Bosch Gen 4 Lock Ring

[Nautical Biker]

I have recently replaced the chainring on my Trek Rail and noted that there was no rubber O ring fitted between the lock ring nut and the chain ring. I believe there is supposed to be one. The chain ring was a SRAM type, which I have replaced with a KMC. I just refitted the nut and torqued it up. Does anyone know of the O ring is required or optional? I note that E-Thirteen recommends not fitting one at all.

 

[irie]

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...

www.emtbforums.com

Follow this ^^^ link

 

[Stihldog]

Sometimes, rather than a rubber “o” ring there is a brass one. I believe that this behaves like a spacer when used with the thin plastic “o” ring.

When I installed the ethirteen chainring I only needed the thin plastic “O” ring. Also, the castle nut, or retaining nut, can become stretched, deformed or damaged during removal and replacement. Some say that a small amount of blue Lo-tight is helpful to prevent loosening of the chainring. That may not be necessary if a new nut is used.

 

[irie]

I used a "belt and braces" approach: new castle nut torqued to the 35Nm marked on it + no O-ring + medium thread locker + tell tales. Nothing come loose since last June.

 

[Mikerb]

I used a "belt and braces" approach: new castle nut torqued to the 35Nm marked on it + no O-ring + medium thread locker + tell tales. Nothing come loose since last June.

 

[Mikerb]

View attachment 153241

I would add, always use a new lockring if changing the chainwheel. Never had a chainwheel come loose on any EMTB bike I have owned over 6 years, and on all but my latest bike I have changed the chainwheel at least once.

 

[irie]

I would add, always use a new lockring if changing the chainwheel. Never had a chainwheel come loose on any EMTB bike I have owned over 6 years, and on all but my latest bike I have changed the chainwheel at least once.

What you have missed are:

1. The recommendation to use the O-ring was made long before the castle nut torque recommendation was increased from 28-30Nm to 35Nm.

2. Some bike manufacturers do not fit the O-ring.

3. An O-ring is a static compression sealing device.

 

[Mikerb]

What you have missed are:

1. The recommendation to use the O-ring was made long before the castle nut torque recommendation was increased from 28-30Nm to 35Nm.

2. Some bike manufacturers do not fit the O-ring.

3. An O-ring is a static compression sealing device.

yes the O ring is a gasket providing a seal once compressed........whether 28 or 35 nm would make no difference, the oring would be compressed already at much lower torques than that. I assume its purpose is to help protect the threads of the locknut from water so probably not essential .
I have a small stock of locknuts all of which have the lower torque setting marked on them.....as do the locknuts on both of my bikes ( one of them a 2024 model)........the difference being just a different supplier using a harder ally I reckon. Best to apply whatever the locknut has marked on it since that is what the manufacturer tested it at. Either torque makes no difference to the motor spindle which is steel.

 

[folmonty]

There's been lots of discussion about this in the Trek forum. Based on most of the comments I'd say riders are not using the o-ring any longer to prevent the lock nut from backing off under load.