Chainring or cassette?
 

I will be doing loaded touring this summer towing my Burley Nomad trailer. I have a triple (50,39,30) and my cassette is a SRAM 11-26. I will be encountering a fairly hilly terrain and I personally weigh 250.

My question. Which would be best? Change out my 30 chaninring to smaller or just get a different rear cassette? I've heard others pop a 24 chainring on although I'm not sure about the smoothness in shifting from a 39 to 24 and back? If I go with a different cassette, I'd like to keep the 11 for top end speed. I have Tiagra on the rear.

Thanks in advance.

Both: 50-39-24 and a 11-34 cassette.

Either is OK assuming your RD has sufficient chain take up capacity. Be aware that most mechanics fit chains as short as possible so a larger cassette may mean a new chain.

Use a gear chart, to determine which arrangement will give you the best selection of the mid-high gears where you'll do 90% of your riding, combined with an acceptable low.

In your shoes, I'd go for the granny solution, 24 or 26t if I expected to use it only as a bailout and stay in the 39t most of the time. In that scenario, you'd have the benefit of the tighter cassette for smoother shifting, and tighter middle gearing, and while upshifting out of the granny may be crappy, it won't be so frequent as to be an issue.

Any derailleur issues with either? I have Sora FD, Tiagra RD.

This makes a lot of sense. I do like the ratio of my rear cassette (for shifting) and wondered about mucking with that.

The cheapest change would be to a smaller granny ring like a 26 or 24T. I've made the change to a 26T on several road triple with 52/42 or 53/42 larger rings and it works well. The granny to middle upshifts aren't lightening fast but they are ok.

However, will that give you a low enough low gear? A 24x26 is a 25 gear-inch low and that's not real low for loaded touring in hilly areas. Pulling a trailer will add even more weight than panniers so you will be quite loaded down.

Lower gearing will require a wider range cassette like a 11x32 or 11x34 and probably a new MTB rear derailleur.

Sundance89, Your bike is geared similar to one of mine, I'd opt for the smaller chainring, 24T if you already use the 30T alot. I'd hate to mess with a cassette that provides the middle gear ratios I like.

Brad

Well, he weighs 250 and will be pulling a loaded trailer up a lot of hills. The desirable good gear progression may have to be sacrificed to get the essential low gears.

Years ago someone (Sun Tour?) made a freewheel with fairly closely spaced smaller cogs but then a huge jump to a bail-out largest cog. Sounds like that would be ideal if it were available these days. Say a 12x25 9-speed with a 32T 10th cog.

Sounds like a good start, but weight plus trailer plus hills leads me to second 10speeds' recommendation -- both cassette and ring. Then put some Shoe-goo around the cleats, so it's easier to walk when you need just one more lower gear.

I'd recommend a 12-32 or 12-34 cassette and mountain type rear dérailleur, a longer chain may be needed. I would also try a 28 or 26 small chainring. Chainrings are cheap and your needs probably call for some experimentation. With this setup you can at any time switch back to a closer ratio cassette for flatter faster rides.

Hillrider, Your post reminded me of my sister's mountain bike's gearing. I think it's a Mega Range 8S with 11-34 gearing.

Brad

I second the recommendations for going to a different cassette, but know that you'll need a long cage derailleur to pull off a 32 or 34 tooth in the rear. Your stock derailleur most likely isn't long cage, but I can't be certain. Also you'll need a new chain as was mentioned earlier by FBinNY.

I have a Tiagra RD, I'm not sure if it's long cage or not? (How to tell for sure?) If I do in fact need a new long cage RD, wouldn't that preclude me from switching cassettes back and forth? Just as the "regular" RD can't work with 11-34, likewise, wouldn't a long cage RD not work with a 11-26?

I ask the above because switching cassettes back and forth is a very good idea as this bike is also my commuter bike.

Your current setup (with triple crankset) must have a long cage derailleur. But it's a road long cage der ("GS" in Shimano); this is different than a long cage "mtb" derailleur ("SGS"). The GS lacks the chainwrap and higher maximum cog capacities of the SGS. Deore and Deore LX SGS derailleurs can be bought for <$50.

And you can indeed run your narrow range cassette with the longer cage; there aren't limits at the other end of the spectrum, only a slight penalty in weight and (possibly) shifting speed, but those aren't concerns when touring.

Well I just eyeballed it and it appears that I definitely have a long cage RD. I have a Motobecane Cross bike (basically a build at this point). I forgot to mention that I upgraded to some TA Carmina 185 crank arms (38" inseam) and while I love the fit and additional power the longer length provides, the "slower spin" only makes me need this change in gearing even more for hills.

Thanks. Every mod I make to my bikes I learn that much more about wrenching and compatibility.

Can you explain this a little more? I just did some searches on chainwrap with RD's and will spend more time later. But why wouldn't a road long cage do the same as a mtb? I'm not sure about the cog capacities either? I'm assuming you mean the cog wheel is bigger on the mtb?

The cassettes commonly used for MTB riding have larger low cogs than cassettes used for road riding (32 to 36 tooth versus 28 tooth and smaller). Cassettes on MTBs also have wider ranges than what we see and use on road bikes; an 11-32 cassette used in conjunction with your 50/39/30 crankset technically requires a RD that can handle a chainwrap capacity 41, whereas your 11-26 cassette with that same crank only requires a capacity of 35.

MTB RDs handle the extra chain required by having a longer cage. If you put a "long cage" road RD next to a "long cage" MTB RD, you can see that the MTB RD cage is noticeably longer. The amount of chain, when not needed in some gear combinations, has to have somewhere to go; in this case, the longer cage holds some of the extra chain in the greater distance between the two RD pulleys, while yet more of the extra chain resides in the lower run of the chain loop...which has also been made longer by the longer dimension of the RD cage.

Think of it this way: In a world of limited choices, the RD manufacturer could offer us one type of RD that would function for MTB and road use, and that RD would be a long-cage MTB derailleur. It has the chainwrap capacity to handle up to 45t, but has no lower limit. But road cyclists want to use components that are light and offer snappier shifting. The result is a road RD that has the smallest dimensions possible that can still perform well with 27t and 28t max cogs and narrower range cassettes.

Sorry. I only make it sound complicated.

I put the 24 on Ten Wheel's bike. You will fing that the shift is not as smooth, but it works. A 24-26 will give a 25 inch low gear. That's considered a little high for a tourer. A 24-32 will get 20 inches and closer to a loaded tourers gearing. Lower is even better. If you need lower gears and don't have them you can make yourself miserable pulling a load uphill.
You could even drop the 50 and go for a 48.

It's not just about cage length and chain wrap. A mountain type Shimano rear derailleur has a different geometry in its upper half that allows for a larger cog, like a 34 or 36.

You might try your triple road rd with a 32t cassette. Sometimes it will work. If you cannot adjust the rd top pulley away from the 32t cog, you know you need a mtb rd. A 34t cog has virtually no chance of working without a mtb rd.

Yes, and I barely touched on that. It really didn't matter, since he will most likely need a mtb rd for any of the proposed gearing changes to work reliably or even at all.
That's a thought, but even if his Tiagra rd can handle a 32t cog on his frame, it's not designed for that amount of chainwrap. And then it results in only a 25" low gear, exactly what he'd get if he kept his current cassette and changed out his inner ring for a 24t but at considerably greater cost.