Lazarus Short

I was overhauling a front hub yesterday, and after niggling out the bearing balls, I counted them: 19. Rats. Now I had to scrounge up one ball. Well, I could use nine balls per side - no, not gonna do that. I could tear down that spare Maillard hub - no, then I'd have two hubs to overhaul. I took to the www, and found a commercial seller of bike parts. Loose balls were sold two ways: in packs of 25, Grade 25, cheap; and in carded 12-pack units (obviously for dealers shelves), Grade 300, not so cheap (but way more balls). I did not know if Grade 25 or 300 was better, so I did some digging, coming up with this:

https://americandad.biz/gradechart.htm

Once I saw that Grade 25 balls were precision, and Grade 300 balls were not (called "cubes" in the trade), I could see that the balls I might buy from a dealer might easily be non-precision. I recall that I'd never thought to ask before, just gimme the right size, thank you. What do we want rolling around in our bearings, anyway - spheres or cubes?

Folks, we need to be upfront with dealers - ask for and insist on precision balls. We also need to consider upgrading balls next time we overhaul. I think I'm laying in a stock of Grade 25's.

Yo Spiff

Good information to know, thanks.

Continuity

Yeah - I asked in two of my LBSes what the grade of the balls on the card were, and they couldn't tell me - they didn't know.

I found out later online that they could be either Grade 300 or Grade 1000, depending on which of the 2 major brands of 'cards' they stocked that tend to be popular in LBSes.

I would have thought that the extra profit in selling these lower grades over say 25s is really small, especially if you're buying bulk. If the 25s are not available in pre-filled bags on those cards, then I wouldn't have thought it would be that much effort to have the Sat shop guy bag some from a jar into plastic snap baggies.

I wonder if the guys who work at these shops use these bearings themselves, or if they would use some from a 'stash' of better ones?

Calling the 300-1000s 'cubes' is amusing, but slightly misleading, I think - AFAIK, the grade refers to the amount of variance within the batch of bearings, and not how 'not ball-shaped' they might be.

Lazarus Short

300? 1000?? Yikes!!! No wonder bearings feel rough...

HillRider

Grade 25 balls are significantly rounder and more precise than Grade 300 balls but calling them "cubes" is a major overstatement. Bike hub bearings run at very low rotational speeds (373 rpm at 30 mph) and at such low loads and temperatures compared to the industrial demands bearing balls are intended for so even Grade 300 are plenty good. If your dealer uses Grade 300 or 200 balls in his service department, no one is harmed.

That said, since it's my bike and the cost difference between Grade 25 and Grade 300 is so minor in the overall cost of bike ownership, I always buy Grade 25 balls.

Continuity

Indeed - I was just about to quote this old post of yours, Hillrider:

gyozadude

How do you know if a Dealer is simply putting lower quality balls into smaller packs and charging a higher price and labeling them as such?

IME, at least on lower and mid-end bikes, the biggest problem with hubs isn't bearings, but being too tight and either the wrong lube or insufficient lube. Proper initial adjustment before riding is important. And then there's the cones/cups that are misaligned in the hub itself and made of inferior steel that pits easily. Maybe it could be that I've never encountered these grade 300 bearing before.

Andrew R Stewart 

As a shop guy I always preferred bulk bottles of balls. The time to count out 25 balls (but charge for 20, sell 20 charge for 18, etc depending on application count always give a few at N/C) is minimal and i usually talk about the job the customer is doing at the same time. We use small zip lock like bags or even folded over paper to contain them. BITD I tried to stock grade 25 but these days a shop does so little bearing rebuilding and the condition of the cups, cones are often in less then new shape so now i am happy with grade 100. Andy.

Lazarus Short

Gyozadude, so what do you lube hubs with? I never got the straight and skinny on that, just decided on my own that white lithium grease was not the best.

Andy, you are quite correct! I was in a good hub mode of thinking, but some bike bearings just do not need precision balls. I've ridden such bikes myself.

gyozadude

You could use green Phil Wood Grease, which used to be my standard for hubs and primarily because I bought into the psychological marketing that having small micro-fibres in the grease helps the grease work and stay in the nooks and crannies. But over the years, I found that standard, decent quality Marine grease (like the stuff they inject boat trailer bearings/hubs with that need to go underwater at boat ramps) is the best price-performance. I look for the best viscosity and stickiness. Some of the cartridge ones aren't very viscous and they actually separate out (oil and solids) during the summer (yes, I do pry up the caps and look). The best stuff I found a long time ago was Yamaha Marine grease. Haven't seen it around recently, but 10+ years was what a big tub lasted. And an even better deal, I found in Canada, the house brand Canadian Tire Marine Grease in the tub. Not sure that's still true at current exchange rates. But I brought a bunch of that stuff back with me. Works wonders for saltwater fishing reels too.

Lazarus Short

Thanks to all for their responses and advise! I managed to get a ball from the fellow who sold me the wheel, and he gave me a dollop of grease from a tub which looked like it was some years old. Sure enough, it was marine wheel bearing grease, in a blue-green color, and there had been no separation. It should do well. Perhaps the coolest thing about the Exage hub is the two little plastic rings on each bearing cone, which contact the inside edge of the dustcap, to seal the mechanism. Now for the rear wheel...

FBinNY 

I find this interesting. By replacing a single ball, you've downgraded a set of grade 25s (if that's what they were) to grade 100 or lower. Balls have two tolerances.

The first is the overall dimensional tolerance, and the second it the lot tolerance, which is typically one order tighter than the overall tolerance.

Think of it as you would paint. Brand X eggshell paint is mixed to a standard, so when you buy eggshell you get eggshell. But if you're painting one room with more than one gallon you want both to be from the same lot. Otherwise the paints will be a reasonably close match that wouldn't matter in different rooms, but you'll see the difference when you change form one to the other on the same wall.

Like others here, I always buy grade 25s, not because my hubs need them (they don't) but because it's so cheap to go 1st class that I can't pass it up.

3alarmer 

If you live anywhere near a major metropolitan area, you're always better
off buying bearings from a bearing supply place.

Here in Sacramento, I use Motion Industries which has a local outlet.
But wherever you are, Google "bearing supply" and "your city."


Interestingly, the guys here no longer keep all the various sizes of ball
bearings in stock, because there is very little call for them any more.


Everything, including bikes, seems to be made with some kinda cartridge
or other unitized bearing assembly. But they are very happy to order them
for me in any grade that is available....usually grade 25.

davidad

For bike usage you don't need grade 25. 300 is more than adequate. In fact we would be fine with high quality bronze bushings. A wheel is turning about 335 rpm at 30mph.

davidad

No such animal as lot tolerance. The dimensions are too tight.
From: jbrandt@hpl.hp.com (Jobst Brandt)Newsgroups: rec.bicycles.techSubject: Re: How Bearings are MadeDate: 22 Nov 1999 23:05:20 GMTRoger (who?) writes:> Did you know you should only ever use ball bearings from the same> batch in one side of a race? They're not exactly the same size> between batches. Never simply replace that naughty one that bounced> into the corner of the garage - replace the other 10 (or whatever)> too!You are making this up. The tolerance between bearing balls is sosmall as to be below a small fraction of the elastic compliance of thesteel bearing. Besides, the races of bicycle bearings are so roughthat a tight bearing feels lumpy. In high precision bearings used oncomputer disk storage devices, preload causes a smooth viscous drag.Even for these bearings the balls are not identical but are made to aprescribed tolerance. I don't believe I understand what you mean bythe same batch. Each bearing is not made in the same finishingprocess as the others in a shipment of balls.Jobst Brandt <jbrandt@hpl.hp.com>

Lazarus Short

Looks like I've stirred things up a bit. My bad.

First, look at the chart I linked to in my OP. Do you see the column "Lot Diameter Variation"? It has a measurement with a +/-, so is that not a tolerance? A lot-to-lot tolerance? Maybe it's semantics...

Second, Jobst Brandt? The fellow who wrote The Bicycle Wheel? The fellow who, in his book, stated that a bike stands on the spokes?? I remember reading that with utter disbelief. I am no engineer, but knew a bike hangs from its spokes. Never mind - we're talking about bearing balls. Davidad and FBinNY, what you both say is well spoken, and I do intend to redo the wheel with matching balls ASAP. 3alarmer, there just happens to be a bearing supply outfit in this desert town, so I'll be getting that stock of balls soon.

Again, thanks to all for the advise!

FBinNY 

There are two issues here. The first is the actual tolerance, and the second is whether it's material.

If you bring up a ball tolerance chart you'll see that the lot tolerance (yes, it exists) is one order narrower than the general tolerance for any grade

That means that if you look at random sample of all grade 25 balls, they'll span a range of 0.0002" from the smallest to the biggest (probably less because ball makers avoid the fringes). However within any one single production lot the size span is narrower, running 0.000050 from smallest to biggest. So that answers the first part.

However, we also have the question of whether it's material. Most of us agree that grade 25 is overkill for bike hubs, and grade 100 or even 300 is plenty adequate to the task. Since any grade 25 ball, whether from a single lot or from mixed lots will be within the lot tolerance of grade 100 balls, it's therefore immaterial whether we mix lots of grade 25.

However if we start with a coarser grade, and mix lots then it might become material, or at least more so.

My point was that I find it interesting that folks pay a premium for grade 25 balls, then mix lots, and make them into grade 100. If they wanted grade 100 they could have saved their pennies and bought grade 100 in the first place.

Lazarus Short

OK, FBinNY, that brings things into sharp focus. Thanks for the clarification!

Sixty Fiver

I have had a few customers insist that they could tell the difference between grade 25 (precision) and grade 100 (semi precision) bearings... these are usually the same princesses who also think they can feel the difference between ceramic and high grade steel bearings and think that cartridge bearings are always smoother running.

We use cartridge bearings because their service life is much longer, the resist contamination better, and because it makes sub assemblies easier to manufacture... but not because they are any smoother than their loose ball counterparts.

HillRider

OK, but if they mixed lots of Grade 100 balls they would make them into Grade 300 and so it goes.

FBinNY 

Absolutely, which is why people who work with precision stuff learn early on, never mix lots whether it matters or not. It's much easier to mix stuff up than to unmix it later.

ksisler

Exactly right. Also willing to bet one would be hard pressed to find any of the cups or races on a typical bike that were machined to better than a few thousanths, so the balls aren't even close to the limiting factor... and given the low rpm, it is not worth worrying about much /K

Flying Merkel

Sensible answer. Our precious bikes aren't really precision machines. We enjoy big tolerances, low RPMs, and light loads.

And white grease is poop. Turns to a sticky gummy mess eventually. I've used Moly D automotive grease for years.

FBinNY 

I'll take that bet. Even the cheapest cups and cones are held to within .001" or better for roundness. Ground cups and cones such as used on better components are round to within 10ths (.0001") Roundness is fairly easy to achieve, and the beauty of the bike world's angular contact systems is that it's very forgiving of actual dimensions (within reason) as long as roundness is kept to spec.

Likewise for bike purposes, the actual size of the balls doesn't matter, and even roundness isn't as critical (both within reason) but the matching of the balls within a set is very critical. Matched balls ensure that each ball takes it's share of the load and the contact pressure is distributed evenly. With unmatched balls, only a few, as few as the three largest, support the bearing with the others doing nothing. The hardened steel of bearing races cannot accommodate the variation, so while poorly made balls won't cause the vibration and heat buildup of high speed bearings, it does cause increased wear through fretting and shorter life.

If you look at the extremely long life of better hubs like Campag, or Dura Ace, it's the precision of the ground races and the use of matched balls that makes it possible.

Whatever quality level ball you choose to buy, good practices in keeping sets from single lots, like good cleanliness and lubrication ensures you'll the service life you paid for. Conversely, with bad practices, it doesn't matter how much you spend.

Retro Grouch 

Yeah, right.