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Comet rear springing too stiff, remedies?


Active Forum Website User
VOC Member
Dear all,
My MOT (vehicle road safety) tester declared the rear springing of my unmodified '52 Comet too stiff, and we only just passed the test.
It would be unfair to make a comparison with modern bikes, but my tester is an estimated 70+ so presumably has done a few of these before (whether he remembers or not is another matter...).

I'd like to remedy the situation but as bike contact time is limited, have been drafting a check list:

a) Spring lengths- this thread has some details of unloaded spring lengths
b) Spring gauge- as springs are of unknown provenance
c) RFM bearing binding

Is there anything else I've missed? What should I be aiming for? I weigh ~70kg though sometimes there are two of us.
Unfortunately any upgrades are limited by meagre funds so solutions will have to be the cheap sort :)

Looking forward to your replies,



Well Known and Active Forum Website User
VOC Member
how did he test it?
My tester originally said the same thing, until I balanced on the bike and made the suspension work by bouncing on the foot rests. All became clear to him then.
He also said the same for the forks, above demo convinced him otherwise. Now when I go for an M.O.T all is ok..John


Well Known and Active Forum Website User
VOC Member
Wow! Were the Testers comparing them to the most poular suspension of the time - rigids? There are a few remedies that make the bike much more compliant and safer, but unfortunately, none are cheap.



Active Forum Website User
VOC Member
Tested by putting weight onto the saddle. It doesn't move particularly much for me and he weighs less, but this is rather subjective.
Timetraveller, I did not alter the rear friction dampers. I shall add that to my list of things to check, thanks.

Hugo Myatt

Well Known and Active Forum Website User
VOC Member
To demonstrate front fork movement stand to the left of the bike, apply the rear brake with the right foot and push down on the handlebars. On the twin, particularly, let the inspector watch while you kickstart it. This will surely demonstrate rear suspension movement!

Simon Dinsdale

VOC Machine Registrar
VOC Member
VOC Forum Website Moderator
Does the bike handle OK on the road and absorb the bumps with no problems. If so and you are only worried about passing further MOT's then don't worry. See:
Your latest MOT may well be the last the Comet will have to pass if it really goes ahead and there is no u-turn.

With regard to the rear suspension, when I put my C rapide on the road with standard rear suspension / seat stays I always thought the rear end was to hard and lacked movement. When I fitted a rear luggage carrier system that also supported the rear of the seat thus removing the seat stays, the rear suspension came alive, moved a lot more and is a lot comfy to sit on.


Well Known and Active Forum Website User
VOC Member
When we take the racing Comet to a new scrutineer and he has spent some time with the previous stream of tele forked jobs he starts to look worried when the girdralics do their 'thing' on compression and then he nearly gets a hernia trying to twist them while holding the wheel in his knees.
Normally he gives up at that point but some can argue like an MOT tester But we can generally settle any argument by pointing out the wear marks on the side wall and the chamfered gearchange

chankly bore

Well Known and Active Forum Website User
Non-VOC Member
Original spring free length 6 3/4". With rider seated, 1 1/4" of inner springbox should protrude. Original wire diameter on Comets is .276" but .300" is used nowadays. If your springs are longer they are possibly Petteford ones.
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