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C15T rear shocks - also chain slider?

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cee-b:
My rear shocks are a bit pogo-ish so I'm after new ones.

The existing ones are 12'5", but all the info I can get (not much) points to the correct shock being 11.9". This is the length given for both the C15 and B40, but no mention mention is made of Trials. Is it the same for the T? Can anyone knowledgeable please confirm?

Also, the chain currently runs directly over/on the swing arm pivot and is wearing slight slots into it. Is this correct or should there be some manner of chain slider to protect the frame from wear?

JulianS:
Photos from a Girling catalogue. Various lengths for different models of C15.

cee-b:
Thanks for that Julian.

Unfortunately, I am now a little perplexed; that chart has me needing an 11.4" shock (same as a Bantam) but all the suppliers of classic bike bits spec an 11.9" for both C15 and B40.

At least I know that the 12.5" ones currently fitted are definitely wrong!

AWJDThumper:
cee-b: What year is your C15T? I assume it is pre-66 and has a swan neck frame rather than the later welded duplex frame? Normally with a C15, the rear shock length is limited to 11.9" otherwise the swinging arm will hit the rear footrest frame extensions. The other problem, as you have found, it that even with the standard set up, the clearance of the rear chain above the swinging arm pivot is marginal.

In the case of the earlier C15T, the footrest frame extensions are missing but the rear shock length is still limited by the swinging arm pivot clearance of the chain. As standard they weren't fitted with a chain slipper and so the rear shock length was limited to 11.9" I believe the greater ground clearance for the C15T was achieved simply by using a 18" rear wheel rather than the standard 17" used on the road bike.

The original rear shocks were slightly different from the road bike but all that is available nowadays is the standard C15 shocks. Unless you are going for a non-standard C15T set up (eg by adding a chain slipper) the standard shocks are probably your only choice if you are trying to keep things looking original.

cee-b:
Thanks for that 'Thumper', I really should have given more detailed info about the bike.

It is 1961 and is actually a C15T engine in a B40 frame; apparently this was a favourite combination on the trials scene at the time. As both C15 and B40 are spec'd for the same rear shocks I didn't think it was significant - but I may well be wrong.

I hadn't appreciated that the extra length of the shocks currently fitted was the cause of the chain/pivot interference, but now you point it out it makes perfect sense. I'll replace with 11.9" and see if I get clearance.

I'm currently awaiting a reply from Bike Revival regarding what shocks they would recommend. I'm planning to ride the bike mainly at club days in forestry and some Long Distance Trials around Exmoor. I will be riding the LDTs for fun rather than competitively, but I'd still rather put something decent on it, not just the Emgo stuff you get on eBay.

Any recommendations would be appreciated.

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