What size bottom bracket do I need?
01-09-13 | 07:44 PM
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What size bottom bracket do I need?
It's for an Open Road 3000GT, a 90's? Taiwanese 10 speed I'm fixing up for my sister in law. Here's what's got me stumped:
The axle has "5S" stamped on it and according to Sheldon Brown's site at https://sheldonbrown.com/bbsize.html 5 series axles fit 70mm Italian style bottom brackets. The bottom bracket shell measures 70mm in width. So far, so good.
However, according to Wikipedia at https://en.wikipedia.org/wiki/Bottom_bracket Italian style bottom brackets have an internal diameter of 34.6-34.9 mm and right-hand threads on both sides. This particular bottom bracket measures 33.5-34mm internal diameter and has left-hand threads on the drive side, matching Wikipedia's specs for an English style bracket.
So, which is it? Since I'm replacing the crankset as well I gather that I should select a bottom bracket matching the length recommended for that crankset, in this case 118mm. But I don't know if I need a 68x118 or a 70x118
Thanks,
Terry
The axle has "5S" stamped on it and according to Sheldon Brown's site at https://sheldonbrown.com/bbsize.html 5 series axles fit 70mm Italian style bottom brackets. The bottom bracket shell measures 70mm in width. So far, so good.
However, according to Wikipedia at https://en.wikipedia.org/wiki/Bottom_bracket Italian style bottom brackets have an internal diameter of 34.6-34.9 mm and right-hand threads on both sides. This particular bottom bracket measures 33.5-34mm internal diameter and has left-hand threads on the drive side, matching Wikipedia's specs for an English style bracket.
So, which is it? Since I'm replacing the crankset as well I gather that I should select a bottom bracket matching the length recommended for that crankset, in this case 118mm. But I don't know if I need a 68x118 or a 70x118
Thanks,
Terry
