Replacement frame for folding bike

[Rob Archer]

The frame of my Viking VN45 has cracked at the top of the seat tube. It's partly my own fault. I'm 5'10" and 92kg and the seat post has been at it's maximum extension. I bought the bike second and was always a bit concerned that the seatpost diameter was only 27.2mm which seemed rather thin for such a long post. The original aluminium one started to bend where it goes into the seat tube and I suspected it could break so I replaced it with a steel one. I suspect the crack is because the steel one has more inherent flex than the aluminium around it. The frame isn't repairable sadly. The rest of the kit on the bike (some of which I've upgraded) is fine. Unfortunately nobody sells just frames for folding bikes. I need one that takes 20 inch wheels and a fatter seatpost.

Any ideas?

[gaz]

I'd probably look for another pre-loved folder.

You could also try C H White & Son. Nothing suitable of their website at the moment but may be worth a call.

[Brucey]

you can often buy a used Viking folder on ebay for about £50.

If you want your seat post/frame not to break then

a) the seat pin has to be a perfect fit in the frame; i.e. no wobbling with the binder bolt loose. This might mean reaming the frame and using a 27.4mm pin in it. If it is not a perfect fit then it will always exert uneven loading on the frame and with aluminium frames that can cause them to break.

b) make sure the seat pin is as far as possible into the frame. If necessary have a custom long seat pin made up, so that there is about 8" or more of it inside the frame.

c) if you want to increase the stiffness of the seat pin, have a sleeve made up in aluminium, and have it bonded inside the a steel seat pin , for at least the insertion length.

c.h.white sell dahon, tern and bickerton spares. They may be able to advise you of a frame that is suitable for you.

cheers