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Replace 28/38/48 with 26/36/48 crankset - any issues with front derailleur?

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Replace 28/38/48 with 26/36/48 crankset - any issues with front derailleur?

Old 02-14-18, 03:18 PM
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sjfoote081
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Replace 28/38/48 with 26/36/48 crankset - any issues with front derailleur?

Can I replace the 28/38/48 crankset on my Cannondale quick 4 with a 26/36/48 without re-positioning the front derailleur? Seems like it should work with no issues but wanted to check with the experts here. Thanks
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Old 02-14-18, 03:41 PM
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bradtx
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sjfoote081, Probably okay. FD position is determined by the big ring anyhow, which remains the same.

Brad
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Old 02-14-18, 03:51 PM
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tyrion
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FWIW on my 48-36-26 Deore 10 speed crank I replaced the 26 with a 22. I didn't have to move the FD or anything.
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Old 02-14-18, 04:21 PM
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The height of the FD is determined by the big ring which appears to be the same in both cranksets. That said, a two tooth difference between the two smaller rings and their counterparts on the new crankset will be completely and absolutely imperceptible to a rider. The smallest possible granny on a road triple is 24T and the smallest allowable on a MTB triple is 22T. There would have to be a real good reason for me to go through the time and $$$ to find and fit a completely new crankset and not get maximum bang for the buck and get the smallest granny the crank allows. Certainly not for anything less than a four tooth difference between the outgoing and the new. FWIW.
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Old 02-14-18, 05:38 PM
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On one of the bikes i built, i fitted an STX fd rated for 42t with 28-38-48. The curvature fits the chainring perfectly.

Any triple mtb fd should fit anything from 42-48 easily.
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Old 02-14-18, 05:45 PM
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Replacing a crankset to permit lower gears is an expensive way to go. More information about why you wish to make this change would be very useful if you wish to get more advice. You could easily and at much less expense buy a cassette with a wider range. A cassette with 2 more teeth on the largest cog would be much more effective than 2 fewer on your smallest chainring
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Old 02-14-18, 06:25 PM
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sjfoote081
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Thanks, all. I have changed the cassette from 11-32 to 11-34 and that has helped. There are many very hilly rides in the area where I have actually used the granny gear to get back to the car after 35 miles or so. If the 26T small ring gets me just a few more gear inches it may be useful one day. My thinking is that most of the bikes I would purchase to replace the Quick have 26/36/48 cranks with 11-32 cassettes. If I bought one of them, I would probably swap the cassette for the 34T anyway, so since I like pretty much everything about the Quick, why not just change the crankset and keep riding this bike for a few more years?

Once again, thanks for the help!
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Old 02-14-18, 08:37 PM
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Put a 24 or 22 on the front for the lowest gears.
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Old 02-14-18, 09:50 PM
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I am a home mechanic, not an expert. Sheldon Brown says that the triple FDs are optimised for a specific top-middle tooth difference: https://www.sheldonbrown.com/front-d...l#doubletriple (On the other hand, you can replace the granny ring with almost no effect.)
You are changing the top-middle tooth difference from 10 to 12. Not sure how significant it is. I use an FD-5504 specced for 52-42-30 with 48-36-22 with no problem.

If your bottom bracket is 123 mm, you can get M361 crankset for $30 in 28-38-48 and replace the 28 with a smaller chainring. Add $20 for the new BB (if you have some non-Shimano crankset which needs a different spindle length) and the small granny ring, the total is $50. It is cheaper than the 48-36-26 crankset with external bearings + granny ring for it.

I think you may have to move the FD vertically a bit if the chainline changes (say from 47.5 to 50mm).
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Old 02-15-18, 12:18 AM
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Originally Posted by davidad View Post
Put a 24 or 22 on the front for the lowest gears.
This. ~$20+
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Old 02-15-18, 01:14 PM
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Originally Posted by hermanchauw View Post
on one of the bikes i built, i fitted an stx fd rated for 42t with 28-38-48. The curvature fits the chainring perfectly.

Any triple mtb fd should fit anything from 42-48 easily.
+1
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Old 02-15-18, 03:46 PM
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Thanks for the replies.

After further review it is clear that my crankset (FC-M311) uses riveted chainrings - bummer. As previously mentioned I could switch to M361 crankset (28/38/48) and just swap out the small ring. Now the cost is starting to add up more than it is probably worth. Shimano also makes the FC-M311 crankset with mountain bike gearing of 22/32/42 and it uses the same bottom bracket and the chain line is the same too - but that seems too drastic of a change. The rear derailleur is Alivio which should support chain wrap of 43, so with 11/34 cassette and 22/32/42 crankset, I would be at that limit. Shimano tech doc says the front derailleur also works with both of these sets. Still thinking....
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Old 02-15-18, 05:02 PM
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Originally Posted by sjfoote081 View Post
The rear derailleur is Alivio which should support chain wrap of 43, so with 11/34 cassette and 22/32/42 crankset, I would be at that limit. Shimano tech doc says the front derailleur also works with both of these sets. Still thinking....
Do not worry about the rear der. It has enough capacity. With 48-38-22 (or 24) and 11-34 cassette chain wrap is 26+23=49 (or 47 if you use 24 in the front). That will exceed the total capacity, but in reality the chain will be slack only in the small-small combinations, which you are not going to use anyway. I run 48-36-22 with 11-30 and rd-4600 with official 40t wrap capacity, works OK.

$40 for FC-M361 + small granny ring + shipping is cheaper than the 48-36-26 crankset. I checked the current Cannondale specs and thought your bike had Suntour crankset, which may have different BB. Since you have Shimano, it makes things even easier, you have the right BB for M361.

IMO the upgrade is totally worth it.
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