Just an update that in a true Chumba Quest for Compatibility fashion all of our frames with sliding dropouts are compatible with the new SRAM Transmission! That includes existing boost frames with sliding dropouts.
We and other members of the framebuilding community have been coordinating this with PMW over the last few weeks. There will be a corresponding nondrive side insert that will maintain 160 PM direct mounting. The inserts will likely add $35-50 to each order, cost is forthcoming.
Sendero Titanium featuring the new SRAM X01 Wireless Transmission.
This will be a retro fit to all our models new and old, the inner "nut" will be stainless.
We'll have working samples in 4-6 weeks and if you need a set let us know and we can likely get them added to this first run. It is possible that the 2nd run may see minor revisions to this, but that is not expected at this time. Our final insert will see additional shaping/machining for aesthetics as well.
We can get the SRAM Transmission kits if interested, they are instock. They are now listed on our custom build quote tool as well.
Q and A on the new SRAM Transmission system. Feel free to add your questions in the comments.
Is it awesome and exciting? Yes.
Is it practical for Chumba bikepackers? Not at this time, there are no replacement parts out yet, it’s all groupo only options, replacement parts appear to be instock in the coming months. Doubtful you would find an extra derailleur or even a chain in most shops for a bit. We recommend sticking with the proven current AXS system for that if looking for wireless shifting. It works awesome for bikepacking.
Who would Chumba recommend this kit for? The XO kit looks exciting for trail riders and the XX kits for racers.
Can I run a different crank then the SRAM one? The Transmission comes, as you’d expect, in a groupset only. Currently, if you want to run another crank you’d still have to order the SRAM one also. 3rd party options appear best with an Absolute Black 0mm offset ring for a super boost chainline on a SRAM, 5Dev or Cane Creek crank so far.
What’s the chainline on this system? 55mm. The Transmission also uses a new chainline so there will be some complications moving to a third party crank/ring combo to sort out. The 55mm chainline works on Boost 148mm frames like ours, the derailleur cage angles towards the ring as it moves through the gears. The one chainline option makes it so the derailleur better understands where that ring is to keep things shifting smooth.
Does the new Transmission work with Force AXS levers for things like a Yaupon? Yes on the Yaupon!
What about older frames with 142mm rear ends or something like a Terlingua Mullet drivetrain? Keep in mind on the Terlingua we’d need to do some major figuring on that 55mm chainline. So for a gravel setup your crank q factor would be MTB level wide and is thus not recommended… yet. It is possible we can adapt the chainline to work accounting for the difference in the 142 rear end from the 148mm rear end, but this will need some testing before we recommend it. On older 142mm MTB frames, it may work same logic applies. Needs testing first. Mathing it out a Boost 52ish chainline paired to a 142mm rear end should equate to a 55mm chainline paired to a 148mm rear end.
Should I run out and hit my new SRAM Transmission with a hammer like in all the product reviews: No, please don’t. Why am I having to say this… what a world!
Can I stand on it: Come on already!
Should I keep riding my Chumba as a singlespeed? 100%
Cheers, - Chumba