Bosch cx (Gen 3) Q:

Shane(NZ)

New Member
Just interested in how long(Km) the small front chain ring lasts on the Bosch CX performance line (Gen 3) motor, pretty sure its a 16tooth one on my Trek Powerfly(off road use mainly)
I have just replaced the chain on mine, do people replace theres every 2-3 chains or something like that?

Cheers Shane
 

JayVee

Well-Known Member
Your mileage will vary greatly depending on use. It’s crucial to change the chain regularly with Bosch systems that have the smaller sprockets. You will most likely know when the sprocket is shot because you’ll start to have shifting problems after putting on a new chain. Your gears will start to slip randomly when going uphill or under load. This will increase in frequency until no gear can be held under load. A tell tale sign is if the teeth become spiked too much. The sprocket teeth should be spaced evenly. This is more difficult to see on a sprocket than on a traditional chainring because of the curvature. The reason you get skipping of the chain is because the space between the sprocket teeth doesn’t correspond to the chain link length any more after a while. This causes the chain to jump during a revolution of the crank and when that happens the tension of the chain going through the rear derailleur varies causing slippage. You won’t see this on the workbench. The chain has to be under load, meaning you riding it.

As for mileage, it can vary a lot. You could do 5000 or 15,000. If you have a mountain bike, you’ll almost certainly notice when the sprocket is shot after putting on a new chain. Your indexing will suddenly feel a little off with gears slipping and making noise under load. That’s when it becomes imperative to change the sprocket.
 

tallpaul

Active Member
JayVee's answer is well said. I had to replace mine at 5000 miles. Riding buddy of mine about the same. Haibike has a special one for Bosch motors and it is just south of $200!
There are alternatives but I think you need to do research to get the right offset spacing so i went with the OEM chainring.
Not too difficult if you are comfortable working on your bike to replace but does require a special sprocket to remove lockring.
I believe the OEM Bosch one is around $40. I found an aftermarket one that did the job and seems well made: IceToolz Bosch Lockring Tool - M801 for $18.

.

Also be aware that you need to pull the crank off which also requires a crank puller.

Speaking of longevity in the drivetrain I am only able to get 1000-1200 miles out of a chain,. I use the KMC e10 made for ebikes. That's with over 90% road riding. And cleaning and lubing the chain religiously! In the end though I feel it is money and efforts well spent for the enjoyment I get from riding. Also enjoy keeping the bike well maintained.

Looking forward to the new generation Bosch motors that have a larger chainring and eliminate the need for the SES small pocket behind the chainring. I think these small sprockets are harder on the chains. And add noise.
 

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Shane(NZ)

New Member
So just a update, I have been for a ride with the new chain, (mtb trails) and the chain is very noisy and keeped getting chain suck at low rpm high load and would lock.
I have removed crank arm and chain ring which is quite worn, have ordered new Bosch 15 tooth C/R which I well fit tomorrow and try again on weekend.
Hopefully it hasn't damaged the new chain.
Bosch chain ring is $30nz so actually not too expensive imo
 

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Alaskan

Well-Known Member
I use the Sram X-sync Bosch chain rings. They are cast, not stamped, with reinforced teeth and by far the most durable, smoothest shifting. Quite reasonably priced at $18.25 They are available at 14,16 &18 teeth. They come with a 2mm offset spacer ring.


00.6218.007.001.jpg
 

Shane(NZ)

New Member
I use the Sram X-sync Bosch chain rings. They are cast, not stamped, with reinforced teeth and by far the most durable, smoothest shifting. Quite reasonably priced at $18.25 They are available at 14,16 &18 teeth. They come with a 2mm offset spacer ring.


View attachment 43786
Well that work with a 12 spd system?
Does look well made.
 

Shane(NZ)

New Member
I don't believe that the front chain ring is specific to any particular cassette.
Its designed for a 8 spd system so may be wider, the 12 spd has quite a narrow chain so may not fit over that chain ring.
I have e-mailed a local shop that sells them to see if they can be used on the 12 spd,I think probley not ,be great if it did though.
 

Alaskan

Well-Known Member
I am using it with an Shimano XT 11 speed system and have put over 4,000 miles on it in the past year, without any issues. I can't say that it will work with a 12 speed.
 

steve mercier

Well-Known Member
So just a update, I have been for a ride with the new chain, (mtb trails) and the chain is very noisy and keeped getting chain suck at low rpm high load and would lock.
I have removed crank arm and chain ring which is quite worn, have ordered new Bosch 15 tooth C/R which I well fit tomorrow and try again on weekend.
Hopefully it hasn't damaged the new chain.
Bosch chain ring is $30nz so actually not too expensive imo
FYI ...You can reverse the worn front chain ring and get more life out of it.
 
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Mr. Coffee

Well-Known Member
I seem to go through them about once a year.

It is also made interesting by the fact that the chain ring on a Rohloff-equipped e-bike seems to be a component that isn't commonly available. So I had to special-order them from R&M. Actually, I was wise and special-ordered two.

Oh, and the part in question isn't symmetric so you can't merely flip it over and wear the teeth on the opposite side. The fact that the cog isn't symmetric is a lot of what seems to make it a special-order item.
 

steve mercier

Well-Known Member
I seem to go through them about once a year.

It is also made interesting by the fact that the chain ring on a Rohloff-equipped e-bike seems to be a component that isn't commonly available. So I had to special-order them from R&M. Actually, I was wise and special-ordered two.

Oh, and the part in question isn't symmetric so you can't merely flip it over and wear the teeth on the opposite side. The fact that the cog isn't symmetric is a lot of what seems to make it a special-order item.
I am referring to Shane(NZ) not you, and to the front ring on a bike with a derailleur like on my R+M Charger GT tour ,not about belt-driven setups on Rohloffs ,and the 18 , 19 or20t, I use on mine are symmetrical. My bike came with 19t but I am using a 20 now. I would like to try the SRAM that Alaskan mentioned but it looks like it is only available up to 18t? But after re- looking at the pic of Shane's chainring it does look asymmetrical. I wonder why some are and some are not?
 
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steve mercier

Well-Known Member
Just interested in how long(Km) the small front chain ring lasts on the Bosch CX performance line (Gen 3) motor, pretty sure its a 16tooth one on my Trek Powerfly(off road use mainly)
I have just replaced the chain on mine, do people replace theres every 2-3 chains or something like that?

Cheers Shane
Is it a Gen 2 or Gen 4 motor? I think Gen 3 refers to Active line and Gen 2/4 = Performance CX?
 

Alaskan

Well-Known Member
I seem to go through them about once a year.

It is also made interesting by the fact that the chain ring on a Rohloff-equipped e-bike seems to be a component that isn't commonly available. So I had to special-order them from R&M. Actually, I was wise and special-ordered two.

Oh, and the part in question isn't symmetric so you can't merely flip it over and wear the teeth on the opposite side. The fact that the cog isn't symmetric is a lot of what seems to make it a special-order item.
I think the chain ring with the offset on the inside, pushing it out to the right, is the same on my Delight Mountain. I have been able to use the Sram X-sync because it comes with a 2mm spacer ring that you put over the drive spline first and then slip on the chain ring. This also allows one to flip the chain ring to get longer life out of it. The Sram X-sync is machined with reinforced teeth. And @Shane(NZ) I checked in the local Trek store where they have quite a few mountain bikes with the 12 speed Sram setup and the chain ring has the same machined profile on the teeth that they use on the Bosch compatible ring.
 

steve mercier

Well-Known Member
Gen 3 performance cx
Nice looking bike ...could you take the pic from the other side of the motor? So that looks like a 2019 which has a Gen 2 performance CX . My understanding is that the Gen 3 motor is on Active line and Active plus bikes and Gen 4 Performance CX is on the 2020 bikes.
 
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Shane(NZ)

New Member
Nice looking bike ...could you take the pic from the other side of the motor? So that looks like a 2019 which has a Gen 2 performance CX . My understanding is that the Gen 3 motor is on Active line and Active plus bikes and Gen 4 Performance CX is on the 2020 bikes.
I was just guessing on the Gen 3 part , most of the sales info just says Bosch Performance Line CX.

I have ordered the Sram x-sync 2 16t from LBS who said they are showing 2 at the wholesalers, hope that arrives tomorro so I can ride it.
Also have a 15t on order(BBS brand),that might arrive this week or next who knows, but I well have a spare now.
I have fitted a 29'er on the front so really keen to see how that goes.
 

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steve mercier

Well-Known Member
I was just guessing on the Gen 3 part , most of the sales info just says Bosch Performance Line CX.

I have ordered the Sram x-sync 2 16t from LBS who said they are showing 2 at the wholesalers, hope that arrives tomorro so I can ride it.
Also have a 15t on order(BBS brand),that might arrive this week or next who knows, but I well have a spare now.
I have fitted a 29'er on the front so really keen to see how that goes.
Yes that is the same Gen 2 motor we have. That is an interesting idea to put a 29 on the front! I had not thought of that. Is the original 15t ring reversible on that bike?