So, I know being in the big cog front and back is not a usual ratio to use, and it looks like I have the chain too short. But why when on both small cogs front and back why is there so much slack? I had a 105 rear derailleur on previously, put this GRX on when that broke.
by Boltinggnome6
11 Comments
Which GRX RD did you put on? The 1x RD doesn’t have enough chain capacity a 2x system. I’m no mechanic, but the b screw looks like it’s barely hanging on… is the derailleur aligned properly on the hanger?
The rear mech is a different dimension? Did you check on size before you put the new one on? Long and short cage rear mechs are a thing.
Check the specs for this specific derailleur model. It will have a rated spec for the largest rear cog it can accommodate, and also for how large of a jump between front chainrings it can handle
Your RD is most likely designed for 1x cranks.
That derailleur doesn’t look like it’s mounted correctly. I *think* that’s a direct-mount hanger, which shouldn’t use the B-link (the little black piece on the derailleur).
[https://wheelsmfg.com/blog/standard-mount-vs-direct-mount-derailleur-hangers.html](https://wheelsmfg.com/blog/standard-mount-vs-direct-mount-derailleur-hangers.html)
is that derailleur [compatible](https://www.google.com/search?q=Cassette+derailleur+compatibility+shimano+105+%26+grx&client=safari&sca_esv=49f8345e411de2b2&hl=en-us&biw=375&bih=621&ei=e-ktaJCxILnX5NoPp7r-yAs&oq=Cassette+derailleur+compatibility+shimano+105+%26+grx&gs_lp=EhNtb2JpbGUtZ3dzLXdpei1zZXJwIjNDYXNzZXR0ZSBkZXJhaWxsZXVyIGNvbXBhdGliaWxpdHkgc2hpbWFubyAxMDUgJiBncngyBRAhGKABMgUQIRigATIFECEYoAEyBRAhGKABMgUQIRigATIFECEYnwUyBRAhGJ8FMgUQIRifBUjgNVDSDFiUMnAAeAOQAQCYAXqgAbUHqgEDOC4yuAEDyAEA-AEBmAIMoALxB8ICBBAAGEfCAgYQABgWGB7CAgsQABiABBiGAxiKBcICBRAhGKsCwgIFEAAY7wXCAggQABiiBBiJBZgDAIgGAZAGCJIHAzcuNaAHlk-yBwM1LjW4B-cHwgcHMC4zLjguMcgHNw&sclient=mobile-gws-wiz-serp) with your old 105 drivetrain? it’s not always as easy as plug + play
Which GRX? There are two: one designed for a single front ring and one designed for a double. The single doesn’t have enough capacity to run on a double.
Rear derailleur capacity is the maximum amount of chain slack the derailleur can take up – the number of sprocket teeth. It’s calculated by adding the difference between the largest and smallest chainrings to the difference between the largest and smallest cassette cogs: (biggest cog teeth – smallest cog teeth) + (biggest chainring teeth – smallest chainring teeth).
GRX singles have a capacity of 31 teeth and doubles have a capacity of 40. Your 105 (if it was an SGS) had a capacity of 39 teeth.
Cross-chaining is probably not necessary. Like, youd have to be going 40+mph to even think about using big/big. And small/small is just get off and walk the bike territory.
Your b link isn’t oriented correctly. Look onoine for how to do it.
I don’t know the answer to your problem, but why would you ever need to do these gear combos? Cross chaining big/big and small/small is kind of a no-no, right?
It’s definitely the 2×11 version. What I’m not sure about is that it’s installed in the hanger correctly, the B tension screw looks to be striking it at a really tangential angle