Took apart a 99’ GT’s bottom bracket. Has a big spindle, two threaded cones and a bunch of ball bearings. The spindle is not equal length on each side. From the photo, the left side from the ridge is 1.75 in. The right side from the ridge is 2 in. Which side goes onto the driveside? Any way of reassembling this that ensures all the bearings sit in place?
by evanssinatra
4 Comments
Vintage….. 😍
The longer side is drive side.. to accommodate the width of the crankset.
To keep the bearing in place, I usually make a thick bead of grease around the race and then just plop the bearings into the ring. They stay put long enough for you to install.
Longer side in almost all cases goes on the driveside. The numbers should be right side up if you’re standing over the bike. If you’re using loose ball bearings just pack them in grease and put your hamfists away and bust out your smooth R&B hands.
Three piece bottom brackets like this were what existed until Shimano released the cartridge BB in the early 90s. They faded out of existence over the next few years after. And yes, asymmetry was common. God help you if you need to find a replacement today (they often mated with a specific crank). I haven’t missed them in the least. Despite being heavier, Shimano did us a huge favor with the cartridge BB. And of course, that’s antiquated tech today (tho reliable AF).