jabara572

HOLY CRAP THIS IS THE MECHANICS SECTION!!!! STFU WITH TRIPLE BASHING!!!!



bcart, in case you havnt gotten a real answer yet. No problems using the triple as a double. Most mid range cranksets have the same arms on both the triple and double models except that they have posts to mount the granny gear on triple models. Thus, the chainline would be identical. On your FSA model, a few mm wont matter. It would be shifting fine if you were using it with the granny gear as a triple. Simply taking off the granny doesnt move the other two gears, it will shift perfectly. Just set up your front derailer limits correctly, and ride on.

and yeah, for the record, triple road bikes look bad!!

bikefix

YO bcart. I'm a bike mechanic and a dedicated, lifelong, year-round road commuter. Currntly a student at WBI Pro-Bike Mechanics Course.

Removing the inner ring will be fine. Not recommended esp. since u said u can't adjust the BB cuz your chainline will not b ideal thus more d/train wear and more friction. Also, doesnt hurt to have it incase chain drops.

If removing it: U shld then adjust the Low limit screw by hand not shifter to go upto the mid-ring and then re-adjust the frnt shifting and barrel adjstr approx. 1 turn out.

Adjusting the actual chainline is the absolute last resort (it requires an extensive process)!

Pls. lemme know how it works out.

slim_77

When I replaced my triple with a double last year that is exactly what I did. Works fine.

Zouf

The cons of turning a triple into double:
1. The left brifter will be more tricky to use, since it will try to shift the FD, which will be stopped by the limit screw. So you'll get "empty clicks" at the end of travel.
2. The chainline will likely be off (a triple is usually setup with middle gear centered on middle of cassette, while a double usually centers the halfway point between chainrings on the middle of the cassette). Depending on how good/bad the chainline was to start with, and on chainstay length, this may/may not be a problem.
3. Chainring gearing is not usually the same for triples than doubles, i.e. middle gear tends to be 42-44T, which is high for a small chainring - but you seem to indicate this is not the case for your installation.

Apart from that, disregard the "don't do it", "why do it" crowd - who cares, it's your bike. The time spent ranting useless info in forums is inversely proportional to the time spent having a life, in genenral.

jabara572

The chainline warnings are completely not true. Do triples shift horrible because they have bad chainlines?

the answer is NO!!!!!!!!

Removing the inner ring= same chainline, you arent moving the crank people. Stating the chainline will be out of whack is saying that everyone who runs a triple has a messed up chainline.

IF you have a triple shifter, no problem. You wont have to deal with empty clicks. Undo cable to FD. Adjust limit screw for the middle chainring. Make sure your shifter is in "1st" ie pulling no cable. Rehook the cable to FD. This way, the shifter olny uses its 1-2 shift. The High limit screw will prevent it from clicking up to "3rd"

tjspiel

Just so there's no confusion, my comments regarding chainline were comparing a triple with a double, not comparing a triple with 3 chainrings to the same triple with 2.

Also, the triple on my bike does (IMHO) have a less than great chainline because of the short chain stays and the fact the chain rings are too far away from the center line. It favors the smaller chain rings which I spend the least time in.

Technically a triple could give you better chainlines if you stick to certain gear combos but that requires keeping track of what cogs/rings you're on and maybe a lot more shifting. It's easier to do with the new brifters that display the gear. I prefer to stay on the large chain ring while cruising and drop to the middle as necessary.

DMF 

Is to laugh. The post you replied to contained no information.


Actually, there is something that will cause you problems that you didn't ask about: Shimano chainrings do not all have the same thickness and offset from the mounting surface, so replacing a triple 42 with a double 39 - even between Shimano cranksets of the same group - might change the spacing between the rings enough that index shifting will be a problem.

There's a thread about this, but since Search is broken I can't find it. Maybe someone else will have better luck.

bcart1991

Well as long as I (or the LBS) can tune it right, I shouldn't have any problems.

FWIW, I'm going from a Shimano 105 octalink 53/39 to an FSA SL-K 53/39/xx. According to FSA, there is only about 2mm chainline difference in their double and triple SL-K cranksets.

I was having a little fun with bekologist...

Bekologist

...and I was having some fun with you. You going to keep your triple derailluer? Kep the 'fred ' look consistent? I'd recommend, next time, if you want a double crank, buy a double crank.

having fun.....

bcart1991

You do know that most derailleurs are triple and double compatible, n'est-ce pas? I was thinking about tossing an old MTB derailleur on there, just for you.

Maybe you need to smoke less moss and pine needles.

epic lulz

Have fun at Starbucks, k?

Bekologist

actually, triples are double compatible but not the other way around. you know that, of course.

I have a triple front derailluer running a double crank on one of my bikes- but I'm a fred. et tu.

starbucks is a cruel joke we foist on the rest of the country.

your wanting to turn a triple into a double is also a joke. thanks for the laugh!

bcart1991

If you're talking about shifters, then yes. Derailleurs don't really care who's doing the pulling.

Yes, I'm obviously the joke here. I make my decisions based on what others think. That is absolutely how I want to live my life. Enjoy!

Bekologist

if you try using a double cage derailluer to shift a triple, you're going to have some drivetrain 'issues' but not the other way around....

urban_assault

Actually, I was just trying to be concise in answering the original question. Most of the other posts before mine were berating the OP on the concept alone. I think the OP and I understood what I was saying.

DMF 

2mm difference isn't bad, but I'm not talking about chainline. You can't "tune" an indexed dérailleur throw.

bcart1991

Yeah, I'll be tuning a double shifter throw with the new crank, it just seems I'll be tuning it 2mm outward.

Jackologist doesn't seem to understand this.

nun

Assuming that you have a triple FD and friction shifting I don't see any issue leaving the inner ring off. You might want to adjust the FD stop to prevent you dropping the chain. If you want to be able to use both rings with all your rear cogs you might adjust the BB spindle inboard a bit (if you have adjustment like on Phil Wood BBs).

I use a Sugino XD triple as a double with a 42t middle ring and 26t inner, no outer ring. I have moved the spindle out a bit so that the gap between the front rings is aligned to the center of the cassette. I use a 105 double FD and all gear combos work ok, even the cross chain ones, which I obviously usually avoid.

nun

Bekologist, I don't think using a triple as a double is a joke. I prefer a double on my touring bike, fewer gears to worry about and less changing. The way I got a 42/26 double working was to use the middle and inner positions of a 110/74 Sugino XD triple, combined with an 11-34 cassette I have an 18 gear bike with a gear range of 103" to 21" and not much duplication.

RT

Kumbaya, people.

bcart1991

No, it's more fun this way.

Bekologist

yeah, no doubt. I just threw in my 2 cents for the dissent, and then it got entertaining.


go, fred, go! join the club - maybe you could J-B weld shut the triple ring holes in your crank and really make it look like a double with a crappy chainline.

jim p

How does the bike ride with the new crank? It only takes about 30 minutes to change out a crank and it is now 3 days later that the first post. What is going on?

I just put a tripple crank on a bike that had a double. I am using friction shifting and things are working great on the bench. I have not gotten to ride the bike yet but I am expecting things to go well. The bike is a 7 speed and the chain line seems to be good for front small ring and the 1,2 and 3 cog in the rear. The middle chain ring is lined up well with cog 3,4 and 5 and the outer chain ring is lined up well with the 5,6 and 7 cog. If I only use these combination of gears then I can use the short rear derailer with no problems. If I decide that I have to cross chain more then the longer derailer will be needed.

So once again how is it riding?

too much typing makes me too tired to work on my bike or ride it.

bcart1991

lol I'm lazy and it's still really cold outside.

Tennis
Soccer
Car stuff

going on as well

DMF 

Finally found the ring thickness thread.

cmdr

All right, I'm going to step in here and just answer the question. Everything will work fine. You can adjust the derailleur to stop on the middle ring, there will be no chain-line issue, and you won't drop your chain. I know this because it's how one of my bikes roll. I actually forgot that that's how I had it set up until I started reading this absolutely ridiculous thread. To the OP, sorry about all the hassle you had to deal with.