye, and the other piece so that it fits on the OUTER casing of the bush. Never push the bush into place with pressure applied to the centre tube. The bushes are chamfered on one end, and this end goes in first. Before applying pressure with the vice square up the bush so that it will go in straight. When you fir the 18mm bushes they should be flush with the track rod and drag link eyes, but with the 28mm bushes, an equal amount of bush should protrude either side of the track rod eyes.
The drop arm bush can also be fitted in on the vice, but unfortunately not so with the bush fitted into the alloy arm part of the steering knuckle. This one has to be done in place, so it is al ittle more difficult, but, with adequate light and a little patience all should be well. Here you will need a long threaded bolt and nut and your two pieces of tube as described in the previous paragraph. Place your bush as square as possible on the top side of the alloy arm, and then push in the bolt with tube and large washer from the top. Underneath the alloy arm put over the bolt the larger tube, large flat washer, and then the nut. By tightening the nut you will draw the Silentbloc bush into place. Remember not to pull the 28mm bush through too far, or when you re-
The bush fitted into the drop arm must protrude outwards so that the bolt head clears the mudguard arch. All four Silentbloc bushes are of the same diameter, and have ribs on the outer casing for ease of fitting. Remember, always start the bush in with the chamfered end, which can be seen on inspection.
When all the bushes and bolts are in place, and not before, tighten up the nuts, but make sure the steering wheels are straight ahead. This is important as you will obtain a longer life from your bushes. Don't forget the safety washers on the track rod. These washers are often missing, but they are most important. They are plain washers, slightly larger than the eye of the track rod end, and go on last before the castellated nut. I use the following washers; one thin one under the bolt head and above the alloy lug, followed by a thicker washer, followed by the thin safety washer, nut and split pin. I have found that these bushes last about 4 years on average. The rubber twists in the bushes when the steering is turned, and have a self centering effect.
Finally, always park your isetta with wheels straight ahead to avoid undue strain on the bushes, and remember, they are rubber and operate dry, so never oil them.