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7-8-9 speed cranks???(2 posts)

7-8-9 speed cranks???weswu
Oct 14, 2001 5:20 PM
OK, so I go to eBay and look for some cranks. I find listings for all sorts of stuff including differentiation between 7, 8 and 9 speed cranks. Is this a joke? Have any of the manufacturers actually changed anything to make cranks for different gearing in back?

The only things I can think of are the size of the teeth on the rings to accommodate narrower chains and the distance between the small and large rings. The first makes some sense to me, the second doesn't.

So.. the question is, is this sales gimmicking by the sellers, or is there something to this?

re: 7-8-9 speed cranks???grzy
Oct 15, 2001 2:38 PM
Well the reason why the spacing between the chainrings decresed from 8 to 9 speed was so that the narrow 9 speed chain wouldn't hang up between gears. Make sense?

Really. there is a difference between the cranks - it's part of Shimano's plan for total dominance through planned obsolecence program (POP for short). There are only a few critical dimensions on a crank, but Shimano (et al) has seen fit to mess with every singloe one of them:arm length, offset, BB interface pattern, CR spacing, available gear ratios, shifting ramps,and least we forget shape of ring itself ala elliptical biopace rings.

Do yourself a huge favor - find out exactly which crank you need/want (by PN) and only get that exact one - especially if it goes on an MTB. You cannot begin to believe how easy it is to get all messed up trying to make a "bargain" on a crank actually work *well* on your particular bike. You'd think it would be pretty simple, but it's not. As a self proclaimed "gear head" I have been around and around on this one. the Road bike stuff is a little easier, but only a little. Stick to a quality crank and make sure it's the one you need. Even if you get the thing all mounted on your bike you can find that the chainline can be off and while your bike looks great it shifts like crap. A deal on something that you can't actually use isn't much of a deal.