davidallenxyz

Just been going over a second-hand bike I bought for my son.

Now this was a cheap bike when it was new and it was a even cheaper bike when I bought it.

The bearings, in general, are very "crunchy".

But it seems to me that most of the problems with the bearings have been caused by excessive tightening in the factory itself.

Whenever I rebuild a bearing (we're taking about cone/cup types here), I always manage to get a nice, free running movement with close to zero backlash. I'm yet to have a bearing fail.

Yet the (cheap) factories seem to crank the cones down tight so that nothing rotates smoothly.

Why?

fietsbob

For the wheel assembly machines, perhaps?

Dan Burkhart 

Your observations are correct. Bike factories crank out machines at a blistering pace, and adjusting bearings to precise preload takes more time than they are willing to spend.
Part of what goes into dealer prep at better bike shops is to correct these issues.

CliffordK

It is my opinion that it is in the cones themselves.

Shimano races tend to be similar quality throughout their product line, but the cones for the cheaper products are poorly finished.

I find that I just can not adjust them to get out that gravel feel without getting them loose.

I've started popping them off and hand polishing my cones before install. It takes only a couple of minutes in a drill.

It may be that there is an expectation for the bearings to bed into the cones slightly, and the tighter ones are better.

Andrew R Stewart 

A bearing that is even a tad loose can be felt by the consumer. But many buyers can't feel the difference between just right and way too tight. A lot of shops have new bike assembly standards that send out bearings (hubs a lot and ft hub especially) in what I consider to be a way too tight (and likely not corrected from the manufacturer's boxed bike). I years ago read of cone polishing (in Bike World, and that dates me). The more I thought about it I decided that just riding the bike for a few dozen miles then readdressing the hub adjustment does much the same. What is common knowledge is that most riders won't do a follow up service till there's some felt problem. So the as delivered from the hub making company spec is for too tight a bearing adjustment. The wheel making company likes this as it eliminated rim run out slop due to loose bearings. Many "shops" like this as they can save a few minutes per bike assembly and know that the rider won't feel it when new. The cheaper the bike/bearing the more likely that the rolling surfaces will bed in after initial use, how much is the question. Andy

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altenwrencher

The story I heard in the 1970s was that hubs were too tight from the factory because that made the bearing surfaces and balls less subject to damage from vibrations during shipment. Adjusting hubs, bottom brackets and headset bearings was always done on every bike we sold.

fietsbob

+1, with Andrew...
less finished cones do ball burnish races by their own bearing balls with a bit of use..

not replacing balls Cleaning and re greasing can go on to pit, pothole, those races,

because few bother doing that.



.

cpach

Most cup and cone assemblies come tight regardless of quality. I still adjust the preload on a new dura ace hub. Mostly this is a time/quality problem at final assembly--getting an ideal adjustment in an efficient amount of time requires skill and for me at least is easier with an axle vise. Many mid end bikes come with an adjustment that is tighter than ideal but also almost impossible to perceive without actually spinning the axle by hand, and many assemblers will choose to improve their build times by lowering their standards. Also many customers under tighten QRs and so if your adjustment relies on that as part of the preload the customer may find themselves with some hub play.
On really cheap parts--mostly solid axle cruisers and kid bikes, it's pretty much impossible to eliminate play and get a smooth feeling bearing assembly, but these bikes also often get beaten on many years and remain serviceable for their application.