WashWizards727

I got a 520 about a little over a year ago and want to replace the standard 50/39/30 tiagra crankset. I've looked at the shimano lx and other cranksets that have 44/32/22, but I want a inner chainring of 20. Are there any cranksets out there or can I buy a 64mm 20 tooth chainring and switch out the 22 tooth?

oldpedalpusher

I'm not sure, but I don't think there are any 20T arms to fit your BB.

I run a 20 year old 24-34-46 Shimano LX...



...with an ultraclose ratio 14-23 7sp cassette in very hilly country, and it works great even on a cheap, relatively heavy MTB.


Greg

Gonzo Bob

I know you can get 20T rings for 5-arm 94/58mm BCD cranks but I don't know about 4-arm 104/64mm

This one says it's for 4-arm but lists the BCD as 58mm which is very unusual (as it also states). https://www.biketoolsetc.com/index.cg..._id=SG-CSS5820

cachehiker

I've changed the rings on my tourer to Salsa 24/38/48. They won't shift quite as slick without the ramps and pins but they really don't need to with the bar-con shifters. I'm never going to do any racing with it anyway. The best part about doing so was I didn't need to change to a mountain bike front derailleur.

Michel Gagnon

"24" is indeed the smallest chainring you are able to install on your crankset. It is relatively inexpensive and will give you about 2-3 gears that are lower than what you have. Otherwise:
– Replace the inner gear with an adaptor from Mountain Quad Tamer; it will allow you to install an 18 or 20 teeth granny. Fine, except that jumping from 20 to 39 will be a major break in cadence.
– Replace everything with a mountain crankset. A Shimano mountain crankset will give you something like 44-34-22. The 44 is large enough for your needs (unless you like fast-paced pack racking). A warning : you'll need another bottom bracket too.

WashWizards727

my tiagra crankset is hollowtech. Can I not get a moutain crank (shimano deore lx or something similiar) with that is hollowtech?

tcs

With 700x32 tires and the 520's stock cassette with it's 32T large cog, a 22T chainwheel would give you 18.6 gear inches, a very low gear. A 20T chainwheel would yield an even lower 16.9 gear inches. With such a low gear, you may well have problems spinning the cranks at high enough rpm to produce enough speed to maintain steerage.

HTH,
tcs

Mr IGH

How low do you need to go? My wife and I road all over the Rockies, I had 50lbs of gear, she had 30lbs. Our low gear was 30x30 with 700C wheels (27 inch gear).

Tabor

Harris Cyclery sells the Sugino XD600 in 26/36/46. That is what I would get, personally. You will need a new BB, but so what?

rtciv

This is an interesting thread. I have a Dawes Galaxy with two chainrings: 42T and 52T. At the rear I have 5 sprockets and I can't remember how many teeth they have, but I'm fairly sure the smallest has 13, and the largest is... 28T maybe?

In any case - I find the two chainrings to be far too large, and I spend most of my time in one of my lowest gears. My town is quite hilly and it's really starting to wear me down, and get to my knees. The chainrings strike me as quite large for a touring bike.

oldpedalpusher

Same here...
I can climb anything with a 27 inch gear (24x23 and 26 inch wheels).


Greg

Gonzo Bob

Bet you can't!

My brother and I recently finished an Alpine/Pyranean tour (Munich to Barcelona) with ~27-inch low gears (I had 44x34 with 11-34 and 700C wheels and he had 44x29 with 11-30 and 700C wheels). We both had about 15kg of gear and we made all the major mountain passes just fine because they generaly didn't get much above 10% grade but we had to walk a couple of steep hills (20-25% grade) to get to some of the hostels we stayed at.

I can see needing lower than 27-inches for someone carrying more gear and/or traveling the smaller mountain roads with steeper grades.

cachehiker

Of course you can if you've got deep enough pockets.

The bottom bracket will get swapped along with the crank.

The front derailleur will need to be lowered and potentially swapped out altogether. It will depend upon how well you really want the front to shift and how much chain rub you're willing to tolerate.

However, as was stated before, 22-32 is a really low gear for touring at 18.6 inches. Some people like it although I'd be using it to pull stumps. Until I'm carrying more than my bike is capable of, I get by just fine with 24-28 and 23.1 gear inches. In fact, I can't recall having used the lowest gear although the original 30-32 was used once carrying 50 lbs. in pouring rain. I would've drowned in my own sweat if I hadn't because my heavy duty rain gear doesn't breathe all that well.

Barrettscv 

Yes, the 52t & 42t are large and will be a problem on hills.

Your bike must be 25 years old or more. Upgrading the gearing is possible, but may not be cost effective. Are you looking to upgrade this bike?

Michael

oldpedalpusher

Yeah, you're right...

I should have said anything in the canyons where I live.


Greg