smaller ring for touring?

[cindysue]

Hi folks,

I'm planning on riding to Santa Barbara late spring (mid June). I have a 52-42-30 triple chainring. I'm wondering if I should switch the third ring to a 24 tooth ring. I'll be carrying a loaded (35lbs?) trailer behind me.

Any comments/suggestions are appreciated. Thanks!

Cindy

[biker_james]

I think its a great plan. Its the simplest way to get the low gears you need, or at leat may need pulling the extra weight. Our touring bikes came with the road triple like yours. We changed the rings to get a 24/39/48, which makes the big ring much more usable, but the big thing is having low enough gears.

[valygrl]

Agree - I switched my gearing to 50/38/26 and 11-34, and I'm pretty happy with that.

[RussellSeaton]

My 1991 Trek 520 came with 50-45-28 gearing from the factory.  I had the shop switch the 28 inner ring to a 24 tooth ring as a condition of sale.  A few months later I found a loose 32 tooth rear cog and replaced the 28 tooth on the cassette with the 32.  The bike came with a 12-28 7 speed cassette.  I was mighty glad to have a 24x32 low gear in the European mountains.

Assuming you have a mountain bike rear derailleur with a longer cage than the road bike triple rear derailleurs, and do not use the smallest cogs with the inner chainring, the derailleur should wrap up the chain and not let it sag loose.

About the only problem is when you switch to the inner ring from the middle ring, it will be a large change and you will have to be ready for it.  With a 30 tooth inner ring, I notice many people just dropping from the middle to the inner ring and not really noticing much because the change is not too large.  But with a 42 to 24 drop, you will have to be ready for the much less pedal resistance and will have to shift down 3-4 gears or so in back to continue a linear gear progression.

[damselfli]

Anyone switch gears using a 10spd shimano?
Do you have to use barcon shifters?

Valygrl, you have 50/38/26 - can you elaborate who makes your gearing, shifters etc?

Thanks.

[DaveB]

I've never switched the granny ring on a 10-speed but I've done it successfully on 7, 8 and 9-speed drive trains using a 26T in place of the stock 30T.  I see no reason it won't work on 10-speed.  STI's work just fine with this setup and barcons, which will also work, aren't needed.


Switching just the granny ring is relatively cheap.  Switching the middle and big rings can be very pricey and will approach the cost of a new crank.  

[FredHiltz]

Chainrings run $15 - $25 at http://thethirdhand.com/, somewhat more at your local bike shop. Cranksets run about ten times that.

Fred Hiltz

[DaveB]

Chainrings run $15 - $25 at http://thethirdhand.com/, somewhat more at your local bike shop..

That's for old-style flat (read: poor shifting and won't work properly with indexing) chainrings for 8-speed or older cranks. The newer ramped type, particularly 9 or 10-speed, rings are much more expensive.   Even so you are into a $50 expense for obsolete rings.

Cranksets run about ten times that.

No they don't unless you insist on the latest carbon type.  Nashbar currently lists a Shimano Ultegra triple 9-speed crank (will work fine with 10-speed) for $99 and a housebrand triple "touring" crank (48/38/28 rings, 110 mm BCD) for $75. They also show a 9-speed Shimano LX MTB crank, (44/32/22 rings) complete with the newest type outboard bearing bottom bracket for $162.

[valygrl]

damselfli,

It's a Trek 520, Shimano 9spd barcons

Front:
Shimano 105 cranks (stock) with replacement rings - the rings were recently Vuelta brand (6000 miles, actually that was 50-39-26) but I just switched the middle and inner rings to Salsa's (300 miles so far, no problems).  I didn't need the ramp and pin rings, b/c it's friction shift in front.  

Back:
LX 9spd derailler, now with a SRAM 9spd cassette (from Performance) and SRAM chain.  Before that, it was the original (shimano?) chain with a cassette purchased in New Zealand, think it might have been a Shimano LX 9spd.

[DaveB]

I didn't need the ramp and pin rings, b/c it's friction shift in front.

I agree you don't need ramped and pinned rings with friction shifting but they certainly improve shifting, particularly under load.  Two examples:

I have a beater bike with an old Suguino crank and the flat chainrings that came on it.  It has barcon shifters and the front shifting is poor, as it always was before indexing came along and we knew better. And, yes, the front derailleur is a modern design in good condition.

I also have a second bike with a newer Deore LX crank with modern configured rings that also has a barcon (friction) front shifter.  The shifting performance is night and day better.  

My conclusion is shaped rings greatly improve front  shifting no matter what shifters you use. They are essential with indexing but a tremendous benefit even with friction shifters.    

[driftlessregion]

I switched my 30 for a 24 last summer before hitting the mountains. It worked great but sometimes the chain would over shoot the 24 on downshifts using STI. I quickly found that with a device that looks like a big thumb attached to the seat tube below the front der no problems with the chain overshooting the ring. I'm sorry that I can't remember the name of the "thumb"; maybe someone else does.

[RussellSeaton]

Switching the inner chainring on a triple crankset from the factory 30 tooth to a much smaller 24 tooth can be done with few or no changes to the bike.  And no to minimal changes in shifting.  Assuming its a "road" triple crankset, it will use the 74mm bolt circle diameter for the inner chainring.  You can buy this size inner chainring for $5-$10 mail order.  No reason to pay for a name brand.  There are never, ever any shifting ramps on inner chainrings because the chain just falls onto the top of this inner chainring or gets lifted off the top to go to the middle chainring.  The inside side of the middle and outer chainring may have shifting ramps to improve shifting.

The only changes you may need is the rear derailleur.  The "mountain" bike rear derailleur will have a longer cage so it can wrap more chain and keep it taut in more gears.  If you use the inner chainring, 24 tooth, with the smaller cogs in back, the chain will hang loose.  The longer cage "mountain" bike rear derailleur will keep the chain taut in more of the smaller cogs.  Whether the chain hangs loose is not really a big concern, but its possible a loose hanging chain could get wrapped around something or jump off the pulleys.  In reality you most likely will only use the inner chainring with the bigger cogs on the cassette when climbing steep grades so the hanging chain will never really materialize.  But something to keep in mind.

STI shifters slam the chain from the middle to inner chainring in one rapid movement.  No finesse to them.  Bar end shifters and Ergo shifters have several ratchets that allow you to slowly move the chain down to the inner chainring.  With STI's rapid forceful shifting style, it is likely you will drop the chain onto the bottom bracket shell more often.  Particularly with a smaller inner ring because the chain has more free air to fall in before it hits the top of the inner ring.

To prevent dropping the chain, get a Third Eye chain watcher.  Or the N Gear Jump Stop chain watcher.  I use them on all of my bikes, except the fixed gear of course.  Cheap insurance to protect the paint from being chewed up by the chain if you drop the chain.  Below are some links to the devices.

http://www.bikepro.com/products/chains/chainretainer.html

http://www.peterwhitecycles.com/accessories.asp

http://www.cambriabike.com/ShopDisplayProducts.asp?ID=20&cat=Chain+Guides/Transit/Protctrs

http://sheldonbrown.com/harris/chains.html#deflectors

[cindysue]

thanks everyone. Ye, it is a road triple w/STI and a long cage in the rear. The freewheel is 12-25, 9 speed.

[damselfli]

cindysue,
be glad you don't have a 10 speed!

i am still working on a fix for my gearing.
you can read more (on second page) about changing out the gearing here:
http://www.adventurecycling.org/forums/viewmessages.cfm?forum=6&topic=382

[cindysue]

Thanks Damselfli,

I'd be heartbroken if my LBS called and said they couldn't get the part. So far, so good. MY LBS is ordering a Shimano XT Derailler, 12-34 cassette, and new chain. I'll keep my 52-42-30 chainring.

Based on the post you referred me too, it sounds like the shifters will work best with this set-up. Thanks for all your input!

Cheers! Cindy  

P.S. Turns out I could have saved $70 bucks if I ordered the parts from nashbar.com