Bosch Gen 4 - How to change the chainring?

[sandyman44]

can anyone give any tips as to how to get the cranks off bosch gen4 ebike? I have a scott genius e-ride 2020. The website spec says the cranks are SRAM X1. they are certainly SRAM.
I want to change the chainring (currently has SRAM direct mount boost 34T) to a smaller 30T. I have bought raceface NW 30T, together with FSA 104BCD bosch gen4 boost spider. These look like they will be the right fit. I've also bought the unior chainring locknut tool, which again looks like it will be the right fit.

however I am defeated at the first obstacle. Can't get the cranks off. only need to remove the drive side, to change the ring.

There is an outer retaining bolt with a 10mm hex . this (re)moves easily. through this there is another bolt with 8mm hex hole. This doesn't move at all. my understanding is that they make a self-extracting pair, I should leave the outer bolt in place, turn the inner one, the crank will self extract. however, inner doesn't move AT ALL, with or without the outer bolt. I have an 8mm hex wrench about the same length as crank, pushed into the inner bolts hole. It fits nicely. I am putting one hand on the end of the crank, other hand on the end of the wrench with the two opposed at 180 degrees horizontally, as much weight as I can get down through them, nothing moves at all. My understanding is that the inner bolt should be a "normal " thread so I am trying to move it anti-clockwise.

is there some special secret or is it just about leverage / torque? I've never had a crank that works like this before so I am trying to work it out without breaking it. many crank removal youtube tutorials of course but none of them seem to be for SRAM cranks with an bosch gen4.

pics with and without the outer bolt below

 

[Paul Mac]

You are doing everything right, it is a self extracting system and it is a normal thread.
You have just had a monkey torque it up to 10000 nm.
Mine was the same, thought I was going to break it while undoing.

 

[sandyman44]

You have just had a monkey torque it up to 10000 nm.
Mine was the same, thought I was going to break it while undoing.

thanks, that is what I was afraid of. if it was a wheel nut on the car, I'd use a 2 foot breaker bar as the wrench and stand on the end (holding the bonnet or roof for stability). Achieving the same leverage on a bike is a lot more difficult. any tips? need to stop the crank moving as well as increasing the wrench leverage. I tried adapting my 1/2" drive 2 foot breaker bar down to 8mm hex, but ended up with about a 10cm long stack with 4 joins from one adapter to the next, to get the size down, did not feel stable...

 

[Giff]

Can you borrow an impact driver.....the battery DeWalt ones for example ?

 

[GrahamPaul]

Strap the other crank to the chain stay so that you can use both hands on your breaker bar? Saves on skinned knuckles too...

 

[Like a Boss]

thanks, that is what I was afraid of. if it was a wheel nut on the car, I'd use a 2 foot breaker bar as the wrench and stand on the end (holding the bonnet or roof for stability). Achieving the same leverage on a bike is a lot more difficult. any tips? need to stop the crank moving as well as increasing the wrench leverage. I tried adapting my 1/2" drive 2 foot breaker bar down to 8mm hex, but ended up with about a 10cm long stack with 4 joins from one adapter to the next, to get the size down, did not feel stable...

I have used a 1/2" drive breaker bar, with a four foot pipe on the handle, to remove Sram cranks. It helps to have a second person. You might get the "snap" you need with the long breaker bar, and stand on the opposite pedal. A long breaker bar vs a 165mm opposite crank doesn't sound balanced, and it's not. But I think that's what I did last time. The sound it made when it came free was alarming, but that the way it is. So, one guy on the breaker bar, and the other standing over the bike, on the opposite pedal, and somehow keeping the breaker bar tightly in the crank. Something like that.

 

[HORSPWR]

can anyone give any tips as to how to get the cranks off bosch gen4 ebike? I have a scott genius e-ride 2020. The website spec says the cranks are SRAM X1. they are certainly SRAM.
I want to change the chainring (currently has SRAM direct mount boost 34T) to a smaller 30T. I have bought raceface NW 30T, together with FSA 104BCD bosch gen4 boost spider. These look like they will be the right fit. I've also bought the unior chainring locknut tool, which again looks like it will be the right fit.

however I am defeated at the first obstacle. Can't get the cranks off. only need to remove the drive side, to change the ring.

There is an outer retaining bolt with a 10mm hex . this (re)moves easily. through this there is another bolt with 8mm hex hole. This doesn't move at all. my understanding is that they make a self-extracting pair, I should leave the outer bolt in place, turn the inner one, the crank will self extract. however, inner doesn't move AT ALL, with or without the outer bolt. I have an 8mm hex wrench about the same length as crank, pushed into the inner bolts hole. It fits nicely. I am putting one hand on the end of the crank, other hand on the end of the wrench with the two opposed at 180 degrees horizontally, as much weight as I can get down through them, nothing moves at all. My understanding is that the inner bolt should be a "normal " thread so I am trying to move it anti-clockwise.

is there some special secret or is it just about leverage / torque? I've never had a crank that works like this before so I am trying to work it out without breaking it. many crank removal youtube tutorials of course but none of them seem to be for SRAM cranks with an bosch gen4.

pics with and without the outer bolt below View attachment 36273 View attachment 36274

You're not supposed to remove the outer bolt. You undo the inner bolt and when it backs out it comes up against the outer bolt and then draws the crank off the spindle, it acts like its own puller. You just need more force like a breaker bar with an allen key socket.

 

[sandyman44]

You're not supposed to remove the outer bolt. You undo the inner bolt and when it backs out it comes up against the outer bolt and then draws the crank off the spindle, it acts like its own puller. You just need more force like a breaker bar with an allen key socket.

yep, I was pretty sure that was how it worked, just wanted to see if it was that. as there is no definitive manual for this exact setup that I can find. I've got some 1/2" drive hex bits on order now, so I can connect them directly to my breaker bar, waiting for those to turn up before trying again. I do have a ryobi one+ impact driver so I may also try that, although probably will need to buy a longer hex bit to get it to reach in. despite having multiple tool sets you never seem to have the right one! hadn't thought to try power tools always a bit wary of that on a bike. I have mashed screw heads with this tool before, needs a lot of pressure to stop the bit bouncing out. can't believe need to do this much mechanical engineering just to remove a crank!

 

[HORSPWR]

yep, I was pretty sure that was how it worked, just wanted to see if it was that. as there is no definitive manual for this exact setup that I can find. I've got some 1/2" drive hex bits on order now, so I can connect them directly to my breaker bar, waiting for those to turn up before trying again. I do have a ryobi one+ impact driver so I may also try that, although probably will need to buy a longer hex bit to get it to reach in. despite having multiple tool sets you never seem to have the right one! hadn't thought to try power tools always a bit wary of that on a bike. I have mashed screw heads with this tool before, needs a lot of pressure to stop the bit bouncing out. can't believe need to do this much mechanical engineering just to remove a crank!

Don't worry, next time it'll probably fall off...when you're riding it ?

 

[sandyman44]

Don't worry, next time it'll probably fall off...when you're riding it ?

I did the job with the 2ft breaker bar and a 1/2" hex-end socket set ALLEN KEY / HEX BIT SOCKET SET US PRO TOOLS 1/2" Drive 4mm to 17mm 3383 | eBay. Bike propped in corner against wall so it can't go forwards, right foot on right pedal, full weight, then transfer 1/2 weight to left foot on breaker bar parallel with the chainstay. couple of pumps with the left leg and the torque did the job.

chainring locknut was comparatively easy to remove. the unior 1671.2/4 is a perfect fit for that job and way cheaper than the bosch branded tool. got mine from germany, none of the uk shops had one.

I now have new ring and spider fitted. I put 50NM on the crank extraction bolt when refitting. now need to remove some links from the chain now as dropping 4T on the ring leaves it too long, not ridden it yet. chainline is about 2 mm further out than the factory sram chainring, which is perhaps due to the racefact ring having these threaded holes with standoff, I may have been able to go with the non-boost version of this spider.

 

[HORSPWR]

I did the job with the 2ft breaker bar and a 1/2" hex-end socket set ALLEN KEY / HEX BIT SOCKET SET US PRO TOOLS 1/2" Drive 4mm to 17mm 3383 | eBay. Bike propped in corner against wall so it can't go forwards, right foot on right pedal, full weight, then transfer 1/2 weight to left foot on breaker bar parallel with the chainstay. couple of pumps with the left leg and the torque did the job.

chainring locknut was comparatively easy to remove. the unior 1671.2/4 is a perfect fit for that job and way cheaper than the bosch branded tool. got mine from germany, none of the uk shops had one.

I now have new ring and spider fitted. I put 50NM on the crank extraction bolt when refitting. now need to remove some links from the chain now as dropping 4T on the ring leaves it too long, not ridden it yet. chainline is about 2 mm further out than the factory sram chainring, which is perhaps due to the racefact ring having these threaded holes with standoff, I may have been able to go with the non-boost version of this spider.

View attachment 36749 View attachment 36750

That should make chainring changes easier next time!

 

[Like a Boss]

That should make chainring changes easier next time!

Are folks even bothering about the o-ring, or omitting it altogether?

 

[HORSPWR]

Are folks even bothering about the o-ring, or omitting it altogether?

I've read where others are omitting it, personally if it was mine I'd pin it so it can't come lose such as drilling a hole the spider and installing a roll pin in the nut cutout.

 

[deertrackdoctor]

thanks guys this post was helpful . I down graded my drive train to Micro shift advent X .I got 1200km from chain and cassette without paying attention to chain wear . Fot info i managed to Purchase the unior lock ting tool and the e thirteen chainting in the UK from Tredz .I hope that info helps someone in the future .
Ive purchased a chain wear guide this time so hope to get more than 1200km out the new cassette by chainging chain at proper time . cant complain as replacement cost of cassette and chain is only £65 .Ive no regrets selling the 12 speed drive train when new and fitting 10 speed micro shift advent x . I can live with new cassette and couoke of chains every 2000km

 

[daytrader]

I did the job with the 2ft breaker bar and a 1/2" hex-end socket set ALLEN KEY / HEX BIT SOCKET SET US PRO TOOLS 1/2" Drive 4mm to 17mm 3383 | eBay. Bike propped in corner against wall so it can't go forwards, right foot on right pedal, full weight, then transfer 1/2 weight to left foot on breaker bar parallel with the chainstay. couple of pumps with the left leg and the torque did the job.

chainring locknut was comparatively easy to remove. the unior 1671.2/4 is a perfect fit for that job and way cheaper than the bosch branded tool. got mine from germany, none of the uk shops had one.

I now have new ring and spider fitted. I put 50NM on the crank extraction bolt when refitting. now need to remove some links from the chain now as dropping 4T on the ring leaves it too long, not ridden it yet. chainline is about 2 mm further out than the factory sram chainring, which is perhaps due to the racefact ring having these threaded holes with standoff, I may have been able to go with the non-boost version of this spider.

What is your experience with the 30T chainring?

Did you leave the chainline as it is or did you change to a different (non boost)spider?

Which FSA Spider was it exactly with the 2mm offset? The article number W0138?


Thank you in advance

 

[Singletrackmind]

Has anyone who has changed the chainring on a Gen 4 motor noticed an aluminum washer between the motor and the chainring? Had a the new Sram Transmission installed on my bike and lockring used to fasten the front chainring to the motor kept coming loose. Noticed it was barely grabbing any threads and after purchasing a new lockring, took front chainring off before installing and noticed an aluminum washer between the chainring and motor. Removed the washer and now the lockring is held on by more threads and seems to be very secure. Went on a neighborhood ride and lockring has not loosened. Maybe stock chainring requires a washer? Any insight would be greatly appreciated.

 

[Giff]

My Whyte e160rs is a boost offset and I don’t think it has an aluminium washer there. There is a thin rubber O ring.

 

[Paul Mac]

Depends what chain ring you took off.
If it was the sram one, it has a thick washer bonded to it from new. In use the bond breaks and when you take the chain ring off it leaves the washer behind.
If it was a e13 chain ring, some come with a washer to make the chain ring a boost fitment.

 

[slorider]

Has anyone who has changed the chainring on a Gen 4 motor noticed an aluminum washer between the motor and the chainring? Had a the new Sram Transmission installed on my bike and lockring used to fasten the front chainring to the motor kept coming loose. Noticed it was barely grabbing any threads and after purchasing a new lockring, took front chainring off before installing and noticed an aluminum washer between the chainring and motor. Removed the washer and now the lockring is held on by more threads and seems to be very secure. Went on a neighborhood ride and lockring has not loosened. Maybe stock chainring requires a washer? Any insight would be greatly appreciated.

Did you ever figure out what this washer was? I have a Trek Rails and found the same washer. I can barely get the locking ring back on with the washer. Did you just leave the washer off?

 

[Singletrackmind]

Did you ever figure out what this washer was? I have a Trek Rails and found the same washer. I can barely get the locking ring back on with the washer. Did you just leave the washer off?

I did leave the washer off. Found out it was the stock washer thst you need for the E13 chainring that comes on the Orbea Wild. I upgraded my Drivetrain to the Sram AXS TRANSMISSION and the Sram chainring comes with the washer "built in" to its design. Once I removed the washer, lockring was easy to get on and is held on by all the threads. Put a little blue Locktite just incase. Have gone on a couple rides and no issues whatsoever!