Sealed for life bearings

[Burnerman]

A bit of a sequel to my biking episode really - I fitted new sealed for life bearings (i.e those with the plastic cover enclosing the ball races).
Before whacking them in, I thought I'd prise off the covers to see how much grease was inside. Guess what? Next to nowt - more like a splash of light oil......so I filled them with HMP grease (not fully though) and replaced the seals.
Hopefully they'll last a bit longer - and jet washing is definitely out. Mind you, it was never 'in'.
John

 

[Peter.N.]

Hi John

You have probably noticed the same problem with ball joints particularly drop links, I always loosen the boot and squirt some extra in. Some people have complained about the relatively short life of pattern parts and I think that's likely why.

Peter

 

[Avocet]

Modern plastics have evolved into extremely complex compounds these days - pretty much self-lubricating in many cases. I think the poor life of "pattern" parts is more to do with the poorer grades of plastic, sometimes poorer geometry and surface finish on the mating steel parts, and poorer quality seals. Some lubricants (especially spray greases) can even attack some plastics.

 

[Peter.N.]

These are metal balljoints I am thinking of and they do have a little grease in them but I'm sure its not enough. I have only recently come across the plastic ones - what will they think of next.

Peter

 

[empip]

...Excessive amounts of grease will cause the operating temperature within the bearing to rise rapidly, particularly when running at high speeds. As a general rule, when starting up only the bearing should be completely filled, while the free space in the housing should be partly filled with grease. Before operating at full speed, the excess grease in the bearing must be enabled to settle or escape during a running-in period. At the end of the running-in period the operating temperature will drop considerably, indicating that the grease has been distributed in the bearing arrangement...

Ah but !

...However, where bearings are to operate at very low speeds and good protection against contamination and corrosion is required, it is advisable to fill the housing completely with grease...

-0-

 

[Burnerman]

An interesting post!
When I used to build racing Kart engines (Rotax) I used to wash the grease out of the bearings and only oil them, naturally enough minimising drag.
With 'sealed for life' bearings, would the average user be able to remove the grease seal without damaging it? That I doubt!
John

 

[Avocet]

These are metal balljoints I am thinking of and they do have a little grease in them but I'm sure its not enough. I have only recently come across the plastic ones - what will they think of next.

Peter

I think most "metal" balljoints actually have a plastic liner as the friction surface - at least for automotive applications. Some low-load ones like anti-roll bar droplinks are now starting to appear as complete plastic mouldings with only a steel ball pin in them.

 

[Avocet]

An interesting post!
When I used to build racing Kart engines (Rotax) I used to wash the grease out of the bearings and only oil them, naturally enough minimising drag.
With 'sealed for life' bearings, would the average user be able to remove the grease seal without damaging it? That I doubt!
John

Probably not, but would they care? I buy cheap and nasty taper roller bearings for my boat trailer and put quite a lot of grease in them because they get dunked in water regularly but don't have to turn very fast. There's no point in buying good bearings because even a genuine Timken will rust long before it wears out in this application. If it was a car, I'd probably be much keener to get a good quality bearing and then I wouldn't bother trying to take the seal off anyway. A good quality one would have all the grease it needed for a resonable life. Too much and it just oozes out past the seal as the bearing warms up.

 

[wotan]

An interesting post!
When I used to build racing Kart engines (Rotax) I used to wash the grease out of the bearings and only oil them, naturally enough minimising drag.
With 'sealed for life' bearings, would the average user be able to remove the grease seal without damaging it? That I doubt!
John

Probably not, but would they care? I buy cheap and nasty taper roller bearings for my boat trailer and put quite a lot of grease in them because they get dunked in water regularly but don't have to turn very fast. There's no point in buying good bearings because even a genuine Timken will rust long before it wears out in this application. If it was a car, I'd probably be much keener to get a good quality bearing and then I wouldn't bother trying to take the seal off anyway. A good quality one would have all the grease it needed for a resonable life. Too much and it just oozes out past the seal as the bearing warms up.

For boat trailer use, the bearings should be packed with lithium grease, inject fresh grease just before entering water.

Wotan

 

[Avocet]

Already using that, to be honest. Putting more in just prior to launch is impractical for me (no grease nipples)! You can buy "bearing savers" or "bearing buddies" - just a spring loaded plunger that pushes into the centre boss where the plastic (or steel) outer blanking plug used to go. It keeps (or is supposed to keep!) a positive pressure in the bearing cavity all the time. One of the biggest problems is that when you arrive at the slipway, the bearings are usually warm, and as they go into the water, the air in the space cools and contracts. The grease seals only work against internal pressure trying to escape, so the water just finds its way in and then can't get out as easily. I've never found a completely satisfactory solution - the rust gets them all in the end! I just buy Chinese "no-name" bearings at £4 each and replace as required.