Hi
The answer to your questions.
"how do i tell if their the cheap bearings?"
Yes you have "cheap" bearings.
This does not mean they are bad bearings.
Your bearings (in your case) consist of balls and races .
There are very technical specific that control the grade of the bearing.
But for a basic "cheap" bicycle you are at the mercy of the supplier.
Most likely they are adequate or better
In reality the adjustment and lubrication of the bearing will determine the the longevity.
So in short if your bearing is correctly lubricated and adjusted it should give good life less any manufacture defects (can happen but not likely).
Find someone that understands how bearings work (a GOOD bicycle mechanic, machinist or engineer) to set the bearings and and explain to you how they work and need to be set and you should be fine with what you have.
This should be a regular maintenance item not to be ignored (adjust & lube)
Most all of the wheel bearing failures that I have seen photos seen here look like adjustment, lubrication or abuse problems.
Like all things in life it's the little things that make a difference
GOOG LUK
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so i toom apart my bearing of my wheel to re-grease with high temp grease. how do i tell if their the cheap bearings? and where to find bearings and correct fittings to make my bike last.
i've heard beach cruisers are meant to be 8-10 mph. i will put an engine soon and hope everything will last for awhile.
also is it possible to convert coaster brake wheels to disc brake? if the threads are compatible with disc brake adapters.