The infamous "Spin Test"

In the over 8 years we've been making ceramic BBs, there has never been as much interest in how long our BBs spin as there has been recently.  Apparently some companies have drilled it into people's minds that the longer a crank spins, the better the BB is.  This is not true.

We've blogged about grease and seals and break-in time before, so read those posts for more info on that.  Apparently the thinking on the interwebs is that if a crank spins for 30 rotations versus a crank that spins for 20, for example, the BB that spun 30 times is better.

Typically with some good riding and adequate break-in, our BBs will spin for about 15-20 rotations (see more on this below).  This is fairly normal.  The reason you don't want it to spin much more than that is that is a sign of not enough grease and possibly too light of a seal.  As you ride a BB (any BB) the grease is constantly being spread and used up while being pushed away from the rotating balls.  The grease will eventually get used up and if checking how long the crank spins at this point, it might spin a good 25+ times.  Great?  No!  That is far past the time to relube your bearings.

I do a simple check with my ceramic BB.  Every week or two I take the chain off and give the bike a good cleaning.  A this time I will spin the crank and see how it is spinning.  If it spins too freely or for too long, that's when I know to pull the cranks and lube the bearings.

It is very important to keep enough grease inside the bearings so they are lubed properly, which enhances performance and longevity.

I understand it makes complete sense that "if it spins longer, it must be better" but that is not always true.  You want the crank to spin nice and smooth, with no binding, but you don't want it to spin too long.  Can I give you an exact number as to how many times the crank should spin?  No, there are too many variables here as heavier pedals will make it spin more while a lighter crank would spin less, as the mass rotating has a great affect on spin times.  Also, how hard you spin the cranks will affect the time, did you lightly turn them or spin them as hard as you could?  Although, a good rule of thumb is that it should spin freely and quite smoothly.

I cringe writing this as I am sure someone will say, "my crank only spun 14 times", but if I had to give you a number, the 15-20 range is pretty normal for one of our BBs once broken in.  It could be more (and it could spin less too, don't obsess), but too much more and you need to grease the bearings as mentioned above.  If it only spins something really low, let's say, 3-4 times, the crank is probably too tight and binding the BB.  I personally use a Shimano Dura Ace crank, so my spin times are based on our Shimano 10 Ceramic BB, other cranks and systems like BB30 would spin differently, since they tension in a whole different way.

The energy required by your legs to overcome the grease and seal friction is so small that you would never notice it while riding.  It is noticeable when spinning a crank because the crank doesn't weigh very much, so any seal/grease drag will affect it's spin time.  When I relube my bearings, the crank will go from spinning close to 20 times down to about 6-8 times, simply because I added grease.  Then with riding it will slowly increase it's spinning time again over time, back to around 20 at which time I add more grease.

The reason our ceramic BBs are so fast, is the near perfect balls mated to the near perfect races.  When riding, the balls spin with almost no friction on the race ways, making the BB very fast.  So whether the BB spins 6-8 times after I grease it or closer to 20 when greasing is needed, it rides the same because of the balls and races.

In closing, do not obsess about how long your BB spins.  You should obsess about riding more and making sure you are in as good of shape as possible, so that our super fast BB will be paired with a super fast you!

While this post focuses on our BB, you could also substitute wheel bearings or pulleys every place we mention a BB and the same would be true.  With the main difference with pulleys being that they weigh so little, so their spin times by default will be very, very low.