Tiagra bottom bracket - crap?

NikProwse

Hi

I have a Genesis Equilibrium with mainly Tiagra components. While having the bike serviced the mechanic told me that there's a lot of play in the bottom bracket and that it needs to be replaced, which came as a surprise since it's less than a year old. I don't know what my annual mileage is, but it's not particularly high - less than 2000 miles, I would think.

Does this match other people's experiences? Is Tiagra crap, and should I fit a 105 or something higher?

Thanks
Nik

mattv

These hollowtech 2 bottom brackets rely on being fitted to a well prepared frame. Everything has to be parallel, else they collapse pretty quickly. If fitted correctly to a well prepped frame they last thousands of miles!

plumpy

This sounds like nonsense Nik - I strongly suspect they just want to make some money out of you.

The Tiagra BB is one of Shimano's Hollowtech BB's where the sealed bearings sit in separate bearing cups either side of the threaded bottom bracket in the frame. The most obvious reasons for "the bottom bracket to have developed play" are either (i) the chainset itself has worked loose because the the non-driveside crankarm bolts have loosened since installation, or (ii) either or both of the BB cups have loosened in the frame's BB threads. Both of those things are perfectly plausible but both of them can be sorted with a torque wrench and/or Shimano BB spannner and maybe some threadlock - no new parts needed. The suggestion that either or both of the sealed bearings themselves have deteriorated to an extent which is causing palpable looseness in the BB, sounds like B.S.

Tiagra is definitely not "crap" - I assume there must be some difference in bearing quality between Tiagra BB cups and 105 cups, but it will be absolutely marginal.

NikProwse

Plumpy and Matt, that is very useful info. As it happens I told the bike shop not to fit a new bracket (as they had other work to do and was hoping for a fairly low-cost service), and decided to check it myself & maybe get a 2nd opinion. I'll check out the tightening/threadlock options.

Much obliged
Nik

mattv

They can and do develop play, sometimes quickly, if fitted poorly.

keef66

I've read lots of tales of HT2 BBs failing prematurely, but my 105 BB is coming up to 6 years old and still going strong.

My conclusion based on a sample size of one is that they are fine if they are installed properly in a BB shell that's been faced, the correct preload applied when installing the cranks, and the BB area is never pressure washed.

Mine have the additional protection of full chromoplastic mudguards for much of the year.

(None of this stopped me buying an Ultegra BB when I noticed CRC selling them for £11! Nice to have a spare )

plumpy

Not sure what is meant by "fitted poorly" - they are simply screwed into the frame's BB threads (and you couldn't possibly screw one in all the way cross-threaded).

I can imagine that they will deteriorate if the frame has not been faced properly, so when they are tightened they are not parallel, but in that case Nik has got a defective frame and the BB shell needs re-facing. Simply screwing in another (more expensive) Hollowtech BB is hardly the answer. The mechanic seems to be suggesting the latter rather than the former?

mattv

By poorly fitted I mean an unfaced shell. At one point shimano pointed out a void warranty if the frame is not faced each time a new bb is fitted. A spot of grease on the threads stops creaks too.

Bozman

I'd like to see someone cock up the installation of a HTII BB, I've fitted them to plenty of frames, old and new and they're simple to install and last well, as for facing.... Old wives tale, modern frames don't need facing.
If you want to experience a crap BB get a frame with BB30.

k-dog

^ I changed mine last year. Just removed the old one and fitted the new one.

Didn't ever feel much better than the old one and after 6 months was poor.

Had the BB faced and carefully fitted the new one with a torque wrench and it's been smoother since day one and has so far last longer too. It does seem to make a difference how good the frame and installation is.

drlodge

If my BB had developed some play, I'd want to first understand where the play was coming from and why it got into that situation e.g. is it the bearings, sloppy fit (bearing pre-load) or something else. That way you can at least understand why you have to shell out more money and hopefully prevent it happening again.

agent nomad

Water ingress into the bearing will rapidly accelerate bearing wear/failure there are a few ways that water can get in, washing the bike with a pressure washer, washing the bike with a standard garden hose, and riding in the rain grit and muck gather around the bottom bracket area and can find their way into the bearings and then the bearing will start to fail due to wear.

Bearings that are used in the BB are light weight simple ball bearings and are normally 2RS type ( 2 rubber seals) behind the seals are the balls and a plastic cage to hold them place and some grease, the industry standard for the amount of grease is 1/3 of its free volume for standard bearing for a 1500 rpm use. The grease is almost certainly soap based and therefore emulsify with water and become more runny and leak out, leaving you with an under lubricated bearing so leading to failure,

On my winter and training bikes what I do to help reduce this and extend the life of the bearing is wash the bike with a bucket and sponge only, no hose pipes etc. And when fitting a new BB where possible some designs will not allow this, I carefully remove the bearing seals and add some grease, then replacing the seal, this will make the bearing a little stiff to turn but it will last a lot longer in wet conditions.

I have ver 33 years experience in mechanical maintenance in all sorts of extreme environments and know the above to work.

onbike 1939

Bozman wrote:

I'd like to see someone fool up the installation of a HTII BB, I've fitted them to plenty of frames, old and new and they're simple to install and last well, as for facing.... Old wives tale, modern frames don't need facing.
If you want to experience a crap BB get a frame with BB30.

This will come as a revelation to most bike mechanics. I've found new bikes fitted with outboard bearings and the BB had not been faced. "Modern frames" are still painted and this can contaminate the surfaces of the BB shell and will need removing. A glance at the cycling forums will show that there is plenty of evidence that fitting these bearings on surfaces which haven't been faced will shorten the lives of the bearings.

mididoctors

onbike 1939 wrote:

Bozman wrote:

I'd like to see someone fool up the installation of a HTII BB, I've fitted them to plenty of frames, old and new and they're simple to install and last well, as for facing.... Old wives tale, modern frames don't need facing.
If you want to experience a crap BB get a frame with BB30.

This will come as a revelation to most bike mechanics. I've found new bikes fitted with outboard bearings and the BB had not been faced. "Modern frames" are still painted and this can contaminate the surfaces of the BB shell and will need removing. A glance at the cycling forums will show that there is plenty of evidence that fitting these bearings on surfaces which haven't been faced will shorten the lives of the bearings.

how does facing improve the bearing life... if its flex then the threads must be deforming in the space that is created by a uneven paint job?

drlodge

mididoctors wrote:

how does facing improve the bearing life... if its flex then the threads must be deforming in the space that is created by a uneven paint job?

The threads are not super tight, therefore the cups can wobble slightly in the threads as they're screwed in. If the face is not straight, the cup will be at a slight angle when its tightened and that causes increased wear.

mididoctors

drlodge wrote:

mididoctors wrote:

how does facing improve the bearing life... if its flex then the threads must be deforming in the space that is created by a uneven paint job?

The threads are not super tight, therefore the cups can wobble slightly in the threads as they're screwed in. If the face is not straight, the cup will be at a slight angle when its tightened and that causes increased wear.

really?

well maybe but i struggle to give that credence to be honest.

IME outboard bearings still have poor life expectancy on faced BB shells?... ditched the lot and gone back to square taper.

if was back racing I guess the stiffness would be worth the aggro

onbike 1939

mididoctors wrote:

drlodge wrote:

mididoctors wrote:

how does facing improve the bearing life... if its flex then the threads must be deforming in the space that is created by a uneven paint job?

The threads are not super tight, therefore the cups can wobble slightly in the threads as they're screwed in. If the face is not straight, the cup will be at a slight angle when its tightened and that causes increased wear.

really?

well maybe but i struggle to give that credence to be honest.

IME outboard bearings still have poor life expectancy on faced BB shells?... ditched the lot and gone back to square taper.

if was back racing I guess the stiffness would be worth the aggro

Unlike square taper BBs which are very tolerant of imperfections to the faces, the outboard type relies on these being parallel and even paint can prevent this. If bike workshops could avoid the cost of the Facing tool then believe me they would as it's an expensive item.

I agree with you that unless stiffness is paramount (and I would bet that not many riders would be in this category) then it makes a lot of sense to stick with the traditional variety...but then I'm an old fogey.

mididoctors

onbike 1939 wrote:

Unlike square taper BBs which are very tolerant of imperfections to the faces, the outboard type relies on these being parallel and even paint can prevent this. If bike workshops could avoid the cost of the Facing tool then believe me they would as it's an expensive item.

surely if the threads are not correct then facing the shell will mean nothing when it comes to a parallel fit... the outboard cups are going to be parallel even if you cut the bb shell faces off at a absurd visible angle?

facing the shell for a super snug fit may reduce movement...perhaps if there really is slop in the threads that allows for wobble

.

drlodge

mididoctors wrote:

surely if the threads are not correct then facing the shell will mean nothing when it comes to a parallel fit... the outboard cups are going to be parallel even if you cut the bb shell faces off at a absurd visible angle?

facing the shell for a super snug fit may reduce movement...perhaps if there really is slop in the threads that allows for wobble

.

If the threads are out, then you'll likely end up with cups that are not aligned. You might get away with a small amount of deviation in the threads if the faces are parallel, but only tiny amounts - since there is some play in the threads but its very very small.

You really need both the faces to be parallel AND the threads to be cut properly. If one or the other is out, your bearing life is going to be reduced. Of course there are also press fit BBs which are a different ball game entrely.

Monty Dog

If the threads are straight, regardless of the shell being painted / faced typical tightening torques for the cups should never distort the metal cups sufficiently to impact on bearing alignment - any competent mechanical engineering designer would understand this. It's a wholly different story with old frames where BB threads were hand-cut and alignment was a problem. IMO The whole cup facing thing is BS cooked-up by the bike trade to try and explain-away cr@p bearing life and justify expensive workshop time / frame prep. I also wouldn't trust the numpty mechanics down most LBS with the worn/knackered tools I regularly encounter to be able to do the job properly either.

quartzknight

I bought a Dura Ace BB, 36x24 and it's dying after < 5 months. I've been warned that Italian threaded cups put more wear on the bearings due to smaller diameter and ignored this. Now I'm paying the price