Ball bearing quality

[Russell160]

Just wanted to check what 25 Grade ball bearings are. Is this a measure of hardness or smoothness. More generally, is there any benefit in the little bit extra cost ?
Here's examples from SJS and second an earlier discussion that is inconclusive.

http://www.sjscycles.co.uk/page/find/?name=ball bearings&page=1

[Russell160]

viewtopic.php?f=5&t=15713&p=123604&hilit=ball+bearings#p123604

[thirdcrank]

... an earlier discussion that is inconclusive....

Here's an earlier thread with more - and different - detail.

viewtopic.php?f=5&t=33638&p=269256

Tere's a very detailed explanation (by my layman's standards) here.

http://en.wikipedia.org/wiki/Ball_(bearing)

[RJC]

One other thing to consider if thinking about higher quality replacement bearings is whether to get chrome steel or stainless bearings.
Stainless bearings are not as hard but more corrosion resistant. You need to know what type of stainless and hardness as they vary
significantly, 440C can be almost as hard as chrome steel bearings. Silicon nitride ceramic bearings don't rust and are harder than steel
but they are 10x the price.

I haven't come to any conclusion whether a slight trade off in hardness is worthwhile for more corrosion resistance but I noticed that Shimano
say they use stainless bearings in Dura Ace & XTR hubs.

[john.will.wright]

I've never noticed my bearings corroding before, I wouldn't think it very likely when they're bathed in grease. Has anyone actually noticed corrosion of their bearings?

I'd say hardness is by far the most important factor, pitting seems more of an issue than corrosion to me.

[RJC]

I've never noticed my bearings corroding before, I wouldn't think it very likely when they're bathed in grease. Has anyone actually noticed corrosion of their bearings?

I'd say hardness is by far the most important factor, pitting seems more of an issue than corrosion to me.

That was my initial thoughts but it would seem unlikely Shimano would use slighty inferior bearings on their top of line hubs.

[Mick F]

I've never noticed my bearings corroding before, I wouldn't think it very likely when they're bathed in grease. Has anyone actually noticed corrosion of their bearings?

I'd say hardness is by far the most important factor, pitting seems more of an issue than corrosion to me.

Yes, I've had corroded bearings.

They are only steel - hard steel, but steel nonetheless.

Let water get in to a bearing, and you will have corrosion. Grease is not waterproof. It's a mixture of oil and soap(of some description) and will wash out easily, that's why you have seals on bearings. The better the seal, the more the friction, so bikes don't have much in the way of seals.

Worst bearings for corrosion - and wear - is the bottom race of the headset, second is the bottom bracket, and third is the drive-side of the rear bearing.

The BB actually doesn't suffer too much because the bearings can have good seals. This is because the rotation-rate is low and any losses of friction will be small. However, because people forget about them over time, they suffer long term damage.

Keep an eye on the headset and the BB, and also the rear bearings.

[BigG]

One of the benefits of mudguards is that they offer some protection to the headset bearings.

[thirdcrank]

I presume thre needs to be some matching of the quality of the ball bearings to the equipment they are used in.

[Steve Kish]

I presume thre needs to be some matching of the quality of the ball bearings to the equipment they are used in.

Very good point.

I was once told that ball bearings should wear before the contact surfaces against which they are fitted, as these are much cheaper and easier to replace. If this is correct, it might seem best to use stainless ones and check on a regular basis, with replacement as necessary.

[gregoryoftours]

Also corrosion is less likely if you use marine boat trailer grease in your bearings