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I have a 2004 Jamis Aurora with a 52/42/30 triple and an 11-32 cassette in the back. 30x32 (25.3 gear inches) being the lowest gear is frustrating for the hilly terrain where I live (e.g., 7% grade average over several miles, with higher local steepness), and so I'd like to lower my gearing.

I'd like advice on how to most simply do this. The basic problem is that replacing any given part appears to have cascading compatibility issues which may or may not be solvable, and I'm becoming confused.

I do use the full range up to 52x11 (127.6 gear inches), but only on descents that are fast anyway, so I am happy to lose the higher gears and coast instead. There is essentially no level terrain where I live.

Relevant specs (all parts stock in 2004):

  • 9 speed
  • Crankset: Truvativ Touro 52/42/30, 130/74mm BCD
  • Front derailleur: Sora 28.6mm, clamped
  • Cassette: SRAM 11-32
  • Rear derailleur: Deore SGS
  • Shifters: Tiagra
  • Bottom bracket: TruVativ sealed cartridge, 68 x 113mm

Options that I've found so far:

  1. Add a larger cog in back, such as the new Shimano 12-36 cassette. As far as I can tell, this will require a new rear derailleur and a new chain, but that's it. This makes the lowest gear 30x36 (22.5 gear inches), 12.5% lower, and the highest 52x12 (117 gear inches). A downside is the excessive size of the rear cassette.

  2. Replace the crankset, for example with a 48-36-24. This makes the lowest gear 24x32 (20.3 gear inches), 25% lower, and the highest 48x11 (118 gear inches). At first glance, this one is the most appealing, but it seems to also raise the thorniest compatibility questions; the ones I'm aware of so far are (a) finding a front derailleur which is compatible with both my road shifters and the smaller large chainring (one possibility), and (b) differing chainline offsets of road and MTB cranksets.

  3. Swap in a lower granny chainring, say 24 teeth, resulting in a 52/42/24 crankset. My concerns here are (a) whether my derailleur can handle the 18-tooth jump between low and middle and/or the lowness of the granny gear, (b) the awkwardly wide jump between low and middle (75%, or about 5 sprockets), and (c) retaining very high gears that are feasible only for making a fast descent faster.

  4. Swap in 3 new chainrings. This seems to raise similar concerns to item 2.

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Kind of odd that you have such large rings, if this is a purpose-made touring bike. I'm looking at the Novara Randonee specs (a respected "middle-class" touring bike) and it's got 44/32/22 front and 11-32 rear. –  Daniel R Hicks Jun 4 '12 at 0:25
    
I think it'd be fine in a flatter part of the world (it was just right in Minneapolis). Even the newer version has a pretty similar setup, though the crankset is smaller to start, making my mod easier: jamisbikes.com/usa/thebikes/pdfs/12_aurora.pdf –  Reid Jun 4 '12 at 1:02
    
I live near Rochester (MN) and have been pretty happy with the Radonee (though a much older model -- don't recall the specs on it). –  Daniel R Hicks Jun 4 '12 at 1:51
    
I would say make the change in front. You might have to swap out some other components, depending on what your current derailer and spider can handle, but you have more options and can pick and choose what your tradeoffs are. –  Daniel R Hicks Jun 4 '12 at 16:41
    
Do you know what the specs are on your current front derailer in terms of minimum big ring size and max ring size differential? –  Daniel R Hicks Jun 5 '12 at 11:01

6 Answers 6

up vote 8 down vote accepted

I think everyone has provided some pretty sound advice, especially Daniel Hicks and his recommendation to go with the quickest and cost effective option by replacing your chainrings! With a 130/74 BCD, an ideal setup would be to swap in a 24/36/48 which would give you a great range at a cheap price.

The front derailleur is probably the least necessary component on your bike and, while shifting compatibility is a concern, I would recommend swapping in your new chainrings and setting everything up to test for compatibility before spending more money on a new derailleur. I have used mountain FDs on road triples and road FDs on mountain triples with a variety of indexed and non-indexed shifters and have had very little trouble over the years. Really, the only requirement is ensuring that the front derailleur is a triple and has the correct seat tube diameter/pull direction. (Your cascade of compatibility issues is something I've dealt with, but don't worry! There are lots of manufacturers who design compatibility issues into their gear, but they generally don't cater to the average touring enthusiast.)

Since you have an SGS derailleur (long-cage) you shouldn't have any issue with chain slack. For touring, the Deore SGS set up with an 11-32 is a great choice. At most, you may prefer to remove 1 or 2 links just to clean everything up. (I ride in New England on 24/38/48 x 13-32 and even with a full load I maybe walk it once a year).

When you start changing components such as your crankset you have to deal with special tools, frame clearance issues, bottom bracket fit, and Q-factor (the horizontal distance between your pedals). Mountain cranks have smaller BCDs but have much wider Q-factors which, for some people, can cause knee and hip irritation (which is exacerbated by long rides and clipless pedals). Long story short, if you are comfortable with your bikes ergonomics on long rides, leave it (or give yourself enough time to work out the bugs before attempting a 2k fully loaded).

Otherwise, take things one step at a time. If smaller chainrings don't give you enough oomph, throw on a new cassette which is quick and has few compatibility issues (12-36 is a common low touring range). More compact road cranks have a 110/74 BCD which won't help you on the low end (though, if your leg length permits a longer crank arm it might provide a very small advantage). Some mountain cranks have BCDs as low as 58mm x 20t, but I suspect that this option may be more trouble than it is worth. Some handy online gear resources include: rivbike.com, velo-orange.com, universalcycles.com, and sheldonbrown.com.

A cheaper way to ease the inherent suffering of long, steep climbs would be to trim some bike fat and touring load (a good technical and philosophical resource might be The Ultralight Backpacker by Ryel Kestenbaum or Just Ride by Grant Petersen). Some people might recommend trimming some actual fat, but we live in a world where everyone gets to ride a bike, not just 130 pound-25-year-olds. (No offense to the 25-year-old cyclists out there!)

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awesome answer. –  user973810 Jun 5 '12 at 19:04
    
Believe me, dropping several pounds of fat is on the agenda too! And I'll see about becoming 25 again. :) –  Reid Jul 4 '12 at 17:57

The simple answer is that there is no simple answer. You have a triple, and a decent gear range on the cassette, so there is no obvious direction to go which you can use to say, "This is the right way. Do this."

Any of the options you show should work. If it were me, I'd do the first one:

Add a larger cog in back, such as the new Shimano 12-36 cassette. As far as I can tell, this will require a new rear derailleur and a new chain, but that's it. This makes the lowest gear 30x36 (22.5 gear inches), 12.5% lower, and the highest 52x12 (117 gear inches). A downside is the excessive size of the rear cassette

Size of the cassette is not much of a downside, and anything else on your list is likely to cause you headaches. The issues can be worked out, but not without a lot more detailed information about what components you have.

Of course, if it were me, I'd not feel a need for an easier gear than 25 inches per revolution, but that's a personal thing.

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If you tour with a load, I suggest at least putting in a 22T ring up front. On loaded tour going up hill, in the rain, you have the greatest range of low gears. If present cost is a factor, this also reduces your chances of having to replace the chain.

If cost is not a problem, and you love to tour hilly country and you pack gear, the cost of a new chain, new cassette, and whatever it takes to get a 22T in front, IMO, is still pretty affordable. If your LBS has outrageous rates, they'll charge you more for labor than the approx $80USD in parts this new drivetrain will cost you.

On my Xtracycle, I run a 42-32-22/34-11 and I am frequently in 22/34 when I'm loaded up or on a hill. I might be hauling 60 extra pounds, but that 22 in front keeps me from killing myself and I rarely have to stand on my pedals.

I'm investing in a newer cargo bike, and I'm requesting it have a 9sp 42-32-22/36-11 setup. This is not a light bike, but I know I'll load it up. I could go lower if I wanted 10sp and get a 22/38T combo.

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Mountain derailleurs (which fit mountain gearing) are readily available. However, mountain and road derailleurs use different indexing, so you need a shifting adapter. John Allen, the person to whom Sheldon Brown passed the torch, so to speak, states on http://www.sheldonbrown.com/drivetrain-mixing.shtml#adapters about using a JTek Shiftmate pulley for correcting cable pull.

On JTek's site, they have two varieties of Shiftmate: the standard (for mixing SRAM, Shimano, and Campagnolo RD's and shifters), and the straight one (for mixing Campangolo, SRAM road, SRAM non-road, Shimano road, and Shimano mountain).

As your shifter is Tiagra and you're correcting the front shifting, you're going to want the Shiftmate Straight #7S in order to use a mountain FD.

Bike shops and distributors stocking JTek products can be found on http://jtekengineering.com/dealers.htm.

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There are a small number of “road” derailleurs which can handle a mountain crankset, but you’re correct that it’s much easier to find a mountain derailleur. I've proposed an edit to your answer to moderate the claim, but otherwise +1. –  Reid Jun 5 '12 at 4:37
    
And, if you notice, he is already using a mountain derailleur. He only needs a newer version of it fo more tooth capacity. –  zenbike Jun 5 '12 at 5:27
1  
@zenbike, no actually, it's a Sora which is a road group. –  Reid Jun 7 '12 at 4:54
    
But the rear is a Deore SGS, which is mountain bike. –  zenbike Jun 9 '12 at 3:09
    
The cable pull compatibility concern is with the front, though, which is what this answer addresses. –  Reid Jun 9 '12 at 16:09

For touring in the high mountains I use Tiagra STIs, a Tiagra 4503 front derailleur, a Deore M530 chainset set up with 48/32/22, an XT M761 rear derailleur and an XT 11-34 cassette.

Having the FD high enough for the 48T ring means that it won't shift into the granny from the middle when in sprockets 6-9 on the rear, but otherwise this combination works fine.

I haven't found this to be a problematic restriction since if I need the granny I am probably in the lower range of the cassette already, so on a long tour I might accidently leave it in too high a sprocket say 2-3 times. Note that with a 44T ring the derailleur works fine.

So my advice would be to get an MTB chainset and BB, and move the FD down and it should work fine. Depending on the chainline of the chainset (usually 50mm for MTB versus 43-45mm for a road triple), you might need to shim out the FD on the drive side of the seat tube so that the reach is correct for the chainset.

PS: I use the 48T when trying to set my personal speed records down steep mountains, and this is just too much fun to sacrifice (currently 54.2 mph). For normal flat cruising with my preferred cadence however, the 32T middle puts the chain right in the middle of the cassette.

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I have a touring bike with a 48-34-24 chain ring combination and a older Ultegra front derailleur and it shifts quite well. If you are concerned about the front derailleur, IRD makes a front derailleur called the Alpina-D that is optimized for a 48-36-24 and works with standard Shimano shifters. (I've not used it but I've looked at it.)

Follow-up: I recently rebuilt my bike and installed and IRD Alpina-D front derailleur. The front shifting did improve. The different profile of the cage made shifting and adjustment easier.

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The Shimano Deore LX will handle 44/32/22. –  Daniel R Hicks Jun 5 '12 at 0:15
1  
IIRC, most mountain bike front derailleurs aren't compatible with road-style shifters unless you use an adapter like the JTek Shiftmate's listed above. I skimmed through Shimano's website and didn't see one listed but I may have missed it. The IRD FD is designed to work with road shifters and work with a "compact triple". –  casevh Jun 5 '12 at 3:53

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