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Help selecting cranks/chainrings for new TT bike
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Hello! I have recently acquired a S-Works Shiv TT Disc frame to build up. I want 12-speed SRAM electronic shifting for the quick swappable batteries and wireless shifters. I also want a 2x drivetrain because this bike will be used on ultra distance races that may have some moderate elevation where a small ring will be needed. However, SRAM doesn't offer any standard or large size chainrings for a 2x system unless you buy the ones with an integrated power meter. For specific events, I can see wanting different gearing with the big ring being anywhere from 48 to 54t to maintain my desired average speed without leaving the big ring or spending a lot of time at extreme chainline angles.

SRAM only offers their 2x chainrings in 52t, 54t, and 56t as the SRAM Red integrated power meter, none of which are "aero" chainrings like their 1x offerings. I definitely don't want to pay for a new power meter for different chainring sizes. What is the best combination of cranks, power meter, and aero chainrings to use that would allow me to use a non-pedal power meter (I already have specific pedals I want to use) and still have good compatibility with a SRAM wireless front derailleur?
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Re: Help selecting cranks/chainrings for new TT bike [Blue Hubbard] [ In reply to ]
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I like Rotor.
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Re: Help selecting cranks/chainrings for new TT bike [jimatbeyond] [ In reply to ]
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jimatbeyond wrote:
I like Rotor.

Do Rotor chainrings work with SRAM 12-speed chains and the AXS front derailleur?
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Re: Help selecting cranks/chainrings for new TT bike [Blue Hubbard] [ In reply to ]
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If you a firmly committed to 2x, please disregard the following -

I'd suggest 1x using an 11-25 12 speed cassette, and changing the front chainring size as the course dictates. Without the front derailleur, this is a simple, couple of bolts, no adjustments needed, no need to break the chain, procedure.
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Re: Help selecting cranks/chainrings for new TT bike [Hanginon] [ In reply to ]
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Hanginon wrote:
If you a firmly committed to 2x, please disregard the following -

I'd suggest 1x using an 11-25 12 speed cassette, and changing the front chainring size as the course dictates. Without the front derailleur, this is a simple, couple of bolts, no adjustments needed, no need to break the chain, procedure.

That’s definitely crossed my mind. Some of my courses will be very predictable for what gearing I’ll need, such as 24-hour time trials that run on a loop. There are some other races and rides though that may need a wider range. I live in a pretty flat area, so my road bike with 52t chainring can stay in the big ring on all of our rolling hills with a 11-34 cassette. Huge gaps in gearing though for actual time trial use. Maybe I just use a 50 or 52t chainring and a wide range cassette for training, and then swap in the bigger chainring and tight cassette for my races? My concern is if I plan to use the bike for a long race that includes a couple actual climbs. I know the TT bike isn’t a good climbing and descending bike, but if I’m self supported and only able to run one bike, and the elevation only comprises 10-15-% of my ride time, I feel like the TT bike would be a faster overall time.
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Re: Help selecting cranks/chainrings for new TT bike [Blue Hubbard] [ In reply to ]
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You'll have to make a compromise on jumps in the back or using AXS. Are you open to using the 11sp eTap or Shimano 11/12sp?

The reason I ask is that it sounds like you might have the similar preference as me: small jumps in the back than what youd need on a 1x.

AXS, by design, has bigger jumps in the back to make up for a smaller range in the front (13t instead of 16t) even on a 2x setup

This year I got the Wickwerks Ultra Wide rings and I'm a huge fan for hilly races. 53/34t and it shifts really well. Better than the 52/36t rings I've tried from Rotor and AbsoluteBlack.

With the Wickwerks chainrings you basically have a big ring for 90% of the time and a bailout ring for the steep climbs. The 19t jump allows you to run a cassette with close gearing.

Something else you could consider is running 1x with a Classified hub.
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Re: Help selecting cranks/chainrings for new TT bike [Blue Hubbard] [ In reply to ]
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Blue Hubbard wrote:
jimatbeyond wrote:
I like Rotor.

Do Rotor chainrings work with SRAM 12-speed chains and the AXS front derailleur?

I’d bought bike with full SRAM Rival AXS group and have changed Rival crank to Rotor ALDHU with Rotor aero chainrings 54/42 and everything works fine with SRAM chain.
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Re: Help selecting cranks/chainrings for new TT bike [Blue Hubbard] [ In reply to ]
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That is tricky. My first thought would be see what Pyramid Cycle Design has. They have been my go to for weird chainring ideas and if they don’t have something they can probably tell you who might.

The other is to use a Shimano/Sram hybrid. Someone on the forum recently said they used the SRAM rear derailleur with a Shimano 12 sp cassette and chain. I have used all sorts of 11sp Campy/SRAM/Shimano/Wheels Manufacturing combos with no issues and the roller diameter incompatiblity probably doesn’t matter for jockey wheels (or just swap to after market jockey wheels).

I do like the Classfied hub idea and Parcourse makes a disc wheel.
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Re: Help selecting cranks/chainrings for new TT bike [grumpier.mike] [ In reply to ]
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Yep I've been using sram/shimano hybrid. Sram rival 12s rear derailleur with both sram and shimano front chainring. Shimano cassette and KMC chain. It works but it doesn't shift perfectly in the back.

https://acprestation.se/
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