Rail 9.7 chainring rubbing

[Paul Mac]

I run the sram chainring and sram chain and have never had an issue.
As these items are cross compatible with your shimano cassette why not just try them, they are both cheap so nothing to lose.
This definitely looks like a chain suck issue, so can only be chainring or chain.

 

[neiloxford]

The KMC part number is BFCB45234. I can’t make out all of the numbers on the chainring but the 234 definitely match up; you will be able to check the rest.

The other thing making me think it’s KMC is the small holes on the chainring. Only KMC has these holes.

I would try a new front chainring. SRAM or e13 come with the bikes but make sure they are the boost version. trek head office should be able to tell you the exact part numbers. I think the chains can be either Shimano or SRAM but swap to SRAM if you still have an issue.

I also have the SRAM chain and chainring on my trek rail and no issues.

 

[Donny B]

The KMC part number is BFCB45234. I can’t make out all of the numbers on the chainring but the 234 definitely match up; you will be able to check the rest.

The other thing making me think it’s KMC is the small holes on the chainring. Only KMC has these holes.

I would try a new front chainring. SRAM or e13 come with the bikes but make sure they are the boost version. trek head office should be able to tell you the exact part numbers. I think the chains can be either Shimano or SRAM but swap to SRAM if you still have an issue.

I also have the SRAM chain and chainring on my trek rail and no issues.

 

[Donny B]

Little feedback.
The guys from the shop (Breuls Maasmechelen Belgium) just called after my mail with some pictures and they are going to replace everything at once. Chain, chainwheel and cassette.
Because after every incident only the broken part was replaced and between there where several hundred kilometers.
So for now i can only hope this superbe action from the dealership is going to fix my problem.
Thanks for thinking with me.
Have a safe ride?

 

[RowanTheKiwi]

Well this thread is fascinating...

Done 3600km on my 2021 9.8 XT, then had a chainstay crack on me a few weeks ago. So to their credit Trek replaced it airfreighting one from Oz so I could do a trip in a weeks time. Was out riding tonight on the way home "bugger- the crank is loose", look down, and nooooooo.

8 hours after chainstay replacement. Same bike, no component change other than a broken derailluer replacement. I have no idea if the techs put everything back together 100% the way it should have been.

 

[RowanTheKiwi]

..... after reading the thread, I thought I'd go back to the garage and have a look. 1 motor mount bolt missing (I didn't notice but you can see it on the above picture) and one other mount bolt loose (drive side). Which logically allows the motor to move away from the drive side under pedalling/cornering/right foot down hard.

Problem solved. Bike store are absolute _______g muppets.

That's going to be one heck of a google review depending on whether they're tail between the legs "whoops, sorry, we'll make it right" or....

 

[Stihldog]

This^, made me check the torque on the Gen4 motor mount bolts. (6). Also the brackets are fastened with torx plus security bolts. If these loosen…there’s a number of problems which can develop.

This is not my motor but the drive side casing bracket bolts sheared off. New casing and bracket is probably needed. So much damage can occur in this area. Btw, I use a ethirteen 34 chainring. No problems yet.

 

[themoon]

Checked my rail 9.7, there were a few minor scratches. No biggie, have put helitape, still intact after a couple of hard rides. Bike has about 500 km now. Anyway, not really happy how axs wireless derailer works with SLX cassettes, and shimano chains seem to be just made of soft cheese, as compared to my other bike, which was running the same derailer with NX steel cassette and cheap chains, which lasted much longer. Pulled a trigger on a new wheelset, xx1 cassette and chain...now thinking it is also a good idea to replace stock e13 34T chainring to something like DM chainring for Bosch Gen4 (because of matching color with cassette and chain ), just wondering what they mean by -11 offset? This won't fit, right?

P.S. Bike rides just superb. After installing Ohlins coil shock it just rips! (waiting for coil smashpot upgrade for the fork now)

32T, Offset -11mm or 34T, Offset -11mm

 

[Wilbur]

This^, made me check the torque on the Gen4 motor mount bolts. (6). Also the brackets are fastened with torx plus security bolts. If these loosen…there’s a number of problems which can develop.
View attachment 104754
This is not my motor but the drive side casing bracket bolts sheared off. New casing and bracket is probably needed. So much damage can occur in this area. Btw, I use a ethirteen 34 chainring. No problems yet.

Are the mounting plate screws on your Gen4 the same as the ones in the pics? (5-point security bit M5 thread). Apparently Bosch have upgraded them to std Torx M6, if the other thread is correct..

 

[Stihldog]

Are the mounting plate screws on your Gen4 the same as the ones in the pics? (5-point security bit M5 thread). Apparently Bosch have upgraded them to std Torx M6, if the other thread is correct..

Yes, M5 security. I just read, in the past 24hours that the latest version has M6 bolts. I might re-new the claim for a new Bosch motor. With this occurring and Trek/Bosch claiming “peddle strikes”, it might be an opportunity to have them fix or replace their screw-up.
This would definitely make my neighbour happy. ($800 for a new motor btw…wtf.)

 

[Jatem]

Recently I had the chainring scratching my chainstay. It was due to the alu motor mounting plates coming loose from the motor. I torqued the alu motor plate bolts to 8-9 nm, and the main frame mounting bolts to 20nm, with blue loctite. One thing I learned was that you need to wait 24 hours for loctite to harden fully. I have never been patient with loctite in the past, but I waited this time. It won’t be effective if it’s still liquid.

 

[ralfturfsmurf]

I had the chainring rub. Got a new chainstay on warranty. Not fun to replace however. There is more info and more cases in the "Bosch CX gen 4 chainring nut" thread. This problem could easily be solved with a few millimeters of more clearance during CAD/manufacturing.

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