stripping out a Truvativ powerspline BB

freeagent

Need a bit of newbie advice.. so please be nice..

I have a Boardman sport MTB, which currently has a Truvativ 5D chainset, and Truvativ powerspline BB.
The BB is knackered, and I fancied a Chainset upgrade so have bought a Shimano SLX double and Bash chainset, complete with Hollowtech BB.

I'm going to have a crack at swapping them over myself, I've ordered the right tools to install the Hollowtech BB (large socket I can put on a torque wrench, and small plastic 'key' to put the nut on the non-drive side) but don't want to buy any special tools to strip the old powerspline out as they'll never get used again.

Does anyone have any tips or good ideas on how I can get the old BB out? I don't mind if it gets trashed, but don't want to damage my frame while i'm at it..

I've not had much experience at pulling bikes apart, but am a competant mechanical Engineer who knows what a torque wrench is, and how to use it!

nicklouse

yep get the standard BB tool.

or get your LBS to do it as they will need to face the BB shell before you fit the external bearings.

freeagent

OK, standard BB tool is only a fiver from superstar.. will get one on order.

As for facing the BB, am going take a look at it and run the calipers over it first, not convinced its worth it, Shimano don't say anywhere on their instructions that the frame needs to be faced...

nicklouse

the callipers will tell you nothing.

the faces need to be 1 parallel and 2 perpendicular to the centreline of the BB.

freeagent

I'm not convinced by those BB facing gadgets, they seem to clamp onto the BB body rather than picking up on the threads inside, so I don't see how they can produce a face which is perpendicular to the main axis.

The idea of chasing, or trying to alter the threads in some way is not good either, they are a very fine thread, and any efforts to try and alter the main axis will just remove metal and weaken the thread.

You've got no control over the axis of each bearing, as it is determined by the pre-cut threads, facing the BB shell only allows the bearing casing to sit flush against the shell, as far as i'm concerned you are better off winding it in, taking a look at where it is a bit high (if its not flat all the way round) then whipping the bearing out and running a file over the 'high side'

Most mass produced frames will have the tubes cut on an automated saw, which should cut at 90 degrees, and the threads will have been machine cut, so they should be fairly striaght.

nicklouse

freeagent wrote:

I'm not convinced by those BB facing gadgets, they seem to clamp onto the BB body rather than picking up on the threads inside, so I don't see how they can produce a face which is perpendicular to the main axis.

The idea of chasing, or trying to alter the threads in some way is not good either, they are a very fine thread, and any efforts to try and alter the main axis will just remove metal and weaken the thread.

You've got no control over the axis of each bearing, as it is determined by the pre-cut threads, facing the BB shell only allows the bearing casing to sit flush against the shell, as far as i'm concerned you are better off winding it in, taking a look at where it is a bit high (if its not flat all the way round) then whipping the bearing out and running a file over the 'high side'

Most mass produced frames will have the tubes cut on an automated saw, which should cut at 90 degrees, and the threads will have been machine cut, so they should be fairly striaght.

seems like you have no idea as to how things work

have a read

http://www.bikeradar.com/forum/viewtopic.php?t=12654663

yes it uses the threads.

no they dont alter the threads, just clean.

and you would be surprised how badly out a £2000 frame can be.

freeagent

looks like a quick trip to the LBS for me then...

freeagent

looks like a quick trip to the LBS for me then...

freeagent

looks like a quick trip to the LBS for me then...

freeagent

looks like a quick trip to the LBS for me then...

97th choice

10 print 'looks like a quick trip to the LBS for me then...'
20 goto 10

The Rookie

It should only need one trip to the LBS, not 4.

If your going to fit an external BB without facing it, buy2 as you'll soon need the second BB!

Simon