Swing Arm Refurb 1966 Unit 500

66Triumph · Jun 22, 2023

I have a 66 unit 500 and am biting the bullet and refitting a new swing arm spindle and bushes(a very involved job Im not looking forward to). The 66 frame`s rear frame loop is rough and I have a later 71 rear frame loop in excellent condition that I would like to fit. I know that the later frame loop needs a longer swing arm spindle to accommodate the grease the revised grease ports but as Im getting a new spindle can I simply get the later longer spindle and with a few shims would it enable me to fit the later frame loop in the 66 frame? Any other tips on this job is much appreciated....

DaveQ · Jun 30, 2023

Hi there. Sorry for the late reply but I’ve just seen your post.

You pose an interesting question. I also have a ‘66 T100 which I’m currently trying to rebuild from a basket case and I looked briefly at the mod you mention as I thought it would be a useful improvement to stiffen the rear suspension on the ‘66 set up. I found that there does seem to be a number of snags though.

Firstly, in ‘67 (after H49833), the main and rear frame and swinging arm incorporated a number of changes. On the rear frame, apart from the triangular support brackets for the S/arm pivot, in ‘68 the l/h side panel and tool holder mountings were modified. The S/arm was redesigned and stiffened in 67 to accommodate a wider tyre. There also seems to have been other minor mods to the tool tray and battery carrier

The w/shop manual (section E12) also indicates that pre H49832 the S/arm pivot shaft is an interference fit that requires a puller tool to remove and refit while on later models the shaft is a tight push-in fit and can be driven out with a drift and light hammer. So, unless you try it there’s no telling whether the longer spindle will fit in the centre part. The later/longer spindle also requires two different spacers and shimming to get the correct alignment and specific securing bolts to secure at the new outer brackets. These are not part of the earlier fittings. (See the parts lists).

At about that point I put any further thoughts of this modification on the back burner as I’ve got plenty of other things to do to it. Luckily for me the pivot is about the only thing that doesn’t require replacement on this bike so it can wait for a while.

I hasten to add that I’m no expert in this. I know there are others on this board that are more technically sound than me and have probably done this mod without any problems. But I don’t think that it’s just a case of replacing the shaft. I’d also be happy to hear from anyone that’s done it satisfactorily.

Dave

66Triumph · Jul 20, 2023

Thanks Dave,food for thought.If that is the case I will likely refurb the original rear loop and use the original sized spindle set up.Either way,its going to be a pig of a job.I`ll likely need an industrial bearing press to take out the original spindle,then the hole will have to be checked for concentricity and there is a strong chance that it will have to be mounted on a milling machine,bored out oversize and a(bespoke turned) sleeve pressed in to accept the new spindle,then the bushes need to be line reamed.Not looking forward to this....