szachariah

I have a Specialized Sirrus 2.0 purchased 2020.
I no longer have the original (loose) axle ball bearings for the front and rear.
The back seems to be 9 x 1/4" on each side.
For the front, I can't tell if should be 10 x 3/16" or 9 x 1/4" per side.

Does anyone here know the answer? Or know a way to determine what size the ball bearings should be?

Thanks

Bill Kapaun

Does it have a Shimano hub? One could look up the docs if they knew the model #.
The only bikes I've seen with 1/4" balls in front were Huffy's. That certainly doesn't mean it's not impossible to have other sizes, but I'd expect 3/16"
Another reason to buy 100 packs of BB's of the sizes you use. You're already prepared.


BTW, how long does it take to remove the wheel and back off a cone a ways and look?

FBinNY 

I assume you no longer have the originals. As noted front hubs with 1/4" balls are rare, but not unheard of. If you have stock in both sizes, an easy trial and error method should give you the answer.

The different sized balls will stack axially by different amounts. So, assemble the hub with either size and measure the OLD, or note the amount the cone extends past the dust cap, compared to marks which might show prior position.

Andrew R Stewart 

Most likely 3/16" x 10. One can mark the cone's curved ball surface with marker then assemble the hub with the best guess (3/16") balls with 1 less ball then you think (from 10 to 9 in this case) dry of any lube. Adjust the preload a hair tight and spin the axle a bunch. Take it all apart and you'll see where on that curved surface the ball track is. The correct ball diameter and more than half the correct ball count will produce the contract track, showing by the removed marking only where there's contact. If a too large ball is used that contract track will be at the VERY small end of the surface. The correct ball size will have the track only within the ends of the curved surface, usually towards the middle portion. Clean it all up and install with the now known correct ball size.

As to how many balls are correct- one too many will result in a hard time getting the preload adjustment spot on (generally it goes from too loose to too tight with VERY little additional preload) and the rim will now look to be out of true. That extra 1 too many balls will ride up within the "ring of balls". If one were to try to true the rim now the deviation will seem to travel about the wheel as that ball cocks the wheel off angle. This off angle usually rotates at about half the RPM of the wheel. One few balls is OK but not advised.

There have been some alloy "nice" hubs with 1/4" balls. The BMX world is well known for this. Andy

szachariah

Thank you Andy, this is very useful information.

JohnDThompson 

Some front hubs will use 7/32" balls. It's hard to know what your hub needs without knowing the make and model of the hub. If you have the tools, open the hub and take a look.

Jeff Neese

You know to buy Grade 25 or better, right?

Andrew R Stewart 

Jeff- I've heard this suggestion so many times over the years. While I do agree with using as high quality a part as one can afford I also feel there's a point of diminishing returns at play. So many other conditions grow with time that will overwhelm the tiny added tolerance control of a more costly set of balls. Wobbling axles (rear on freewheel hubs being very common), cone wear from the previous condition not being caught/serviced before further use, poor hub construction (especially on multi piece hubs) and the inability or lack of follow up bearing preload adjustments after the factory assembly are all common examples.

I can't say how many loose ball/cup and cone bearing systems I have serviced with reusing the old balls (only if they are still consistently shinny) and cones. Maybe in the hundreds by now. I also can't say how few returns have been due to bearing issues that I could have replaced (and I don't include the pressed in ball cup cracking failures in this) because I didn't have any that I remember. I have had returns from my mistakenly replacing cones with ones that didn't match the ball track surfaces, from using the wrong size balls (and this is avoided if the old balls were able to be reused) and from the wrong ball count (only did this a very few times way back when, but that's how I learned about this affecting rim true too).

When I work on high end stuff I do pay more attention to ball tolerance claims however I still feel that this is a topic that has greater discussion interest than actual performance effects. Andy

FBinNY 

Grade 25 is what's used on electric motor bearings rated for well over 10,000 hours of continued service at 3,600rpm.

Better grades are generally reserved for higher speed applications where vibration is a serious concern. The higher precision comes with s considerable cost premium.

As it is, grade 25 is well above what's necessary for bicycles. I buy them because, given the volume, the cost difference is small. But I don't fool myself into believing it makes a difference.

FWIW typical bike cup/cone systems are supplied with grade 100 balls, and only elite brands using grade 25.

Jeff Neese

Typical high-quality hubs (Shimano, for example) use grade 25. I've seen reference to Campy using grade 10, and bike shops will recommend grade 10 for rebuilding Campy hubs. I would tend to believe that Walmart bikes probably use either grade 100 or worse. Grade 25 is good enough though, and they're certainly cheap enough that there's no reason to go lower quality. These are what I use - about $6 for a pack of 100.

3/16 INCH Chrome Ball, Grade 25, (100 Count)

Jeff Neese

Diminishing returns is certainly in play, but since grade 25 bearings (Boca, for example) are only about six bucks for a package of 100, it doesn't make sense to go any lower. Most good hubs use grade 25, and Campy reportedly uses grade 10. There is a significant price difference between grade 25 and grade 10, and unless you're rebuilding Campy hubs, grade 10 is overkill and probably a waste of money.

FBinNY 

Yes, as I mentioned, and like you, I use grade 25 balls. My reference was about "better". There's simply no benefit to using anything better than grade 25 on a bike.

Eyes Roll

Drop the ball bearings as necessary, ensuring they are flush with the surface. Do not overlap them.

If the front takes 9 instead of 10 and the rear takes 8 instead of 9 on one side or both sides, so be it. Recently, when I repacked my front hub, I removed 10 worn ball bearings from each side. However, when filling it with new ones, I only used 9, and 10th one ended-up overlapping and was unnecessary. Knock on wood, my bike rides great, since repacking.

KerryIrons

And yet somehow Campagnolo came to the conclusion that "better than grade 10" was their standard. I assume, with all due sarcasm, that you know better than Campagnolo.

Jeff Neese

That's only because the Campagnolo engineers don't read Bike Forums. They could learn a lot from some of the "experts" here.

Andrew R Stewart 

It's not an issue of knowing more then so and so but whether the differences are noticeable and contribute to the overall performance. For a manufacturer a vast amount of "performance" is how well their product sells and how it's positioned in the market place WRT others. My opinion is that when playing at the top of the pile it is best that so and so can say "we use better bearings", for their low added cost this makes smart marketing sense. Independent of any actual functional improvement.

I'm not arguing that we should all toss out our grade whatever balls we use and only get the cheapest possible (a bit of embellishment here) but that if we did drop a grade I don't think anyone here would notice. The cleaned and freshly lubed condition will be vastly more noticeable. Andy

FBinNY 

I make it a policy never to argue with those not present. So I don't claim to know better than the folks at Campagnolo, nor do I challenge their decision, which may be based on a variety of considerations.

OTOH engineers whose entire focus is on bearings, generally consider grade 25 suitable for commercial and industrial bearings, reserving finer grades for higher speeds (well above 3600rpm) where vibration becomes a greater problem.

So, if you choose to paint the lily, by all means go ahead and use grade 10, otherwise grade 25 is fine.

KerryIrons

My mental picture of why to use higher grade bearings (and this assumes they are paired with better tolerances in the cups/cones and with very straight axles) is that at the "load point" the bearing is essentially passing through a "tunnel" created by the cup and cone. The variations of any of these three components create a "window" of adjustment where the size of the tunnel at its smallest needs to be bigger than the bearing at its biggest. In the case of low grade components, you end up with having to tolerate a little play to avoid binding. If you adjust such a system to eliminate play, you will have binding and subsequent rapid wear. This was the tradeoff back in the day and only high end hubs, bottom brackets, and pedals could be adjusted without play and without binding. While there may have been other brands that met this test, when I was coming up in the world of bicycles, Campagnolo was the only brand I ever had my hands on that did.. And the result, in my experience, was a set of products with extreme durability compared to the rest of the marketplace. I got 90,000 miles out of a Campy BB, hubset, and pedals and the bearings were as smooth as when they were new, still shiny, and with lots of miles left in them. Nobody I knew riding Shimano or other brands of the day came even close.

FBinNY 

I bought my first Campagnolo Record equipped bike in 1967 and, like you, enjoyed many 10s of thousands of trouble and wear free miles.

But, I chalk it up to better steel and greater precision in cups and cones rather than better balls.

The difference in the tolerance if G10 vs. G25 is miniscule compared to the precision of the other parts, and certainly far smaller than what anyone could sense in a manual bearing adjustment, especially those assembling components in production.

In any case, your analogy is flawed. Big balls don't get squeezed into a tight space. Instead the axle is triangulated between the three closest balls, with the other balls doing less work, If 3 large balls are roughly equally spaced, all is good, but the odds are that they're not, causing the axle to and down as smaller balls pass below. It's not much and bearing can handle it, but harmonics can make that tiny movement problematic at high speeds.

So, I'll trust the judgement of folks at bearing companies like skf who reserve higher grades for especially demanding applications.