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@brianb@fosstodon.org

Post #1213074

2026-04-15 00:37 UTC

I got the bottom bracket apart (except the drive side...I need to get a better tool), but the bearings were a mess. How do I size these for replacement? This is a generic kids mountain bike (Dynacraft Magna Echo Ridge model 8153-31Taj) and the manual doesn't have info. Can I just measure the bracket with calipers? #biketooter #askfedi

Replies (4)

  • @isol@mastodon.au 2026-04-15 01:32

    @brianb You can also look at upgrading to a cartridge bottom bracket, instead of those bearings. If it's a cheaper bike, it's probably a BB68, but measure the length of the axle, and the width of the frame across the bottom bracket. #BikeTooter

    Open ##1213095

  • @erikcats@dice.camp 2026-04-15 04:21

    @brianb I feel as if anything I say from here, a country where bikes are so ubiquitous that everything is available everywhere, is going to be a lie in a car-centric country such as yours, but yeah there are many standards so measuring it with calipers should do the trick. The most common standard is BB86/89 (ignore that first bit, that's for racing bikes) which has a crank housing width of 89.5mm. This does require non-imperial calipers tho, or some math 😬

    Open ##1213097

  • @pete@masto.hypertelia.com 2026-04-15 08:05

    @brianb What's the crankset that goes with this? There are perhaps better BB options than replacing like-for-like.

    Open ##1213100

  • @brianb if this is a basically cheap bike, it will either have a bsa 68 or 73mm wide bottom bracket (you can tell by measuring the width on the frame) or it will have an Ashtabula bb, which has pressed in shells. Most likely bsa 68. You also need the spindle length, end to end, in mm. Often stamped on the spindle, like 68-124. If you can find an intact bearing ball to measure, you can repack with just them, use grease, skip the retainer ring, add 2 extra balls, available online.

    Open ##1213101