Bicycle Mechanics - Chainring bolts

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cmcanulty
01-12-11, 06:41 AM
I have to buy 5 chainring bolts and need advice on the size double or triple as I am taking a single 48t crank that is configured so that I can add an outer small ring so the bolts would go through the spider arm and the 2 chainrings without any spacer due to the offset but do I buy double or triple bolts for that situation. Thanks

FBinNY
01-12-11, 09:20 AM
For practical purposes consider the spider to be equal to that of a chainring, roughly 4mm. below is the approximate working length of the various bolt options.

Single is long enough for the spider + 1 chainring. 8mm
double is long enough for the spider + 2 chainrings. 12mm
triple is long enough for the spide +3 chainrings + a spacer the width of the spider between 2nd third rings. (5 widths), 20mm

For your setup, if the spider is between the rings, that's the same as a normal double, but if the rings are both on the same side of the spider, you'll need a spacer between them making it between a double and a triple. For that you'll need a triple, but will probably have to file it shorter.
fietsbob
01-12-11, 10:04 AM
+ the 5 bolts that hold the 3rd granny ring + spacers on, can screw into the sleeve nut for the double combination.

It's length is between 3 rings on the same bolt, and 2. (so as to eliminate that filing)

I fitted a chainguard machined with an offset, to eliminate the spacer
outside the outer chainring.. with that bolt selection.