Chainring Bolt Patterns
 

Hi Guys,

How should I measure my chainrings to find out the bolt pattern?

I've been given two lenghts to check

58/94 and 74/110.

I'm not too sure which one I have.

Many thanks

Rich :)

The Nashbar (USA mail order) catalogue used to have a nifty pattern guide.
You can make your own with a compass. Draw some concentric circle of suitable diamter (58, 74,94 110 mm). Place the chainrings over, and see which circles hit the centre of the bolt holes.

Thanks Michael,

As always you are the fix it guru!!!

I honour you!!!!

:beer:

Rich

You can also try geometry to find the diameter. Divide 360 by the # of bolts, then divide that # by 2. This will give you the half angle of the triangle. The bolt diameter is
(dist between holes)/{cos(90- 'half angle')}
(in degrees, of course.)

Thanks D*Alex,

Maths was never my fortay..... :confused:

Rich :blush: