Buying chainrings, need reccomendations

Discuss light weight issues concerning road bikes & parts.
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eyedrop
Posts: 101
Joined: Wed Jan 27, 2016 5:33 am
Location: Prescott, AZ

by eyedrop

I have an 8 speed Shimano RSX crankset which came with 50/42/30. I want to change it to 50/37/26. Can someone give me shopping links to some? Im looking for something light and relatively innexpensive.

Also, do i need a "chain watcher" to avoid overshifting? Finally, will this setup exceed the derailuers capacity? Im using the stock 8 speed RSX long cage with a 28t cassette.

Valbrona
Posts: 1482
Joined: Fri Oct 28, 2011 3:25 am
Location: United Kingdom of Great Britain and Northern Ireland

by Valbrona

Chainrings usually come in even numbers.

If you want something like 26/36/50 you will have to buy the chainrings separately and create a custom configuration.

Might be asier to buy a new 'off the shelf' crankset with chainring configuration similar to what you want.

by Weenie


eyedrop
Posts: 101
Joined: Wed Jan 27, 2016 5:33 am
Location: Prescott, AZ

by eyedrop

Valbrona wrote:Chainrings usually come in even numbers.

If you want something like 26/36/50 you will have to buy the chainrings separately and create a custom configuration.

Might be asier to buy a new 'off the shelf' crankset with chainring configuration similar to what you want.


I really like that idea, especially since my RSX crankset is heavy. I would also like to get a crank based power meter such as the stages, but i need a more modern Hollowtech II crankset for that. Problem is, all Hollowtech II cranks are 9 speed or higher, and i beleive they cant go any lower than 30t. The other issue is I think i would need a new bottom bracket. Not sure where to go from here... i would really like to get rid of my heavy powertap, get a modern powermeter and keep my ultra low gearing, but i need some specific guidance. Please tell me what to buy...

ooo
Posts: 496
Joined: Sat May 21, 2016 12:59 pm

by ooo

26t small ring on road triple crankset is possible, but you will not find 37t middle ring
lowest middle ring you can find for road shimano triple is 38t (9/10sp 130 BCD)

You can use mtb triple crankset, 9sp 48-36-26T stock rings will be ok for 8sp chain


9sp 48-36-26T crankset 104/64 BCD - Hollowtech - (chainline 50mm with o-spacers on both sides, 45mm when 3 o-spacers on the left)
Shimano FC-M4060
Shimano FC-T4060

9sp 48-36-26T crankset 104/64 BCD - Octalink - (chainline 50mm with 126mm axle; 46mm with 118mm axle)
Shimano FC-T4010
Shimano FC-T3010

9sp 48-36-26T crankset 104/64 BCD - Square - (chainline 50mm with 123mm axle, 45mm with 113mm axle)
Shimano FC-T3010
Last edited by ooo on Thu Jan 05, 2017 9:09 pm, edited 3 times in total.
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eyedrop
Posts: 101
Joined: Wed Jan 27, 2016 5:33 am
Location: Prescott, AZ

by eyedrop

ooo wrote:26t small ring on road triple crankset is possible, but you will not find 37t middle ring
lowest middle ring you can find for road shimano triple is 38t (9/10sp 130 BCD)

You can use mtb triple crankset, 9sp 48-36-26T stock rings will be ok for 8sp chain
Shimano FC-M4060 - Alivio Hollowtech 9sp 48-36-26T crankset 104/64 BCD


A 38 or 39t middle is actually a compromise im willing to make. The Alivio would be nice if it had a 50t or 52t big ring....

After doing some research, i now realize I CAN upgrade to a hollowtech crankset as my bb is 68mm, but i would need a new bottom bracket, which is not a big deal. So i think maybe buying something like a 6503 crankset and just replacing the inner ring would work well and save me weight over going the MTB route. But i do wonder if my front deraileur would work with it. And if i need to upgrade my front deraileur, would the RSX shifter work to control it?

Edit: just realized 6503 crankset is not hollowtech II, so its incompatible with stages... Would a 6603 10 speed crankset work?

ooo
Posts: 496
Joined: Sat May 21, 2016 12:59 pm

by ooo

FC-6603 triple crankset with 130/74 bcd will be ok,
with 8sp chain you will need 8sp or 9sp chainrings (10sp not recomended)
with 9sp chain you can use 10sp chainrings and 8sp everything else

I guess you will need to upgrade FD and it is better to get 8sp-9sp fd
(8sp fd for 8-9sp chain, 9sp fd for 9sp chain, wider cage for wider chain)

50-39-28 will be fine with any FD rated for 50-39-30
50-39-26 - try to google "50-39-26" with your fd candidate model number to find info
RSX 8sp STI and FD compatibility - not sure, my guess it's 7-8-9sp compatible.
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by Weenie


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