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I have Shimano crank (MT300) with triple chainring (44-32-22), I want to change the outer chainring(44) with the bigger (maybe 50 or 52), can I use narrow wide chainring in outer gear? so the new set up will be (50-32-22). Any problem with shifting up and down after I use that new chainring?

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    In addition to @ArgentiApparatus' answer, you would also run into the problem that you have an 18-tooth gap between the middle and outer rings. I don't know if your front derailleur can handle the gap. Road chainrings have 16t gaps at maximum, modern Shimano MTB seems to only have 10t gaps, and the GRX gravel group has a 17t gap. Shifting on a standard 50t ring would probably not be that great. Last, depending on your tire size, 50t is probably getting up to road bike gearing. I know I couldn't push a 50-11 with MTB knobbly tires. If you're that strong ... get a road bike or a gravel bike? – Weiwen Ng Aug 17 at 15:08
  • hi @WeiwenNg, my bike basically is MTB and i modify to hybrid. i want to change to triple chainrings with 50T, but i think it's not possible to use that tooth size in MTB frame. Do you have any suggestion to use bigger tooth in MTB frame? – Dibay95 Aug 17 at 15:34
  • @WeiwenNg I did actually make this point. 44-22 probably is the derailleur capacity limit, adding 10 teeth (~a 20% larger ring) won't work. I would guess that the OP has a 12 tooth smallest sprocket and 26" wheels, but you point about over gearing stands – Argenti Apparatus Aug 17 at 15:40
  • @ArgentiApparatus yep, I missed your comment. Dibay, if you want to ride your MTB on smooth roads, I think that you could just get slick tires, lock your fork out, and just ride the gearing you have. are you actually under-geared for the road? – Weiwen Ng Aug 17 at 17:29
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    Going from 44/11-50/11 on 700C wheels will get you up from 28 to 30 mile per hour at 90RPM. Are you really riding at nearly 30MPH on a modified 26" MTB - if so, you should sign up for a pro team. If not, you would be better served by learning to spin faster. – mattnz Aug 18 at 2:17
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Narrow-wide chainrings are specifically designed for single chainring drivetrains and cannot be used on double or triple derailleur cranks. A 50 tooth ring won't work on your setup either.

Narrow-wide chainrings are designed specifically to stop the chain coming off them, which is exactly what you don't want in a derailleur drivetrain. The derailleur likely will not be able to pull the chain off of or onto the ring at all.

Regular chainrings (and cassette sprockets) have ramps on the inner surface and specially profiled teeth which help the chain hop on and off the ring. A narrow-wide ring lacks those features that and has taller teeth that protrude further through the chain links.

Narrow-wide rings of course have alternating narrow and wide teeth that fit between the alternating inner and outer plates of the chain. If a derailleur were able to shift the chain into a a narrow-wide ring, half the time the teeth and chain links would be mis-aligned and the chain would not be able to drop onto the teeth.

Front derailleurs have a total capacity limit, which is the difference in number of teeth (and hence diameter) between the smallest and largest rings. if you put a 50 tooth ring on the crank you'll have to move the derailleur up on the frame, and the cage will not reach the smallest ring. Additionally the 32-50 tooth size difference between the middle and outer rings would be too large to get the chain to shift properly.

And, mountain bikes typically don't have chain-stay clearance for a 50 tooth ring.

  • Also, aren't narrow-wide chainrings designed specifically for single chainring systems (i.e. 1x, pronounced 1-by)? Might help the original poster if you included that. – Weiwen Ng Aug 17 at 15:01
  • @WeiwenNg edit made – Argenti Apparatus Aug 17 at 15:21
  • thanks for the reply @ArgentiApparatus, so i can't use bigger than 44T in MTB frame? – Dibay95 Aug 17 at 15:35
  • @Dibay95 Probably not much larger, but you'd have to check your frame. Derailleur capacity and shifting is a bigger problem. The basic issue here is that bikes and drivetrains are made for a certain gear ratio range for a specific purpose and trying to expand beyond that does not work well. – Argenti Apparatus Aug 17 at 15:54
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    @Dibay95 Sorry, no. Both cranksets will fit on 68 and 73mm BB shells and the derailleur would work I think; but the MT500 is designed for 142mm rear spacing, 50mm chainline, Sora 3503 for 130/135mm rear spacing and 45mm chainline. Narrower chainline puts the rings closer to the chainstay so clearance problems are worse, and of course the chainline is messed up. (You can find links to Shimano specs in many of my previous answers to other questions.) – Argenti Apparatus Aug 17 at 17:33
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With a nod to the correct information offered in Argenti's answer, I was thinking an option not mentioned for your situation may be to change the crankset to a mountain triple with tooth counts of 48-36-26. Here's a Shimano Deore crankset that has these tooth counts. The 10 speed version, FC-T6010 could work as well. Though not encouraged by Shimano, 10 speed chainsets will work in 9 speed set-ups without much fuss.

Looking at the latest Compatibility Chart from Shimano within the blocks diagraming 9 speed front crank and front derailleur compatibility, one can see that crankset models FC-M4060 and FC-T4060, which have tooth counts of 48-36-26, are housed within the same block as the MT300 (44-32-22). So, not only are these models swappable without changing the bottom bracket, but also have the same compatible front derailleurs of which there are several models, most importantly, the one you already have for the MT300.

Going to the larger crank, you'll likely have to move your front derailleur's mount position a touch higher to accommodate the increased chainwheel diameter of the 48t. In addition you should resize your chain (longer) because of the increased size of the chainwheel. For derailleur bikes that sport a largest rear sprocket of 28 teeth or more, the correct chain length is determined by wrapping the new chain around the large chainwheel and around the large rear sprocket in back WITHOUT going through the rear derailleur. Bring the ends together and at the point the links begin to overlap, add 2 links (1 wide + 1 narrow) to arrive at the correct chain length.

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