Bicycle Mechanics - Chainring Bolt Patterns

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Rich

09-18-01, 04:51 AM

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 :)

MichaelW

09-18-01, 05:10 AM

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.

Rich

09-18-01, 05:23 AM

Thanks Michael,

As always you are the fix it guru!!!

I honour you!!!!

:beer:

Rich

D*Alex

09-18-01, 05:36 AM

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.)

Rich

09-18-01, 05:41 AM

Thanks D*Alex,

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

Rich :blush: