Which goes first, the chicken or the egg ?

[Jaspy]

Curious bunch aren’t we ! Haha Seriously though in reference to the main crank seals n bearings. (1) Do the bearings get pounded out and then the seals go or (2) do the seals go first eventually letting contaminates in taking out the bearings ? Ya I know it can be either but generally which one?

 

[steve_sordy]

Definitely the seals, otherwise the grease in the bearings would not get diluted and gritty.

 

[Jaspy]

Hmmmm perhaps the reason the seal failed is because the bearings did first. The excessive play in the bearings would quickly take out the seal. If that’s the case then, if we checked the play in the crank after Every ride , we could change out the bearings before the seal goes and lets in the nasties . Hence preventative maintenance saving the motor.

 

[Slapbassmunky]

Hmmmm perhaps the reason the seal failed is because the bearings did first. The excessive play in the bearings would quickly take out the seal. If that’s the case then, if we checked the play in the crank after Every ride , we could change out the bearings before the seal goes and lets in the nasties . Hence preventative maintenance saving the motor.

The problem is once the bearings develop noticeable play things are well past preventative maintenance. You would need to swap bearings out the moment they become noisy, which is a matter of weeks for some people.

 

[Rusty]

Conventional bike or eMTB, the only time I have had bearing issues I have found the seal to have failed first. Even though most manufacturers are a bit cheap on their bearing quality it is pretty hard to destroy a well sealed & lubed bearing.
Probably the biggest issue and more than the rating of the bearing is that they tend to assemble things with bearings pretty damned dry. Because motors are what they are it is a take them as they come to avoid warranty issues, but everything else gets checked and lubed properly after the first couple rides.

 

[steve_sordy]

A properly lubed bearing subjected to the speeds and forces within its design parameters should last a long time, provided it is installed properly.

I still favour that it is the seals that go first, subject to correct installation.

 

[Kilham5]

The seal has to be responsible for 99.99% of bearing failures would be my "guess".
And the seal may not fail in a strict sense, just unlikely to be 100% effective when subjected to grit, mud and pressure washers.
Bearing fails because the seal hasn't protected the bearing.

 

[Tim1023]

...so did the seal come before the egg?? I'm confused. Seals don't lay eggs.