Rubber Bushed Trunnions (1998>)

When I first got my 1999 VX Classic and was checking over the front suspension, I was surprised to see what appeared to be grease nipples on the underside of the trunnion horizontal pivots. I also noticed there weren't the usual dished washers and seals at the ends. Odd ??

On closer inspection it became clear that things were very different to the traditional Triumph arrangement. Cleaned up, what had at first appeared to be grease nipples were actually grub screws and locking nuts. These screws were securing bonded rubber bushes in the trunnions, in place of the usual plastic top-hat bushings, sealing rings and steel sleeve. It was also apparent that those traditional parts simply couldn't fit in the gap between the wishbone cheeks.

Looking at the Caterham parts site I did indeed find the complete assembly below (for live axle 1998 onwards, ref: 75131A ), but the rubber bush wasn't listed separately.

When I later came to refurbish the front suspension I decided that these bushes were past their prime but the trunnion threads were perfectly o.k. It seemed ridiculous to replace the entire assemblies, and after removing the locking screw the bush pressed out like any other. Measurements proved it to be a common E2030. (Or equivalent AVMR B602/9 .)

There's very little clearance between the trunnion and the wishbone flanges, so when fitting the new bushes it was important to get equal protrusions of the inner sleeve each side of the trunnion, rather than concentrating on getting the outer sleeve centralised in the body.

The grub screw is an M5x16, with a sharp point, locked with a plain nut but no washer. The point might dig into the sleeve about a millimetre. It seemed sensible to use Loctite to be on the safe side.

As far as I can see there are three types of live axle trunnion wishbone currently available (Apr '21). Earlier ones that accomodate the traditional trunnion bushings (available in normal and negative camber versions), plus a later third type requiring the rubber bush. This last one can be distinguished by an additional brace between the two arms.

It isn't obvious why the design was changed. Perhaps the rubber bush was considered lower maintenance? The original Triump bearing sleeves have certainly been known to rust and seize on the through bolt if neglected...