GRX FC-RX810 48/31 crank - smaller chainrings?!

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Tychom
Posts: 67
Joined: Thu Nov 26, 2015 11:29 am
Location: FR

by Tychom

steveadore wrote:
Tue Apr 11, 2023 9:26 pm
And to be on topic, I really wish it the RX600 and RX810 chainrings were interchangeable (I would prefer the 46/30 on the hollow forged 810 cranks arms), but as far as I understand, they are not compatible
They are compatible. Kind of.

Both the 48 and 46t chainrings have a pin that sits behind the crankarm to catch the chain in case of an over-shift. The 46t pin is longer than that of the 48t because the rear of the RX600 crankarms is different. The RX600 crankarm is concave rather than flat (and hollow) like the RX810 so this pin goes deeper into that cavity.

Now if you mount the 46t chainring on RX810 crankarms that pin will come in contact with the rear of the crankarm and you won't be able to tighten down the bolts (well you could, but you'd warp the chainring quickly :) ).

However that pin has handy marks on it for cutting down to size and use on an RX810 crankset - and that's easily done with a hacksaw.

RX810 with RX600 chainrings:

Image

RX600 with RX810 chainrings:

Image

I'm running the RX810 with RX600 chainrings with zero issues so far.

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voicycle
Posts: 170
Joined: Thu Apr 08, 2021 8:38 am

by voicycle

Amazing post, thank you Tychom! This is exactly the info I needed.

I don't suppose you've also determined whether there's any difference between the 10sp and the 11sp version of the 46t ring? I see some retailers have it listed as a 10/11 and others list both part numbers separately. IIRC from my GRX 1x experiences the only difference between chainrings at different tiers was the label printed on them, so I wouldn't be surprised if it's the same here...

steveadore
Posts: 386
Joined: Wed Mar 04, 2020 10:01 am

by steveadore

Tychom wrote:
Wed Apr 12, 2023 3:03 pm
steveadore wrote:
Tue Apr 11, 2023 9:26 pm
And to be on topic, I really wish it the RX600 and RX810 chainrings were interchangeable (I would prefer the 46/30 on the hollow forged 810 cranks arms), but as far as I understand, they are not compatible
They are compatible. Kind of.

Both the 48 and 46t chainrings have a pin that sits behind the crankarm to catch the chain in case of an over-shift. The 46t pin is longer than that of the 48t because the rear of the RX600 crankarms is different. The RX600 crankarm is concave rather than flat (and hollow) like the RX810 so this pin goes deeper into that cavity.

Now if you mount the 46t chainring on RX810 crankarms that pin will come in contact with the rear of the crankarm and you won't be able to tighten down the bolts (well you could, but you'd warp the chainring quickly :) ).

However that pin has handy marks on it for cutting down to size and use on an RX810 crankset - and that's easily done with a hacksaw.

I'm running the RX810 with RX600 chainrings with zero issues so far.
Amazing! Thanks! :thumbup: I assumed from the technical manuals that the bolts were different (they have different numbers). But you're saying the bolts actually fit? So it doesn't really matter if you use the 810 or the 600 bolts with the 600 chain rings on the 810 cranks?
And from photos, I also assumed that the curve of the four arms (where the bolt holes are) are slightly different between the two models, but I can see from your pictures that this is not actually the case.

So the only thing you need to do then is to cut that single pin to size? Wow!

Tychom
Posts: 67
Joined: Thu Nov 26, 2015 11:29 am
Location: FR

by Tychom

Yeah the shaping is all the same and they fit in place just fine.

As for the bolts, I can't recall now exactly but I believe they might be crankset specific, but they're not chainring specific. So e.g. you buy an RX810 crankset, sell the rings, put on RX600 rings (chop the pin). But you don't buy separate bolts.

The bolts fit perfectly in the recessed part of the small chainring in all cases.

I've not seen the 10 speed small rings myself so can't comment on that.

voicycle
Posts: 170
Joined: Thu Apr 08, 2021 8:38 am

by voicycle

If the bolts are anything like the road groupsets then literally the only difference is they are an allen key up to 105 level (RX600) and then Ultegra/DA get torx heads. IIRC I ordered all the different bolt part numbers when I went from 1x to 2x because of stock availability issues - will see if I can locate the spares and make any observations about them.

EDIT:
Turns out my spares aren’t GRX at all. I guess I was just buying anything that looked close in hopes that something would fit. Looking at my emails it seems like I bought the series-correct GRX810 bolts from a different retailer about a month after ordering the ones in the photo. Inner and outer chainring bolts on my 810 chainset are all torx key.

Image

satanas
Posts: 315
Joined: Sat Jul 04, 2020 5:45 pm

by satanas

Has anyone actually managed to buy the 2xTA rings, and if so how do their recommended sets shift compared with Shimano?

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