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Double FD with Triple Crank

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Double FD with Triple Crank

Old 03-19-16, 09:54 PM
  #1  
farmerjg
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Double FD with Triple Crank

Hey there everyone, I've been a long time lurker and now first time poster. Unless I'm just awful at Google I don't think I could find another instance of my situation. A couple months ago my triple Tiagra FD broke. A very generous co-worker of mine then gave me one of his old Ultegra double FD's for free. Since I installed the double I can not seem to get it adjusted to where there's no chain rub. I can make it better here or there, but it's always to the detriment of some other operating point.

So, first question, does that "sound right" that I can't get it adjusted to not rub? Do I have way too many apples and oranges going on for that to work? If it's user error and going to my LBS will fix it, then I'll do it, but I'd like to at least hear everyone's thoughts first.

So, as a follow on, if it does seem like I have a bad mix, I have found I can get an Ultegra double crank and a corresponding BB (octalink V1 and 109.5mm) for around $30 combined. Other than just getting another triple FD, do you guys see many cheaper options than going to the Ultegra/BB combo? I don't use the granny gear so I wouldn't mind dumping it with this opportunity, but again, I don't do a ton of my own bike work so this plan has just kind of been cobbled together in my mind. Anybody's thoughts and opinions would be greatly appreciated!!!!

Anything incredible obvious (and silly) that I'm missing here?

Thanks.
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Old 03-19-16, 10:52 PM
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Your cheapest option usually replacing the FD with a triple specific one. While you can just ditch the granny ring you'd have a much smaller range than is typical on a double, triples generally have about 10 tooth differences while doubles usually have about 16 tooth differences.

That being said $30 is an amazing price for a crankset/BB combo so you may want to pursue it.
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Old 03-19-16, 11:36 PM
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Originally Posted by farmerjg View Post
... Since I installed the double I can not seem to get it adjusted to where there's no chain rub. I can make it better here or there, but it's always to the detriment of some other operating point.

So, first question, does that "sound right" that I can't get it adjusted to not rub? Do I have way too many apples and oranges going on for that to work? If it's user error and going to my LBS will fix it, then I'll do it, but I'd like to at least hear everyone's thoughts first. ...
Hi farmerjg,

If you plan to ignore the innermost chainring and just use the middle and outer chainrings, then the 2x FD should work okay as long as it matches your chain width. For example, if your rear cassette is a 10x, then you need a front derailleur that is also made for a 10x chain. If your FD is made for an 11x chain, then you can expect problems because its cage may be a little more narrow to fit the narrower width of an 11x chain.

But you should not expect your 2x FD to work with a 3x crank because the 2x FD cage will not be correct. A 3x FD cage is much taller to accommodate the greater travel of the chain down to the small innermost chainring. I would expect trouble if you try to use a 2x FD with a 3x crank and expect it to shift down to the innermost chainring. Plus, some 2x FD may not have as far of a travel as a 3x FD and the adjustment screws may not have adequate range.

My personal opinion is to simplify the front of your drivetrain whenever possible. The front derailleur never shifts as well as the rear derailleur and 3x cranks are the absolute worse. I recently converted my road bike to a 1x setup. I removed my front derailleur and both 2x chainrings (50 and 34T). Then I installed a single 50T 1x chainring. I'm using an 11x28T 10x cassette. It offers plenty of range for the moderate hills that I encounter and I love the simpler drivetrain. If I were in your shoes and wanted to keep my costs down and minimize the work, I would get the 2x crank and new bottom bracket. Since you said that you never use the innermost chainring, you won't need to change the gearing of your rear cassette and should be good to go.

Kind regards, RoadLight
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Old 03-20-16, 07:19 AM
  #4  
farmerjg
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Originally Posted by Bezalel View Post
Your cheapest option usually replacing the FD with a triple specific one. While you can just ditch the granny ring you'd have a much smaller range than is typical on a double, triples generally have about 10 tooth differences while doubles usually have about 16 tooth differences.

That being said $30 is an amazing price for a crankset/BB combo so you may want to pursue it.
Thanks for pointing out the teeth difference. Right now I've got a 30/42/52 and the Ultegra would be 39/53. I effectively gave up that 30 when I installed the double FD because I've got it set up (albeit poorly) to let me have the 42/52 and not the 30. I think I would like the double being at 39/53. Like you said, at $30 it may just be worth finding out. And at a minimum, I love to tinker on stuff and this seems like a pretty cheap tinker project.
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Old 03-20-16, 07:28 AM
  #5  
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Originally Posted by RoadLight View Post
[I] My personal opinion is to simplify the front of your drivetrain whenever possible. The front derailleur never shifts as well as the rear derailleur and 3x cranks are the absolute worse. I recently converted my road bike to a 1x setup. I removed my front derailleur and both 2x chainrings (50 and 34T). Then I installed a single 50T 1x chainring. I'm using an 11x28T 10x cassette. It offers plenty of range for the moderate hills that I encounter and I love the simpler drivetrain. If I were in your shoes and wanted to keep my costs down and minimize the work, I would get the 2x crank and new bottom bracket. Since you said that you never use the innermost chainring, you won't need to change the gearing of your rear cassette and should be good to go.
First, triple cranks can and do shift well. The "myth" that they are more problematic than a double is just that, a myth. Second, a 1X does not and cannot have the overall range of a 2X or, better 3X crank. A wide range 1X is going to have huge gaps in the interior gears that may work on an MTB but will be a real nuisance on a road bike and will still have a more limited range.

I don't know where you live but around me many of the hills are anything but "moderate" and a 50x28 low gear would be inadequate.

I do agree that if the OP does not use his granny chainring going to a double crank will not cause him any problems.
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Old 03-20-16, 07:32 AM
  #6  
farmerjg
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Originally Posted by RoadLight View Post
If you plan to ignore the innermost chainring and just use the middle and outer chainrings, then the 2x FD should work okay as long as it matches your chain width. For example, if your rear cassette is a 10x, then you need a front derailleur that is also made for a 10x chain. If your FD is made for an 11x chain, then you can expect problems because its cage may be a little more narrow to fit the narrower width of an 11x chain.
How would I find out the FD's intended chain width? I don't know what bike it came off of or what it's original setup was. I am able to see that my chain today is the same width as what was intended for the Ultegra double crank I am looking at, so that's good, but obviously that doesn't fix the fact that my FD could still be wrong.

Originally Posted by RoadLight View Post
But you should not expect your 2x FD to work with a 3x crank because the 2x FD cage will not be correct. A 3x FD cage is much taller to accommodate the greater travel of the chain down to the small innermost chainring. I would expect trouble if you try to use a 2x FD with a 3x crank and expect it to shift down to the innermost chainring. Plus, some 2x FD may not have as far of a travel as a 3x FD and the adjustment screws may not have adequate range.
Yeah, I gave up the innermost ring when I did this last summer. I rode without it the rest of summer, all fall, and so far this early spring so I'm confident I'm ok without it........but dang is it annoying with that chain rubbing ALL THE TIME!!!!

Originally Posted by RoadLight View Post
My personal opinion is to simplify the front of your drivetrain whenever possible. The front derailleur never shifts as well as the rear derailleur and 3x cranks are the absolute worse. I recently converted my road bike to a 1x setup. I removed my front derailleur and both 2x chainrings (50 and 34T). Then I installed a single 50T 1x chainring. I'm using an 11x28T 10x cassette. It offers plenty of range for the moderate hills that I encounter and I love the simpler drivetrain. If I were in your shoes and wanted to keep my costs down and minimize the work, I would get the 2x crank and new bottom bracket. Since you said that you never use the innermost chainring, you won't need to change the gearing of your rear cassette and should be good to go.
I love simplifying! I think you guys might be providing me the encouragement I need to try to make the jump! The worst that happens is I'm out $30 in parts (which I can always try to sell if I switch back).

Thanks for the help guys.
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Old 03-20-16, 08:07 AM
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Come on man!

Shimano Tiagra 4703 Triple 10 Speed Front Mech | Chain Reaction Cycles
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Old 03-20-16, 09:43 AM
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I had actually looked at that one when my co-worker ended up giving me the Ultegra for free last summer. With shipping that guy comes to $37, so I kind of need to decide if I want to take a chance on the Ultegra/BB combo (and try a double for a while) or replace what I had and go back to my old ways. These are life's big decisions.
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Old 03-20-16, 07:11 PM
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Sorry, misread the OP
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Old 03-20-16, 07:16 PM
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The cable pull between an inner and middle and the middle and big ring are not the same. Andy.
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Old 03-20-16, 08:33 PM
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Hi HillRider,

Originally Posted by HillRider View Post
First, triple cranks can and do shift well. The "myth" that they are more problematic than a double is just that, a myth. ...
I'm glad to know that you're the cycling "myth buster". :-) My experience helping clients and family with triple cranks leads me to conclude that they ARE more problematic. I've seen more scratched (and in the case of carbon frames---cut) bottom bracket shells from chains derailing inside the innermost chainring with triples than doubles. And the innermost chainring of a triple is too close to the frame to fit a chain catcher. The driveline (chainline) is way more problematic because of the greater angle that the chain must travel between chainrings and cogs of opposing sides. The teeth on the chainrings and cassette wear more unevenly because of the wider extremes of the chainline which causes degradation in shifting of a triple before that of a double. I don't know what you've seen, but I've seen lots of problems with triples.


Originally Posted by HillRider
... Second, a 1X does not and cannot have the overall range of a 2X or, better 3X crank. A wide range 1X is going to have huge gaps in the interior gears that may work on an MTB but will be a real nuisance on a road bike and will still have a more limited range. ...
Regarding the "overall range" we're agreed. But I think you're mistaken about the "huge gaps". First, there are some excellent wide-range cassettes for road bikes now (like 11x36t). Second, with 10-speed and 11-speed cassettes, we have plenty of steps so that the gap from one cog size to the next is still relatively small for most cyclists. You may not agree with me---and that's fine if you don't---but I think modern bikes have too many gear combinations and the steps between gears is too small in many 2x10 and 2x11 road bike drivetrains.


Originally Posted by HillRider
... I don't know where you live but around me many of the hills are anything but "moderate" and a 50x28 low gear would be inadequate. ...
That's fine---I never said nor implied that my setup would work for everyone. I just offered my experience as an example of how I simplified my drivetrain. I cycle on smoothly paved (blacktop) roads along the eastern side of Lake Michigan in the U.S. The terrain is forested over mostly-moderate rolling sand dunes. One of the annual centuries that I ride goes from South Haven to Holland (both are port cities on Lake Michigan). The inland part of the route has a couple of long uphill climbs. The biggest annual century that I ride is the famous Apple Cider Century in Three Oaks. It dips into some very hilly terrain in northern Indiana. As a test, I rode the entire 2015 season (4,300 miles) without using my small chainring. At the time, I had an 11x26t cassette on the back and compact 50x34t chainrings on the front. The lowest gear ratio available without the 34t chainring was 1.92 (50/26t). I had no problem with the hills---not even the steep ones.

When planning the gear ratios for a drivetrain, each rider must consider both their route and their fitness. The "hills" on your route may be much steeper and/or longer than mine. As for fitness, I've got strong legs (I used to leg-press 1,000 lbs for 12 reps). I'm not anticipating any problems this season with my new 1x setup which will offer a 50:28 ratio when it's needed.

I used to live in the western U.S. (Colorado and California) and am hoping to plan a cycling vacation that direction. If I do, I'll want a wider range of cogs on a second wheel and I haven't decided whether to go with an 11x32t or 11x36t cassette. But I never even came close to needing the slowest 1.30 gear ratio (34/26t) of my original 2x10 drivetrain in the foothills of the Rocky, Sierra, San Bernadino and San Gabriel mountain ranges. If you know anything about U.S. mountains, you'll understand that these are not trivial mountains. But I should be able to comfortably ride them with a 1x drivetrain. If I go with the 11x36t cassette, I'll have a 1.38 gear ratio at the slowest end (50/36t) which seems to be plenty adequate based on my past experience. Would this be adequate for everyone? Of course not! Each rider must make these kinds of choices independently.


Originally Posted by HillRider
... I do agree that if the OP does not use his granny chainring going to a double crank will not cause him any problems.
That's the salient point. The OP is not using his smallest chainring now, so the best thing would probably be to switch to a 2x crank. He'll be able to choose from a wider selection of parts in the future, have less weight and (hopefully) less trouble.

Kind regards, RoadLight
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Old 03-20-16, 08:37 PM
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Originally Posted by farmerjg View Post
How would I find out the FD's intended chain width? ...
Hi farmerjg,

You should be able to find the make and model number of your 2x FD on it somewhere. If you post it here, someone should be able to look it up for you. If you can't, then take some good closeup photos of it and post them.

Kind regards, RoadLight
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