If it looked like that in big-big it would be fine. It could be too short
HeeMakker on
Usually you put the chain on the largest wheels (which you did) but do the following:
You determine it as follows:
– Place the open chain on the largest sprocket & chainring (like in your picture) but NOT through the derailleur.
– The point where two ends meet is the “zero”
– Add count two extra links (each link is the “oval thing with 2 eyes”)
– If both ends are the same, add half a link so you have a matching pair.
If your rear sprocket has less than 42t, you would route it through the derailleur to measure it but therefore in your case, you have to do it for the measurement without the derailleur.
While the chain length wasn’t an issue, I’ve failed to get my 40t cassette working with the grx400 derailleur without massively reducing chain wrap around the smallest cog. The chain would have worn it away in a few rides.
Malte_1234 on
As long as it feels ok, I would ride it, but avoid this gear combination obviously.
shweeney on
at the very least it’ll discourage you from riding in big/big
ProjectAshamed8193 on
I would add one link.
jkakua on
At this point I think half of this sub is just people trolling with ridiculous things 😂
SlowRider30 on
Your cassette is not compatible with 2x transmission (maximum is 34t for 10/11s and 36t for 12s).
On largest cog and chainring it looks like the chain is not enough.
Your config will probably never be able to work properly.
Overall this will work, but it is far from perfect.
Switch the chain to the smallest cog and chainring in the front and back and post a photo, it help to understand if it is possible to lengthen the chain in your case.
blorg on
RD-RX400 capacity is 41T and max cog 36T, so you are well out of spec with 11-42 and I’m guessing 46-30 front, that’s 47T capacity.
This is absolutely not to state it won’t work, I know many people stick on larger than spec cassettes with GRX. But you do need to consider that given it’s out of spec, and 6T on both max cog and capacity is quite a bit out. It’s capacity that is the issue with chain length, which is basically how much slack the cage can take up, longer cage= more capacity.
So you’re not likely to get “perfect” in terms of the sizing, it’s going to be something that if you can have it working without siezing up or the chain falling off, good job.
You shouldn’t use big-big or small-small but it needs to be able to shift in there without ripping the derailleur off if you do it by accident. To me it looks like it’s OK on that front. If you lengthened the chain given you’re already 6T over, it will probably fall off a lot downshifting into the small ring. If you do have this issue, a chain catcher can help. But I wouldn’t lengthen the chain if you can shift up into that and it spins reasonably without seeming strained, you need the tightness to keep the chain on too.
BD59 on
Looks like it will shift to the big/big combination without breaking anything. The chain may be hanging loose on the smaller cogs in the small chainring, but that’s better than breaking stuff if you go into the big/big.
Many years ago, I ran a triple chainring, half step and granny crankset, with 50/46/26 chainring and a 13-32 freewheel. Yes, the chain went slack in the three smallest cogs with the 26 tooth ring, but I never used those combinations.
TJhambone09 on
Speaking from experience with this exact combo and chainstays roughly the length of yours, you’re going to want to consider a chain too short to shift into big-big. Not because one can’t make big-big AND small-small work with this rear derailleur, but because if you can clear the big cog while in the big ring you will have significantly compromised chainwrap in the small cog.
Primary_Employ_1798 on
If it goes through all gears without notching derailleur on cassette in lowest/highest then you’re good
17 Comments
Looks good
How does it look in small small?
The chain looks too short – see the instructions on page 11. https://si.shimano.com/en/pdfs/dm/GARD001/DM-GARD001-02-ENG.pdf
Too short
If it looked like that in big-big it would be fine. It could be too short
Usually you put the chain on the largest wheels (which you did) but do the following:
You determine it as follows:
– Place the open chain on the largest sprocket & chainring (like in your picture) but NOT through the derailleur.
– The point where two ends meet is the “zero”
– Add count two extra links (each link is the “oval thing with 2 eyes”)
– If both ends are the same, add half a link so you have a matching pair.
If your rear sprocket has less than 42t, you would route it through the derailleur to measure it but therefore in your case, you have to do it for the measurement without the derailleur.
More info here: [Chain Length Sizing | Park Tool](https://www.parktool.com/en-int/blog/repair-help/chain-length-sizing)
It’s a little snug but I’d send it
While the chain length wasn’t an issue, I’ve failed to get my 40t cassette working with the grx400 derailleur without massively reducing chain wrap around the smallest cog. The chain would have worn it away in a few rides.
As long as it feels ok, I would ride it, but avoid this gear combination obviously.
at the very least it’ll discourage you from riding in big/big
I would add one link.
At this point I think half of this sub is just people trolling with ridiculous things 😂
Your cassette is not compatible with 2x transmission (maximum is 34t for 10/11s and 36t for 12s).
On largest cog and chainring it looks like the chain is not enough.
Your config will probably never be able to work properly.
Overall this will work, but it is far from perfect.
Switch the chain to the smallest cog and chainring in the front and back and post a photo, it help to understand if it is possible to lengthen the chain in your case.
RD-RX400 capacity is 41T and max cog 36T, so you are well out of spec with 11-42 and I’m guessing 46-30 front, that’s 47T capacity.
This is absolutely not to state it won’t work, I know many people stick on larger than spec cassettes with GRX. But you do need to consider that given it’s out of spec, and 6T on both max cog and capacity is quite a bit out. It’s capacity that is the issue with chain length, which is basically how much slack the cage can take up, longer cage= more capacity.
So you’re not likely to get “perfect” in terms of the sizing, it’s going to be something that if you can have it working without siezing up or the chain falling off, good job.
You shouldn’t use big-big or small-small but it needs to be able to shift in there without ripping the derailleur off if you do it by accident. To me it looks like it’s OK on that front. If you lengthened the chain given you’re already 6T over, it will probably fall off a lot downshifting into the small ring. If you do have this issue, a chain catcher can help. But I wouldn’t lengthen the chain if you can shift up into that and it spins reasonably without seeming strained, you need the tightness to keep the chain on too.
Looks like it will shift to the big/big combination without breaking anything. The chain may be hanging loose on the smaller cogs in the small chainring, but that’s better than breaking stuff if you go into the big/big.
Many years ago, I ran a triple chainring, half step and granny crankset, with 50/46/26 chainring and a 13-32 freewheel. Yes, the chain went slack in the three smallest cogs with the 26 tooth ring, but I never used those combinations.
Speaking from experience with this exact combo and chainstays roughly the length of yours, you’re going to want to consider a chain too short to shift into big-big. Not because one can’t make big-big AND small-small work with this rear derailleur, but because if you can clear the big cog while in the big ring you will have significantly compromised chainwrap in the small cog.
If it goes through all gears without notching derailleur on cassette in lowest/highest then you’re good