Determining size of cartridge BB replacement for asymmetrical cup/cone BB
08-30-18, 07:52 AM
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Determining size of cartridge BB replacement for asymmetrical cup/cone BB
I'm trying to restore an old road bike and would like to replace the asymmetrical cup/cone BB (126mm spindle - 35.0x52x39.0) with a new sealed cartridge BB but I'm having trouble figuring out which size I need to get. I did check Sheldons BB size database page but it's not listed there unfortunately. Can anyone help with this please?
08-30-18, 08:20 AM
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A 127mm UN55 will get your RH side w/in a couple of mms of where it was before. That's 52/2=26, 26+39=65, 2x65=130.So a 127 is 1.5mm closer on the RH side. Here's the assumptions you are making here. That the crank arms have JIS taper, that you had at least 1.5 extra clearance between the inner ring and the stay to loose and still have adequate clearance remaining (about 3mm to allow future arm draw up). The 1.5mm shift of the crank's chainline shouldn't be a problem unless you were already really off line before or that the ft der was already at it's inner travel limit.
Fitting square taper cranks/BBs isn't an exact science but one can get very close so only minor retweaking of ft der limits is usually needed and the chain running/chain line works well too. Of course not yet mentioned is that the LH arm will shift outward by about 3mms, usually not a big factor unless your are very sensitivity to the Q/tread width. Andy
Fitting square taper cranks/BBs isn't an exact science but one can get very close so only minor retweaking of ft der limits is usually needed and the chain running/chain line works well too. Of course not yet mentioned is that the LH arm will shift outward by about 3mms, usually not a big factor unless your are very sensitivity to the Q/tread width. Andy
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AndrewRStewart
AndrewRStewart
08-30-18, 10:26 AM
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With the 39mm dimension, you pretty much have to use the longest cartridge BB available.
If you just need a spindle, a 3-T is still available here-
Husky Bicycles: Bottom Bracket Parts
No idea on quality.
If you just need a spindle, a 3-T is still available here-
Husky Bicycles: Bottom Bracket Parts
No idea on quality.
08-30-18, 08:33 PM
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Hmm yeah I think I'll just stick with the cup/cone BB then to avoid any potential issues. Was only considering a replacement because the fixed cup was totally loose when I went to service the BB and I don't have the correct tool to reinstall it. The spindle is in great condition and I found some different cups that take a modern cartridge BB tool so I'll probably buy a set of those to use instead.
Thanks guys.
Thanks guys.
08-31-18, 10:36 AM
#5
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Not cheap (MUSA), but Phil Wood uses a precise press fit,
BB axle OD to Bearing ID.. via friction..
It is that fit that keeps the axle where it is placed,
But, you can pull it through the bearing
and dial in an offset that serves you best.. It is not fixed.. So can be fine tuned.
BB axle OD to Bearing ID.. via friction..
It is that fit that keeps the axle where it is placed,
But, you can pull it through the bearing
and dial in an offset that serves you best.. It is not fixed.. So can be fine tuned.
