joel2old

I have a soma double cross that I use for touring and I pull a BoB. It has a shimano compact 50-34 crank with a 10 speed Ird 11-34 cassette with a rear long cage shimano derailleur. This setup as worked great for the tours I have done but I have not yet hit the big boys of the Rockies(also I am getting older). I would like to be able to put a triple crank on bike for the harder tours that I hope to ride someday. What do I need to get and do? What gear ratio, brand? Do I need a new front derailleur(have a double on bike)? Will the 11-34 cassette work with a triple? All help welcomed.

Lawrence08648

Unless it's a MTB rear derailleur, it won't work with a 34. It will work with a 28 and some have said it works with a 30 and unless your front shifter is a combo double/triple, you'll need a new front shifter and I believe a new front derailleur also.

JiveTurkey

The OPs already using a 34t cassette.

As mentioned above, going to a triple will require a triple-specific FD and possibly a new shifter.

Try a touring/trekking triple like a 48/38/26T (or similar) crank. This setup should work with a road triple front derailleur.

If you go much smaller like a standard 44/32/22T MTB crank, a road FD may not work as well. Unfortunately, Shimano road and MTB FDs use different ratios.

If your front shifter is friction (bar-ends?), you can pretty much run any crank and matching FD.

joel2old

Quote"The OPs already using a 34t cassette. "

Yes the 34t cassette does work with setup

Quote"As mentioned above, going to a triple will require a triple-specific FD and possibly a new shifter."

I want to avoid changing shifter , changeing FD would be ok

Quote"Try a touring/trekking triple like a 48/38/26T (or similar) crank. This setup should work with a road triple front derailleur.

Who makes this type of crank and where to buy?



Quote"If your front shifter is friction (bar-ends?), you can pretty much run any crank and matching FD.[/QUOTE]

Shimano 10 speed STI


I want to make this as simple of a change over as I can so I will be able to go back and forth wtih cranks.

Camilo

What's the model number of your STI shifter? Look it up on the Shimano website and see if it's double-triple.

joel2old

Its a double!

JiveTurkey

To use a triple crank, you will need a triple shifter; no way around that.

How about using a 48/36/26T trekking crank and just not using the outer position? Either replace it with a chain guard or remove it and install shorter single-speed/BMX chainring bolts. Perhaps the current FD can be lowered.

Look at Shimano's MTB line, such as SLX or XT. You should find a 44/32/22T and 48/36/26T version (or close to those tooth counts).

This may be a tall order.

ClarkinHawaii

I started with a bike with 105 brifters, 105 front and rear derails, 34-50 compact crankset and 11-25 cassette. The left brifter (5600?) works equally well on double or triple.

I'm now running 105 triple front derail, xtr long cage rear derail, 105 triple crankset with inner ring changed from 30t to 24t, and 11-34 IRD elite cassette. Not the fastest and smoothest setup in the world, but good enough for recreational cycling.

joejack951

Are you sure? Simply because your crank is a double does not mean that your shifter is. Many 105 equipped bikes used double/triple compatible STIs. If that's the case for your bike, a triple crankset (and appropriate bottom bracket), triple front derailler, and possibly a long cage MTB rear derailler (only if you are using a medium cage MTB rear derailler now) should do the trick. Swapping back to the compact would require changing cranks only then making a bunch of adjustments to the front derailler. Why would you want to do this?

joel2old

The bike setup works great for riding around home and on the tours I have taken. When I do the big hills in my future I want the gears that I will need. When that ends I want to go back to originnal setup if possibble.

JiveTurkey

OK, here's an idea. Get yourself a road triple FD and triple shifter (if yours is not already triple-compatible). Replace the crank with a 5-bolt 110/74 BCD and put on your current 50/34 rings and a 24, 26, 28, or 30T on the inside.

110/74 was a very common mountain bike crank BCD. 110 almost died till the road compact revived it.

Here' are some cranks: https://www.google.com/products?q=110%2F74+crank&aq=f
And 74 BCD chainrings: https://www.sheldonbrown.com/harris/chainrings/74.html

You can have the 50/34 you're used to and have the bailout gear. No need to swap out cranks and mess with the FD depending on the ride.

Potential issues:

I think the FD will best handle a 28T or bigger inner ring as road triple FDs are rated for a max spread of 22T between smallest and largest rings. However, this is exceeded all the time. Sheldon recommends opening up the Low limit screw a bit and using a chain stopper to prevent the chain from derailing onto your bottom bracket: https://www.sheldonbrown.com/harris/d...tml#deflectors

Also, a long cage (SGS) MTB RD RD has a wrap capacity of 45T, so if there's already a difference in the rear of 23T (34 minus 11), then the front can only have a 22T difference (50 minus 28). However, the wrap capacity can be exceeded as long as you size the chain using the largest chainring and largest cog plus one inch method, and don't use the small chainring with the smallest few cogs (why would you?), then it should work.

Since your current 34T ring is meant for an inner and not middle position, it lacks ramps/pins to aid in upshifting. It should still work okay (people used chainrings without shift aids for a long time), or replace it with a middle-specific ring, like this T.A. ring: https://www.sheldonbrown.com/harris/c...gs/110.html#34

LeeG

get rid of that 50t chainring. all it's doing is requiring your rear derailleur to take up more chain so you can have very high gears that have no practical use for touring, especially leading a trailer down hill which is the only place you'd ever use a 50/11-15.

Chris_W

Post the model number of your shifter and people here will tell you whether it's already capable of operating a triple FD.

I would also recommend a 110 / 74 BCD triple crank. The Stronglight Impact is a solid model, as is Sugino.