Currently got a 53/39/30 triple on the commuter/occasional tourer, and I'd like to lower the gearing a bit. I've seen quite a nice old XT M730 46/36/26 set on eBay which looks just the job, but I don't know if it'll work on a 9spd set up as I think it would originally have been for 6spd?
Any ideas?
i wasnt aware shimano did an xt crank in 6sp...unless you mean 7 or 8sp
it should work without any issues. you may need to change the chainrings though
EDIT: just had a look and you are correct that its 6sp...should work as long as the BCD is 104 or compatible with the other current BCD sizes then you just need correct 9sp rings
Ah, sorry, should have said, the chainrings are on it already, and they're the ones I want to use.
I've just had another Google and M730 also seemed to be 7spd?
I suspect the rings might be too wide for a 9spd chain.
You'll be able to do it but it might not be very smooth. I did similar with a mix of M650, M730 and some modern kit but it was all a bit crunchy.
A decent M730 crankset should go for £40+ so I'd just spend the money on a 9sp crankset.
never really understood this as all 3/32 chains are nominally the same internal width ...it's the outer width that varies with the different speeds ( 7/8/9/10/11... so why ..(if they do) ...do chainrings differ in width . I can understand spacing differences but width?
found this on sheldon's (RIP) website :
Chainrings/CranksOld Chainrings, New Chains
There is a lot of confusion about the compatibility of narrow 9- and 10-speed chains with older cranksets. Shimano says you should replace the inner chainring(s) with specially designated 9- or 10-speed ones, but then they're all too eager to sell you stuff, whether you need it or not.
These chainrings have the teeth slightly farther to the right than the older chainrings to work a little better with the narrower chains. There is no difference whatever in the crank spiders.The manufacturers also are concerned about clueless users. The worst-case scenario is that you will be riding along with the bike in its highest gear (large front, small rear) and then for some bizarre reason shift down in front before downshifting in the back. (There is no shift pattern in which it is reasonable to shift in this sequence.) [Not with a 9- or 10-speed cassette, to be sure -- John Allen] If you do shift this way, there's a small chance that the chain might "skate" over the edges of the teeth for maybe half a turn.
In practice this "problem" almost never materializes. Many, many cyclists are using 9- and 10-speed chains with older cranksets and having no problems whatever.
New Chainrings, Old Chains
Going the other direction, using wider chains with chainrings intended for narrower chains is not generally a major problem if there's only a one- or two- generation difference. The only problem you might run into is that the chain will be more liable to rub on the inside of the bigger chainrings in the small/small crossover gears, gears you shouldn't be using in any case.
I reckon you'd be ok ..[u]possibly [/u]not perfect due to possible front derailleur range capability.