Rail (750Wh) Trek Rail Chainring Swap, Is Reprogramming Required?

[BuckSaw]

I want to swap the stock e13 34t chainring on my Trek Rail 7 Gen 2 for a 32t ring. My local trails are technical with lots of punchy climbs and granite. I find that I'm hardly ever in the smaller cogs and a smaller chainring helps with the trials moves that my local trails demand. If I swap the chainring for something with fewer teeth do I have to take the bike back to the shop for reprogramming?

 

[JP-NZ]

I want to swap the stock e13 34t chainring on my Trek Rail 7 Gen 2 for a 32t ring. My local trails are technical with lots of punchy climbs and granite. I find that I'm hardly ever in the smaller cogs and a smaller chainring helps with the trials moves that my local trails demand. If I swap the chainring for something with fewer teeth do I have to take the bike back to the shop for reprogramming?

No, I don't believe so.

 

[Tony4wd]

I found that going from a 38t chainring to a 34 (bosch cx4) caused errors when using the biggest rear sprocket. You might get away with a change of only 2 teeth.

 

[BuckSaw]

I spoke with Trek support today and they told me that a change in chainring size on the Rail 7 requires reprogramming. Unfortunately my local Trek dealer sucks. They had my bike for two months last summer to replace the crankset under warranty, and didn't replace the crankset.

 

[Bones]

Personally I would fit the smaller chainring and see what happens!
If it throws some errors up then swop back and then think about getting it reprogrammed.
On my gen 2 Bosch motor I put a bigger chainring on without any issues despite being told it won't work without being plugged in and altered.

 

[schra]

I changed the chainring from 34 to 38 on my 2021 trek rail without reprogramming, after 4000 kms no errors yet