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Vol. 2, Issue 25 - Jan / Feb 2010

Posted: Saturday 02nd January 2010

Author: Peter Underwood

A very Happy New Year to all our readers! I’ve just realised that this is the 50th Edition of the combined Cambridge Lightweight News (25 editions) and Lightweight News (another 25). For a technical reason we changed the name midway but from the next edition will revert to Cambridge Lightweight News as I always think of it this way, having to admit it is often just a gossipy account of what we do from here in Cambridge, but helped from time to time with some informative pieces from a core of contributors. If you are able to contribute, please submit as a Word document to the email address above.

Lightweight News started as a letter to a couple of friends in Hampshire telling them what we were doing with our lightweights locally in Cambridge. The letters were copied on and gradually became Cambridge Lightweight News No. 1.

Measuring frames can be confusing. Several years ago if the frame was measured in inches then the measurement for the seat tube was centre of the bottom bracket to top of top tube. If it was metric it was centre to centre. Sadly this tradition has been lost and there is often confusion as to the exact size of the frame.

Nowadays there is yet another variant thrown into the equation, the sloping top tube. Manufacturers sometimes use the ‘virtual’ or apparent measurement, i.e. where the top tube would intersect the seat pillar if it were horizontal. Not all do this, some measure the head tube instead!! This leaves you to work out the real size of the frame. I have been trying to work out what size I want in a new frame. The last one I bought was done by visiting the shop with an existing machine and holding it alongside another stock machine and then adjusting the new seat and bars to match, which again doesn’t seem very scientific. When I next visited the shop the new bike was built up without bar tape and there was still a chance finely to adjust stem height and seat height. As it happens it was just a tweak of the brake position on the bars plus bar angle changed minutely. After this the bars were taped up and I have been happy on it since.

Having long passed the date when I could acquire a bus pass there is another slight difficulty to cope with. I have the centre of the bars some 6cm below the seat top whereas younger riders today have at least double the difference. This is why they can have smaller frames and not too many spacers (if any) between the Ahead set and the stem. I have to choose slightly larger frames to avoid an extreme of spacers but I never think the larger frames are so well proportioned as the small to middle sized ones. This goes for classic lightweights as well. Another possibility to use is that of a stem which rises slightly rather than being parallel with the ground; I wondered why some of these looked all right whereas others didn’t. I eventually found out that the sloping stem will match up to a sloping top tube but will probably look wrong with a horizontal one.

Some 54 cm sloping frames are actually 58 but this information cannot always be found in specifications. I suppose us oldies were brought up in an era where you could order a frame to built within a quarter-inch, even an eighth in some cases. Now it is often ‘small, ‘medium’, ‘large’.

We also used to talk all the time about angles and I was a believer that 74/72 were the bees knees. It is a tricky job to check classic frame angles due to the lugs coming in the way just where you want to measure. I have a parallel shaped tool for measuring but still have to hold it clear of the lugs and eye the tubes up to the edges, not very scientific I’m afraid. It helps to set the angle to what you think it is and then eye it up – if it is wrong it will be apparent then

We often get measurements from the States for the website and they regularly mention ‘standover height’. I think I can guess where they are coming from but have never heard of this done in the UK – perhaps we are not so delicate in the nether regions! I can understand this in relation to classics but can’t imagine how it is done for the modern sloping top tube machines, if indeed it is, as the variation from front to rear is often several centimetres.

So now there are two new measurements to consider, standover height and head tube length. As an example, here is a Colnago measurement table, an honorary degree in mathematics awarded to anyone who can decipher it first time:

Thanks for reading

Posted: Saturday 02nd January 2010

Author: Peter Underwood

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