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  1. #1
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    Is a larger chainring possible?

    Due to some shoulder and arm issues I have switched from commuting on a road bike to a Cannondale M500 with slick tires. I absolutely love the fit/ride of the bike (more than the road bike).
    The only thing that I miss about the road bike is the bigger gears. I spend most of my commute in the top gear and am constantly wishing that I had more gears on the top end. I took the M500 in for a tune up and at the same time switched from a 42t to 44t front chainring. I do notice the change, but it is definitely not enough.
    The mechanic said that he would not suggest a larger chainring as it would create shifting problems. I am pretty sure I had a 52t on the road bike, and would love to have that on the Cannondale. The smallest cog in the back is 11 so I don't think I can change that.
    I only use the top two chainrings, and never use the smallest, so I would not miss it. Any thoughts?
    I don't really want to look at another bike with different gearing, as this Cannondale is the best fitting bike I have ever owned.
    I really appreciate the help!
    Mike

  2. #2
    Senior Member BCRider's Avatar
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    There's no reason at all that you can't fit a road crankset on your bike. I think what the mechanic was reffering to badly is the fact that MTB fronts have a cage with a curvature that matches smaller chainrings better. If you shift over to a road crankset then you'll want to swap your MTB FD over to a road FD so it matches. But other than that this is a simple mod that sounds like it'll do what you want.

    If it turns out to be too much gearing to carry with a situp position then a switch to a Cyclocross set of rings would be a nice middle ground. 48 teeth typically on the big ring.
    Model airplanes are cool too!.....

  3. #3
    I have senior moments... bikinfool's Avatar
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    You can get a 48t for that crank fairly easily, or do you want bigger? How much room do your stays allow? Then what, a crank? Then you'll probably want bigger wheels....
    suum quique
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  4. #4
    Gear Combo Guru Chris_W's Avatar
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    Putting a 48 tooth on there should be pretty straightforward, just move the front derailleur up to accommodate it, and you'll probably need to lengthen your chain, which may well mean replacing the chain if the current one is already reasonably worn. There will then be a few things that you will officially be exceeding Shimano recommendations on, but they shouldn't cause too much of a problem. First, your current FD will not have the correct curvature, making it slightly easier for the chain to overshift and fall off of the outside of the big ring, but this is still unlikely and I wouldn't worry about it (but , Shimano does make some MTB FDs designed for 48 tooth large rings if you want to have it perfect). Second, your RD will not have enough chain wrap capacity, but this just means that you need to avoid the small-small gear combinations. If you're not using the small chainring anyway, then this also won't be a problem (to fix it, you could change your middle and inner rings to 26 and 36 tooth versions, or get a whole new crankset that comes stock with 26,36,48 rings).

    Using a road crankset (with at least a 50 tooth large ring), as mentioned above, would cause more problems because then you really would need to change your front derailleur for a road model, and this would not be compatible with your current front shifter, so you'd also need to change that. In addition, you'd have to make sure that the cranks of the road crankset will clear your chainstays, because the road cranksets tend to be quite a bit narrower. Overall, I wouldn't go down that route, and would instead keep the MTB components and get a 48 tooth big ring.

  5. #5
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    Thanks for the information!! I really appreciate it!

  6. #6
    Don from Austin Texas
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    Quote Originally Posted by Chris_W View Post
    Putting a 48 tooth on there should be pretty straightforward, just move the front derailleur up to accommodate it, and you'll probably need to lengthen your chain, which may well mean replacing the chain if the current one is already reasonably worn. There will then be a few things that you will officially be exceeding Shimano recommendations on, but they shouldn't cause too much of a problem. First, your current FD will not have the correct curvature, making it slightly easier for the chain to overshift and fall off of the outside of the big ring, but this is still unlikely and I wouldn't worry about it (but , Shimano does make some MTB FDs designed for 48 tooth large rings if you want to have it perfect). Second, your RD will not have enough chain wrap capacity, but this just means that you need to avoid the small-small gear combinations. If you're not using the small chainring anyway, then this also won't be a problem (to fix it, you could change your middle and inner rings to 26 and 36 tooth versions, or get a whole new crankset that comes stock with 26,36,48 rings).

    Using a road crankset (with at least a 50 tooth large ring), as mentioned above, would cause more problems because then you really would need to change your front derailleur for a road model, and this would not be compatible with your current front shifter, so you'd also need to change that. In addition, you'd have to make sure that the cranks of the road crankset will clear your chainstays, because the road cranksets tend to be quite a bit narrower. Overall, I wouldn't go down that route, and would instead keep the MTB components and get a 48 tooth big ring.
    I went up to a 52 tooth big chainring on my Cannondale MTB. The existing derailleur didn't work too well. A road bike derailleur has incorrect travel for the MTB shifters. Sheldon Brown is our friend: http://sheldonbrown.com/harris/derailers-front.html Specifically he mentions the Shimano derailleur for just this situation: "R453 (formerly R443) for "road" chainwheels with straight (mtb) handlebars $39.95 This is the only model Shimano makes that is designed to work with full-sized chainrings, up to 53 teeth, and with shifters made for upright (mountain) handlebars." That's what I did and it worked out pretty well.

    Don in Austin

  7. #7
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    i'm curious as to why you think you need it. I run a 42 front on my MTB commuter which lets me reach +26 MPH/40 KMH before spinning out. Basically this means that for my 15 mile/24 km commute there's one descent where I'm off power for a few seconds.

    Either you're amazingly fast, or your're not following general cadence recommendations.

  8. #8
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    I am definitely not "amazingly fast" I just prefer to ride at a slower cadence against the bigger gear. I know that most people recommend pedaling at a higher cadence as that decreases the potential for knee injury etc..
    I guess everybody has different preferences. I run 40+ miles a week, and consider that my cardio workout. My bike is an enjoyable form of primary transportation, so I just want it set up the way I would most enjoy.

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