New build - Shimano RD-7000 short cage with 11-36 cassette?

[MyNameIsEarl]

Hi, I've just built a new bikepacking/touring bike and just noticed that I've used a 11 speed RD-7000 short cage with an 11-36 cassette (the SS RD is supposed to be 30T max). I only realised as there was a bit of noise when shifting. Oddly, with the B-screw all the way in, I still have 5mm space between the jockey wheel and the largest cog.

I'm also running that setup with a 46/30 GRX RX600 crankset.

Am I okay running the bike as it is? Other than noisy shifting, are there any other potential problems?

I think I'll order a RD-7000 GS Medium cage anyway, which has a 34T capacity, but was just worried that I've ballsed something up.

Thanks in advance!

 

[Dogtrousers]

It's not so much max sprocket as capacity that would worry me.

If I've done my sums right (big if) you need big+big minus small+small. That's (46+36)-(30+11)=41T capacity.

According to the Spa Cycles website:
The RD-R7000 SS has 35T capacity (and max sprocket 30T)
The GS has capacity 39T (max sprocket 34T)

So in both cases you're a bit short of capacity but it's better with the GS which has 39 vs your required 41.

And what will happen? Well if you don't have enough capacity and you fit a chain long enough for big/big then if/when you ruin in small/small or small/smallish the mech won't be able to take up the slack and your chain will flop about.

Is this bad? I don't know cos I've never done it but I'd guess it might be more susceptible to the chain coming off and it might bash into your chain stay and take the paint off. Shifting might suffer too, chain might come off the lower jockey wheel ... I don't know.

Usual caveats apply: I am an idiot and probably wrong.

 

[roubaixtuesday]

Wot DogT sed ^^^^

And above all else, make sure it'll run in big big before riding. The consequence of too short a chain for that is far worse than too long a chain for little little.

 

[MyNameIsEarl]

Usual caveats apply: I am an idiot and probably wrong.

I completely relate to this

 

[MyNameIsEarl]

The weird thing is, although I wouldn't run it in 'big-big' or 'small-small', there's still a bit of slack in big-big, and some tension in small-small, so the only problem seems to be the noise.

From what you've said Dogtrousers, I do agree and don't think I'll take that chance - I'll just change it for a medium cage.

Thanks!

 

[roubaixtuesday]

The weird thing is, although I wouldn't run it in 'big-big' or 'small-small', there's still a bit of slack in big-big, and some tension in small-small, so the only problem seems to be the noise

That's amazing. Are you *sure* is an SS?

 

[oxoman]

I did similar to yourself and struggled with noisy chain and swapped to long cage ultegra and then subsequently swapped to single up front which is still working today.

 

[wafter]

If you're replacing the RD anyway a GRX item makes sense..

 

[MyNameIsEarl]

That's amazing. Are you *sure* is an SS?

Yep. Obviously I took the photo at just the wrong angle (doh!), but you can see the 'S' of the SS on the back of the derailleur. Also showing biggie-bigs and smallie-smalls.

Also shows 5mm gap between the jockey wheel and the largest cog. To reduce the tension on big-big, I actually turned the B-screw out a few turns giving a 3mm gap, which improved shifting noise a bit. I still wouldn't go into biggie-big - with a bit of chain noise on the FD at the second to largest cog, that'll be my reminder to drop down to the small chainring.

I've ordered the medium cage anyway, but am a bit less worried about it now.

Thanks all for confirming I'm not doing something horribly wrong though.