Bike Forums - View Single Post - Installing adjustable bottom bracket

05-19-11 | 08:21 PM

#3

Suburban Grind

occasional cyclist

Joined: Jul 2010

Posts: 141

Likes: 1

Well, the bottom bracket is a Dura Ace 7700 v1 octalink. It's interchangeable (I think) with the 105 and Ultegra octalink v1. Which is a Shimano proprietary (JIS 2 degree?) tapered 8-tooth spline spindle. Each of the screw-in cups contains a set of needle roller bearings and a set of angular contact ball bearings. They are not cartridge bearings. It seems after seal removal, those can be removed from the cup and replaced or cleaned, regreased, and replaced as I did.. Both bearings on both sides are caged, and the spindle has removeable hardened races that set the position against the ball bearing axially. With the other parts in place, as you tighten the Non Drive Side cup into the bottom bracket shell it seems as though you can set the play or the preload against the angular contact ball berarings - also seems like you could go too far and bind it up. When the bottom bracket is fully installed, the bearings will be locating the spindle inside the bottom bracket shell. To me, that makes it an old-school adjustable internal-bearing crank. I thought external bearings actually locate the rolling elements of the bearings outside the confines of the bottom bracket shell for better resistance to radial loads (more precise positioning or ability to use a cheaper bearing?), and usually have the spindle integrated into the Drive Side crank.

The frame is my '92 Miyata Team steel road racing bike that I am building as 9-speed.Dura Ace. As noted 130mm dropouts on rear axle, 68mm wide English threaded bb shell, was a version of 7400 Dura Ace 8-speed when it was sold as a complete bike - but this was frame/ forks only. My impression is bottom shell can flex laterally somewhat more than other heavier steel bikes I have, so maybe I'll need more clearance than usual between the chainrings and chainstay and the crank arm and chainstay?

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