Bottom Bracket Longevity Question

RobinS

Über Member
Location
Norwich
So, as I have lots of time on my hands I have stripped down and rebuilt mine and JanetS' tourers - complete clean, degrease, re-grease and lube, new chains (Cassettes replaced 5000km ago seem OK with the new chains), new tyres, new Butterfly bar foam and grips, new bar tape and saddle for me, new brake and gear cables all round, new brake disc pads etc......
Janet's middle chainring is bent, so I have a new one on order, but looking at chainrings led me to think about bottom brackets, Janet has a Shimano Hollowtech, mine is Shimano square taper - they have done around 20,000km heavily loaded touring, and while they are not displaying any symptoms of excess wear, would it be sensible to replace them now while I have plenty of time? - they are not particularly expensive, but i don't want to throw the current ones away if they are good for many 000's of Km yet.

Thoughts?
 

Cycleops

Legendary Member
Location
Accra, Ghana
Square tapers can go on for intergalatic mileages but not so sure about Hollowtech.
 

YukonBoy

The Monch
Location
Inside my skull
Hollowtech can also goes on for aeons. I had one fail quite early back in 2011, so bought three replacements, at a discount. The first replacement I fitted was still going strong in 2018 till the bike frame cracked, and that's at 11,000 miles per year average.
 

PpPete

Guru
Location
Chandler's Ford
Hollowtech II is somewhat more susceptible to any misalignment (holes & threads drilled from either side of the frame not quite being on same axis) and can end up creaking much sooner than square taper. On the other hand it can save quite a bit of weight over square taper.
 
OP
RobinS

RobinS

Über Member
Location
Norwich
Thanks all, have checked them both and as there is no play, or feeling of roughness have decided to leave them alone for now. I am normally of the "if it ain't broke don't fix it" persuasion, but have to balance that with not wanting things to break while on 3 month tours!
It did occur to me that the only bottom bracket I have ever had to replace in about the last 30 years was the bottom of the shimano range one on the MTB I used for winter series racing, and winter training back in the 1990s - and that did get real hammer in the mud, sand and grit.
 

rogerzilla

Legendary Member
HT2 is so cheap to replace that it may come down to whether it's worth refitting a used set of bearings. When I moved the parts from a Hewitt to a Surly frame two years ago, I bought new XT bearings for about £12 because it didn't seem worth the bother of refitting the old Deore ones and maybe having to remove the cranks and take them out again sooner rather than later.

You should have the BB shell faced for HT2 unless the frame is known to have had it done from new. Admittedly, with plastic spacers*, they're not precision parts, but you want to give them the best chance of a long life.

*alloy ones are available
 

Ajax Bay

Veteran
Location
East Devon
HT2 is so cheap to replace that it may come down to whether it's worth refitting a used set of bearings.
Is anyone suggesting "refitting a used set of bearings"?
Perfectly reasonable, after 20,000km and before a significant/heavily loaded tour, to replace an HT2 BB (and indeed a square taper (with a UN-55)).
 
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