[Closed] what size sram rear mech for 36t middle chainring?

You say middle ring, top end? Are you 1 x 10?

If that's your only ring up front, it doesn't matter what size ring it is, as it stays constant. The sprung cage on a mech is there to take up the slack in the chain when you use smaller sprockets, so in your system, the only difference is from biggest sprocket and smallest sprocket on the cassette. 11-36?

How much slack a mech can take up is called the capacity of the mech, and is stated in number of teeth. eg 2x10, you might have 26-38 chainrings and a 11-34 cassette. difference from smallest to biggest = 38 minus 26 = 12, plus 34 minus 11 = 23. Total tooth difference is 35, you'd need a mech with a capacity of 35 T.

So from that ^ you'll see that if you're 1 x anything, you won't need a long cage mech.

Just checked the link, and they don't state the capacity, just the "compatibility" with a 36T cassette, which is another thing.

You need the mech to be able to move at an angle that it won't run into he largest cassette cassette sprocket. a road mech will move along a lower angle, as they're desigend to work with smaller range of sprockets (11-25?) on a road cassette. If you had a 40T sprocket on your cassette, these mechs wouldn't move down far wnough to work with it.

Hope all that helps!

[url= http://cdn.sram.com/cdn/farfuture/LJH1vaSvuSBBt_2FVIDwRbfJHuO0kaLua0Kk5NdI_jw/mtime:1372788174/sites/default/files/techdocs/gen.0000000004184_rev_a_compatibility_map_my13_mtb_components_0.pdf ]This chart by SRAM[/url] should clear things up!

Edit: To summarise though, if you're 1x on the front and a normal X9 cassette (up to 36t - without any of the bigger ring adapter thingies) then you'd be fine with a short cage (which is good as that's my setup!)

Mech capacity refers to the largest sprocket on the cassette, where as short, mid, long can be thought of as, single, double or triple chainring. The two are not Really related.

Olly - No, they aren't, but you're not quite right about "capacity"

http://www.sheldonbrown.com/derailleur.html

Hey,

I am running the small and middle chainrings.

I want to get the best range out of the 20 gears available, with minimum cross over. I need to still get up the hills, but want a little more at the top, hence 36t for the middle chainring.

I currently have 34t on my cassette, but I'm gathering I will be looking at more like 40t with 10x cassette? I am also running 32t on my middle chainring and 22t on my small.

I think I'll be looking at getting a 11t-36 x10 with 22t & 36t for my chain rings. Could I go to 38t for the middle chainring or will I loose some gears in the middle?

BTW, what size sram mech would i need for that set up?

Thanks so much 🙂

36/22 with a 36-11 cassette needs a long cage going by the SRAM chart.

SRAM/Mr Blobby's clear-as-mud chart (eventually) says long. but you wouldn't be able to go bigger at the back than 36T, which should be plenty of you've got 22 ring up front.

What's wrong with that chart 😉

22-36 is for winching yourself up a wall. Do you really need gearing that low?

Ah,

thank you very much people.... looks like I'm going long 🙂

Just out of interest. If I went say, 38t, for the chainring, will I lose any gears in the middle?

Probably not, been a long time since I've ridden a double on the mtb but there's usually a fair bit of overlap (can't be bothered plugging it into sheldonbrown). Will be a bigger jump though when shifting at the front which may be annoying.

None at all. You've got duplicated (near enough) ratios from about half way up the cassette

If you want to check you can put your chainring/cassette numbers into the calculator here - http://sheldonbrown.com/gears/

The numbers themselves don't matter so much, but you can see how they relate, and where the corssover is between the gears available from the big chainring and the gears available from the small chainring

bit behind Mr blobby again!

... but a lot more thorough in your response 🙂

Cheers guys, might go for a 22t/38t combo then with a long mech 🙂

Much appreciated 🙂

I was running a 12-36 rear (9 speed) with 24-38 front rings using a X7 medium cage with no problems whatsoever.

Yup need long cage for that capacity

You can definitely get away with a smaller cage if you don't cross the chain from biggest at the front to biggest at the back, and smallest-smallest, which you shouldn't be doing anyway.

Ok guys,

went for the long cage as I do sometimes cross the chain, which I have done for 5.5 years on my old x9 setup and was fine.

Here's my stuff. Think this should all work ok?

Sram X9 Type 2 Carbon Long Cage 10 Speed Rear Mech
SRAM PG1070 10 Speed Cassette - 11-36t
SRAM PC1091 10 Speed Hollow Pin Chain
Blackspire super pro 34t - Ended up wanting nice shifting from the 22 so went a bit smaller
Blackspire super pro 22t
hope lightweight bashguard 32 - 34t - Looks quite pimp and a bit lighter than the huge thing i have now...
SRAM X9 10sp Trigger Shifter 2014 - pair 2x10sp

So much for a frugal month 😉 Looks like a student diet for the rest of the month 😉

oh.... and not forgetting one of these 🙂

Blackspire Stinger - ISCG Mount/Red

"CLICK"..... noise of padlock on wallet... "Step away from the credit card sir....!"