SQ4 - bushing the saddle nose

Updated: First published June 2021

Since I've had it on the road, the Square Four has felt a bit wayward around the rear end. Since I had rebuilt the rear suspension and knew that it had no wear, I suspected the tyre and wheel though they were both new and rebuilt - until I realised the problem was closer to home. Literally much closer, to my backside.

The saddle nose bracket on an Ariel frame is quite small, giving little bearing area. Coupled with a bolt with an over-long thread, used as a bearing surface produces this effect after a few years:

This picture shows the saddle removed, but with the bolt in position. The red circle shows a portion of the thread used as a bearing - a very poor idea:

So, the first job is to make those worn holes round again. The bolt is 5/16" (0.312", or around 8mm), and they are both worn to over 0.350". I used an adjustable reamer on them to remove the ovality.

Ovality in the frame holes is not the only problem - the holes in the saddle frame are also very large. I have another problem in this area in that the fuel tank has very little clearance around the saddle nose bolt and I have solved both these problems in one go. In this picture, the original bolt has had it's head thickness reduced to produce a shoulder which fits in the saddle frame hole with very little clearance, and the full nut used at the other end has been reduced to the thickness of a half nut, again with a shoulder. This enabled the bolt length to be reduced, to get more clearance for the tank, and removed the whole assembly to the right to move the thread out of the bearing area.

Next job was to make two shouldered bushes to fit in the holes:

The bushes pass right through the fixed frame lugs, to provide maximum bearing area; there is a minimal shoulder to allow the bush to be retained in place (or removed).

This repair has removed virtually all the play from the saddle nose bearing.

Three years after I wrote this, I sorted out another problem - that of the bushes coming out of the frame lug and all play returning. I made a spacer on the lathe:

It's just a bit of 1/2" round bar with a clearance hole for the bolt; it's relieved slightly in the middle as the pivot bolt is very close to the frame lug.

Posterior stability has been restored.