fietsbob

You say its a 50/39/30. just change the 30 for something smaller , a 24 will fit on a 74 bcd.

the 38t is as small as will fit on a 130 , and 1 tooth is not worth getting in a Bother over.


I too use a <C> triples , 50-40-24 & 52-42-26.. my old M730 110-74 is also using a 50-40-24.

I only Upshift out of the granny at the crest of hills, getting ready to head downhill, again.

Tourist in MSN

I do not often use the 24t inner ring. It downshifts onto that just fine, but if I did not have a chain catcher it might drop the chain on some shifts. The upshifts are a bit slower, but I can usually make that shift within about 30 feet of distance. For the upshift I have to move the shift lever a bit farther than I want it, then after the shift is complete slightly move it back. That is why I said it probably is best with a friction shifter.

Front derailleur is a vintage Suntour. I assume a newer derailleur would work fine too, but I prefer a high normal front shifter, thus using the vintage Suntour.

The two gears with the 24t front and the 11 or 12t rear cogs are unusable, the rear derailleur cage will not take up all the chain slack, but since those are badly cross chained, I do not use those gears anyway.

I am not very familiar with the new mountain doubles, but apparently those also have a pretty big spread between chainring sizes and people are not having problems shifting those.

ModeratedUser

OK I ended up winning a chainring on ebay. I got a 26t TA ring.

One thing I saw that I never thought they had was a setup that turns a double into a triple! Not bad, I do like the 50/34 on a compact crankset. Making that a triple really opens things up. Assuming that that conversion setup works good.

50/34/24 anyone?

tarwheel 

By the time you change out chain rings, you could have bought a Sugino crankset for less money and with more appropriate gearing for loaded touring. I've got touring bikes with Shimano 105 and Sugino triple cranks, and the Sugino has much better gearing for riding with loads.

DropBarFan

IIRC the FC-M590 was called a trekking crankset but I'm not positive about that considering Shimano's dizzying array of products & terminology. Also IIRC I could never find out the official "Q" or tread for the FC-M590--I was worried it would be too wide but I haven't had a problem so I never bothered to measure. I think 4-arm was sort of the std for MTB & 5 for road...of course Shimano adds confusion with a 4-arm road crank & naturally (!) the the chainwheel mount holes are not evenly spaced; it's like a flattened X.

Whichever crank you pick, I'd check to see if TA or other firm makes chainrings that fit. While buying separate chainrings is expensive, it's nice to know if the option is available. I agree uphill gearing is far more important than downhill but OTOH I'm surprised how few tourists like a high-ish top gear. I'm no speed demon but there's some advantage: on descents one can pedal at low cadence to keep muscle circulation going; a high descending cadence can be unstable esp with mountain winds buffeting pannier-loaded bike; & I have a theory that low cadence vs coasting might give more control. I mean, I seem to ~run out of gear around 30 mph.

ModeratedUser

Yeah it's really a little difficult trying to nail down exactly the gears ratios I want. I do know what I don't want though! I'm just going to change my inner ring and see how I like that and how well things will work. I did manage to get the TA ring at a pretty good price today ($16.50 w/shipping). Heck the triple that I'm using I got for $25 on CL. I'll spring for something when I know what I want.

Tourist in MSN

Agree on higher gears for pedaling instead of coasting. I rarely get to use my 52 front with 11 or 12 rear, but the long shallow downhills with those high gears are really nice. Or, strong tail winds on the flats can be just as useful to get into the high gears. On my last tour I used a 46 instead of 52, that was almost as good.

DropBarFan

It's weird: I've made spreadsheet gearing tables for current touring bikes vs previous racing bikes & it almost seems like Ive made a mistake in the formulas since I could descend much faster & easier on prev racing bikes even though the old 52-14 combo(622 mm wheel) was less "inches" apparently than current top gear 48-11 (559 mm wheel). Probably due to racing bikes being easier to spin on & also panniers causing aero drag. & BTW I've found that touring bikes oddly give less confident feel in descending than racing bikes. I had thought that stretched-out touring geometry would be more stable & less twitchy but it seems the reverse is true.