On Fri, 07 Apr 2017 07:56:51 -0500, AMuzi wrote:

On 4/7/2017 3:57 AM, John B. wrote:

I'm thinking of replacing the old three piece BB on one of my bikes
with a Shimano cartridge bearing and I see that Shimano markets a
UN-26 and UN-55 cartridge bottom bracket. I believe that the UN-26
has a solid spindle and a plastic bushing on the non-drive side while
there is reference to a hollow spindle and steel bushing on the UN-55.
Both are made for the 69 and 73 mm frames and in roughly the same
spindle lengths.

In normal use is there a practical difference? Disregarding the weight
difference, if any, is there a noticeable difference in service life?

The UN-26 seems to be the cheaper version and is quite common in shops
here while the UN-55 is somewhat rare, probably due to price. But if
the UN-55 lasts (for example) five years while the UN-26 only lasts
two years it is probably worth searching out the higher priced
version.

No practical difference and I believe both are hollow
spindle now (earlier less expensive models were solid). In
theory, higher quality bearing on the 55 but neither are
true replaceable cartridge bearings[1]. Nylon vs metal left
cup is an argument without practical relevance and the
outside spacer of either spindle may be removed and thrown
out to no detriment.

[1] A pair of name-brand premium seal cartridge bearings
cost more than either Shimano BB:
http://www.philwood.com/products/bearinghome.php

Thanks. It is about what I thought so will just go with what I find.

--
Cheers,

John B.