Seb1987

Today I opened up my hubs to inspect, clean and grease them for the 1st time in 4 years. I believe I may need to get new ball bearings but are all hub ball bearings the same size?

Geepig

Great! Yes and no.

It really depends on what kind of equipment you have, but generally the balls are larger at the rear and some of the largest I have found were supporting the rear sprocket of a kiddie bike. As I tend to work at the cheaper/older end of the bike spectrum I notice that the cones tend to suffer more damage than the balls, it often looks like damp settles on one side of the cone and begins to corrode them out in that area if left in one position for several years. The balls generally do not show the same level of damage, but I suggest examining the bearing surfaces carefully, maybe with a magnifying glass, to look for pitting. If they look good, then there is no harm in replacing the balls.

The best thing of all is cleaning, regreasing and adjusting.

FTB

Good idea replacing the ball bearings , can make a big difference especially in conjunction with the fresh grease, but I guess you knew that.
Two things to keep in mind

1. Bearing size
2. Bearing grade/tolerance specifications

Ball bearings come in different sizes so you need to mkae sure you purchase the correct ones for your hub. If you have a shimano hub, you can search up the tech docs for your hub here using the product discipline and search function (road hubs > 'road' etc) and often find out the ball bearing size just to be 100% sure otherwise you can often search online. This is different for front and rear hubs even in the same series. https://si.shimano.com/#/en/search/Component
Bearing grades - the lower the number, the better the ball tolerances are, so grade 3 is best and grade 100 is worse etc.

Moe Zhoost

Buy a digital caliper and measure what you have. These devices are inexpensive and answer a lot of questions. Typically bearing balls are 3/16" front and 1/4" rear, but some hubs don't follow this convention.

Why do you think that you need to replace them? If, after cleaning bearing balls, cones, and cups, you see nice smooth bearing tracks with no chipping or galling, just regrease and adjust.

HillRider

Also, don't overbuy bearing grade. Grade 25 balls are the most commonly used and are far more than good enough but low enough in price to splurge on. Paying a huge premium for Grade 10 or for ceramic balls is a waste of money for no benefit.

dedhed

At $11/hundred or so there is no reason not to stock & replace most bearing balls if you plan to work on bikes.
https://www.bocabearings.com/product...-(100-pcs)-411

pdlamb

I'm on both sides.

If you've got fresh bearings ready to go (or you need a break, run down to the LBS to get some), put in new bearings.

If the old bearings are clean and shiny, re-use them.

The only time you need to put yourself out to get new bearings is when the old ones are cracked, pitted, or (heaven forbid) rusty. Then you need to get new bearings if you don't have any. Take a couple with you when you go the your LBS, or measure them carefully if you need to mail-order.

davidad

If the bearings have their original finish they a good to reuse.

cbrstar

There's actually quite a few sizes. Go down to your LBS and they will have a special ruler to measure them and they probably have what you need in stock.

Russ Roth

Not really true though the quality of the hubs can have an impact as well. Dura Ace and Record come with higher grade bearings because they spin better and can last longer. Although I think ceramic often costs stupid amounts of money spending a little extra on hubs will help them spin a little better.

OP: Get the park spoke ruler for future such repairs, it has holes for all the sizes of bearings bikes use, which ever hole it barely manages to drop through is the size. When it doubt bring one of each to the LBS and they'll do just that or a good mechanic will just know by sight in all likelihood. Nothing wrong with changing them every few years, even if everything looks good bearings can deform from the pressures on them over time and new bearings will keep everything running smooth.

dedhed

Really better yet is to get a cheap digital caliper as it is useful in all things bike related. Measuring seatpost diameters, stems, frame spacing, and even bearing diameters for about the same price.

Bill Kapaun

It's easy to measure bearings with a simple 12" ruler.
Line the bearings up along the ruler.
1/4" = 4 per inch or 8 per 2".....
3/16" = 8 per 1.5" or 12 per 2.25" or 16 per 3"......

Why does something that simple require special measuring tools when just a bit of thought......

Russ Roth

1. those puppies just like to roll away on me with the slightest breeze.
2. honestly this method never occurred to me. I can just tell by visual now but used the ruler in the past.

HillRider

Anything better than Grade 25 barrs is an absolute waste of money. Cheap hubs may use Grade 100 or Grade 200 balls but the upper level cup-and-cone hubs are served very well with Grade 25. I have a Dura Ace rear hub with over 75,000 miles still in daily use It has never seen anything but Grade 25 balls, redone at 7000 mile intervals, and both the original cones and races are still in excellent shape and smooth as glass. I remember people claiming that Campy Record hubs used "matched sets of Grade 5 balls" which was more hype than any benefit.

+1 on that Park ruler and it's useful for more than sizing bearing balls. It has spoke length measuring slots, the somewhat obsolete sizing holes for crank cotters and is a good rigid 12+" ruler for measuring chain "stretch". It's cheap for all that it does.

pdlamb

Seconded.

Geepig

A small empty box with an inch marked from one corner, and those balls are not going anywhere.

grizzly59

If you are going to reuse balls, I would put them back in the same side of the hub they came out of.

bitpuddle

What hubs are these? Do the bearings appear pitted/worn?

I’d just clean the hub and bearings and add fresh grease, unless something seems worn (there is play or they feel rough).

davidad

It doesn't mater. The tolerances for the balls is too small to make a difference.

Seb1987

I'll go to my LBS then with one of the ball bearings cause just one of them looked like it has a tiny tiny bit og rust on it.