Replacing Hollowtech II Bearings

For discussions about bikes and equipment.
User avatar
geomannie
Posts: 1093
Joined: 13 May 2009, 6:07pm

Replacing Hollowtech II Bearings

Post by geomannie »

It is possible, but not Shimano advised, to replace the bearing in a Hollowtech II bottom bracket http://www.mountainbikerides.co.uk/fett ... ement.html. Having removed my old BB after only 2000 miles I was shocked by-

a) just how small the bearings are given the load they have to take, and
b) how poorly protected they are from water ingress (hence their failure). The bearings that were fitted had seals on one side but the single seal was fitted on the inside (doesn't make sense to me either).

Its likely that my newly replaced BB will fail after another couple of thousand miles so I was wondering what off-the-shelf replacement 6805 bearings (dimensions 25x37x7mm) might be more robust than the Shimano original. Ebay list bearings from about £1.26 upward.

Anyone have any idea what quality I should aim for to improve on the Shimano pattern part? Would a ceramic bearing be a good choice at ~£14.26/each* or would that be over-kill? Would a stainless bearing with 2 seals at £7.49/each** be a better compromise?

Thanks

* http://www.ebay.co.uk/itm/MTB-Ceramic-H ... 53fd54bd5a
** http://www.ebay.co.uk/itm/6800-2RS-6180 ... 51b01b5362
geomannie
User avatar
fossala
Posts: 1369
Joined: 21 May 2013, 8:29am

Re: Replacing Hollowtech II Bearings

Post by fossala »

If you are not racing I would advise against using hollowtech BB/Chainset for this reason. It's only really needed to shave microseconds off times. Yet again I will say that racing has taken over cycling and pretty much everything is geared to it. Shifters that cost over 200 quid, BB that are stiff but don't last more than 6 months, wheels that can't take much over 90kg including rider/bike/gear, frames that need expensive x-ray machines to check over if you crash them. They must be laughing at us (you)...
mattsccm
Posts: 5103
Joined: 28 Nov 2009, 9:44pm

Re: Replacing Hollowtech II Bearings

Post by mattsccm »

Just do as I do, Bang the old ones out and bung some new ones in. Cheap is good as expensive ones get as wet.

The design isn't about long life but stiffness. Compare the two like you compare beer and chocolate.
You have what you have.
User avatar
meic
Posts: 19355
Joined: 1 Feb 2007, 9:37pm
Location: Caerfyrddin (Carmarthen)

Re: Replacing Hollowtech II Bearings

Post by meic »

This question has been asked before.

viewtopic.php?f=5&t=57475&hilit=bearing+grease

The answer was comprehensive, perhaps as is the case so often on this forum, a little too comprehensive. :lol:
Yma o Hyd
Brucey
Posts: 44529
Joined: 4 Jan 2012, 6:25pm

Re: Replacing Hollowtech II Bearings

Post by Brucey »

The shimano bearings have a single seal mounted in the inner face of the bearing and a separate external seal. The external seal appears to fail and let the water in. The seal can only work (and not wear) if the seal lip is wetted with lubricant, so it isn't a bad idea to spray some lube (e.g. semi-fluid spray grease) in the little gap from time to time.

If refitting bearings to cups, I think it makes sense to fit both seals on the outside, and to whack as much grease as possible inside the BB housing between the (now open at the rear) bearings.

Stainless bearings will certainly have a longer life if the water is going to get in, but may have a slightly shorter life in the (admittedly unlikely) event that it doesn't.

Ceramic bearings are a needlessly expensive method of elongating the life of a badly sealed bearing IMHO. Better to improve the seals and the lubrication.

cheers
-------------------------------------------------------------------------------
~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~
Big T
Posts: 2105
Joined: 16 Jul 2007, 1:44pm
Location: Nottingham
Contact:

Re: Replacing Hollowtech II Bearings

Post by Big T »

Cut your losses now and go for a square taper chainset. You can get a reasonable one for £60-70 and the BB will last 15,000 miles.
My JOGLE blog:
http://www.jogler2009.blogspot.com
twitter: @bikingtrev
the_mikey
Posts: 12
Joined: 20 Sep 2011, 7:46pm

Re: Replacing Hollowtech II Bearings

Post by the_mikey »

Depends on the bearings, but the shimano tiagra HT2 bearing cup set is an inexpensive replacement, cheaper than a replacement tyre even. The last set of bearing cups I had lasted two years before showing signs of wear, but they're very quick and easy to replace.
User avatar
meic
Posts: 19355
Joined: 1 Feb 2007, 9:37pm
Location: Caerfyrddin (Carmarthen)

Re: Replacing Hollowtech II Bearings

Post by meic »

The last person I spoke to on the subject had done 8,000 miles on a set of 105 EBB bearings, no problem yet.

I think that 2,000 miles points to either being overtightened or near submersion.

My FSA have been showing rather a lot of play for over 1,000 miles now but on inspection they look alright and certainly work, apart from an annoying click every revolution.
Yma o Hyd
Richard A Thackeray
Posts: 165
Joined: 21 Aug 2013, 11:20pm
Location: Normanton, Wakefield. West Riding of Yorkshire
Contact:

Re: Replacing Hollowtech II Bearings

Post by Richard A Thackeray »

Big T wrote:Cut your losses now and go for a square taper chainset. You can get a reasonable one for £60-70 and the BB will last 15,000 miles.

Agreed, the Campag Chorus on my Dyna-Tech is 19 years old, never disassembled, was used as a commuter in all weathers for the past 5 years (until being superceded by a Ribble 'Audax,/'winter' bike in June)
I can drop the chain, & it still spins absolutely freely, with no graunching at all. And no discernible play either


Chainset was Campag Chorus too, & the finish on it is almost as good as new (barring a couple of scratches where cranks have caught the ground pushing down/up steps
Yorkshire Born & Bred. And, Proud Of It

Generally to be found plodding along; with www.ackworthroadrunnersandac.co.uk

The 'Wheels go round & round' with; http://www.featherstoneroadclub.co.uk/
Brucey
Posts: 44529
Joined: 4 Jan 2012, 6:25pm

Re: Replacing Hollowtech II Bearings

Post by Brucey »

some would say that having long-lasting BB bearings is a mixed blessing... when time finally comes to change them, they can turn out to be in the frame for good... :wink: :roll:

cheers
-------------------------------------------------------------------------------
~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~
User avatar
geomannie
Posts: 1093
Joined: 13 May 2009, 6:07pm

Re: Replacing Hollowtech II Bearings

Post by geomannie »

Thanks folks for the recommendations to change to a square taper BB but as I have a fairly new Hollowtech setup, this is not going to happen. It makes far more sense for me to change the bearing for a few quid every now and then, rather than fit a new BB and chain-set at considerably higher cost. I'm just finding it hard to decide which bearings will offer the best life at lowest cost.

Maybe come time a square taper BB will get fitted.

Cheers
geomannie
peterbayliss
Posts: 94
Joined: 8 Apr 2008, 12:47pm

Re: Replacing Hollowtech II Bearings

Post by peterbayliss »

I found this company which sell replacement seals and bearing for Hollowtech II bottom brakects. http://www.enduroforkseals.com/id227.html they claim to improve the sealing. I haven't used them and they are USA based but it looks interesting.
Brucey
Posts: 44529
Joined: 4 Jan 2012, 6:25pm

Re: Replacing Hollowtech II Bearings

Post by Brucey »

I've used their bearings which were fitted to some chi-chi hubs that I bought. The bearings are pretty good, but are probably only different in detail vs other commercially available stainless steel bearings.

Not BTDT myself but people have good things to say about Hope H-II BB units but then perhaps they should do at the price. They use stainless bearings too IIRC.

cheers
-------------------------------------------------------------------------------
~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~
robc02
Posts: 1824
Joined: 23 Apr 2009, 7:12pm
Location: Stafford

Re: Replacing Hollowtech II Bearings

Post by robc02 »

I've been thinking for some time (but not yet got around to doing anything about it!) that picking out the inner bearing seals and then flooding the spacer tube with heavy oil or semi fluid grease would be a good idea. A good way to do it would be to push the axle about 2/3 way through, squirt in the oil/grease, and then push the axle the rest of the way through. It would keep a constant supply of lubricant to the bearings and seal lips, and would be easy to refill.

I have a Hope external BB on a road bike that saw a couple of heavy winters daily use and is still in perfect order. Unfortunately I have no mileage recorded. It's longevity to date is one of the reasons I haven't got around to the above.
Brucey
Posts: 44529
Joined: 4 Jan 2012, 6:25pm

Re: Replacing Hollowtech II Bearings

Post by Brucey »

robc02 wrote: .... then flooding the spacer tube with heavy oil or semi fluid grease would be a good idea. A good way to do it would be to push the axle about 2/3 way through, squirt in the oil/grease, and then push the axle the rest of the way through. It would keep a constant supply of lubricant to the bearings and seal lips, and would be easy to refill.


yes, exactly; and on shimano ones turning the bearings so that both seals are on the outside makes perfect sense for a scheme like this. If you lay the bike on its side when adding the lube, it should be possible to get loads of lube in there.

I think that if the right lube is used ( a semi-fluid grease I reckon) and there is usually a little leaking out, no water will get in, and even standard shimano bearings -once turned- may last for years like this.

cheers
-------------------------------------------------------------------------------
~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~
Post Reply