From square taper to hollowtech II BB. Advantages?

[meic]

Yes but if you prise open your old Tiagras and later I prise open my old FSA MegaExos and somebody else prises open their Dura-Ace we may find out if there is any real difference.

[niggle]

Yes but if you prise open your old Tiagras and later I prise open my old FSA MegaExos and somebody else prises open their Dura-Ace we may find out if there is any real difference.

OK will do.

EDIT: Best prices on line:

Tiagra 4600 £11.24 http://www.tweekscycles.com/Product.do? ... 20Brackets

105 5700 £16.75 http://www.pedalon.co.uk/acatalog/shima ... acket.html

Ultegra 6700 £18.75 http://www.tweekscycles.com/Product.do? ... 20Brackets

Dura Ace 7900 £20.75 (aprox inc P+P) http://www.bike-discount.de/shop/a11440 ... html?lg=en

or £26 http://www.sigmasport.co.uk/Product/192 ... leShopping

[Brucey]

Yes but if you prise open your old Tiagras and later I prise open my old FSA MegaExos and somebody else prises open their Dura-Ace we may find out if there is any real difference.

Hmm, maybe... thing is that unless they really are the same manufacturer etc they may not be the 'same thing' even if they have the same number on.

Most 'standard bearings' are available at different price points and although they should all be 'OK' (i.e. meet a certain minimum specification) the manufacturer's specs sometimes tell a different story.

edit: see here for some more bearing info:
http://www.diymtb.com.au/displayItems.asp?cid=14

I'll be interested to see what you find.

cheers

[meic]

Looking around, I see that both Hope and Raceface supply bearings which they have obviously had made up to their own specification because they have their names on them.

http://www.chainreactioncycles.com/Mode ... elID=40287

That one even does us the favour of showing its specification. Edit The Raceface is 7mm wide, Shimano are 6mm wide

I remember a website where somebody had taken apart the bearings in a failed external BB and been horrified at the specification of those bearings.

If you really wish to economise and feel that a bearing is just a bearing then follow this

http://www.mountainbikerides.co.uk/fett ... ement.html

with a pair of these
http://www.ebay.co.uk/itm/1-X-6805-2rs- ... 3a7124306b

and the job is done for £3.40.

If you like a decent spec pair of bearings use these
http://www.chainreactioncycles.com/Mode ... elID=64642

Zooming in showed they are the same RaceFace bearing as in my first link.

or you could use those Enduro bearings that Brucey linked to earlier which can be found on ebay for twice that price.
Getting them from a standard bearing retailer like simply bearings costs even more! Despite looking like poorer bearings.

Though with a pair of Tiagra cups at the price they are and with the speed and simplicity of swapping external bracket cups it really does seem the best way to go.

I do find it hard to believe that Shimano would put better quality bearings in the higher range models WITHOUT telling us so. Though their seals around the bearings could well be better.
I am also curious as to why my FSA Bottom Brackets are more expensive than even the Dura_Ace ones.

[niggle]

If you really wish to economise and feel that a bearing is just a bearing then follow this

http://www.mountainbikerides.co.uk/fett ... ement.html

Bother: wish I had seen this before ordering a new set ofTiagras, then I would have gone for some SKFs or Toyos (which I have used in motorcycle wheels with very good success, i.e. once fitted never replaced again).

I am also curious as to why my FSA Bottom Brackets are more expensive than even the Dura_Ace ones.

Marketing I suspect, as I think a lot of this is other than Hope etc.

I will practice removing the old bearings once the new cups arrive, and take the old bearings apart to see how & why they have failed.

[meic]

According to the critics of external BBs, your chance will come again soon enough.

Now you will have plenty of time to carefully remove your old bearings and replace them with some "nice" ones ready for when the Tiagras fail (Some time next month? ).

[Smut Pedaller]

I've owned two bikes with external BB's and whilst I think generally they're good I'm still a fan of square taper. However I think the standard external BB that threads into a normal BB shell is a bit counterintuitive. The standard BSA/Italian BB shells were always meant for the BB unit to sit inside it, however putting them outside has forced Q-factors to increase by quite a lot compared to square taper. Old square taper Stronglight and TA cranksets can get down to 130-135mm which is a lot narrower than say current Campag cranks which are about 142.5mm or Shimano/SRAM which are a little wider from memory.

The BB30 standard makes more sense to me, to press the bearings into the frame much like a horizontal headset. However no one can seem to agree on a future standard for BB's which is irritating. The thing about square taper with a cartridge BB that I do love is that as long as you install it properly, you won't have to touch it for a very long time. It may be old hat, but it's simple, tough and it works with no faff.

[niggle]

Err, I think I meant Koyo not Toyo

These look interesting: http://www.ebay.co.uk/itm/6805-2RS-SKF- ... 0316740638

[reohn2]

...........The thing about square taper with a cartridge BB that I do love is that as long as you install it properly, you won't have to touch it for a very long time. It may be old hat, but it's simple, tough and it works with no faff.

Spot on!
Thats my experience too

[Brucey]

BTW does anyone know the bearing number for campag BB bearings these days? No worries if not, I'm just curious at this stage....

cheers

[niggle]

Result of the autopsy of the Tiagra External BB: Water ingress leading to corrosion of the right hand bearing, the left hand bearing is unaffected.

There were some traces of water and corrosion in the Genesis' BB shell as well so I am not entirely sure which way the water got into the bearing TBH. (I will have to pay close attention to all possible water entry points on the Genesis frame and sort this out, particularly as it is steel). Replacing with new Tiagra cups (£11.24 from Tweeks) was a doddle and a fair bit quicker than doing a square taper BB, so at least if you are paying a shop to do it they ought not charge much labour.

Dismantling the bearing reveals it to have a plastic 'top hat' spacer/washer, then a bespoke rubber seal between that and the bearing. The bearing is marked 6805-RD on the underside only visible after dismantling (clever that), no maker's name marked. A 6805 bearing is normally 25mm ID, 37mm OD, and 7mm thick, but the metal bearing race is only 6mm deep, the outer seal and plastic washer making it up to 7mm, and the ID of the inner race must be a tad over 25mm as the sleeve of the plastic washer runs between it and the axle. It would be nice if someone could confirm that the axle is 25mm as I forgot to check before reassembly.

It would seem that you have to ditch the plastic washer and seal when replacing with a 'standard' 6805 industrial bearing, and I think I will go that way next time as the Shimano bearing seems unimpressive: 15 undernourished looking balls with big gaps between. I have not pulled it apart completely yet, I will do later, however Googling suggests they are 1/8", is that appropriate?

[Brucey]

good autopsy work there!

16 balls doesn't sound like enough to me!

I have converted some bearings (not H-II ones yet) to 'full complement' ones by grinding 'loading slots' into the bearings and slotting balls in. If they are a tight fit through the slots and the slots are angled against the usual bearing motion, it seems the balls are unlikely to leap out again through the slots. Might be worth a go.

[Edit; Campagnolo Ultra-torque bearings are 51805-R51. A quick measure shows them to be 37x25x6mm (I will confirm this later). The inner shoulders of the bearings are 79mm apart when the crank is installed, and the bearings are a push fit onto the axle, and a sliding fit in the cups. There is a wave washer in the cups to take up any variations in BB shell width.

So.... new question... how far apart are the bearings in a shimano H-II setup? If the dimensions work out OK maybe using campag cups/bearings on shimano cranks is the way to go for a readily servicable setup????]

cheers

[Erudin]

Did the Nutty nuns audax recently and Tiagra external bottom bracket got submerged in flooded roads a few times wrecking the bearings. The sealing on the LX hubs was excellent though, no sign of water damage when I regreased them.

Going to try putting in some cheap replacement bearings using the links supplied by Meic (thanks for the info), they are 1mm wider than the Shimano ones but should work if the plastic insert is modified. Hammered out the bearings with an old screwdriver.

The design of the Hope external bb's looks good as they have an extra seal, they also make a tool for replacing the bearings (youtube showing it in use here). The Chris King Bottom Bracket can be regreased using a special tool. KCNC do a Taper Roller Bottom Bracket which has greater load bearing capacity than standard ball race bearings.

Shimano uses a 24mm OD axle for all their external BB crank-sets. There are 15 x 1/8"(3.2mm) bearings in each of the two sealed bearings in the Tiagra bb (Enduro uses larger 5/32''(3.96mm) balls in their Hollowtech II upgrade bearing kit).



Update:

Invested in the Hope bb tool (£19). The job can also be done without specialist tools (eg. vice, hammer and drift, see vid here). I filed the centre hole of the shimano cups so diameter was big enough so the tool would fit in making it easy to get the bearings out in future. Pressed in the cheap ebay bearings (branded Zen) using a vice and the Hope tool. I filed the lips off of the nylon bearing "Top Hat" caps (needed as replacement bearings are 7mm wide rather then the 6mm ones they replaced), otherwise caps can be bought, eg. RaceFace X-Type Bottom Bracket Bearing Cap. Fitted refurbished bottom bracket to bike and it's running as good as new.



See also: http://www.mountainbikerides.co.uk/fett ... ement.html
http://www.smbbearings.com/BB_BRGS.htm
http://faqload.com/faqs/bicycle-compone ... ng-service
http://www.peterverdone.com/archive/bik ... ackets.htm
http://bicyclingaustralia.com.au/conten ... t-overhaul
Katec outdoors specific bearings
http://tech.rushsportscycling.com/article/how-to-overhaul-sealed-cartridge-bearings/

[GRAVELBIKE]

Interesting thread, as I just posted a one-year review of Shimano's SM-BB7900 on my blog.

I don't know if Shimano specs different bearings in the 7900 unit, but their website does claim that it has "improved seals." Whether the improvements are limited to the DA line/model, or across the board, it's not clear.

I've been quite pleased with the 7900's performance, and have them on two of my bikes.

[meic]

I have been trying to trace a clicking on my bike, that is partly coincident with pedaling and I have play in my cranks but it still turns smooth and easily.
So I have done a little exploration.

Crank removal and adjuster cap, one Allen key and about 30 seconds, job done.

Then I could feel the non-gear side bearing was a little rough, on installation when I made the bike I had broken the black spacer and seal unit*, so it just pulled out. It has a lip on it with a thin rubber ring which I didnt notice when i refixed it years ago and it may have got twisted at that time.

It looks like the one in Erudin's review and the sealing ring goes on the ridge that he has marked.

So the outside of the FSA cups is quite well sealed.

Now there was a 6805 2RS bearing in front of me, so I prised off the seal with a small screwdriver, I wish I could manage that without damaging them.

So in about 3 minutes I have the ball bearings exposed for cleaning and regreasing.

These cartridges contain 30 small balls each and you can see a little loading dent in both inner and outer races.

A few flushes of maintenance fluid to clean the bearings, then I will grease and reassemble.

I was too shy to open up the bearings before as I was scared of damaging a good unit. As it appears to have started suffering, I thought I had more to gain than loose. It wasnt rusty inside but the bearing isnt smooth running anymore.

It really is a dead simple job and if you wanted to prolong the life of your external BBs they could be serviced as easily as an old cup and cone job but wouldnt need it as often.

Having said all that I will leave the drive side alone as I dont want to risk damage to the black plastic cap** while removing it as the bearing is still fine, just some oil around the gap where the seal is. Which I have been doing since Brucey mentioned it.


* This is why they give you that green plastic tool to restrain the seal when you push the axle through.
** for sale at UK bikestore for almost all of £3.