Wear's the problem?

A new cassette and chain were fitted to my bike recently. After less than 300 miles, the 11-tooth sprocket is skipping, particularly under heavy load. My local shop said that it is worn and that I need another new cassette. I expected to get a lot more wear than that! They said that I should spin more in a lower gear but I want to use the highest gears. They have agreed to replace it free of charge, but is such early replacement reasonable?

Dave Reid

Er, no. The top gear on your bike should be able to take ‘heavy load’ without complaint. Top road sprinters such as Mark Cavendish use their highest gears, apply a very heavy load to the transmission, and would not be best pleased to find it skipping midway through the final gallop. Furthermore, the smallest sprocket generally gets little use and should wear slowly. Finally, it is unlikely you have worn out a chain in 300 miles. The most likely culprit for the symptoms you describe is poor rear derailleur adjustment. Look at the outside throw screw first – it’s typically marked with an H.

Richard Hallett

​​Cycle’s Technical Editor

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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