Gravel Grinder cassette choice?

Hey so I’m building up my gravel grinder. I’ve gone with a SRAM Rival group but looking to run a long cage X9 rear derailleur so I can run up to a 11-36 cassette. Cause I’m thinking those 4 extra teeth will help me get up the really steep stuff. Probably overkill but keen to hear people’s thoughts… Any major downsides to running a long cage derailleur? chain slap? chain suck? Longevity of chains?

Slightly sloppier shifting. I wouldn’t worry about the extra teeth in the cassette if you do a lot of road riding, the gaps will shit you to tears. I think your better off swapping about front rings. Or if you do a big mix of loaded riding and commuting maybe even look into a triple on the front.

I did this oneon a 34T compact crank with a 27/12 cassette and it was fine.

I’d rather go lower at the front to avoid a long cage RD. It’ll depend on your own preference, weight & strength but if I’m on 34/27 and it’s still too steep then I’m probably better off walking.

i run a ultegra road triple groupset on my cross check, (30-39-52) up front with an 11-28 cassette and a medium cage derailleur i believe., i’ve done light touring and daily commuting

11-36T on a MTB works fine, so technically no problem at all. What frame is it going on?

long cage sticks out more (obviously) so it’s more likely to get caught up in sticks n shit

cage length won’t get you to the big sprocket, the parallelogram angle will. The cage wraps more chain to help with the large delta between granny-small & big-big. If you don’t have a triple you can probably get away with a med cage just fine, most of the current stuff can reach a 34/36 easy. Check the specs, run your numbers and see.

if you’re going to do some kiddie hauling / overnighters etc, a 32/34 on the rear would be useful in lieu of a twenty something granny ring.

Blakey speakth the truth.
Been down this path. Shimano 105 and higher will only get you a 27/28T (depending on vintage) rear sprocket regardless of cage size.
Pretty sure the Tiagra/Sora RD will give you 30T but this might only be in 10 speed and not 9 speed.

I still think the Shimano XT M771 GS is one of the better 9 speed options, max. sprocket is 34T and you can get 1:1 with a standard road compact crankset.
But the gaps in ratios couple be really annoying as shakes pointed out.

Thanks for al your replies guys.

Firstly H, its a(nother) Cross Check. About 80% there. Would be nice to have it done for Deeds, but we’ll see, I’m not rushing it.

Shakes, Thanks for that. I think you’re right. I might end up adjusting the Chainrings too, but with a 16 tooth spread between rings I’ll still need a med/long cage anyway, so I’ve been told. Really trying to avoid a triple if I can because I’m a terrible crossringer and should only be allowed to run a double up front. :o

Blakey, thanks for that. You’re bang on the money, baby hauling and bikepacking makes me wanna be able to run a MTB cassette. To be honest I’m finding it tricky to find the information as to whether I’m best running a medium or long cage. According to the reading I’ve done I’d require a long cage because the 50-34 + 11-34 or 11-36 = 39 or 41T slack. The medium cage has a manufacturer’s stated capacity of 37T, the long 43T. That stated I’m wonder how conservative those stated capacities are…

Some relevant reading for those interested:
10 SP SRAM Rival to a 9 SP SRAM X9: I wan to keep my shirt on please… [Archive] - Bike Forums
When to use a Long Cage vs Short Cage Derailleur? - Mtbr Forums

Cheers guys!

Alternative is to go for CX chainring, 46/36 and you’re in like Flinn.

You legend! 46 - 11 is still 112.9GI - that’d be more than plenty. Awesome.

Whats all this “works best with 36T”, what would be the difference than running it with a 34T?

They are fairly bang on, go more than a couple of teeth outside of them and you will start having chain length issues. Which then becomes a big compromise between shift quality, keeping the chain tensioned and being able to get the entire range of gears. I am running a 11-32 with a 32t front ring and 29x2.2 tires the spread of the gears on the rear shits me to tears and next cassette will be much tighter. and I’m finding it’s rare to use the larger couple of gears on the back or drop into the granny unless I am towing 30kg of kid and trailer and junk. Even then I dont really need to.

As larfinboy said go cx rings, if your really concerned make sure you get a crankset that will allow a 30t or even 28t small that you can swap out for gg’s or touring. For that a mid cage should be fine (do the maths though)

I think the ‘works best’ is more like ‘works’ compared to another model which isn’t spec’d for a 36T but ‘may work’.
It will work perfectly well with a 34T.