C121958 rear suspension units

[Joe L]

I recently replaced my rear suspension units but, unfortunately, they are too long. When I put the bike on the main stand, the back wheel does not lift off the ground at all. I've spoken to Hagon Shocks and they inform me the shocks they have available are the same size (180mm centres). I bought the bike in bits with no dampers so unable to check the  correct size for that year. BSA probably had their own sizing for 1958 I would rather replace the shocks to the original size than adapt the centre stand as suggested. Does anyone have an original pair for sale or advise me of the dimensions for 1958 model . Thanks. Joe 

[Spaceman]

I'm no expert on the C12 but I assume we are talking swinging arm model. If so, a couple of sites give the rear shock length as 10.9" or 276 mm. I assume you meant 280 mm rather than 180 mm?

I'm not familiar with the C12 centre stand but a common problem with the C15/B40 centre stand is that the pivot wears over time resulting in the deployed angle for the stand becoming too shallow and the corresponding lift of the bike gets significantly reduced. My B40 had this problem resulting in the back wheel not being lifted off the ground but, with the pivot holes repaired, the centre stand is now working correctly.

Worth checking where the problem actually lies?

[Greenfield]

Classic Bike Shop has C12 '56 - '58 rear shocks with centres 289mm. Might be worth giving them a ring.

[Joe L]

Thanks for your comments and information. I did mean 280mm not 180mm (typing error or my fat fingers). I'll carry on and try and locate some shorter shocks or, if all else fails, consider adapting the centre stand. Thanks again.

[Spaceman]

The C12 rear shocks are the same as used on the earlier Bantams and the Tiger cub. From what I can see, the length of them was 10.9". If you fit shocks that are 1" shorter, for example, this might have unintentional consequences such as a low seat height and could possibly affect the bike's handling because of the change in overall geometry. It sounds as though the problem with the back wheel not being lifted clear of the ground is probably down to a worn centre stand that could be due to a worn pivot bearing or be due to worn stops. It would certainly be worth taking a close look at the centre stand especially with the spring removed so that you can test for free play.