Rail (625Wh) chainring replacement

2021 Rail, replacing cassette and chain soon, wondering about chainring (about 3700 miles and I let this last chain really stretch since I knew I was going to replace the cassette.

Anyone move to 36t and if so what chainring?

Leaving your chain stretch beyond the allowable level may cause excessive wear on other transmissions components. (Chaining, cassette, jockey wheels etc). The cogs are designed to fit or accept a useable chain.

Chain-suck at the chainring is an indication that things are worn out. Inspect or replace those parts. Noise, chain-skip, or poor shifting can also be an indication of worn out transmission components.

I’m not sure what the benefits would be by increasing the chainring size, this is an eMTB after all, but that may be something I don’t find necessary for the type of riding I do.

I’ve replaced the chaining twice on my Rail after it became worn out. An ethirteen 34t was my choice.


The clearance was not an issue with this 34t chainring. However a small ring-washer had to be omitted for proper alignment. A raised portion on the new chainring eliminated the need for this washer.

While you’re replacing the chainring, do a bearing seal service.



You may need a few special tools.


This site or YouTube can show installation and removal techniques.

Hope this helps.

Thanks, I hadn’t thought about the wear on jockey wheels, but now thinking I might as well replace those while I’m at it, and the chainring.


The motor is about 11 months old, so I’ll leave it be. (There was a tiny amount of play in the crank, as if bottom bracket bearings were worn. I compared it to my brother’s new Rail, which had zero play, and as I was a week short of the two-year-warranty mark, I brought it to Trek. Bosch seems to be good about investigating unexpected wear, etc, and swapped out the motor).

Thanks!

EDIT: went to e13’s website, noticed they have aluminum and steel (out of stock) chainrings, with this difference:

Chainline:

Steel: 52mm
Aluminum: 53mm (Boost chainline)

Looks like you have the Aluminum one, and Rail specs show the original is steel … I wonder if that 1mm chainline difference is where the ring washer comes into play.

markloch said:

Thanks, I hadn’t thought about the wear on jockey wheels, but now thinking I might as well replace those while I’m at it, and the chainring.


The motor is about 11 months old, so I’ll leave it be. (There was a tiny amount of play in the crank, as if bottom bracket bearings were worn. I compared it to my brother’s new Rail, which had zero play, and as I was a week short of the two-year-warranty mark, I brought it to Trek. Bosch seems to be good about investigating unexpected wear, etc, and swapped out the motor).

Thanks!

EDIT: went to e13’s website, noticed they have aluminum and steel (out of stock) chainrings, with this difference:

Chainline:

Steel: 52mm
Aluminum: 53mm (Boost chainline)

Looks like you have the Aluminum one, and Rail specs show the original is steel … I wonder if that 1mm chainline difference is where the ring washer comes into play.

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The wear on the jockey wheels is not that critical …but occasionally maintaining them can be important.

The difference between steel chainrings vs alloy chainrings is wear vs weight …respectfully. I prefer an aluminum chainring.

I really recommend the bearing seal kit for the Bosch CX motor. The type of grease used is more resistant to water ingress. Removal of the crank bearings is not necessary or required during installation of the bearing seal kit. Both drive side and non-drive side is fairly easy when installing the seal kit. Apparently once a year is recommended. The kit is usually less than $20.

Stihldog said:

The wear on the jockey wheels is not that critical …but occasionally maintaining them can be important.

The difference between steel chainrings vs alloy chainrings is wear vs weight …respectfully. I prefer an aluminum chainring.

I really recommend the bearing seal kit for the Bosch CX motor. The type of grease used is more resistant to water ingress. Removal of the crank bearings is not necessary or required during installation of the bearing seal kit. Both drive side and non-drive side is fairly easy when installing the seal kit. Apparently once a year is recommended. The kit is usually less than $20.

Click to expand...

I'm just gathering all the components to do this with my Focus Sam which is now approaching the 3500km mark. It's on its 2nd chain already and I can't say I've had any shifting problems and can't see any real wear but it must have after that many Kms.
Could you please let me know the name or the place you purchased you chain ring locking nut removal tool (for want of a better description).
Is there much a drama with the seal kit installation as this is something I haven't thought about but can see the benefits of replacing while I have it apart. Thanks in advance, cheers Steve

Husky430 said:

I'm just gathering all the components to do this with my Focus Sam which is now approaching the 3500km mark. It's on its 2nd chain already and I can't say I've had any shifting problems and can't see any real wear but it must have after that many Kms.
Could you please let me know the name or the place you purchased you chain ring locking nut removal tool (for want of a better description).
Is there much a drama with the seal kit installation as this is something I haven't thought about but can see the benefits of replacing while I have it apart. Thanks in advance, cheers Steve

Click to expand...

I believe I ordered the Castle socket, or spider socket, through my LBS (Trek).

The first time I installed a bearing seal I had to familiarize myself with the process. The next kit I installed was easy(45min maybe?