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  1. #1
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    Shimano 5700/5750 : Double Chainring vs Compact

    Ended up buying a sweet synapse 6. I chose saving a few hundred over the 105 model.

    That being said, I will be upgrading my crank in the next day or so to the shimano 105.

    From google, I learned that the 5700 is double chainring, 5703 is triple, and 5750 is compact. Im assuming I need the compact.

    One thing I wanted to confirm is, aren't compacts technically double chainrings as well? Would it be incorrect to refer to the 5750 as a Compact Double Chainring or is a Double Chainring (5700) somehow different that only applies to a standard?

    Also, would anybody know what the length comes default on the FSA crank?

  2. #2
    Senior Member RollCNY's Avatar
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    5700 is a standard double, 5750 is a compact double. Yes, they are both doubles.

    Crank length tends to be a variable with size of the frame, so look in the specs of the bike you bought for your model size.

  3. #3
    L-I-V-I-N dtrain's Avatar
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    What is the current crank? BB30?

    Edit: nm, I see the FSA now. Length should be stamped near the pedal hole (backside). There may be some issues with the bottom bracket (BB30) though.
    Last edited by dtrain; 07-02-14 at 09:38 AM.
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  4. #4
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    Quote Originally Posted by dtrain View Post
    What is the current crank? BB30?
    Correct. FSA BB30.

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    Senior Member fstshrk's Avatar
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    Quote Originally Posted by isuckatbiking View Post
    Correct. FSA BB30.
    You need an adapter to be able to run a shimano crankset. Why are you upgrading? There is nothing inherently wrong with the FSA crank that comes on that bike.
    Shimano may shift a bit crisper but other than that, not much to gain and a waste of money.
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  6. #6
    Senior Member bikemig's Avatar
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    You realize that your bike came stock with a compact crank? I'm not sure why you want to "upgrade" (I'm skeptical that this is much of an upgrade) but if you need to do this for some reason, you will want to think about the gear ratios that you need given where you ride, your fitness level, etc. Sticking with a compact is a safe choice because of the wide range gearing you get.

  7. #7
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    Quote Originally Posted by fstshrk View Post
    You need an adapter to be able to run a shimano crankset. Why are you upgrading? There is nothing inherently wrong with the FSA crank that comes on that bike.
    Shimano may shift a bit crisper but other than that, not much to gain and a waste of money.
    Yeah totally slipped my mind that I needed other parts. Guess the excitement got to me.

    But side question, I can either buy the adapter for the FSA or just buy a Shimano 5700 BB instead right? The Shimano BB shouldn't have any fit issues? Are diameters of BB all mainly universal?

  8. #8
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    Quote Originally Posted by bikemig View Post
    You realize that your bike came stock with a compact crank? I'm not sure why you want to "upgrade" (I'm skeptical that this is much of an upgrade) but if you need to do this for some reason, you will want to think about the gear ratios that you need given where you ride, your fitness level, etc. Sticking with a compact is a safe choice because of the wide range gearing you get.
    I was going to go with a 5750 which is also a compact, unless im missing something here

    But yeah, I'm def sticking with a compact.

  9. #9
    L-I-V-I-N dtrain's Avatar
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    Not universal. BB30 /= Shimano. Can be done with adapters, but what's the point?
    "The older you do get, the more rules they're gonna try to get you to follow. You just gotta keep livin', man, L-I-V-I-N." - Wooderson

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    Going from FSA Gossamer BB30 to Shimano 105 isn't an upgrade.

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    there are at least 3 or 4 different BB shell internal diameters, and 3 or 4 widths. they may or may not be threaded. so that's upwards of 30 possible combinations some of which aren't offered. in addition, there are at least three spindle diameters that i am aware of, not to mention adapters and various spindle lengths.

    caveat emptor.

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    Alright so I came across a pretty good deal for an ultegra crankset. Thats if my friend ends up switching to sram like he said he would.

    One thing Im confused about still is, if my bike came with mostly 5700 parts, wouldn't it only make sense to get a 5700 or 6700 crankset? But as I research more, it seems as though while all the other parts might be 5700, the crankset I need to keep my compact would be a 5750 or 6750.

    Also, Im a bit confused on how my BB is a BB30 yet the crankset (the fsa one) it comes with is a BB30a.

    So what exactly am I looking for, a BB30 adapter or BB30a?

    That leads me to my final questions

    I have no idea what adapter to buy. What else I need other than an adapter? (rings, mounts, etc i duno) and whether its an easy process.

    Wiggle | Wheels Manufacturing BB30 to 24mm Crank Spindle Shims | Bottom Brackets

    If only FSA didn't make such ugly cranks.

  13. #13
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    It's as if FSA purposely designed their cranks as ugly as they can just to look different

  14. #14
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    My Orbea came with everything Ultegra except for the FSA Gossamer compact crankset. It was fine for me.

    When I'm riding my bike, I can't see what the crankset looks like.

    My suggestion is to save your money until something wears out. By then, you'll know what really needs upgrading or not.

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    Senior Member fstshrk's Avatar
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    Quote Originally Posted by isuckatbiking View Post
    Alright so I came across a pretty good deal for an ultegra crankset. Thats if my friend ends up switching to sram like he said he would.

    One thing Im confused about still is, if my bike came with mostly 5700 parts, wouldn't it only make sense to get a 5700 or 6700 crankset? But as I research more, it seems as though while all the other parts might be 5700, the crankset I need to keep my compact would be a 5750 or 6750.

    Also, Im a bit confused on how my BB is a BB30 yet the crankset (the fsa one) it comes with is a BB30a.

    So what exactly am I looking for, a BB30 adapter or BB30a?

    That leads me to my final questions

    I have no idea what adapter to buy. What else I need other than an adapter? (rings, mounts, etc i duno) and whether its an easy process.

    Wiggle | Wheels Manufacturing BB30 to 24mm Crank Spindle Shims | Bottom Brackets

    If only FSA didn't make such ugly cranks.
    Based on the questions you are asking, your best bet is to take the bike to where you bought it from and ask them to swap the cranksets for you.
    It would be cheaper and more reliable for you in the long run.

    BTW, I still think what you are doing is a waste of money. Run the crankset until the rings wear off, then upgrade.
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    Quote Originally Posted by Elvo View Post
    Going from FSA Gossamer BB30 to Shimano 105 isn't an upgrade.
    Yes it is, but probably not enough to warrant swapping it out in this case.
    2012 Pinarello FP Due,2010 Scattante X-330(Cyclocross),1988 Fuji Sagres SP (Road Bike)

  17. #17
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    OP you are confusing OCD with bike design principles. There is no reason why your crank brand and model should match your other drivetrain parts. The FSA crank is just fine and allows you the benefits of the BB30. Shimano was not used for the crank partly because that brand refuses to make cranks that are compatible with the BB30 system barring an adapter which discards all the benefits, of course. Keep what you have or buy a better FSA crank that is immediately compatible with your BB30. But it is not necessary to do anything. Except ride the snot out of that bike, of course.
    Robert

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  18. #18
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    Also I have three road bikes with SRAM drivetrains except for the FSA cranks. Surprisingly I have no desire to change the cranks. That could be because I spec'ed all the parts on the bike in the first place.
    Robert

    "Wish I didn't know now what I didn't know then." (Bob Seger, "Against the Wind")

  19. #19
    Senior Member Jiggle's Avatar
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    Quote Originally Posted by isuckatbiking View Post

    I have no idea what adapter to buy. What else I need other than an adapter? (rings, mounts, etc i duno) and whether its an easy process.

    Wiggle | Wheels Manufacturing BB30 to 24mm Crank Spindle Shims | Bottom Brackets
    I have those on a Cannondale BB30 frame using a 105 crankset. All you need are those adapters, BB30 bearings, and the crankset.

  20. #20
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    Quote Originally Posted by knobd View Post
    Yes it is, but probably not enough to warrant swapping it out in this case.
    Gossamer BB30 with bearings is 900g. Shimano 105 with bb + adapters is 1000g. Pretty sure they are equally stiff so it isn't really an upgrade

  21. #21
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    So let's get back to the fact that this "upgrade" won't be an upgrade, that you already have exactly what you'd be getting, materially speaking, and that the only weight savings to be had...

    will be in your wallet.

    If we're clear on all of those, then the above should give you all the answers you need about making this change.
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