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Rotor 3df replacement

by Huckfinn
Tue, Feb 16, 2021 11:07
9

So, I'd like to replace a Crankset : Rotor 3DF, 36/46 with something better suited for my hills here, like a 31/48. Seems like (from rotor website) that compatibility isn't an issue. Can anyone confirm this...?

Thanks!!!

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9 comments

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Joe Totale | 3 years ago
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I'm not sure what you're asking but here's my two pence worth.

I've got a Rotor 3DF crank and it's great, super stiff. It's got a 30mm axle whilst all Shimano ones have 24mm axles. You'll need either a different bottom bracket or reducers in your current one. 

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Mathemagician | 3 years ago
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Compatibility with what exactly?

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mdavidford replied to Mathemagician | 3 years ago
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Determinism?

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Huckfinn replied to Mathemagician | 3 years ago
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Thanks. Yeah, sorry about that! For example, the Shimano GRX 46/30?

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Mathemagician replied to Huckfinn | 3 years ago
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Sorry, I'm still not clear on what question you're asking here. You seem to be asking whether a Shimano GRX 46/30 is compatible with a Rotor 3DF 46/36...do you mean to ask whether you can replace the Rotor 3DF with the GRX? If so, yes, you should be able to.

But...can you not just swap out the chainrings on the crankset you have? I'm guessing the 3DF is a 5 bolt 110 mm BCD, which I'm fairly sure you can get a 32T chainring for?

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Huckfinn replied to Mathemagician | 3 years ago
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Ok, thanks to all and sorry if I wasn’t clear. I simply want to replace the 46/36 with something that is easier on my legs on our very steep hills. At Rotor they told me the smallest inner ring for the 3df is 34t. A 32t (any 32t) 110 bcd doesn’t exist. Hence my question of what my chainsets replacements are. How do I get a 32, 31 or 30t inner on my bike?(apparently sram back derailleur does 11-36max)..... 32,31 or 30 front with 36 back would be great!

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Mathemagician replied to Huckfinn | 3 years ago
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Ah right, I'm with you now- sorry. Ok so if you can't get a small enough chainring then I guess a new chainset it is. The GRX will require a new bottom bracket I think...I believe the 3DF has a 30 mm aluminium axle, while the GRX will have a 24 mm axle. Your chainline might be slightly different too, though I doubt this will cause any problems other than having to readjust your front derailleur.

Edit: I'd check to see whether the front derailleur you have will go down to a 30T...you may not be able to lower it far enough. It might be fine, but not sure.

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Joe Totale replied to Huckfinn | 3 years ago
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Rotor are wrong, you can get 48/32 5 bolt, 110bcd chainrings but it's expensive:

https://absoluteblack.cc/oval-sub-compact-chainrings-48-32-for-110-5-bcd/

I have an oval chainring on my CX bike, you don't notice really notice it but I'd alos say that I don't really notice any benefits over round ones. 

Pair it with an 11-34 cassette and you can climb anything. 

 

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wtjs replied to Huckfinn | 3 years ago
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 A 32t (any 32t) 110 bcd doesn’t exist

This doesn't help on the original question, but the worry I had when buying my Vitus gravel was the FSD 4 bolt 120/90s which came with 48/32 and 11-32. I knew I really needed 46/30 and 11-34 for pulling a trailer etc. I couldn't find any replacement rings at all initially and I thought that there may never be any because Big S went for  4 bolt 110/80 on GRX. Eventually, I found 46/30 and bought the bike, which proved to be one of my best ever cycling decisions. I'm still using the originals because I feel it's my duty to wear things out! So if you can get 30 on 90 BCD, it seems likely you can get 32 on 80. However, strange things happen with bolt patterns and chainrings...

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