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1x RD with 2x FD - Why Not?

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1x RD with 2x FD - Why Not?

Old 08-21-22, 04:22 AM
  #1  
jlaw
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1x RD with 2x FD - Why Not?

Hello,
I currently have a 1x SRAM Apex RD with a 1x SRAM Apex 40T crank (GXP BB) and 11-42 cassette on a bike. I want to try 2x on this bike so I bought a SRAM 38/24 crank (GXP BB) for the purpose. Looking at the SRAM website I noticed that the existing Apex RD on the bike is spec'd as only for use with 1x drivetrains.

What might happen if I try to use this 1x RD with a 2x crank and FD?

Thanks!
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Old 08-21-22, 04:41 AM
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The Apex 1 rear derailleur doesn't have the chain wrap capacity to take up the extra slack in the chain when you shift into the small chainring at the front. You have the parts in hand, so it can't hurt to try them and find out.
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Old 08-21-22, 09:18 AM
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There will be some pretty major slack in the chain in the small ring/smaller cogs. Because the rear derailleur doesn't have the chain wrap capacity for a 2X...which is why SRAM specs it for 1X. This set up will not work correctly. You can try it, but it's going to be compromised because it's the wrong derailleur.
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Old 08-21-22, 05:12 PM
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Ok - makes sense re: lack of chain wrap capability.

I found a SRAM GX 2x11 RD that will take a 42T cog - $85 new. It should work with the Apex brifter thanks to 'X Actuation'.

For the FD I'm thinking of using the GRX 400 braze on using a bar end shifter to actuate.

Thanks.


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Old 08-21-22, 07:26 PM
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'Shifter'.
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Old 08-22-22, 08:13 AM
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Originally Posted by cxwrench View Post
'Shifter'.
Gesundheit!
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