Removing play from a cottered crank bottom bracket
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In this video 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.
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.
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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.
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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.
Even if you removed 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.
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.
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Music is from the TH-cam Audio Library
Song is "Song of Sadhana" from Jesse Gallagher
Everything old is new again! I found your video struggling with an old Miami Sun Trike. The last bottom bracket I dealt with was this exact model bike you have back in 83. Thanks for the help and great memories. See you on FB!
Glad it helped!
Thanks for the help!
So I see you adjusting the play by holding the crank arm and tightening the large nut against the slotted washer and cover. How do you lock that nut once you get it where you want it? Is there a second nut to lock it against? Or a Lock-Tite agent being used that I didn't see?
Thanks for putting up this video! Have been going crazy trying to figure out a restoration on my own... well a Get-It-Up-And-Rideable anyways!
This bike doesn't have a locknut. I assume the crank was never tampered with and that it never held a locknut in the first place. Lock-Tite definitely help if you're in a similar situation. I might be able to add something that would serve as a lock nut if there's enough threading.
The cottered crank system I've seen is that the cup houses the caged bearings, and the cone threads onto the axle. The bottom bracket opening is then covered with what functions as a cap or lid, this part is not threaded, only placed over the bearings. The axle has a groove for a lockring -- effectively a washer with an extrusion that fits into the groove in the axle, to prevent the part from rotating. Finally, a nut compresses the lid and locking washer, and I think the whole arrangement also works to keep the cone from moving. To service this system, however, the crank arm and lid must be removed for access to the cone, which is really what controls the axle play.
What is shown in the video looks to be what I am describing, but of course I can't be sure without seeing it up close.
I have a similar system on one of my bikes. The problem I have is that locknut is always going loose no matter how hard I tightened it down.
try loctite on the threads