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I'm cleaning out most of the bearings on my new (second hand) bike.

I'm replacing the grease inside the pedal bearings and I was wondering.

How many ball bearings should be inside? I thought there had to be just enough to fill the full circle, but a friend of mine told me I should fill the circle to its fullest and then remove one ball.

The reason, he said, is that else there is to much pressure on the bearings.

Is this true? And is it true for all the bearings (say, the ones in my hubs)?

And also, I'm putting vaseline (the yellow heavy-duty variant) inside the bearings – is that a good idea?

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  • I'll just toss in here that the most common "loose" ball counts are 7 and 9, with an occasional 8. Commented Jun 3, 2019 at 12:24

6 Answers 6

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The reason behind the "full less one" is that you need at least half the race full (rounded up) for it to work and performance improves with more balls past that point, but if it's too full you get a dramatic loss in performance. So "full less one" is an easy guide.

In practice most bearings spread a little as you tighten the cones so "full" when you're adding balls is not actually full in use. You can usually see this - when you're adding balls they generally sit in against the axle, then when you add the cone it spreads the bearings slightly. So filling the race is almost always fine.

Don't be tempted to add one more to fill in the extra space created when you tighten it up, this is exactly the situation the "full less one" guide is trying to avoid. That "full plus one" means all the load is on one bearing (and one section of the cone), plus the bearings are really grnding against each other as the wheel rotates. If you're lucky the wheel won't rotate in this situation, but if you're unlucky you're wreck the cups and have to replace the cups (or hub, if the cups are not replaceable).

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  • +1 This happened to me. I put seven ¼" bearings and there was a gap of about half a bearing, not enough for another one, but enough to cause concern in someone inexperienced (i.e. me). I thought it was supposed to be full and, stupidly, put a smaller bearing I had previously taken out from the same hub, about ⅛". Two weeks of unexplained grinding later and I'm finally realising how much I've wrecked this hub.
    – Sputnik
    Commented Apr 27, 2021 at 12:16
  • Full less one is a similar principle to how we set the preload on cup and cone hubs (in lay parlance we might say tighten the hub)
    – Weiwen Ng
    Commented Jan 22 at 12:49
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The general rule is a full race minus one ball. But if the race holds, say, 20.5 balls (ie, has space for more than 1/2 additional ball but not a full additional ball) then you can use as many as will fit (without forcing).

There probably is a (very small) rolling resistance advantage in using fewer balls (down to perhaps 3/4 full) but it would be at the expense of increased wear on the cones and races.

Do note that you should try to use all new balls or all balls that are originally from the same axle. The balls wear slightly over time and adding a new ball to a bunch of used ones will mean the new ball is slightly larger and will create additional wear and resistance.

You should use a good bicycle bearing grease for the bearings. This will resemble your standard black/brown/gray automotive grease but is better formulated for the conditions in a bicycle hub. At the very least use the automotive grease -- I would not expect petroleum jelly to hold up very well in a bike axle.

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  • so no vaseline you'd say?
    – romeovs
    Commented Jun 25, 2011 at 10:04
  • I'd say. Vaseline is not intended to be a lubricant of things mechanical and is (among other things) apt to run out when it gets too warm (and a bike bearing will get warm after a few minutes use). Commented Jun 25, 2011 at 13:39
  • The vaseline I'm talking about came from a hardware shop (it's not the luvvy-duvvy kind of pink gel), it's a thick yellow paste. I'm also talkin about the ball bearing inside the pedals, do these get hot too?
    – romeovs
    Commented Jun 25, 2011 at 13:43
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    Not familiar with the variety of Vaseline you're describing -- I'm guessing it's a food-grade lube intended for kitchen appliances, etc. Might be OK, might not. Pedals are a special problem since they tend to collect dirt, grit, and moisture faster than any other bearing. The specialized bike lubes are generally designed to repel dirt and moisture better than standard lubes. Commented Jun 25, 2011 at 19:24
  • It's not so much a question of wear as a question of manufacturing tolerances. Reuse all the old balls if you have to, otherwise use all new balls from the same batch. If you have a few new balls left from one packet, don't mix them with new balls from a different packet. sheldonbrown.com/harris/bearings.html
    – armb
    Commented Jun 3, 2019 at 12:00
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Did you not count the ones you removed? That's basic...

Also, be sure to take a couple of the old ones to the shop so that they can match the size; most are standard but some bikes have odd-ball sizes. And be sure to buy new bearings; they are cheap and most authorities recommend that old ones not be re-used.

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    I did count them, but I had one axle where a couple of them broke. I couldn't make out how many broke and so how many to put back in..
    – romeovs
    Commented Jun 22, 2011 at 5:58
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    Yep, counting the existing bearings is the basic method. The advanced method is to find out how many there should be, and why. The last owner could have put too many in
    – Swifty
    Commented Jun 1, 2019 at 11:29
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    Also, if you had a bearing with balls in retainers, and you are changing it to loose balls, you'll want roughly twice as many.
    – armb
    Commented Jun 3, 2019 at 12:03
  • This sounds fine in principle, but counting is only valid if you know the diameter of the old bearings. In practice, I've seen ⅛" and 3/16" bearings in Shimano hubs, when they're supposed to be ¼". You might be even more unlucky with sizes if the hub is especially old.
    – Sputnik
    Commented Apr 27, 2021 at 12:23
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From an engineers point of view, if any of the balls were deformed or fractured, I would suggest that the cups and cones would be shot also. If they have just one visible line, crater or flat on the bearing contact surface, then new balls will not last very long in any case. When in doubt, use white lithium grease preferred or Castrol boat trailer grease.

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For a Nikishi Eliminator, I had 9 ball bearings with a diameter of 6.35mm (1/4")on each side of the real wheel. I haven't checked if there is the same number at the front wheel.

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  • I don't think this really answers the question. People have already described how to choose the correct number of balls for any bearing, so how does giving the answer for one specific bearing help? If we included an answer for every bearing that appears on any bike, there'd be thousands. Commented Jun 1, 2019 at 11:22
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    Also, the front wheel uses more and smaller balls (makes no sense but that's the way it is)
    – Criggie
    Commented Jun 1, 2019 at 12:45
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    – Gary.Ray
    Commented Jun 1, 2019 at 18:10
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13 bearings each side of each pedal axle with many chinese pedals (thats 53 total both pedals ) . Also lucas grease works best , the better quality the grease the longer the pedal lasts ,(just like car engine with better oil) and keep dust cover plug glued in with a few dabs in a couple spots of some gorilla glue, other wise it is catastrophic pedal death

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    This has already been answered completely by previous answers. The math you stated is suspect and just stating 13 bearings per sides as an almost generic answer is not helpful. There are many possible variations, not this standard.
    – Ted Hohl
    Commented Jan 21 at 11:00

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