Bottom Bracket Life

[Kestevan]

Depends.

The cheapo Sora/Tiagra HT2 on the commuter bike seems to need replacing every year - so 2-3K, but its ridden in all sorts of crappy weather and cleaning regime is best described as "minimal".

The SRAM BB30 on the best bike has done about 2K... but was still spinning buttery smooth when I packed it up for the winter

 

[RecordAceFromNew]

The problem is that there are many variables.

For outboards most believe facing the bb shell is essential, but many still experience poor reliability. If manufacturers can't always assure parallel faces during manufacturing I wonder if we can assume without checking that the drive and non-drive side threads are concentric?

For an oem-skeptic view on shell flex and press-fit in general this is an interesting read.

It is hard to escape the conclusion that all else being equal a well sealed, cartridge bb with fairly large ball bearings like the UN5x should have less reliability issue than the large axle small* ball cartridge bbs (ISIS/octalink), the outboard bbs (e.g. HT2/GXP/MegaExo etc.), and many of the press-fits.

* It is interesting to see what skf resorts to to deliver a reliable isis, at a price...

 

[gwhite]

The problem is that there are many variables.

For outboards most believe facing the bb shell is essential, but many still experience poor reliability. If manufacturers can't always assure parallel faces during manufacturing I wonder if we can assume without checking that the drive and non-drive side threads are concentric?

For an oem-skeptic view on shell flex and press-fit in general this is an interesting read.

It is hard to escape the conclusion that all else being equal a well sealed, cartridge bb with fairly large ball bearings like the UN5x should have less reliability issue than the large axle small* ball cartridge bbs (ISIS/octalink), the outboard bbs (e.g. HT2/GXP/MegaExo etc.), and many of the press-fits.

* It is interesting to see what skf resorts to to deliver a reliable isis, at a price...

+1

Your conclusion I'm sure is being borne out in practice according to reports.

 

[Bodhbh]

The problem is that there are many variables.

For outboards most believe facing the bb shell is essential, but many still experience poor reliability. If manufacturers can't always assure parallel faces during manufacturing I wonder if we can assume without checking that the drive and non-drive side threads are concentric?

I got the frames faced at the LBS after powdercoating - it didn't seem to make much odds. For me the bikes that get all the use, are MTBs with fat slicks. They have full length mudguards, but those big tyres still throw alot of water back down below (time to bodge a mudflap). That said, I've read elsewhere those Deore HT2s last no time at all. I'd swap out of HT2, but once you have several bikes with it, you're stuck.

 

[lay]

Talking of BB's - as we've had a pathetic amount of rain; its seen hubs 'washed' of grease AND now the BB ;/ which hasnt made me very happy! I've a GXP variant c.set/bb combo & got it apart earlier and discovered its possible to grease these upon levering the seal off with a sharp knife.

Question: how is it the plastic sheath that fit between the crank & the RH Cup - and acts as a seal: seems to space away from the cup/frame upon fitting even tho its pressed in as far as I can get it ! Its this 'gap' that i feel has let the rain into it. I'm astounded by the life of this GXP bb type...id expect far longer !!!! I truly regret not getting a campag c.set as the cartridge units are easier to fit.

 

[Moodyman]

One of the commuters came with a low-end square taper. It died after about 3k miles. I replaced it with a Shimano UN54 and it's still rocking 8k miles later.

Other 3 bikes come with Shimano Hollowtech - these range from 200 - 5000 miles. All going strong, but the 5k miler is used for commuting and every 2-3 month, I clean, re-grease and re-install to keep it quiet. It gets both dry and gritty in between the crank, BB and frame interface.

 

[Blue Hills]

mm, seems to be an argument against Hollowtech (yes i know this subject is something of a regular on various forums) - a posh tourer of mine is fitted with Hollowtech but can't help feeling I should have specced square taper.

 

[mrandmrspoves]

I don't have a bracket on my bottom - but I have just checked my bottom and found there is a big crack in it....any advice? Am I safe to continue cycling or will I make it worse? Also it has started to make some creaking noises. ......

 

[Sillyoldman]

I don't have a bracket on my bottom - but I have just checked my bottom and found there is a big crack in it....any advice? Am I safe to continue cycling or will I make it worse? Also it has started to make some creaking noises. ......

Aye, don't wipe it with sandpaper

 

[mrandmrspoves]

Aye, don't wipe it with sandpaper

Is WD40 acceptable as a cleaning agent?

 

[cosmicbike]

I don't have a bracket on my bottom - but I have just checked my bottom and found there is a big crack in it....any advice? Am I safe to continue cycling or will I make it worse? Also it has started to make some creaking noises. ......

If it's cracked then you stop using it immediately, and return for an exchange. Not sure what the creaking is about....

On a more serious note, the BB in my Trek 7500E has started getting crunchy. Only 700 miles, but did get partially submerged recently so perhaps that. No idea what it is though..

 

[RussellZero]

Less than 200 miles on my trek cobia 2013... Warranty claim is in...

 

[marcusjb]

I am on square tapers on both the commuter and the audax bikes.

Commuter - (relatively cheap sealed units) - 5-6000ish miles on average - that is on fixed, so does take a beating.

Audax bike - Royce titanium unit - 25000miles so far. I have some spare bearings, but can not see them being needed quite yet.

Whilst the royce might be silly money, it does start to work out financially over the years.

I have no bikes with external bearings, but riding with those that do, they really do not last long, particularly in poor weather conditions. Luckily, here in the UK, we have such great weather that it isn't an issue really.......

 

[Blue Hills]

Related to my musing above about square-taper being better (and I can definitely see no disadvantage for general cycling) do folks reckon there is any chance of square taper BBs and crank/chainsets being discontinued in the near to medium future?

Knowing the way business often works I am dubious about manufacturers wanting something so good to stick around when other stuff can be flogged.

 

[KneesUp]

I've removed the one from the bike in my avatar, which was my dad's. It's the original, so roughly 30 years old - the bike was used for daily commuting in all weathers for at least a decade. It was a bit rough.

I can't get the new one to screw in though as the threads are too bloomin' rusty, so I must drop it off at my LBS to do. When the weather is nicer.