Converting a Ultegra compact to triple

[kris5006]

Hi everyone
I am currently in the process of buying a new CX bike with a compact chainring (46:39) and Ultegra groupset. As I plan on doing a pretty hilly touring event in September (with a trailer), I think it might be a good idea to convert the crank to a triple. If i did this, would I have to change the front and rear deraileur, and chain, as well as the STIs? I've had a good look at Shimano's website, and it seems to me like there are specific shifters for double and triples in the case of Ultegra. Please, tell me i'm wrong! I really don't wanna spend AU$250 by replacing a new STI with... another brand new one if it isn't necessary at all. Alternatively, I could install bar-ends, but I just loved the 105 STIs on my old bike.

Advice seriously needed, my wallet depends on it

 

[JohnO]

Going triple to double is fairly cheap. Going double to triple is pricey, as you replace not only the crankset and BB but shifters as well. Derailleur might already have enough of a cage to handle a triple. Chain may or may not have to be replaced. Shimano bites you on the STI's - last time I looked, they don't sell individuals so you have to buy both.

If you haven't already bought the bike, you might want to think about buying a bike that already has a triple setup on it. A lot cheaper.

 

[Camilo]

Hi everyone
I am currently in the process of buying a new CX bike with a compact chainring (46:39) and Ultegra groupset. As I plan on doing a pretty hilly touring event in September (with a trailer), I think it might be a good idea to convert the crank to a triple. If i did this, would I have to change the front and rear deraileur, and chain, as well as the STIs? I've had a good look at Shimano's website, and it seems to me like there are specific shifters for double and triples in the case of Ultegra. Please, tell me i'm wrong! I really don't wanna spend AU$250 by replacing a new STI with... another brand new one if it isn't necessary at all. Alternatively, I could install bar-ends, but I just loved the 105 STIs on my old bike.

Advice seriously needed, my wallet depends on it

If you think you need a bike with triple, WHY would you buy a NEW double planning to convert it? It will cost you money for sure - but buying a triple now would not be any meaningful price difference than a double in the same bike.

 

[thomas_cho]

If you think you need a bike with triple, WHY would you buy a NEW double planning to convert it? It will cost you money for sure - but buying a triple now would not be any meaningful price difference than a double in the same bike.

The OP probably did not purchase the bike to specifically and primarily ride the hilly tour, at least I am hoping that you did not.

So what is your reason for getting a CX bike? Is it for doing cyclo cross events?

That gearing (46/39) does not give you additional climbing gears over a standard 53/39 chainring. You have a lower top end speed, but your lower gearing still remains the same. A more common compact gearing would be 50/34.

Touring bikes, road bikes, cyclo-cross bikes all have a different focus, and are set up accordingly. If you were after a touring specific bike, you would be best to thinking about your lower climbing gears rather than your top gearing. Shimano 105 shifters are double/triple compatible. Ultegra and up, you need specific shfiter to do the triple chainring. It is an expensive affair to convert your bike to a triple, you would have to swap out the shfiter, crankset, chain, FD, RD. Thats almost a whole new groupset (just less the brakeset). Better off buying a touring specific bike.

FWIW, touring bikes also have longer wheelbase for more stable loaded riding, and have all the rack lugs you need to mount rear racks, front racks, etc.

 

[alfeng]

I am currently in the process of buying a new CX bike with a compact chainring (46:39) and Ultegra groupset. As I plan on doing a pretty hilly touring event in September (with a trailer), I think it might be a good idea to convert the crank to a triple. If i did this, would I have to change the front and rear deraileur, and chain, as well as the STIs? I've had a good look at Shimano's website, and it seems to me like there are specific shifters for double and triples in the case of Ultegra. Please, tell me i'm wrong! I really don't wanna spend AU$250 by replacing a new STI with... another brand new one if it isn't necessary at all. Alternatively, I could install bar-ends, but I just loved the 105 STIs on my old bike.

Advice seriously needed, my wallet depends on it

Regardless of whether you have a 9-or-10 speed Shimano, consider this -- a 9-speed XTR 950/952 SGS rear derailleur + 11-32 or 12-34 cassette ... that should give you sufficiently low gearing ... you could also swap the 39t inner chainring for a 38t. An XT 750 rear derailleur OR LX equivaent (i.e., standard rise) will also work.

The 9-speed XTR rear derailleur can be interchanged with any 9-speed Shimano ROAD rear derailleur.

To use the Shimano MTB rear derailleurs with a set of 10-speed shifter & a 10-speed cassette (!?!) you will want to use the hubbub.com alternate anchor position which, by my reckoning, makes the rear derailleur equivalent to a 10-speed Shimano rear deraillur (I only did a 2-minute non-road test on a workstand).

You will want a longer chain ... depending on the length of the current chain.

If you have a MTB, you can "borrow"/cannibalize the parts for the hilly rides!

 

[Retro Grouch]

Advice seriously needed, my wallet depends on it

Sounds to me like you're looking for the cheapest solution.

9 or 10 speed cassette? Shimano has different shifters for double or triple chainrings with 10-speed cassettes but specs the exact same part number if you have a 9-speed cassette.

Shimano recommends a long cage rear derailleur for bikes with triple chainrings to take up the chain slack in every potential gear combination. Since you never use the smallest cogs with the granny chainring you could get by with the same derailleur that you have now.

A front derailleur that's designed for double crankset use won't shift as nicely as one that's designed for a triple, but you will probably be able to get by in a pinch. If you only wanted to buy 1 derailleur, I'd get the front because STI triples can be touchy to set up even when all of the parts match.

There are some other, cheaper, ways to get a hill climb gear that's almost as low as is offered by a triple crankset. Replacing your 39 chainring with a 34 (if you have a 110mm bolt circle) would probably be the cheapest and easiest. Using a mountain bike rear cassette and derailleur would be another option.