Subcompact 2x possible on Rotor 3d24?

[naylor343]

Does anyone know of any manufacturers who make either a subcompact 2x spider or 2x direct mount chainrings to fit the Rotor 3d24 crank? Wanting to go smaller than 110bcd and keep the cassette gaps tight. I have searched the net but only find options for the 3d+ 30mm and newer models. Thanks.

[jfranci3]

You likely need a Rotor REX3 Spider or a power2max power meter.
As far as I can tell, the differnces in between the 3D24 and Rex 24mm are just the spidle width and the arms flare, the spider is the same. https://velotechservices.co.uk, https://www.velo-perso.com, or Rotor.

You're probably going to pay $50-100 for the Rex3 part if you can find it + $100-150 Rings & You also need a special tool. An Aldhu is $225+ the 46/30 rings are anogther $150. You can then recover $150 on your current Rotor 3d24 setup.

[naylor343]

You likely need a Rotor REX3 Spider or a power2max power meter.
As far as I can tell, the differnces in between the 3D24 and Rex 24mm are just the spidle width and the arms flare, the spider is the same. https://velotechservices.co.uk, https://www.velo-perso.com, or Rotor.

You're probably going to pay $50-100 for the Rex3 part if you can find it + $100-150 Rings & You also need a special tool. An Aldhu is $225+ the 46/30 rings are anogther $150. You can then recover $150 on your current Rotor 3d24 setup.

Thanks for the info. Looked at the Rex spider, could not find any stock, but it is the opposite problem as only mountain bike rings fit and they are too small. Also as you point out, the cost! New cranks it is.

[Pyotrump]

what about using this?

https://www.crodercycling.com/product/c ... 17fdc47b25

Absolute black also provides similar option.

[satanas]

Rotor at one point made a 110/74 double spider for the 3D cranks, intended for MTB use; I have a set of these cranks. I don't know if there would be chainline issues if you used this with the road length spindle, but it could perhaps do the job. They were never common though.

There are perhaps other options too, depending on what size rings you want, and what shape they need to be. On a 110 BCD spider one can fit:

1. Praxis 48x32 rings - the spider will need relieving for chain clearance
2. Absolute Black 48x32 or 46x30 oval sets - these use different (smaller) bolts and the sizes differ between the two so rings won't interchange between sets
3. BikinGreen 48x31 or 46x30 round sets - these use smaller bolts and offset the rings inboard for chain-to-spider clearance

[naylor343]

Pyotrump & Satanas, thanks for this info guys. The Bikingreen/croder cycling 46/30 combo is exactly what I need, perfect. Get some good reviews too. On 'normal' gravel i am happy with a road compact setup, but where i live the off road leans far more towards MTB territory and some of the climbs are back breakingly long. Also doesn't add any chain line/spacing issues. Extra bonus is I can use these rings on my Power2Max too. For info, I have found them on Ebay for €86, then + import costs as direct from Taiwan. All still cheaper than a new Rotor setup or GRX crank + front derailleur for compatibility. Thanks.

[satanas]

The bikinGreen rings are offset inboard by ~3mm so may indeed cause chainline issues depending on what other bits you have. Top gear may be a tad noisier, but everything else ought to be good, however your FD will need to be able to move further inwards.

[naylor343]

The bikinGreen rings are offset inboard by ~3mm so may indeed cause chainline issues depending on what other bits you have. Top gear may be a tad noisier, but everything else ought to be good, however your FD will need to be able to move further inwards.

OK, is this the same compatibility issue people find with the GRX crank? Is this all counteracted by simply fitting a grx front derailleur?

[jfranci3]

What crank are you moving to?
Rotor sells a DM 46/30 for their lineup - $200 ish w/ spider.
FSA $100 w/ spider.
Praxis (48/32) $132.
Power2max Rotor Aldhu $590 (spider & FSA? rings) or (all in) = or $620 w/ crank (US/CA Store ; EU store $790 for some reason) these can be 104bcd or GRX rings;

[naylor343]

What crank are you moving to?
Rotor sells a DM 46/30 for their lineup - $200 ish w/ spider.
FSA $100 w/ spider.
Praxis (48/32) $132.
Power2max Rotor Aldhu $590 (spider & FSA? rings) or (all in) = or $620 w/ crank (US/CA Store ; EU store $790 for some reason) these can be 104bcd or GRX rings;

I'm going to stay with the rotor 3d24 and combine it with the bikingreen 46/30 rings. I have two 3d24 110bcd crankset, one on a standard spider and one with P2M so I can use with either as and when required. As was pointed out above, the chain line moves in by 3mm so will possibly need a grx front derailleur too. Really happy with this setup as it will give me my original requirements of the 46/30 upfront, plus the added bonus that these rings can also be used with my power2max. Also I have 11-32 cassettes on all my road wheels and this ratio with the 46/30 will be as small as I need to go even off road in the high mountains. I also already have an 11-34 for any really long days. All of the above for an outlay of less than €100 for the rings plus €30 for a new front derailleur. Win win

[jfranci3]

I'm missing something. GRX is 2.5mm outboard. These look to be 3mm inboard. You need to space out your 3d24 a few mm. Get some crank spindle shims and push it out 2mm or so.

[naylor343]

I'm missing something. GRX is 2.5mm outboard. These look to be 3mm inboard. You need to space out your 3d24 a few mm. Get some crank spindle shims and push it out 2mm or so.

OK thanks. As I am sure you have guessed this is all very new to me. Everything else I have is just standard shimano 24mm 110bcd standard on all my bikes, throwing in different chainring offsets, front derailleur offsets and all there compatibility issues is all confusing.

So, if I was to space out 2mm of so, I should be able to continue to use my current r7000 front derailleur, would this be correct?

When I started this post I was content just to get the lower gear via subcompact rings. Now I know that there is a possibility that will also allow me to use my P2M I really want this as I want to train more each week on gravel to get away from the busy summer roads.

Two choices now, bite the bullet and try these rings or just settle for the easier, less desired option, and get a SRAM 11-36 cassette. Easier option is the latter as I know the 11-36 will just work.

[hartox]

I don't think the BikinGreen rings do have an offset (can't seem to find any info on that on the web). The inner ring mounts flush to the spider, I don't see a 3mm inboard offset.. If your FD can be adjusted low enough it should work pretty easy.

[naylor343]

I don't think the BikinGreen rings do have an offset (can't seem to find any info on that on the web). The inner ring mounts flush to the spider, I don't see a 3mm inboard offset.. If your FD can be adjusted low enough it should work pretty easy.

Agreed. The information on the 3mm was provided earlier in this post. Having searched online reviews, people appear to be using it successfully without issues using standard road groupset front derailleur. No mention on these reviews about any offset. I am going to contact the manufacturer just to be sure.

Edit: no FD issues, it's band-on not braze-on.

[jfranci3]

I agree IN/OUT shouldn't be an issue and you can shim it out pretty easily if not, especially with that clamping crank arm. Down to 46/30 might be an issue with a braze-on FD, but you can buy a step down adapter.
You'll want to shim it out for chain line anyway. Probably use a 12sp chain too.

https://www.lordgun.com/fsa-super-compa ... er-bolts-1

https://www.rotorstore.eu/product/rotor ... ers-24-mm/