In this article you’re going to learn how to remove play from an old-style cottered crank bottom bracket. It’s very easy but there are a number of things to take into consideration.
The bicycle we’re talking about is my wife’s restored Ricardo Sport from 1976. Play in cottered crank bottom brackets are commonplace, especially directly after you’ve serviced them. We brought this bike with us on our holiday. And because the bicycle was ridden for many miles, at the end of the holiday my wife noticed the cottered crank moving while riding.
Why you should service a cottered crank with play
As with all moving parts that display play, not servicing them means a higher risk of damage. Since this article concerns play in a cottered crank bottom bracket, a worst-case scenario would mean damage to the bearing races of the bottom bracket cups, or the spindle. The loose ball bearings can also be damaged but are much easier to find replacements for. And this repair is literally one anyone can do, so postponing it would be nothing short of stupid.
The cups of this cottered crank bottom bracket are fixed into the frame with the bearing races pointing outwards. It holds quite a number of loose ball bearings and another cup is pressed on the massive steel spindle.
The spindle itself has a threaded part with a 22 mm nut to tighten the non-driveside cup. Unlike with other bottom brackets, you don’t have to remove the crank arm to fix the play.
Checking the cottered crank bottom bracket for damage
Even if you remove play it can very well be that the spindle does not move freely. So it’s a good thing to check the inside of your bottom bracket if you have the right tools to do so.
In my case I’d already restored this bicycle and the bike wasn’t extensively ridden under wet circumstances. So removing the cotter pin again and servicing the bottom bracket would not be necessary.
How tight should a cottered crank bottom bracket be?
There is quite a bit of discussion about how much you should tighten the cup onto the bearings. It’s a trade-off between minimizing play and having a smooth crank rotation. I prefer minimizing play, because with the crank arms on the bottom bracket you hardly notice the stiffness in rotation. But in the end it’s fairly personal. This is what Sheldon Brown has to say about it:
Bearing play is checked by trying to rock the end of the spindle up and down. Ideally, there should be no play at all, but in almost all cases, if you eliminate the play completely, the bearing will bind. If in doubt, it is better to have the bearing just a bit too loose than too tight [But see Jobst Brandt’s opinion, which is opposite — John Allen]. In my experience, only Campagnolo bottom brackets can be adjusted for no play and still turn as freely as they should.
Whatever you choose, tightening the cup is easy and it’s up to you with the help of the information provided how tight. Always do a final test actually rotating the crank and/or riding the bicycle. As it turned out, I needed to perform some further adjustment while on-the-road.
And that’s how you remove play from your old-style cottered crank bottom brackets!
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