Subcompact 2x possible on Rotor 3d24?

[satanas]

There are at least a few potential issues here...

1. The bikinGreen rings are definitely offset inboard; I have a set. It's difficult to measure exactly how much, but the way they make room for the chain on the 30T ring is to move it inwards, towards the frame, plus the bolts are a smaller diameter and sit on a smaller radius. The chain side plate then fits *between* the inner ring and the spider - there is a gap of ~2mm. (My digital calipers have a flat battery so I can't be more precise.) The outer ring sits partially above the spider tabs rather than outboard of them. The illustrations online DO NOT make this clear; I only found out once the rings arrived. If you have 12 speeds and Di2 your chances of success will be lower...

2. The GRX chainline is +2.5mm outboard, while bikinGreen is -2+mm inboard, so 4.5+mm different; you don't want to run a GRX FD.

3. Depending on your frame, FD mount, etc, it may be the case that the FD parallelogram could bottom out on either the seat tube or itself before shifting reliably. Without seeing things it's impossible to make a reasonable guess.

4. If you have an integrated FD mount + a braze-on FD, the tab may not allow the FD to sit low enough. (FWIW, Sugino make an adapter to fix this.)

5. If you have a spider-based power meter it's likely that anything smaller than a standard inner ring will foul it and thus not fit. If spindle-based or on the crankarm(s) it should be okay.

The Rotor 46x30 one-piece spidering would presumably maintain the standard chainline and so ought to be the safer choice..

[naylor343]

There are at least a few potential issues here...

1. The bikinGreen rings are definitely offset inboard; I have a set. It's difficult to measure exactly how much, but the way they make room for the chain on the 30T ring is to move it inwards, towards the frame, plus the bolts are a smaller diameter and sit on a smaller radius. The chain side plate then fits *between* the inner ring and the spider - there is a gap of ~2mm. (My digital calipers have a flat battery so I can't be more precise.) The outer ring sits partially above the spider tabs rather than outboard of them. The illustrations online DO NOT make this clear; I only found out once the rings arrived. If you have 12 speeds and Di2 your chances of success will be lower...

2. The GRX chainline is +2.5mm outboard, while bikinGreen is -2+mm inboard, so 4.5+mm different; you don't want to run a GRX FD.

3. Depending on your frame, FD mount, etc, it may be the case that the FD parallelogram could bottom out on either the seat tube or itself before shifting reliably. Without seeing things it's impossible to make a reasonable guess.

4. If you have an integrated FD mount + a braze-on FD, the tab may not allow the FD to sit low enough. (FWIW, Sugino make an adapter to fix this.)

5. If you have a spider-based power meter it's likely that anything smaller than a standard inner ring will foul it and thus not fit. If spindle-based or on the crankarm(s) it should be okay.

The Rotor 46x30 one-piece spidering would presumably maintain the standard chainline and so ought to be the safer choice..

Thanks for your detailed response. What cranks do you have them mounted on?

So I now understand that the 2-2.5 mm spacing is to prevent the chain outer plates fouling. I am still keen to go for this set up but am still hoping that it will work with the 110mm power2max. I have contacted the manufacturer but as yet have recieved no reply. There support page states they will work with the P2M, but unhelpfully it only states this for the shimano 4 bolt, but does not say whether or not it will work with the 5 bolt. What difference there could be, is not clear. Also to add to confusion on some older posts on other forums, some say it works with a spider PM and others, as you do here, cast doubt on this.


After thought:

On comparing my rotor 3d spider with my power2max I also now am of the opinion that using the Bikingreen/croder rings will not work well with the P2M. Even with the inboard ring creating a gap, when used with the P2M with the chain in anything but a perfect centre line it will I believe rub the power meter spider. This is not such an issue when just using with a standard spider, as that rub if any, will occur against the outer ring.

Settling for a simple Sram 1130 11-36 cassette, although not my preferred option, is looking more likely.

[frnchy]

FWIW I'm running a set of 46/30 110 BCD 5 bolt Bikingreen rings on a Sigeyi Axo PM spider with no chain rubbing in any (reasonable) gear whilst in the small chainring. I did have issues with my front derailleur not being able to move inboard far enough though. I had to file away a lot of material from the low limit stopper and even then there's a tiny amount of rubbing in the lowest gear, but I can't move it further inboard because then the cage rubs on the tire and tilting the cage out results in chain drops up front unless I adjust the limit screw to the point that it rubs in high gears... so perfect performance is very setup-specific, and probably not achievable with 50mm tires like mine

[satanas]

FWIW, I have both the 4 bolt and 5 bolt 46x30 bikinGreen rings. The 4 bolt are on DA 9000 cranks, but the 5 bolt haven't found their way onto a bike yet. I don't have any power meter spiders but IIRC some people have reported problems with even the TA 33T rings, which puzzles me.

Praxis Works say their 48x32 rings won't work on power meter spiders here...

https://praxiscycles.com/product/road-rings/

"Also, these 48/32 sets will not install on spider based power meters such as Power2Max, SRM or Quarq."

...presumably because they need a step or bevel on the spider tabs for chain clearance. With normal alu spiders one could just file a little metal away, but doing this would void any warranty and so isnt safe to recommend for liability reasons. (If you have cranks that are out of warranty I'd just do it but YMMV.)