Restoration problem

By CyclingUKvolunteer
I have a 1982 Mercian, which had a Regina 5-speed freewheel and double chainwheel until 2010, when the block fell to bits. The rear dropouts were 122mm or thereabouts.
I had the stays opened out by a frame builder to 130mm to take a modern wheel, which it did perfectly. However, the chainwheels will no longer line up satisfactorily with an 8-speed cassette. On the outer rear sprockets, the chain line is so far out that it eventually pulled a side plate off the chain.

Yet when I put the same bottom bracket axle in my modern bike, which has the same bottom bracket shell width and the same chainstay length, all works perfectly. Can you suggest a remedy?

Michael Griffiths

This sounds very much like frame misalignment. If the chainwheels and axle work on the new frame, they should do the same on the old.

One explanation is that, to get the required spacing, the frame builder pulled the stays on one side (probably the gear side) further out than the other – or even pulled them all the way over on one side. In other words, the rear wheel may be offset from the cycle’s centre line.

A quick check is to remove the rear wheel and run a length of string from the inside of one rear dropout, around the head tube and back to the inside of the other rear dropout in a symmetrical arrangement. If the dropouts are evenly spaced from the frame centre line, the string will be equidistant from the sides of the seat tube. Should this prove to be the case, the rear end should be tweaked accordingly.

Richard Hallett

​​​Cycle’s Technical Editor

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This Q&A was published in 'Cycle' the magazine for members of Cycling UK. To contact the experts, email your technical, health, legal or policy questions to editor@cyclinguk.org or write to Cycle Q&A, PO Box 313, Scarborough, YO12 6WZ

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