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First of all a big thank you for everybody who can help out with the question!

The bike is Scott Aspect 960: https://www.scott-sports.com/gb/en/product/scott-aspect-960-red-bike

Currently the highest gear ratio is 36/11. I'm looking to upgrade that to go on a more slower cadence on long gravel routes at a higher speed.

Would replacing the front cassette with this one do the job: https://www.bike-discount.de/en/shop/crank-2-3-x-8-speed-409/l-24

The shifter for the crankset has 2 gears listed, but the crankset here has three gears. What are the solutions for upgrading?


More info: When we need to go with a 2 ring crankset, would this work:

https://bike.shimano.com/en-EU/product/component/shimano/FC-M315-2.html

https://www.modernbike.com/shimano-alivio-m415-42t-7-8-speed-outer-chainring

I'm anyways looking to upgrade the crankset to a Shimano one, so would it fit with this larger chainring?

As I understand, I would need to put on a longer chain then as well?

  • It is hard to say what kind of chainrings your frame can accomodate, is there actually a space for a larger chainring or are the teeth currently close to the chainstay? – Vladimir F Sep 15 at 9:14
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    Please clarify, is there space for a larger chainring on your frame? Show us a clear detailed picture of your chainrings and the chainstay from the top. It is possible that a professional in a bike shop will have to judge that. They may do it for free if you buy the new stuff from them. Do not just order something blindly, it can easily happen that it won't fit. – Vladimir F Sep 15 at 10:21
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You have 2 choices: upgrade to a Shimano 2 chainring crank, keep the left shifter, or upgrade to a 3 chainring crank and replace the left shifter with a 3x version.

In both cases the crank must be compatible with '8 speeds'. Sprocket spacing in both the rear cassette and chainrings get progressively narrower as the number of sprockets goes up, and chains get progressively narrower too.

Before you purchase a crank, you need to check that you have clearance between the chainrings and drive-side chainstay. All bike frame have a maximum chainring size they can accommodate. Also check that you can move the front derailleur up slightly to align with the larger rings.

Replacing just the large chainring is not a great idea. Front derailleurs are designed to work with a certain size difference between the chainrings. If you exceed that upshifting will be poor or will not work at all.

Chainring replacement is tricky, there are many ways for rings to be incompatible with cranks. Many lower end cranks do not even have replaceable rings, the rings and spider are a single stamping and riveted together. The crank you linked to has this construction.

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    In both cases the crank must be compatible with '8 speeds'. True, but there's a larger range of what's "compatible" on the crankset than there is with a cassette. For an 8-speed bike, a 7-speed or a 9-speed crankset would probably work just fine. There's even a small chance a 10-speed or even an 11-speed crankset could work well enough, although I'd suspect those would be very prone to the chain dropping either inside the small ring when shifting to an easier gear or outside the large ring when shifting to a harder gear. The problem is you won't know until you put it on the bike... – Andrew Henle Sep 15 at 15:11
  • (cont) So purchasing something that might not work is usually a bad idea unless you can't get something better, or you're willing to take the chance. – Andrew Henle Sep 15 at 15:13
  • @AndrewHenle a 9 speed crank would be fine but 10 or more would definitely have issues. Given that cranks get more expensive as the number of speeds go up there is zero point spending more money on something that will not perform as well. – Argenti Apparatus Sep 15 at 15:15
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No, you have to stick to 2 ring crankset if you want to keep the front gears.

The problem is that the distance between the rings and different, so your current setup won't work on a 3 ring crankset.

Other solutions could be to just chain the chainring to larger one, although I think 38t is the largest you will be able to go, maybe 40T or 42T.

I would suggest you either visit your local bike shop to see the options, this way, you have some gurantee on the new chainrings.


Answer to "more info" edit.

If you change the bigger chainring, double check the range of the front deraillieur, if you change just the big ring and the range is too big, then the front shifter won't work properly.

And if you need to change the smaller ring, make sure your new bigger small ring doesn't hit the frame.

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Based on the specs listed on your link to your bike, your Left shifter is a 2x only, meaning it will only work with a double front crankset. There is a 3x version of this shifter (M315). Your Shimano front derailleur is what is termed a "double front derailleur" meaning it is designed to work with the 2x crankset. While there are hacks that can enable a double front der to work on a triple chainring crankset (aka 3x), it is limited by the fact it is designed for a max large chainring of 36 teeth. Using it with a larger crankset-- especially a 3x-- will yield shifting problems and chain rub: read frustrating and annoying. With these two facts alone, one can ascertain that if a larger gear ratio is desired, more than just changing the crankset will have to happen.

Regarding the crankset, the chainrings are riveted and thus, cannot be replaced individually. Your proposed Shimano upgrade to FC-M315 doesn't do anything for increasing your gear ratio, as the 2x version is a 36-22 tooth count as well, and these chainrings are also riveted. Your bike has a square taper bottom bracket (the bearing assembly that the crankset fits on to) with a spindle length of 123mm. This is significant because any crankset you switch to must also be a square taper and have a reasonable chainline when on a 123mm spindle (in order to keep your current bottom bracket. You can put a good many cranksets on your bike as long as you also have or install a compatible bottom bracket).

All said, upgrading to a higher gear ratio will involve more than a change of chainrings. At least a different front derailleur for sure and possibly a different front shifter if you go to 3x up front. Regarding the "speed" listed for your crankset (7/8 speed) and any potential replacements: you can utilize a 9 speed crankset within your current set up and retain the same quality of performance as 7/8 speed (the above noted hurdles still exist, but being "9 speed" wouldn't really be an additional one).

While writing this I referred a few times to Shimano's latest Specification and technical document which outlines several details of their current lines of componentry. I noted a listing for a crankset, model FC-TY501-2, which is a double chainring crankset sporting 46 & 30 tooth rings and fits on to a square taper spindle 123mm in length. IF clearance isn't a problem with the larger chainrings, this would be a viable option for you as you could retain your current 2x shifter. You would need a more capable front derailleur (although I would certainly determine how unhappy the current FD became with the larger rings before installing a properly spec'd one). At any rate, front derailleur's are being heavily discounted at many retailers (especially online) as demand for them plummets with the rise of the 1x systems. If all that is required to successfully raise your gear ratios on that bike is a larger crankset and a different front der, that is about as good as you can do from an economical and ease of installation standpoint.

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