Which BB?

efcbluepete

Hi,

I'm hoping somebody may be able to point me in the right direction for a new BB.

My trusty old Trek Alpha is in need of a new BB, and I am unsure what to look for. the bike & BB are around 12 years old, so desparately need replacing (the BB, not the bike just yet).

I have tried to upload a couple fo photos, but can't seem to do it in here. edit - trying to do it via dropbox below... edit - dropbox didn't work, but here are the photobucket links...





The basic dimensions are 70mm across the BB, approx 37mm outer diameter of the BB, and approx 37mm shaft length from frame to outside of centre of pedal. It is a Bontrager pedal/crank set, if that helps any.

Not looking for the latest and greatest but just something that is decent enough to last another few thousand miles and cost less than £50 (less than £20 would be nice :-) ).

thanks in advance,

Pete

arlowood

On a 2005 Aluminium Trek frame, the BB is almost certainly a BSA threaded (British) variety. Looking at your pics the non-drive side crank has no split so it will probably be a square taper fitting like in the link below

http://www.chainreactioncycles.com/shim ... d|271964UK

If so you will also need an extractor to remove the existing cranks - like this:-

http://www.wiggle.co.uk/x-tools-crank-e ... 2283383124

And also a special removal tool to get the old BB out of the frame:-

http://www.chainreactioncycles.com/x-to ... rd|31715UK

Thereafter you can refit a new square taper as linked above but if you want to update to a Hollotech II bottom bracket then you will also have to replace your cranks

efcbluepete

Thanks Arlowood - much appreciated.

I might just get a quote from the local bike shop, to compare with having to buy the various tools, my time, etc.

Pete

keef66

If the last one has managed over a decade, it's probably not worth investing in the tools to DIY. Plus after that length of time it might require some effort to unscrew, so maybe best to let the bike shop have a go and fit a decent quality replacement.

milemuncher1

keef66 wrote:

If the last one has managed over a decade, it's probably not worth investing in the tools to DIY. Plus after that length of time it might require some effort to unscrew, so maybe best to let the bike shop have a go and fit a decent quality replacement.

True. If you want to replace the Chainset as well, you may as well ask the Bike shop for a Shimano Hollowtech 2 English threaded B.B. and HT 2 Chainset. A Tiagra BB and Chainset would be fine ( actually they’re very good ). You didn’t mention how many speeds your current groupset is. It will be less expensive to just keep everything as is, and replace the current square taper B.B. with a UN55 square taper B.B.

keef66

Plus if you bought all the tools to replace this one thinking they'd be useful on your next bike, they probably won't.

(Can't remember the last time I used my splined BB tool or crank extractor...)

You could always borrow them, but I'm assuming from your forum name that Newmarket might be a bit out of your way?

Nick Payne

There doesn't look to be much wrong with the crank at all, just some slight scuffing and a bit of dirt, and the chainring teeth don't look in too bad a condition. Square taper BBs can last a good deal longer than 12 years - as a first step I'd just pull the cranks and spin the BB axle with my fingers to see if there is any perceptible roughness in the bearings. If yes, get the BB replaced, if the BB is fine just replace the crank.

efcbluepete

thanks for all the useful, thought out replies.

I decided to bite the bullet and get the spline tool and the extractor tool (£11 total, so not the end of the world), and get the cranks off per the suggesiton below(above), and see what sort of shape the bearings are in. if the wheel bearings were anything to go by, they were rough as the proverbial bear's buttocks!

I have already put a new chain/sprocket/cassette on, so don't really want/need to do that for a good while yet.

I will post progress on here once the tools arrive and I get an hour or so to go at it. In the meantime I have got some ACF50 on the BB and back of the cranks in the hope it soaks in to make it all a bit easier.

Cheers,

Pete

veronese68

Stick with square taper, they last longer than hollowtech. Just get a like for like replacement, square taper bottom brackets come in different axle lengths so you will need to get the same length as your current one.

arlowood

BB is most likely to be a 68mm x 107mm English thread. The 68mm refers to the shell width of BB on the bike and the 107mm refers to the end-to-end length of the spindle that the cranks are fitted to. You can check both dimensions on your current set-up to make sure you order the correct replacement.

Plenty of YouTube videos to walk you through the process

https://www.youtube.com/watch?v=in0eWKepZ2c

With your BB having been in the bike for 12 years then you may need some leverage to get the BB out of the frame

keef66

arlowood wrote:

With your BB having been in the bike for 12 years then you may need some leverage to get the BB out of the frame

^ definitely that

Bike on the floor, rubber side down.

Tool snugly / fully inserted into splines.

As long a lever as you can get / fabricate (I've hose clipped some 4 foot steel shelf supports to my socket handle before)

Make sure you're turning it the right way, ie remember the drive side will be reverse threaded, so unscrews clockwise.

If it comes out easily first time, go buy a lottery ticket.

Remember to grease or copperslip the threads on the new one before installing and again remember to turn them the right way

efcbluepete

Oh Dear! Just seen the "remove drive side clockwise" comment - aghhh, I've been trying to gently coerce the thing the wrong way! fortunately nothing broken or stripped, and plenty of ACF50 in there working its way into the nooks and crannies.

So to giving it a go the right way later tonight - wish me luck!

btw, pedals came off relatively easy with the puller, and spinning the crank has a horrible grinding sensation to it.

Thanks again for the help and pointers, much appreciated.

Pete

kingdav

Marvellous that you're giving this a go I reckon - good luck!
I bought a UN55 square taper bb to fit at home from the LBS not so long ago (I try to source some things from them and keep them going) but I could have bought the BB and tools as well for less from the online crowd so you probably really have nothing much to lose. I was lucky and the old one came out fairly easily (2008 bike, probably original bb). I used about a 1m long tube for leverage that used to be an old rotary washing line.

keef66

efcbluepete wrote:

Oh Dear! Just seen the "remove drive side clockwise" comment - aghhh, I've been trying to gently coerce the thing the wrong way! fortunately nothing broken or stripped, and plenty of ACF50 in there working its way into the nooks and crannies.

So to giving it a go the right way later tonight - wish me luck!

btw, pedals came off relatively easy with the puller, and spinning the crank has a horrible grinding sensation to it.

Thanks again for the help and pointers, much appreciated.

Pete

Trying it the wrong way can sometimes help when you finally try the right way.

I generally undo the non drive side first, but I'm not sure why. Maybe it's because they go in drive side first...?

milemuncher1

I’ve had a square taper B.B. get hopelessly stuck, it’s not the end of the world. If you hit the spindle good and hard with a hammer, the B.B. will fall apart, then you just ( carefully) chisel the cup away from the thread, which will cause it to fall apart, and then you just wire brush any remaining bits out of the thread, and pop the replacement in. I’ve got an old B’Twin Riverside 300 Hybrid, which that happened to, the replacement UN55 has been in for 3 years now, with no issues.

Matthewfalle

No need to replace crank or anything of that with that stuff MM said. Waste of time and money.

New square taper b/b in there, those cranks, off you go.

Just remember to slather the whole lot in loads of copperslip on reassembly.

Job jobbed.

milemuncher1

Matthewfalle wrote:

No need to replace crank or anything of that with that stuff MM said. Waste of time and money.

New square taper b/b in there, those cranks, off you go.

Just remember to slather the whole lot in loads of copperslip on reassembly.

Job jobbed.

How would you know?

Monty Dog

As long as the chainrings aren't worn / need replacement then simply replacing the BB is what I'd do - I have 40 year old square taper BBs still going, I've had external bearing ones last 6 months. I guess the OP doesn't want to be replacing BBs annually on a bike they've kept for 12+ years?

cycleclinic

square taper rules o.K.

efcbluepete

As many will have found in the past, the BB does not want to move (even when I tried in the right direction!)

Having watched many a video online, I have got to the "drill the buggers out" phase.

Tried long levers, hammers to shock it, acf50, wd40, etc with the tough bit being the spline tool slips out too easy. one of the videos showed a long screw with various washers and sockets to hold the spline tool on, but as the thread inside the square taper would seem to be the imperial equivalent of M8, I don't have any screws to fit that thread.

four broken drill bits later, I am ready to chisle the non-drive side out (my time is very fragmented (a bit like this BB will be once i have finished with it) so can generally only get to do stuff like this at 30 mins here and there). As you may gather, I am more stubborn than the BB I am trying to get out, and will get it out and replaced even though it would have been much more economical to take it down the bike shop to get them to do it with all their experience and tools.

Pete

Monty Dog

The best way to remove these BBs when stuck is literally smash them out - the cups are only ABS plastic - make sure the frame is well supported e.g. over the open jaws of a large bench vice, plenty of rags etc to protect the tubes and give it a firm wallop with a club hammer. This is what we'd do when I worked in a bike shop - out of the view of the customers!

milemuncher1

thecycleclinic wrote:

square taper rules o.K.

They’re like the Duracell battery of the B.B. world.

photonic69

Did the OP die trying to remove this? No update on his progress?

Vino'sGhost

PhotoNic69 wrote:

Did the OP die trying to remove this? No update on his progress?

He probably had a siezure after reading Monty Dogs (excellent) advice

efcbluepete

After breaking approx 10 drill bits and a similar amount of dremmel bits, I have been going at the remnants with hammer & chisel with no joy whatsoever.

I am admitting defeat to this one and will now look for a 2nd hand frame to throw all the components off this onto and put a new square taper BB on. the BB was rough as a bear's, so did need replacing. I will use this as a commute & training bike and look at getting something a bit more fancy for my triathlon attempts this year.

:-( gutted, but I have learned many useful lessons along the way. Thanks to all who entered the debate and offered useful help and advice - very much appreicated.

Pete