Quote:
Originally Posted by NHAero
Mark, are there conditions in which an outer triple is not a good fit for the inner-mounted position of the 2x spiders we have been discussing? I'm not thinking of the counterbore, but rather that how the teeth are located laterally on the thickness of the ring.
One apparent advantage of the inside mounting location on these spiders seems to be that the large ring could be shimmed inwards to reduce the spacing (11 speed is 0.5mm narrower?) and also to help with the cage rub issue. Do you know a good source for a variety of these washers? I expect they are in the 0.5 to 1.5mm range.
|
Well, the chainring bolt counterbore might actually be the biggest problem. If the heads of the chainring bolts stick out, they might snag the chain in certain gear combinations, causing the chain to skip. The smaller the chainring size (a smaller difference between the teeth and the bolt diameter), the bigger the problem this may be.
As you say, the teeth are usually offset from the chainring faces. Outer triple chainrings are intended to mount to the outer face of the spider, but when used as the outer chainring of an MTB double, they mount to the inner face of the spider. There's no standard on chainring thickness - some are machined out of thick plates, others are stamped out of thin plates. This can result in varying amounts of offset to the teeth. But as you say, chainring spacers might be able to help to adjust the offset of the chainrings.
Wheels Manufacturing makes chainring spacers in a variety of sizes, although oddly the smallest increment is 0.6mm (0.015").