£25 to £50

Tooth Count - the number of teeth on the chainring, the higher the number the harder the gear.

Between Adjacent Bolt Holes - the measurement from the centre of any bolt hole to the centre of an adjacent one, if this measurement is the same as that of your crankset and the bolt count is the same then the chainring should fit.

BCD - stands for Bolt Circle Diameter (sometimes referred to as PCD - Pitch Circle Diameter) and is the technical way to determine whether the chainring fits your crankset. To calculate, multiply the distance between adjacent holes (in mm) by 1.709 (you’ll likely need to round the resulting number up or down a little).

Bolt Count - the number of bolts securing the chainring to the chainset. As with the BCD, this must be the same as your chainset.

Chain Width - 3/32” is the standard width for double and triple chainsets, wherease 1/8” chainrings are only found on single ring chainsets, generally for track / singlespeed use and can only be used with a wide 1/8" chain.

Intended Speed - the number of cogs at the back the chainring was designed to be used with. We refer to it as ‘intended’ speed as most double and triple chainsets will actually work with different speeds than originally intended, but the further away you get from the intended speed the more likely you are to experience minor setup issues. The exception being some chainrings intended for 10 speed use or higher, with these it’s better to stick to the intended speed.

Headset Type - the 1" size relates to the outside diameter of your fork's steerer column which should measure 25.4 mm, if it's 25.0 mm your forks should be French threaded. Although it's generally recommended to match threaded parts exactly, with headsets you can technically mix and match, unless you have French or the obscure old Raleigh threads, in which case you need to stick to that type. If you're replacing an old headset the thread may be stamped on there. Oversized 1 1/8" & 1 1/4" sizes are easily identifiable due to their size and the threads are all standard. Headclip headsets were made to fit fork steerers with 1" or the reduced 31/32" size steerers, as well as 1 1/8" versions for tandems.

Cup Size (OD) - the outside diameter of the cups, this must match the inside diameter of your frame's headtube closely for a good fit. For 1" headsets this should be around 30.2 mm unless you require a JIS headset which will be 30.0 mm.

Crown Race (ID) - the inside diameter of the crown race where it sits on the fork steerer, this needs to be close to the outside diameter of your fork steerer at the base to ensure a proper fit.

Stack Height - the overall height of the headset. To check the minimum stack height you require, measure the length of your frame’s head tube & subtract this from the length of the fork steerer column. You can always add spacers if you have a little too much steerer tube but you can't fit a headset with a greater stack height than the space you have available.

For further help with 1" threaded headsets head to our journal.

Axle Type - for square tapers, the ISO introduced a standard for European makers in the early 90s, JIS then did the same in Asia. Before then it was not so simple, and although there is a degree of interchangeability, the best way to make sure you have the right axle is to stick to the same brand from the same era, ideally the proprietary model.

Axle Length (D) - your crankset dictates the axle length you need and the recommendation should be used to avoid issues with chainline. If you're replacing an axle that works perfectly then this can be matched, otherwise you'll need to check the manufacturers spec, a good resource for older bikes is Velobase.

Centre (B) - measured from the outside of the 'shoulders' of the bearing races, as seen in the diagram.

Drive Side (C) - the right side (with any logos etc on the axle facing you), your right crank and chainrings will mount to this side.

Non-Drive Side (A) - the left side, where the left crank arm will be mounted.

Shell Width - the width of the bottom bracket shell the axle was designed to fit, measured at its widest point.