Hi S13, It is nice to know that you new bearings are working well. After reading this long thread, I understand that the small bearings 6000 and 6900 are inside the motor with no risk of water ingress so the seal is ZZ (metal) with low friction .BUT the large bearings 6808 (40x52x7mm) and 6805 (25x37x7mm) are the ones in the axle where the moisture and dirty can ingress and quickly damage the bearing and it is important to choose the right SEAL for them, and this selection is a compromise between friction and water proofness. I know there are many seal types, but the ones mentioned here are:
- 2RS / DD: 2 sides rubber or plastic seal: HIGH FRICTION GOOD WATERPROOF
- ZZ : 2 sides metal seal: LOW FRICTION BUT POOR WATERPROOF
- 2RZ : 2 side low friction rubber seal, splash proof. LOW FRICTION GOOD WATERPROOF. Looks like a good compromise
- LLU: 2 rubber seals with labyrinth sealing. LOW FRICTION GOOD WATERPROOF. Looks like a good compromise
After removing the original Shimano 6808 and 6805, can you please tell us which seal do they have.
I understand that you installed:
- 6808 DD with 2 sides rubber or plastic seal: HIGH FRICTION GOOD WATERPROOF
- 6805 ZZ with 2 sides metal seal: LOW FRICTION BUT POOR WATERPROOF
Can you please explain why you selected different seals for them.
Looks like the 6808LLU and 6805LLU with rubber seals with labyrinth sealing are a good compromise, by searching google I found the ENDURO bearings, but I do not know if these enduro are the rigght bearing for this application.
The original ones in my motor show:
NSK 6805Z and NSK 6808D. However they are sealed on both sides so they are in fact NSK 6805ZZ and 6808DD. They print the number on the seal itself, so perhaps thats why they dont specify the full number on one seal.
So what i installed was exactly as original.
Imo there are 2 major causes of failure for the motor bearings.
1. Water / dirt ingression from the oil seals. There are 3 oil seals, one for each main crank bearing and one for the 17mm needle.
2. High shock forces on the main crank axle, such as result from pedal strikes, jumping, ( being overweight
), etc.
Both these 2 major failure points can cause excessive wear on the main crank bearings 6805ZZ and 6808DD, and also potentially the 17mm needle bearing (though its mostly water / dirt ingression that would cause that to fail)
To be honest, my motor didn't have any noticeable water / dirt ingression. I never use water to clean the bike and usually ride in dry dusty weather. My failure point was definitely nr 2.
The other bearings in the motor should wear out a lot slower like you said, because they are not so much affected by above failure points. So if there is anything critical you would need to replace its at least the 6805ZZ and 6808DD and potentially the 17mm needle bearing.
Also do a good clean of the clutch bearings. You can strip them apart, taking the cage off, and the rollers out. Be careful of the springs, where they came from, how they go back, and use a good quality fine tweezer to reassemble the springs and cages. Work in a clean environment! You can do both clutch bearings this way, you just need to remove a retaining clip from each clutch. Re-grease the clutch bearings with the same white grease that's on the cogs. Im not 100% sure its the right grease, but from what i can tell it looked like it originally came with the white grease on the clutch and so far its working great, no slippage.
Perhaps a labyrinth type could help with failure point nr 1, but it wouldn't help for nr 2. So it's up to you. If you think the compromise is worth it, go for it.
www.performancelinebearings.com
motorex.com
