Avocet bottom bracket
25/02/10 21:55 Filed in: Cycling
So, now I needed a new bottom bracket. As best I could figure, I needed a spindle length of 119mm for an asymmetrical spindle, or 121mm for symmetrical. I was further hampered in my search by the Stronglight’s ISO spindle taper, whereas many modern cranks use JIS. I couldn’t find any modern bottom brackets with ISO taper and the required spindle length. Back to Ebay. Now I was looking at mostly used units of the adjustable cup and cone type.
After much bidding and losing, I finally found a new old stock Avocet 3 bottom bracket with an asymmetrical spindle that was a little long at 122mm. However, the bottom bracket had floating cups allowing for chainline adjustment. Another strange characteristic was the bearing design, which seemed to be somewhere between cup/cone and sealed, in that the bearing followed a sealed design but could be overhauled. This was good, since the grease was pretty dried out by this point. I figured out that the grease seal (lower right in photo) could be carefully pried out, revealing the retaining clip (to left of grease seal). Once this was removed the bearing balls and race (to left of balls) could be taken out and cleaned. There is another grease seal/o-ring which fits in the little groove around the outboard side of the race.
After cleaning all the parts I repacked the assembly with grease and, after repeating the procedure with the other cup/bearing, did a test fit by loosely screwing in the cups and hanging the drive side crank on the spindle. Note that after tightening the crank bolt the crank will sit inboard by at least 1mm. I measured the chainline and tightened the drive side lockring. Moving to the other side, I adjusted the cup to be smooth with as little play as possible, and tightened the lockring, adding a little low strength Locktite (pin spanner and lockring tool required). There seemed to be more drag than I had anticipated, but I’ve since read that this is common with sealed bearings, and that there is usually a break-in period. I’ll see how it feels when ridden.
The derailler inner and outer limit screws now needed adjustment since the chainrings were farther inboard. Next, a road test, as soon as there’s a day that’s a little warmer.
Here are shots of the triple and the double. The third ring is hard to see because the 49 tooth count is so close to the largest 53 tooth ring. For my purposes the difference was negligible. The shot of the double was taken belatedly, thus the grease on the teeth.
After much bidding and losing, I finally found a new old stock Avocet 3 bottom bracket with an asymmetrical spindle that was a little long at 122mm. However, the bottom bracket had floating cups allowing for chainline adjustment. Another strange characteristic was the bearing design, which seemed to be somewhere between cup/cone and sealed, in that the bearing followed a sealed design but could be overhauled. This was good, since the grease was pretty dried out by this point. I figured out that the grease seal (lower right in photo) could be carefully pried out, revealing the retaining clip (to left of grease seal). Once this was removed the bearing balls and race (to left of balls) could be taken out and cleaned. There is another grease seal/o-ring which fits in the little groove around the outboard side of the race.
After cleaning all the parts I repacked the assembly with grease and, after repeating the procedure with the other cup/bearing, did a test fit by loosely screwing in the cups and hanging the drive side crank on the spindle. Note that after tightening the crank bolt the crank will sit inboard by at least 1mm. I measured the chainline and tightened the drive side lockring. Moving to the other side, I adjusted the cup to be smooth with as little play as possible, and tightened the lockring, adding a little low strength Locktite (pin spanner and lockring tool required). There seemed to be more drag than I had anticipated, but I’ve since read that this is common with sealed bearings, and that there is usually a break-in period. I’ll see how it feels when ridden.
The derailler inner and outer limit screws now needed adjustment since the chainrings were farther inboard. Next, a road test, as soon as there’s a day that’s a little warmer.
Here are shots of the triple and the double. The third ring is hard to see because the 49 tooth count is so close to the largest 53 tooth ring. For my purposes the difference was negligible. The shot of the double was taken belatedly, thus the grease on the teeth.