Being and avid fan of my Nimbus performer giraffe, I found it’s only minor irritation was that the crank bearings (bottom bracket) required regular adjustment and occasionally came loose. Apparently, this is common problem on all giraffes, not just Nimbus. The added problem with a twin chain model, is that it is hard to feel that there is an issue unless you loosen the chains.
A bit of research came up with the Shimano BB-UN55 sealed cartridge bottom bracket. The bearings are sealed, rather than the existing cage, require no adjustment or lubricant and are closer to the cranks, which should be better all round.
There are lots of other makes available, but Shimano is a respected brand and at a good price. (By the way, the Shimano BB-UN54 is cheaper but has a plastic end cap – so don’t buy it). My local Halfords (UK Auto & Cycle Store) had a VP branded one, the correct size, for £10 (cheaper than e-bay).
The specific size for mine was the 68 x 122.5 mm (68 is the width of the frame & 122.5 is the length of the cranks – excluding the protruding threaded portion). You will need to measure yours to check this is the case - other sizes are available.
The cartridge comes complete with crank bolts (nuts are used on the Nimbus cranks) but I went for the allen key option with the built in dust-caps as they look way cooler!
Fitting is simple, instructions are supplied, but you will need a Shimano bottom bracket tool. Using this tool means you can tighten them with a torque wrench - way better than a C spanner!
Don’t forget left hand side of the frame has a right-hand thread and the right had side of the frame has a left-hand thread.
First impressions are that it looks much better and feels smoother, only time will tell how long it will last. Cyclist friends tell me they do thousands of miles between bottom bracket changes – that’s an awful lot of pedalling on a 20” wheel with your bum six foot in the air, but on the other hand, cyclist freewheel & don’t pedal backwards or idle.
As for costs, for the bottom bracket, tool, crank bolts and shipping I got change out of £25 – just waiting for Roger at UDC to start listing it as a kit – and Roger, I expect my commission!
Nasher
(aka John the Giraffe)