Author Topic: Swapping compact crankset for triple. Some help with parts selection needed.  (Read 18458 times)

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Offline rhainan

I set up my new Salsa Vaya Ti frameset with an existing complete Shimano 105 (5600) compact groupset from an old road bike.  My first 100 miles have made it clear that I miscalculated and will be needing a triple to get me and my gear up and over the hills of west PA.  I have spent the last ten years on sub-20 pound road bikes so I am in need of some adventure cycling education.

I have read that the 105-5600 STI shifters that I have on the bike now will handle both double and triple cranks.  If that is true, then I believe I will be needing to buy a new front derailleur and a new triple crankset.  I am tentatively planning on a Tiagra crank (50-39-30) and the matching Tiagra derailleur.  Will these new Tiagra components work with my circa 2008 105 shifters?  Also, will I need a Tiagra bottom bracket as well?

I was planning on going with Tiagra due to lower costs.  In ten years of cycling I have run a mix of 105, Ultegra and Dura-Ace cranks and FD's and I have not really noticed a heck of lot of difference between them.  Salsa is putting the Tiagra on their Vaya Ti build kit.

Do you think that this would be the most cost effective route to achive effective lower gearing?  My riding will run the gamut of loaded/unloaded and roads/trails.  My thoughts are to maybe switch out the 30 ring for a 26 or 24 if I still need to go lower.  I do not think I have much range on the rear cassette without going to a long cage derailleur.  I currently am running a 12-15.

Am I on the right track or am I way off base.  Any help or suggestions would be appreciated.  Thanks.

Offline Pat Lamb

I'd go look at some of the mountain bike cranks.  If you're looking to do loaded touring out of western Penna., I'd bet you'll want the lower gears (26, maybe 24, maybe even 22).  Ergo, something like a 48/36/26.  Add in a long-cage derailer, while you're at it, and an 11-32 or 11/34 cassette.  Just make sure your derailer is from a road group.

Offline waynemyer

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I'd go look at some of the mountain bike cranks.  If you're looking to do loaded touring out of western Penna., I'd bet you'll want the lower gears (26, maybe 24, maybe even 22).  Ergo, something like a 48/36/26.  Add in a long-cage derailer, while you're at it, and an 11-32 or 11/34 cassette.  Just make sure your derailer is from a road group.
What road derailleur has ~50T of capacity and can wrap a 34T cassette?
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Offline BrianW

He probably meant "Make sure your FD is from a road group" in order to work with the OP's STI levers.

Offline waynemyer

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He probably meant "Make sure your FD is from a road group" in order to work with the OP's STI levers.
Ah! You just totally dashed my hopes that someone makes a high-capacity road derailleur. You totally saved me hours of poring over Google searches.  ;D

I knew about the front derailleur compatibility issue, but the sentence order made me think that there was some other issue with rear derailleurs.
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Offline rhainan

Thanks for the replies.  Please forgive my ignorance but I don't have any touring friends or a local bike shop to get free advice from.

I am now looking at a more proper touring crankset.  Shimano seems to have a neat XT "trekking" crank that is 10 speed and features a 26/36/48.  However, it seems expensive and only available in Europe at the moment.  I have found the XT 9 speed with a 26/36/48 for about half the price.

If I went with the Deore XT 9 speed triple crank, would it be compatible with road specific components?  I am thinking of using my existing 105 shifters, adding a Tiagra triple FD and a long cage RD to handle a rear cassette of 11-34.

If all of these components work together would that seem to be a reasonable touring setup?

Thanks

Offline BrianW

With the capability to use MTB-type RDs with STI and any other levers, I don't see any reason to use road derailleurs on a touring bike. The 9-speed XT RDs ("Shadow" and regular) have a 45t capacity with the SGS long cage, which is pretty impressive. Even the 9-speed Deore M591 will handle the 45t wrap.

He probably meant "Make sure your FD is from a road group" in order to work with the OP's STI levers.
Ah! You just totally dashed my hopes that someone makes a high-capacity road derailleur. You totally saved me hours of poring over Google searches.  ;D

I knew about the front derailleur compatibility issue, but the sentence order made me think that there was some other issue with rear derailleurs.

Offline RussSeaton

More or less, any crankset will work with any derailleurs, chains, cassettes.  I have an old 7 speed crank with 9 speed rings on a 10 speed cassette/chain touring bike.  44 tooth outer chainring shifted by a 9 speed Tiagra road front derailleur.  In theory mountain bike front derailleurs are curved more to better line up with the smaller outer chainrings on mountain bike cranksets.  But in reality, it doesn't matter.  I suppose if you tried to shift 10 or 11 speed chains with 5 speed chainrings, you might have trouble.  So try to get the chainrings close to the chain size.  9-10-11 can be mixed between chainrings, chains, cassettes.  7-8-9 can be mixed.  About the only thing to make sure matches is cassette and chain.  If using a 7 speed cassette, use a 7 speed chain.  If using a 9 speed cassette, use a 9 speed chain.  If using a 10 speed cassette, use a 10 speed chain.

About the only incompatibility is with the newest 10 speed Shimano mountain bike rear derailleurs.  They do not work with road 10 speed STI shifters.  But older 9 speed mountain bike rear derailleurs work fine with road STI shifters of any gearing, 7-8-9-10.  Shimano 9 speed mountain bike rear derailleurs are really cheap, $20 Deore.  So no reason not to use one.  Low end Shimano front derailleurs, Sora, Tiagra, are also really cheap, $15.  So no reason not to use those either.

You've mentioned using your left front STI Shimano 105 shifter to shift a triple crankset.  It shifts a compact double crankset now.  I'm not so sure Shimano STI can shift both double and triple.  Shimano makes unique double and triple STI shifters in Ultegra and 105 models.  So I'm questioning whether your crankset change will be as smooth as you are implying.  I think you will need a new left STI shifter for the triple crankset.

Offline BrianW

9-speed Ultegra and 105 STI left levers will handle both double and triple cranks by default. The 9-speed Dura-Ace STIs do come in separate versions, though. I'm not sure whether Tiagra STIs can handle both.

You've mentioned using your left front STI Shimano 105 shifter to shift a triple crankset.  It shifts a compact double crankset now.  I'm not so sure Shimano STI can shift both double and triple.  Shimano makes unique double and triple STI shifters in Ultegra and 105 models.  So I'm questioning whether your crankset change will be as smooth as you are implying.  I think you will need a new left STI shifter for the triple crankset.

Offline rhainan

My investigations on the interweb lead me to believe that my 105 left shifter (5600 circa 2008) will handle double or triple chainrings.

I am now planning to go with:

Deore M590 9sp crank - 48/36/26
Deore M511 Front Derailleur
Deore M510 Rear Derailleur
9sp Chain
SRAM 11-34 9sp Cassette

Thanks again for all the help.

Offline DaveB

More or less, any crankset will work with any derailleurs, chains, cassettes.  I have an old 7 speed crank with 9 speed rings on a 10 speed cassette/chain touring bike.  44 tooth outer chainring shifted by a 9 speed Tiagra road front derailleur.  In theory mountain bike front derailleurs are curved more to better line up with the smaller outer chainrings on mountain bike cranksets.  But in reality, it doesn't matter.  I suppose if you tried to shift 10 or 11 speed chains with 5 speed chainrings, you might have trouble.  So try to get the chainrings close to the chain size.  9-10-11 can be mixed between chainrings, chains, cassettes.  7-8-9 can be mixed. 
This is correct for friction shifting which will work with almost anything.  Indexing isn't as tolerant.  Shimano MTB front derailleurs have different cable pull requirements from their road counterparts and won't index properly with road STI's.

About the only incompatibility is with the newest 10 speed Shimano mountain bike rear derailleurs.  They do not work with road 10 speed STI shifters.  But older 9 speed mountain bike rear derailleurs work fine with road STI shifters of any gearing, 7-8-9-10.  Shimano 9 speed mountain bike rear derailleurs are really cheap, $20 Deore.  So no reason not to use one.  Low end Shimano front derailleurs, Sora, Tiagra, are also really cheap, $15.  So no reason not to use those either.
+1 The newest 10-speed MTB rear derailleurs won't work properly with road 10-speed shifters.

Offline BrianW

Using a Deore FD with your 105 STI levers probably won't work. As others have noted, road levers have a different FD cable pull than MTB levers. A road FD like an Ultegra or Tiagra will work fine with the Deore cranks and chainrings you mention. It won't be quite as crisp-shifting as if you were using a road crank and stock rings, but will work fine. I have this setup on three of my bikes (Ultegra STI levers, Ultegra or Dura Ace FD, and 48-36-24 chainrings) and have no problems with it.

Look on Ebay for a used Ultegra triple FD and run that. Either get one with an integrated clamp or get a "braze-on" style model and a separate clamp to fit your seat tube.

Offline PeteJack

I can't address the finer points of derailers. I would urge you to get a 24 or 22 tooth granny. I have 50-39-24 and when you need that 24 you need it. As for derailer capacity I have a 12-32 on the rear with a Deore derailler (it works) on the back but I try to avoid riding with the 32 on the back with the 50 on the front. It does work but the chain seems awful tight and the cage is almost horizontal. Anyway you can get that ratio on the middle ring.

Offline DaveB

.....I try to avoid riding with the 32 on the back with the 50 on the front. It does work but the chain seems awful tight and the cage is almost horizontal. Anyway you can get that ratio on the middle ring.
The 50-32 combination is called cross chaining and avoiding it is a good idea as it's hard on the chain.  However, the chain length HAS to allow that big-big combination, even if you shouldn't use it.  A lapse of concentration or forgetting which chainring you are in can let you shift into to it and if the chain is too short, the damage can be anything from serious to catastrophic. It sounds like your chain is exactly the right length to just permit big-big and that's fine.

Offline PeteJack

Quote
The 50-32 combination is called cross chaining and avoiding it is a good idea as it's hard on the chain.  However, the chain length HAS to allow that big-big combination
Too true. I found this out the hard way. My chain seemed very slack on the 24T ring so I took a link out. Big mistake. I ended up locking the chain up on the Devils Incline just south of SF. The only way I could get enough slack in the chain to unjam it was by removing a derailer pulley. I had to do all this quite literally in the ditch, there is no shoulder. So live with what seems a slack chain on the granny, the amount of time you spend using it is minimal.