bearing replacement question

[geomecc]

is it necessary to remove the shields for the rear (bigger) bearing? I always leave the shields on for the front bearing with no problems. just wondering what other people think.
thanks

[Bob O]

Any rear bearing I've ever used (OS-55) has never had a seal or shield.

[geomecc]

I got a set of aftermarket bearings for my os55 ( I forgot where I got them) and the shields are on both bearings. I couldn't figure out how to get the shields off the bigger bearing.

[Elgyn]

I've done it both ways. It doesn't seem to make a difference.

if the bearings are a shielded then I'll rinse the bearing with methanol(or something similar) to get the manufacture's mystery grease out then oil it up so it's not dry.

[ticedoff8]

The shield on the rear bearing makes a big difference in power and bearing life.

The shield allows enough oil into the bearings to keep them well lubricated, but not too much to cause the bearings to skid instead of roll.
If the balls start skidding, they will ware faster and cause drag.
And, higher drag robs power and causes heat.

Also, the open bearings will allow the excess oil / fuel to froth as there is nothing to separate the fuel in the rear crankcase from the bearing. Imagine a mini-Cuisinart in the back of the engine - piston rod, crankpin and bearings all spinning at 15,000 RPM and frothing the oil / alcohol mixture. This frothing causes drag. If you can keep the bearings behind the shield, then you reduce drag.

Bearings that have no shield are cheaper - not better. Many manufacturers will use the cheaper bearing to keep costs down, not because they are better.

Also, the shield faces the backplate, otherwise, it is useless.

It is like the discussion about steel balls, vs. stainless steel balls vs. ceramic balls in the rear bearings.
The ceramic balls are best but cost a lot more. So, you never see ceramic ball bearings in "factory" engines. But, they are the first upgrade most people do after they get a new motor.

[geomecc]

thanks thats what i was thinking but wanted to see what others thought. i got 30 flights on this set of bearings so far so good with that. im having leaning issues with this os55 im thinking i need a new ring as i fly this model alot and i have 3 seasons on it.