Bosch Gen 4 Chainring Nut printed Torque of 25 to 30 NM is likely wrong

[irie]

Thanks Irie. I think I missed your post. Are the new ones made of a different material do you think?

Look the same to me, but what do I know?

PS - I didn't fit the 'O' ring.

 

[Giff]

 

[KKe]

Any good tip, how to hold the left side crank still when torquing this nut?

 

[irie]

Any good tip, how to hold the left side crank still when torquing this nut?

Hold it with your left hand.

 

[KKe]

I think 40ish Nm with 160mm crank it’s quite hard to keep it with hand. Specially considering positioning when need to be able to torq right side without tool slipping. I don’t know, I have done this nut once before, but without torq wrench. I feel I didn’t get it very tight because wasn’t able to hold left side.

 

[shanesnr]

After following Bosch instructions (grease don't loctite) the chain ring lockring nut to 25 to 30 NM and having it fall off 3 times I was pretty annoyed and about to start looking into drilling it out and using safety wire. I even went to the local Trek Dealer and had them torque it down in case my torque wrench was to blame. Most local Trek dealers just state the Torque is 25 to 30 NM (as printed on the part) - when you call Bosch if you are lucky you will get someone who will read an outdated manual and confirm the old torque spec. However, what Bosch consumer support and most Trek folks don't know is a Technical Service Bulletin was issued by Bosch that stated the spec on the lockring is actually 40 NM to 45 NM. When my wife and I dropped both chain rings while riding on vacation, thankfully we found a local mechanic who actually cared about solving the problem and informed me of the change in torque spec - he torqued the lockrings on both our Trek Rails to 45 NM and so far after 300 miles they have not moved.

V

Imagine that been the case on the old plastic bigger ones !! I gotta be honest i think there no more effective than spacers or washers minus treads.if your chainring and crankarm can tighten up against the chainring id bet it would keep it held but id put as much torgue as the bolts that hold it on onto them,try a Yamaha locknut now thats up in the 50'snm atleast ive seen the opposite side snap the outter piece that a chainring would fit on and it was placed in a strong vice and the pedal put back on the side that gets clamped to the vice but on them there square taper so wouldnt he have been better clamping the actual crank? maybe it would spin sorry for going off topic but there was reason as a extremely tight lockring can cause alot of headache and it was just to change a 20euro casing bearing a job that ive to do but ive a better plan i hope

 

[shanesnr]

Hold it with your left hand.

Or go oldschool if motor still on the bike lean the pedal on a curb

 

[Mikerb]

same as removing a stubborn pedal...........get the non drive side pedal up against a worktop bench leg or similar.

 

[Giff]

Or try this. Carefully!

 

[Arminius]

Or try this. Carefully!

View attachment 154073

No please!
This is the simple way to do it:

same as removing a stubborn pedal...........get the non drive side pedal up against a worktop bench leg or similar.

Good to have a quality nut and fyi Bosch increased over the years the torque for tightening the lockring - think this was mentioned somewhere in this forum before.

Some men on a big island between atlantic and the north sea are able to do it with simples stones along the road!

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[irie]

fyi Bosch increased over the years the torque for tightening the lockring - think this was mentioned somewhere in this forum before.

Chain ring Line??

Looking to overhaul my drive line on my now 2 year old Sam 6.9. Got nearly all the components except the chain ring, looking at buying a Race Face one from Fox Australia as only one I can find but there is a section for chain line in mm's, one is 52mm and the other is 55mm's. Anyone know what...

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""Guess what the new Bosch lockring that I just bought and installed says on it? 35 nm

Lockrings dated 11-2018 said 25-30nm

This lockring dated 10-2023 says 35nm""

 

[KKe]

No please!
This is the simple way to do it:


Good to have a quality nut and fyi Bosch increased over the years the torque for tightening the lockring - think this was mentioned somewhere in this forum before.

Some men on a big island between atlantic and the north sea are able to do it with simples stones along the road!

Pic of the Day

I'm ashamed to say that we have screen protectors on our (non-smart) Kiox displays. I can feel a temporary membership ban coming on🤣

www.emtbforums.com

Yes, probably best way is to mount wheels, take the bike down from stand for tightening.
I think part of my problem on this is shitty parktool bbt 18 tool. It doesn’t accept 1/2 inch driver and is weirdo 8 sided(this must be designed by somebody who never seen any tool before)interface that means ring spanner doesn’t fit also. With open end wrench it’s not very convenient to turn it to 35nm with one hand .

 

[KKe]

I did chainring for two bikes yesterday. I found that chain whip is best way to hold axle for both unthreading and for tightening the nut. This when the bike is on repair stand.

 

[Bermo EMTB]

do you use thread lock by any chance ??

 

[KKe]

do you use thread lock by any chance ??

I did put blue. But not sure if it do much. Thread is so low and with splines. And my opinion the chainring interface needs grease so threads are not completely decreased. Buts what's the thing with that rubber o-ring? What it should do there? On second bike, new one, the o ring was already in several pieces.

 

[irie]

I did put blue. But not sure if it do much. Thread is so low and with splines. And my opinion the chainring interface needs grease so threads are not completely decreased. Buts what's the thing with that rubber o-ring? What it should do there? On second bike, new one, the o ring was already in several pieces.

Many new bikes do not have the O ring fitted, looks like a failed attempt to prevent the lock nut from loosening ...

When I changed the chain ring, as recommended by Bosch, I used a new nut but didn't bother with the O-ring because it was bound to be squashed and/or ripped when the nut goes on. Used a bit of blue Loctite. And IIRC the new nut had 35Nm marked on it instead of the 25-30Nm marked on the old nut.

 

[shanesnr]

Or try this. Carefully!

View attachment 154073

 

[shanesnr]

Ive got this model well atleast i think it is as since the gen4 came out i dont know which year! Ive a gen 3 performance 21 but im sure that wasnt released until 22 so would that make this version a 23? Eitherway i think its a class motor mine was originally a cargobike beltdrive u think youve got tight bolts!but seens its a aluminium nut how i do them is e in 1 oil leave for a hour then try tighten your only lookin 1mm what that does is gets the oil thats around the tight tread into it tap it with a rubber not hard plastic hammer do a few circles to get as much oil moving and then try opening it,ive got much stubborn nuts off and reusable doing this just remember aluminium is softer than what its on u will thread the lockring for sure (sorry for going off topic with the year my bad )

Or try this. Carefully!

View attachment 154073

 

[shanesnr]

No please!
This is the simple way to do it:


Good to have a quality nut and fyi Bosch increased over the years the torque for tightening the lockring - think this was mentioned somewhere in this forum before.

Some men on a big island between atlantic and the north sea are able to do it with simples stones along the road!

Pic of the Day

I'm ashamed to say that we have screen protectors on our (non-smart) Kiox displays. I can feel a temporary membership ban coming on🤣

www.emtbforums.com

Bosch sure have increased over the years anyone remember the big 60mm plastic lockrings mainly on haibike im sure it was just support to hold the chainring in place,gotta admit those classic motors that were put on proper mountain bikes had serious strength there let down was the big plastic cogs and so many of them,they had caps in them the size of a treble a battery 2 of them,my one was like a wild horse lol still runs now and gets used

 

[pinoymamba]

I went to Ibis HQ to have my Bosch motor looked at as the chainring kept getting loose.

A few things that I learned about the chainring area and battery

- rubber o ring is one time use
- lockring is three time use only
- foam piece on the cradle is an issue

The guru for the Oso mentioned to help alleviate the loosening of the chainring he has updated the lockring to the 35nm version and also is using a 1mm washer along with blue loctite.

View attachment Ibis_Oso_February_2025-3.jpeg View attachment Ibis_Oso_February_2025-2.jpeg View attachment Ibis_Oso_February_2025-4.jpeg

 

[Mikerb]

I would argue that the locknut is one time use only......especially if it has come loose.

 

[Stihldog]

I have a few spare lock nuts in the parts kit. I now believe they are a one time use (maybe two). Adding a little wipe of lock tight to the alloy threads probably helps.

I’ve replaced several chainrings and installed the bearing seal kit a few times. I’ve never seen a rubber O ring …just a brass O ring. However, with a new ethirteen chainring the brass O ring wasn’t necessary or even possible because of the shape of the ethirteen chainring. But I did maintain the thin plastic O ring instead. Chain alignment was better or gooder after that. Squished in the special Bosch grease also.

I like the idea of a chain whip around the chain ring for final torquing. Good tip.

 

[irie]

Bosch says that lock nuts are one time use.

Geez, you spend thousands buying your eMTB then try to save a few pennies on a f7cking locknut effectively holding your pedals on?

 

[KKe]

That nut has nothing to do to keeping pedals on
If the nut is in good condition, i would use it again. It is ecological, perfectly fine, and much more convenient than ordering new from somewhere. I would say that already mentioned three times before replacing is reasonable.

 

[irie]

That nut has nothing to do to keeping pedals on

It was a figure of speaking, but when the nut comes loose the chainring comes loose. Guess what comes after that?

If the nut is in good condition, i would use it again. It is ecological, perfectly fine, and much more convenient than ordering new from somewhere. I would say that already mentioned three times before replacing is reasonable.

So you evidently know better than Bosch engineers.

 

[Arminius]

It was a figure of speaking, but when the nut comes loose the chainring comes loose. Guess what comes after that?

So you evidently know better than Bosch engineers.

He does not know better, he is in line with it.

Smart Aleck Mode On:
The pedal (crank arm) will not come loose on a Bosch until loosenig the crank arm screw on the axle (e.g. to pull the crank arm off). Chain ring is separate from crank arm.
Smart Aleck Mode Off

I re-used the lock ring on mine with proper tools and acc. to Bosch manual and had no probs so far.

 

[irie]

He does not know better, he is in line with it.

Smart Aleck Mode On:
The pedal (crank arm) will not come loose on a Bosch until loosenig the crank arm screw on the axle (e.g. to pull the crank arm off). Chain ring is separate from crank arm.
Smart Aleck Mode Off

You are absolutely right, the "pedal (crank arm) will not come loose". As said above, it was a figure of speech. If you look at posts by me on this forum you will see that I do indeed know how to change chainrings and cranks.

I re-used the lock ring on mine with proper tools and acc. to Bosch manual and had no probs so far.

I prefer to follow Bosch instructions for devices it designs, but you are of course perfectly entitled to do whatever you wish with your property. But saying that, "one swallow does not summer make" (English idiom often attributed to Aristotle).

 

[Bear-uk]

I've already posted this picture before.
But when will you lot get real and understand that this is the recognised way of tightening the chain ring nut