Due to circumstances partly beyond my control (and off-topic) I've porked by bike's drive-train. It needs a new chain, new cassette, and new chain-rings. Or maybe it's not (completely) my fault, as it's been through at least four chains and two cassettes; maybe it's just that time.

Bike is a 2010 Giant Transend 1 - https://www.giant-bicycles.com/au/transend-1-2010

I've previously replaced the SRAM PG950 11-34 cassette with (IIRC) a Shimano HG80 11-34. Right now, it looks like I can get a slightly better deal on an XT M770 11-34.

The crankset - 26x36x48T - The BB is an internal sealed-bearing, and it's like new. Can I even get a crankset to fit this? Or is everything external-bearings now? I have a spare crank-set off-site. IIRC it's a Deore M590.

So...

Can I find a new crankset that fits the internal-bearing BB? Or do I need to "upgrade" from the BB?

How much of this should I do myself? How much of this should I pay the shop to do?

I actually like the chain-guard on the old crankset, but I can't find any new cranksets with a chain-guard. What's up with that?

Any other thoughts, considerations, or advice here? Thanks...

You probably have a Deore 590 Trekking crank if you have a chain guard. But I don't think Shimano ever made an Octalink 590 crankset. You'll need to get the exact crank numbers off the back of the crankarm.

But the easiest option is to just replace the chainrings.

John

If you're sure it's an internal bearing bottom bracket, then you probably have something like an Alivio FC-M431

I'm betting it will be cheaper to buy a whole new crank than to try to track down the chainrings for this, if they're even available.

Also, I think there's a newer version of that particular crankset, the FC-T4010 IIRC. Still Octalink, still 9-speed 48-36-26.

The old crank-set is labelled FC-M442/443.

Specified in marketing material as "Deore Class". Magnet says the 2 inner rings are steel and the outer ring is aluminium.

26-36-48. 175.

From what I can find, it would be quite cheap to replace, if I could find a place that actually has one. Seems like the crank-set and chain-rings are no longer available... Which is pushing me towards "upgrading" to the external-bearing crank-set.

Just got off the phone with the LBS. Exact replacements of crank-set or rings aren't available. I can swap out from octa-link BB to square-taper BB, and get a similar crank-set, but then I'd spend about as much (or more) as I would on an FC-M590 (which I think I already have, boxed-up).

Right now I'm leaning towards...

1. Have the LBS remove the old crank-set and "face" the BB-shell.
2. Order an XT M770 11-34 cassette, for less than the cost of an HG80.
3. Install the crank-set I've got boxed up, after I double-check it.

Going this way, my "out of pocket" cost is about $70 for the cassette and $40 for the LBS bench-fee.

If I go this way, is there a 3rd-party add-on chain-guard that I can add to this crank-set?