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Triple to a compact double.

It's time for my next pointless project. I want to change my triple to a compact double. How hard and expensive would this project be. Is it possible to do only replacing the crank?


marvelousm3
2012-01-20 00:29:23

It might be possible by just removing your inner ring depending on what size rings you have.


Or it might get expensive, like switching cranks and your left shifter body.


Perhaps somewhere in between.


bradq
2012-01-20 01:14:18

I never even thought of just removing the granny gear, didn't even know it was possible. I'm guessing I would need a smaller chain... maybe?


marvelousm3
2012-01-20 01:17:51

Hardly worth just pulling off a granny gear, not really saving much in the way of weight.


What crank/chainring sizes do you have now?


eric
2012-01-20 01:25:19

Not trying to save weight I just don't need or want the granny anymore. 50/39/30 I think that is what you are asking. Also I think I just would prefer a double.


marvelousm3
2012-01-20 01:29:19

When I was younger I was really into tricking out cars. Now I like upgrading my Portland. I have no good reason but I just like to keep upgrading it. And now I have a plain 4 door Subaru that sits in my garage because I would rather ride than drive.


marvelousm3
2012-01-20 01:34:20

@Eric, the main point (I believe) is to change the chain-line since mr marvelous cuts through chains and cassettes like butter.




He's using a 50-39-30t tripple.

Interestingly, the 2006 model Portland came with a double.


headloss
2012-01-20 01:42:58

@ headloss you are correct.


marvelousm3
2012-01-20 01:43:51

Personally, I think the typical compact double (50-34) is quite good for riding on PGH terrain. Some folks even drop the big ring down to 48 or so (which is fine if you aren't racing, and probably even if you are). If you do mega-long, mega-hilly rides, the granny is a nice backup, though.


bjanaszek
2012-01-20 01:49:52

Brad Q, why would you need to change shifter levers ? Even if it's a triple lever can't you just lock out the last shift and still use it?


I'm guessing you could just swap out the crank and be done with it.


You probably have a long cage rear der. You'll get a lot of slap with a double but if you cut the chain down a bit that will minimize it. Shouldn't be too much of an issue anyways, that's more of an off road issue.


mayhew
2012-01-20 01:53:51

The cheapest swap is to take off the granny as Brad suggests, however that requires that you find a 74 BCD (Bolt Circle Diameter) ring with 34 or 39 teeth (depending on your preference) to replace the granny with and move the big ring over one.


You're probably better off just finding a good deal on a new crankset but it doesn't hurt to shop around and see what you can find. With a 50-39 set up, your derailleur should be fine (you just need to have it's limits adjusted). If you go 50-34, you might need a different front derailleur (I know that they make a special derailleur for the "compact doubles" as they are called, but I'm not sure if they are necessary for such a setup). I don't imagine that you would need to swap shifters unless you change the brand of your front derailleur... but I could be wrong.


The next upgrade would be a short or medium cage derailleur on the back since you won't need the long cage anymore ;)

Shorter cage = better shifting.


headloss
2012-01-20 01:56:00

This can get complicated. If you are OK with 50-39 hearing, go ahead and pull the granny gear off, and shorten the chain if you want. You should be able to adjust the front derailleur to work with a just 2 rings, I've done it a few times with no problem. And going "by the book" you should use the second and third potions on your shifter, the cable pull is usually different between the granny-middle and middle-big.


If you want to make the switch to a compact double (50-34) you'll need to do a few more things. Your current crank probably can't fit anything smaller than a 38 tooth ring in the middle position and a bigger rings on the inner position may hit the chainstay, so you'll need a new crank, which may or may not need a new BB too. A proper double front derailleur will help with shifting, as will a double front shifter (or use the 2nd and 3rd position).


You can also switch to a short cage rear derailleur, and lop off some chain links.


eric
2012-01-20 01:57:51

I'm under the impression that for different STI or Ergo levers some have a combined double/triple version and some have specific double or triple versions. Correct? Maybe I'm mistaken, I didn't look it up.


I know for some it works just fine locking out the derailleur movements with the limit screws, but given the lack of trim on certain levers I guess I could see it being an issue.


I don't know what is on the bike in question.


bradq
2012-01-20 02:01:12

SRAM-no triple option


Shimano-separate shifters for double and triple use.


Campy-no clue, probably not relevant to the discussion


I'm assuming Shimano shifters, and in practice I've managed to make Shimano triple shifters work OK on all kinds of bodged together doubles, it really depends on a whole host of stuff and how willing you are to put up with not perfect shifting.


eric
2012-01-20 02:12:27

I don't know what exactly is on the bike myself, I'm not very technical. My LBS told my I should be able to use my current shifters but my need to replace the front derailleur. If I only need to replace the crank set and front derailleur this hopefully will be an inexpensive easy swap. But then again thats what I was hoping for my rim project.


marvelousm3
2012-01-20 02:19:22

Not sure about the double vs triple specific shifter, but on the bright side the front brifters are always cheaper to pick up than the rear ones! :P

I think it's more of an issue of, what size is the jump from big ring to small ring than it is about it being a double or triple though... at least from a "how willing you are to put up with not perfect shifting" perspective.

I'm really out of my league on this one though as I'm new to roadbikes. What year is your Portland?


headloss
2012-01-20 02:30:00

2008 it sat on the shelf at Trek for 3 years.


marvelousm3
2012-01-20 02:33:17

I ran an Ultegra triple brifter with a compact double without (too much) trouble. You may want to add a chain watcher, though.


bjanaszek
2012-01-20 02:57:36

"it sat on the shelf at Trek for 3 years."


The best bikes always do! I think price plays a role and they clearly weren't selling a lot of Portlands considering that they quit building them. :( Great bike though! Just too bad Trek likes to charge too much for all of their offerings relative to the competition.


headloss
2012-01-20 03:08:21

I love Trek bikes but not their pricing. If the bike hadn't sat on the shelf for 3 years I wouldn't have been able to buy it. The really wanted to get it sold


marvelousm3
2012-01-20 03:33:47

shouldn't he consider a different bottom bracket for optimal chainline?


I am of the opinion that of all things, you can keep your front derailleur, just set the limit screws so it can't shift down out of the lower chainring.


dmtroyer
2012-01-20 03:43:12

http://www.ebay.com/itm/105-Shimano-Compatible-FSA-Double-Crankset-172-5-Compact-50-34-/130631341202?pt=Cycling_Parts_Accessories&hash=item1e6a3c1492

Is it the Shimano 105 on there? 2 bolts, slide out the triple, slide in the double. Don't even need to change the bottom bracket, with the external type bb's, the chainline alignment is built into the right crank.

And a triple front d should work with a compact double, though a standard road front d (probably) wouldn't work with a triple or compact double, not enough length on the cage. You would use the limit screws to set your shifting to double.


edmonds59
2012-01-20 04:48:38

Not to put ya on the spot Mr. M , but I'd keep it as a triple and learn better shifting technique to keep the chain line straight. At some point you become the golfer who just keeps buying more expensive clubs instead of investing in a couple of lessons.


There might be advantages to having a compact double over a triple – I don’t know enough to have an opinion. But learning to use the equipment you have correctly is probably more important than “I want to buy this new shiny thing” in my opinion. And if going up the hills is getting tough, well rule 5.


But seriously, figure out how the gear ratios overlap from ring to ring. Print it out and tape it to the handlebars for a while if it helps you keep track of the pattern. Look at the ratio that you most often use & how close you can match it on the other rings. If you go ‘up’ one on the front does that equal going down ‘two’ on the back? Using gear inches as the measure is probably the easiest way to compare different front/back combos.


Take the time to learn. In the end you’ll be a better cyclist regardless of the equipment you have because you’ll understand how the bike works.


marko82
2012-01-20 05:16:08

And going "by the book" you should use the second and third potions on your shifter, the cable pull is usually different between the granny-middle and middle-big.


Whoa, you learn something new every day. I always setup the triple on the bottom two, which sometimes lets you ghost shift into the "3rd" ring, which really does nothing but stretch your cable. Good to know, thanks!


In my opinion, triples aren't necessary in today's world with wide range cassettes. Double cranks simplify the system greatly, not just mechanically, but mentally as well.


rice-rocket
2012-01-20 05:58:05

@ rice rocket In my opinion, triples aren't necessary in today's world with wide range cassettes.


I go from about 20 gear-inches to about 108 with my triple ring. Can you do that with a double? (Not trying to be argumentative, here. I'm curious.)


mick
2012-01-20 06:15:45

Or, wide range cassettes aren't necessary when you have a triple. :-)


If Mr. Marv truly doesn't use the small ring now what's the point of changing to a compact double? i.e. if 39 is all he needs why bother with a 34?


salty
2012-01-20 06:38:00

I go from about 20 gear-inches to about 108 with my triple ring. Can you do that with a double? (Not trying to be argumentative, here. I'm curious.)



I used a compact double 50/34 and a 11-34 9-speed cassette on my g/f's bike, which is 26.3 to 119.7 gear inches. If you dropped to a mountain double (44/29? I'm not sure what's "standard"), that's 22.4 to 105.2 G.I. Go to a 11-36 cassette for an even wider range if you want.


Less overlap, less combinations, less "bad" combinations, less confusion. Just my opinion though. The only drawback I see in wide range cassettes is larger jumps between shifts. I'm not one to look for the perfect cadence/wattage combination though, I don't think our terrain/winds stay steady enough for that. I run a 10-speed 11-28 on my personal bike, and think it's a good compromise between huge jumps and gear range.


rice-rocket
2012-01-20 06:51:16

@ marko you just put a big smile on mrs. marvelous's face. She completely agrees with you. You are right I do need to learn how to shift better, it just sounds more fun buying the shiny new thing. I probably will do both learn how to shift and buy a compact double. I do have a question do the stronger riders on the board still use the granny? I just wonder if the strongest riders still use it maybe I should keep it.


marvelousm3
2012-01-20 11:47:41

^Ha ha, I forgot that Mrs. Marv also reads the board.


wow, that's a little wider than my current triple - I would def consider this option on my next bike, but I'll leave the current bike as is.


marko82
2012-01-20 13:49:22

Ok, so as a staring point use the chart below. I made an assumption that your cranks are 172.5 since I'm not certain, but since the gears are all relative to one another anyways, it doesn't really matter for the sake of this exercise.


I'm not an expert so I welcome any criticism on my selection for the Portland's gears. Deeper Red is an absolute no. Medium Red is avoid. Orange is transition. Green is go!




headloss
2012-01-20 14:07:37

You'll probably be happier with a double. Personally I'd prefer 50/36 to 50/34 because of the smaller jump, but it's a little harder to find rings in that combination.


The triple STI shifter is almost certainly ok to use on a double.


I would definitely replace the front derailleur like the shop suggested. Most are only designed to work with a relatively small gap (like 12t) between the big and little ring. You might be able to make it work but probably not that well.


If your crankset is internal bearing you'll also need to change the bottom bracket to one with a shorter spindle, but most newer cranksets are external bearing (integrated spindle) so you probably don't have to worry about that. But when shopping for a new crankset either get one of the same kind (GXP, Hollowtech) or you'll need to buy the matching bottom bracket anyway.


johnwheffner
2012-01-20 14:13:28

Not sure what you're getting at John. Right now he has a der more or less designed for a compact (50/39/30) so the issue of gaps between the chainrings is more or less a non issue.


Speaking from experience a front der designed for 130bcd works just fine with 110 bcd.


Concur on the 36 vs 34. The lower gear is nice but requires three shifts down on the rear when you move from outer to inner.


mayhew
2012-01-20 14:32:23

Triple FD's are often matched to a specific set of rings for whatever that group had, and usually have a smallish gap between the top two (he has 11t right now). Going to 14t or more likely 16t with a compact double may have troubles.


johnwheffner
2012-01-20 14:50:23

Mr M- It's better to have it and not need it than need it and not have it.

Take your bike over to any of the dirty dozen hills and ride up a few times before you make the decision to abandon your granny.


helen-s
2012-01-20 15:32:32

I converted my '08 Kona Kapu from a double to a triple, involved the crank, triple front D, long cage rear D, and brifters. Expensive. But I so needed the granny. Shifting is just not as clean with the triple as with the double, even adjusted within an nth of its life.


edmonds59
2012-01-20 15:45:21

Mr. Marvelous, I would leave your bike as is and just buy a new bike with a compact double. After you purchase a decent crank, detailers, chain, & cassette you are halfway to the cost of a new bike. You almost have to buy a new gruppo to do it properly.


Plus it provides the opportunity to justify the need for multiple bikes!


greasefoot
2012-01-20 16:00:34

Best advice, but Mrs. Marv is coming after you.


edmonds59
2012-01-20 16:09:37

@ mr marvelous, I say enjoy your new rims and learn how to shift. Save your money to buy me a new road bike with a compact double


mrs-marvelous
2012-01-20 16:11:48

Save your money to buy me a new road bike with a compact double

She's a keeper, mr. m.


reddan
2012-01-20 16:15:28

@john and chris - Triple FDs are a slightly different shape. It's more problematic going to a triple with a double FD than vice versa, but front derailleurs are relatively cheap. The shaping allows for less chain rub in certain gear combos. A triple FD's cage sits a little lower on the back side so it can push the chain with a little more force when making the shift. But a FD is cheap. Just change it.


Best argument for a double is better shifting.


There are a couple years where Shimano did a double/triple lever (105 level at least). That didn't last. Everything now has a triple and double specific version. The old 105 (first gen of 10 sp) shifters that did both are notorious for breaking. If the cable went just a hair slack and you accidentally shifted into the third detent, the shifter jammed and broke. They still warranty them, but the went back to double and specific ones after that.


The problem with Eric's suggestion of using the 2 and 3rd clicks is that you can still shift the lever into the first click. Puts a lot of slack into the cable. If you go the other way, the last click will be blocked by the limit (assuming cable tension is adequate).


The moral of the story is use the the right parts and you will have less problems and less chances for things to go wrong.


steve-k
2012-01-20 16:52:42

The other moral of the story: for mechanical advice go to a shop not the bike-pgh board.


johnwheffner
2012-01-20 17:25:25

"The other moral of the story: for mechanical advice go to a shop not the bike-pgh board."


Yessir.


bradq
2012-01-20 17:26:43

Hellen S Take your bike over to any of the dirty dozen hills and ride up a few times before you make the decision to abandon your granny.


+1


Also, there are gears that you won't use -ever- when you are buffed, that come in handy when you couch-potatoed for a few months.


I'm at an age where I hesitate to put Granny on the ice flow. Ever.


mick
2012-01-20 17:39:07

I come to the board before the bike shop to gain a little knowledge before I go into the shop. The board helped me save a good bit of money building my rims, one unnamed very popular bike shop wanted to over charge me and offered me hubs that cost three times more as the ones the board recommended.


marvelousm3
2012-01-20 17:45:23

@ mrs. marvelous um.... ok you get a road bike but not a Cervelo S5, maybe something a little cheaper and I'LL get the Cervelo.

(edit) I really should pay attention to class and not the message board.


marvelousm3
2012-01-20 17:47:21

I'm totally on board with asking around before going to a shop. My guess is if you go to 10 shops you'll get 10 responses to the same question, from "why do you want to do that?" to "we can do that, you have to change everything on the bike. That'll be $1,000.". It's a coin toss anyway. I've even had Gerry K give me dubious solutions to projects I was working on. Bikes aren't that complicated, or expensive, in the relative scheme of things, if you try something and it doesn't work, keep working on it.


edmonds59
2012-01-22 03:06:42

"Bikes aren't that complicated, or expensive, in the relative scheme of things."


Considering that every major repair on my car would be enough $$$ to buy another bike, I tend to agree!


headloss
2012-01-22 04:25:05