Live Axle 'A' Frame Bracket & Bushes

When I first bought my car (a 1999 Classic with a live axle chassis), the 'A' frame bushes were a murky brown colour and appeared to be swollen, despite clearly being made of polyurethane. I decided to replace them with Powerflex ones (part number PF8-903).

When I removed the old 'brown' ones I discovered they too were actually marked with the same Powerflex part number... The exposed parts had simply been stained by oil contamination.

However, the new bushes simply would not, and could not fit - the internal sleeves were too long. When I went to measure the old ones to compare I noticed that there were signs that those sleeves had been roughly cut down with a hacksaw...

Returning to the bracket it became obvious that the two sides weren't quite parallel. The 35mm gap between the flanges at the base would allow the new bushes to fit but the gap was more than a millimetre narrower at the tips.

It took a good deal of effort to straighten things up. I started by putting a length of M12 studding through the holes with two nuts and washers between the flanges. Tightening the nuts against the flanges acted as a spreader which pushed them apart so the flanges were now square to the bracket at the base, but the way they had been bent at the holes meant the tips of the flanges were now flaring outwards. A variety of large clamps, wedeges and levers eventually brought everything back square and the new bushes were fitted.

But there were still problems - the bushes were bulging over the edges of the flanges and distorted again, rather like the first ones. By that time I'd had enough, and decided that that would just have to be good enough for now.

A while later I bought some 'Y16 equivalent' polyurethane bushes on eBay. A different colour (but also Shore 80A as per the purple Powerflex's), but significantly the internal sleeve was a 'top hat' with a large 'brim' on the outer end, and the internal sleeves were shorter. I'd not previously seen a Y16 rubber bush in the flesh but on examining photos on the Caterham parts site realised that that was the way those were constructed as well - obviously preventing the bulging that occurred with Powerflex bushes. These 'Y16 equivalent' sleeves measured a rather awkward 16.7mm, but of course (doh!) this whole assembly would have been designed in imperial units. They are then actually 21/32" each (i.e. 1-5/16" the pair), and the '35mm' distance between the bracket flanges is really 1-3/8".

So why the discrepancy? Looking at my then recently acquired 1999 assembly guide revealed that originally there would have been a washer between the two Y16 bushes: