Pre-65 Trials build

Information relating to the Matchless G85 500cc Heavyweight, AJS 7R, Matchless G45 and Matchless G50
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Matchymarty
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Posts: 198
Joined: Sun Oct 25, 2015 8:19 am
Location: AUSTRALIA

Pre-65 Trials build

Post by Matchymarty »

Hi all,

Been around the traps but getting enthused again. Covid sure knocked the fun out of all things two wheeled in the last 2 years!

I have a '55 US model G80CS pretty original condition that I ride regularily in Historic bike club rallies and rides. I have been doing modern trials for a year now, and feel like my skills are at the point where I can trust myself on an 'old bike' without the fear of trashing it too much.

So, I am starting the thought process of deciding on what bike to buy, build or find!

A friend of mine has an original G3LC trials, believed to be '56, which has the same full width hubs as my G80CS, seemingly correct rear subframe, and gerling shocks. That said, he'd never let me ride it in a trial, however, I've ridden it more than he has!

Finding an original Matchless trials bike here in OZ, would be all but impossible - and as such, I may be forced to convert a road bike or, build one from scratch.

My question really is, is there any documentation or , can anyone point me in the direction of information on the differences between factory rigid and sprung frame geometry?

A modern trials bike has a wheelbase of around 1320mm (52") and a head angle around 26 deg, though unspecified by manufacturers.

Wondering if I'd be better served weight and wheelbase wise (and money wise!) with a rigid matchless frame? I know the front end on my G80CS is very 'slack' and it is hard to steer on the road, suspect it would be hard to steer off road in a trials environment?

IS there any comparisons between wheelbase and head angle on the early rigid vs later 50's sprung frames?
Pic for attention.
Toms Trials.jpg
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Iron Head
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Joined: Sun Jan 24, 2016 7:19 pm
Location: BERKSHIRE UK

Re: Pre-65 Trials build

Post by Iron Head »

Hi Marty, can’t speak reference frame dimensions, wheelbase etc but can confirm that my single seat G80 rigid feels substantially more trials-like versus my sprung ‘54 G80CS. I was lucky to be able to spend many hours in the family’s field on my Bultaco Sherpa 250 and a Greeves in my youth and the G80 rigid, albeit way heavier, has a real trials ‘feel’ on the road. Very easy to keep my feet on the pegs approaching traffic lights at speeds substantially below walking pace. I definitely prefer the two 19” wheels on the G80 rigid and a much lower feeling c of g even if just imagined. Rigid would be my way forward.

Iron Head
SPRIDDLER
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Location: WEST SUSSEX UK

Re: Pre-65 Trials build

Post by SPRIDDLER »

Matchymarty wrote: Tue Oct 19, 2021 10:27 pm
My question really is, is there any documentation or , can anyone point me in the direction of information on the differences between factory rigid and sprung frame geometry?

A modern trials bike has a wheelbase of around 1320mm (52") and a head angle around 26 deg, though unspecified by manufacturers.
Article here about modding a frame for trials use includes mention of changing the headstock angle to 25 deg.

https://www.jampot.com/article_read.asp?id=167

There's a section in Christians Archive for trials bikes with articles that may have some info, here:

http://archives.jampot.dk/editorial/Trials/
I poke badgers with spoons.....from 2 metres.
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