Swapping chainrings
 

Ramping up my riding this year, after some time off, and realized I had a stretched chain. Have a replacement chain and cassette, but the chainrings look a bit worn, so, I'd like to fix that also--I think I've gone through 3 or so chains on this bike, so there is some wear. Right now the bike is a 9 speed, 12-23, with 30/42/52; crank is a Bontrager Select. 74/130BCD. Shimano STI's. Question: can I just buy some Suigino rings? I understand I'll lose the ramps and pins, so shifting performance might suffer. I was not planning on spending that much; I don't feel any play in the bottom bracket so I'm not sure I need to replace it.

While the 30 and 42 is decent the 52 is useless to me. I'm tempted to try 28/39/46, something of that sort.

I wouldn't go changing the tooth count on the front much (or at all) or you may cause yourself some headache with front derailer compatibility. Check shimano's tech docs on your particular derailer (I believe the model number, 'FD-xxxx' will be on the back side of the derailer, viewable from the non-drive side. Bring a magnifying glass and look for text within a rectangular shape).

Are you sure your chainrings are really worn? If you never used your 52 then it might just have cosmetic wear. Though a worn middle, and sometimes low, gear on a triple is pretty common. Even if you don't use your 52, if you ever go to sell the bike the missing gear might be a turn-off. Or you might want it there once you start putting on the miles and get stronger.

If you wanted to emphasize your lower gears, I would have suggested a lower-geared cassette, like a 12-25/27. Or even a junior cassette, like a 14-25. Don't forget to check those tech docs on your rear derailer regarding chain length/tooth capacity

If you're still serious about rings, just keep your eyes open and hunt around for a good deal- triple road rings, and even entire triple road cranks, are pretty cheap. They get dumped because a large majority of people are buying doubles and 1x drivetrains now. If you don't think Suginos will be an improvement over your current hardware, then don't buy them (or feel free to link us to what you're looking at).

Chainrings are made with sculpted teeth nowadays to aid shifting, so they tend to look "worn" even when brand new. You'll see some rounded off teeth and teeth that are shorter than others. A truly worn chainring generally has teeth with a consistent "shark fin" profile all the way around the chainring. And since the load from the chain is spread out on many more teeth, chainrings tend to wear much more slowly than cassettes. If you've been replacing chains regularly, chainrings will typically last through a lot more than three chains.

Yes, you can, but you may find that shifting performance isn't nearly as crisp. And trying to get your front derailleur adjusted juuuuust right may become a futile exercise.

You might find that straying too far from the stock chainring sizes degrades shifting a bit, too, since modern derailleurs are sculpted with specific chainring combinations in mind to aid indexed shifting systems.

I concur. With doubles you can play around a little with the chain rings, and in the days of friction shifting it was no big deal to overshift a little to get the chain over to a balky ring. But with indexing on triples the derailleur is designed for that 10t gap between the middle and outer rings. I've seen 50/39 work very well, and 52/39 isn't bad, but if you're thinking along the line of half-step plus granny, it ain't gonna go. And with indexing you need that ramping on the outer and middle rings.

He's decreasing the gap with a smaller big ring. It could work just fine. Though I'd go for a 48 tooth big ring. 42-46 is too small a difference to bother shifting up front. :) Also, 48 will be closer in size to the original.

I was told by a friend that my big ring looked a big chewed up (it's an alloy gear, the other two are steel), and the middle ring looked worn. I can feel some sharp edges. So I wanted to look into changing them, and if I'm changing, ergo, can I optimize?

A few years ago I changed the cassette from 12-25 to 12-23 so as to intentionally get the 16T (again it's a 9spd cassette). I was very happy to receive that as it filled a gap in the gearing. Honestly, I do think the 42T chainring is pretty good--if I were to have a 1x9 setup I might very well run 42 x 12-23. When in shape I rarely went above 42x14 or 42x13 on the flats. [I found myself frustrated on flat ground, going from 42x17 to 42x15, it came up on a few roads, that gearing gap.] The only time my 52 comes into play is if I can hit a downslope and get my speed above 20mph.

I'm out of shape and am finding it easier to spin in 30x19 instead of mashing 42x19 on our hills; I'm not sure how wise it is to use either end of the cassette when in the middle ring so I only use 42x21 when sitting and spinning and tired. I did notice the change from 25T to 23T when I hit dirt (I'm not afraid to take some fire roads and even some technical stuff on occasion). The 52T chainring is strictly a downhill gear for me. Ergo, the desire to fool around with 28/39/46--pull my two primary chainrings down a bit, and maybe find a spot where the big ring might be usable on the flats for me. If I hadn't already bought a 12-23 I'd give thought to a different cassette, but I'd again want some nice close gears that would mimic the 42x19/17/16/15/14/13 ratios I already have (since I "know" those are my primary gears).

Sounds like though I might not like the change in shifting, and I might not actually have worn out the rings. In which case I'd probably be happier to just leave well enough alone. Maybe I'll just do that instead.

Thanks!