Bicycle Mechanics - question re "tandem" crank arms (sugino xd's)

ok. now. i was browsing QBP's catalog, looking for something cool as far as sugino XD's go. i saw they listed crankarms for tandems, xd600's. these are pretty much what i want, being that i want to throw my own rings on 'em, but i'm terribly frightened that the fact that the things are made for tandems, they might not work on my regular, solo-bike application.

is there really a difference?

i also saw some xd500's, as a compact double, for a half-sweet price, and i was pleased to note that they've got alloy rings and the gearing is almost what i want, but i a worry that they're 8spd. i know, i know; many folks run 8spd cranks with 9spd cassettes, but if it didnt work, i'd feel silly. anyone know if the xd500's are 8spd? the quality catalog doesn't say, and surprise, surprise, the bike shop doesnt know.

so, to recap: what's the difference between tandem sugino xd crank-arms and regular xd crank arms? are the xd500's with the 50/36 rings 9 spd-compatible?

tia,
-rob

A tandem crankset has a chainring on the left side as well.

ok. now. i was browsing QBP's catalog, looking for something cool as far as sugino XD's go. i saw they listed crankarms for tandems, xd600's. these are pretty much what i want, being that i want to throw my own rings on 'em, but i'm terribly frightened that the fact that the things are made for tandems, they might not work on my regular, solo-bike application.

is there really a difference?

Yes. Tandem left arms are threaded for a left pedal, but have a spider for a single chainring.

Tandem right-front arms are threaded for a right pedal, but have no spider (look like an ordinary left peda.)

The right rear arm is not tandem specific.




i also saw some xd500's, as a compact double, for a half-sweet price, and i was pleased to note that they've got alloy rings and the gearing is almost what i want, but i a worry that they're 8spd.
so, to recap: what's the difference between tandem sugino xd crank-arms and regular xd crank arms? are the xd500's with the 50/36 rings 9 spd-compatible?

I get asked about this so often by email that I have a canned boilerplate answer I can paste into an email with a couple of mouse clicks, viz.:

There is a lot of confusion about the compatibility of narrow 9-speed chains with older cranksets. Shimano says you should replace the inner chainring(s) with specially designated 9-speed ones, but then they're all too eager to sell you stuff, whether you need it or not.

Shimano is also 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.) 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-speed chains with older cranksets and having no problems whatever.

Sheldon "Don't Worry About It" Brown


+--------------------------------------------------------------+
| Wherever there is sufficient space for a motor vehicle |
| there must be sufficient space for a bicycle, |
| because the bicycle is smaller. Is that not obviously so? |
| -- John Forester |
+--------------------------------------------------------------+

thank you, both, for your informative replies. it looks like the qbp catalog at the shop has a "normal" xd set of crank-arms, sold sans rings. i reckon i'll get those arms, and a 50t/36t set of chainrings. thanks again
-rob

Or you could buy some version of the XD crank from someone who sells it - the non-tandem version. For my part, I've got basically-new 175mm XD2 with 48/36/26 rings that I'd kinda like to sell. Bottom bracket, too. PM me if you're interested.
Also, Harris (http://sheldonbrown.com/harris/cranks.html#11074) sells the regular XD600 and Rivendell (http://www.rivbike.com/webalog/cranks_bbs_c-rings/12067.html) sells the XD2.

Check www.aebike.com, www.twowheels1love.com and www.airbomb.com. I bought one of these cranks about 4-5 months back and they were all listing the standard one that you want. Don't buy the tandem crank unless you're putting it on a tandem.