# SRAM short-cage rear derailleur w/30t cog?



## SystemShock (Jun 14, 2008)

Quick Q: 

On one of my bikes, I'm running a short-cage SRAM Rival RD. Am thinking of putting a 12-30 cassette on, but the RD is rated for 28t cog max.

I know with most Shimano RDs, you can get away with exceeding the max some, but I don't know if SRAM RDs have less room for error. I read about one person even 'snapping their SRAM RD in half' when trying to run a 30t cog, if that's to be believed. 

Your experiences? I know the SRAM medium-cage RD can handle it, but that's not what I have.


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## cxwrench (Nov 9, 2004)

Guess you'll just have to try it and see what happens. Unless you tell us what frame you have and someone w/ the exact same frame/derailleur/cassette replies...


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## SystemShock (Jun 14, 2008)

cxwrench said:


> Guess you'll just have to try it and see what happens. Unless you tell us what frame you have and someone w/ the exact same frame/derailleur/cassette replies...


Could be. But we're hoping for some less anal-retentive replies.


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## cxwrench (Nov 9, 2004)

SystemShock said:


> Could be. But we're hoping for some less anal-retentive replies.


Maybe you could explain how else you'd like your question answered. I'm all ears. It's not supposed to work, but it might depending on the length of the hanger. So that leaves us where? You guessed it...you'll have to try it and see. I'm not being anal, I'm just honestly answering a fairly vague question.


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## looigi (Nov 24, 2010)

FWIW: On my bike with short cage Red, the B screw needs to be turned all the way in to get adequate clearance between the guide pulley and a 28 cog. To go to a 30 you'd need to move the top of the guide pulley down about 4 mm more, which wouldn't happen on my setup with the stock screw. Perhaps a longer screw might make it work (or maybe tightening the attachment bolt with the stop rotated a bit clockwise)?

That's saying nothing about the capacity of the idle pulley to take up the required chain length.


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## DrSmile (Jul 22, 2006)

The chainring jump would affect this too because of the wrap capacity. If you're running compact 50/34 you have one less link of play than 48/34, 50/36, or standard 50/39.


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## ericm979 (Jun 26, 2005)

I have done it with a 2012 Red short cage derailleur, 12-30 and 11-30 cassettes, with 50/34 chainrings, on a 2009 Cervelo R3SL with Wheels hanger (stock geometry just thicker). I did not even need to adjust the B screw. I use these setups for extreme climbing races.

The 2012 Red spec is for a one tooth larger big cog (28 vs 27) than older Red, and a slightly longer chain wrap as well. I've also done it with a 7900 derailleur.

When you do it you need to try the big ring/big cog combo on the stand once you have gotten it to shift and run acceptably on the 30t cog in the small ring. Be gentle. If the chain is too short you'll need to shift back down and then put a longer chain on.


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## DrSmile (Jul 22, 2006)

One should mention that Sram doesn't make 11-30 nor 12-30 road cassettes. Shimano makes a 12-30 (in 10 speed). Just in case someone wants to try this themselves.


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## skinewmexico (Apr 19, 2010)

I'd answer your question with personal experience, but last time I answered an almost identical question cxwrench negative repped me. So now I'm too scared.


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## SystemShock (Jun 14, 2008)

skinewmexico said:


> I'd answer your question with personal experience, but last time I answered an almost identical question cxwrench negative repped me. So now I'm too scared.


Don't let 'im bully you. :wink5:

'sides, he can't neg-rep you again for a very long time... it's the way rep's set up.

And I just pos-repped you.


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## SystemShock (Jun 14, 2008)

DrSmile said:


> One should mention that Sram doesn't make 11-30 nor 12-30 road cassettes. Shimano makes a 12-30 (in 10 speed). Just in case someone wants to try this themselves.


Yup. It'd be an Ultegra or Tiagra cassette.


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## SystemShock (Jun 14, 2008)

looigi said:


> FWIW: On my bike with short cage Red, the B screw needs to be turned all the way in to get adequate clearance between the guide pulley and a 28 cog. To go to a 30 you'd need to move the top of the guide pulley down about 4 mm more, which wouldn't happen on my setup with the stock screw. Perhaps a longer screw might make it work (or maybe tightening the attachment bolt with the stop rotated a bit clockwise)?
> 
> That's saying nothing about the capacity of the idle pulley to take up the required chain length.


Thanks, Looigi. 

Btw, my proposed setup would require 32 teeth of chainwrap, and the short-cage Rival RD is rated for 33.


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## SystemShock (Jun 14, 2008)

ericm979 said:


> I have done it with a 2012 Red short cage derailleur, 12-30 and 11-30 cassettes, with 50/34 chainrings, on a 2009 Cervelo R3SL with Wheels hanger (stock geometry just thicker). I did not even need to adjust the B screw. I use these setups for extreme climbing races.
> 
> The 2012 Red spec is for a one tooth larger big cog (28 vs 27) than older Red, and a slightly longer chain wrap as well. I've also done it with a 7900 derailleur.
> 
> When you do it you need to try the big ring/big cog combo on the stand once you have gotten it to shift and run acceptably on the 30t cog in the small ring. Be gentle. If the chain is too short you'll need to shift back down and then put a longer chain on.


Thanks for the info, Eric.


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## skinewmexico (Apr 19, 2010)

SystemShock said:


> Don't let 'im bully you. :wink5:
> 
> 'sides, he can't neg-rep you again for a very long time... it's the way rep's set up.
> 
> And I just pos-repped you.


BTW, your mailbox is too full, and you can't receive private messages.


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## cxwrench (Nov 9, 2004)

skinewmexico said:


> I'd answer your question with personal experience, but last time I answered an almost identical question cxwrench negative repped me. So now I'm too scared.


Get over it...there's a difference here. We need someone w/ _specific_ personal experience w/ a certain set of components, not someone w/ _random_ personal experience that most likely has very little to do w/ solving a problem.


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## SystemShock (Jun 14, 2008)

cxwrench said:


> Get over it...there's a difference here. We need someone w/ _specific_ personal experience w/ a certain set of components, not someone w/ _random_ personal experience that most likely has very little to do w/ solving a problem.


Umm... it's my question and my thread, so I think I'll be the judge of what I want. Mmkay?

But thanks anyway.

Ski, feel free to post your experiences.


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## cxwrench (Nov 9, 2004)

SystemShock said:


> Umm... it's my question and my thread, so I think I'll be the judge of what I want. Mmkay?
> 
> But thanks anyway.
> 
> Ski, feel free to post your experiences.


I was talking about the thread that i apparently negative repped him about. Obviously if he has good info for you, then by all means post it up. Jesus, you guys are so sensitive.


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## PlatyPius (Feb 1, 2009)

In my experience, Sram short cage + Tiagra 12-30 rarely works. Just buy a long cage derailleur. Sram derailleurs are less forgiving than Shimano.


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## SystemShock (Jun 14, 2008)

PlatyPius said:


> In my experience, Sram short cage + Tiagra 12-30 rarely works. Just buy a long cage derailleur. Sram derailleurs are less forgiving than Shimano.


Sigh. It is as I feared.

But thanks for confirming, ya LBS-ownin' bastage.


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## skinewmexico (Apr 19, 2010)

A Tiagra 12-30 worked for me with a short-cage Rival on a 2012 Cervelo RS. Only used (and needed) it for 4 days, and did not experiment with any changes in chain length. 

And I don't think we're sensitive, most people are just anti-condescension.


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## SystemShock (Jun 14, 2008)

skinewmexico said:


> A Tiagra 12-30 worked for me with a short-cage Rival on a 2012 Cervelo RS. Only used (and needed) it for 4 days, and did not experiment with any changes in chain length.
> 
> And I don't think we're sensitive, most people are just anti-condescension.


Thanks for the info, Ski.


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## SystemShock (Jun 14, 2008)

Hmm... I think I'm just gonna go with the 28t max cog and not tempt fate. With a Shimano RD I would, but that's ok. 

I know Plat's seen hundreds of bikes come through his shop, and definitely knows of what he speaks.

'sides, 34x28 is a pretty darn low low-gear. With it, I should be able to climb while baking cookies and answering my email. :thumbsup:


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