Changing from powerspline to external BB

[brad890]

Hi guys was wondering if anyone could tell me if its possible to upgrade from a power spline BB which looks like this

 

to a external BB that looks like this

 

without actually having to replace the crankset as well?

 

thanks Brad

[kosmonooit]

Dont think so - bb are crank specific as far as I know. The cranks that use a external bb have a completely different design, drive side normally attached to center shaft.

And not all external bb's are the same ie Shimano type vs GXP?

Generally crankset includes unique bb?

Why?

[Willehond]

no

[Guest Big H]

No, our MTB Tandem has a Shimano Octolink BB. These BB's are not relaiable..... however, it is cheaper to buy and stock a few BB's than buying a new crankset....... Tandems gebruik mos twee vannie goetters!!!!!

[chuck]

You will have to change the crank

[dts29]

Dont know much about these things but the guys at morningside cycles changed my internal bb to external one and I still have the same FSA crank.

 

Its a road bike if that makes a difference but I also thought it was strange when I picked up the bike and saw the external BB. So just for my own curiosity, a crank is restricted to work with one type of bb because of different internal mechanics?

 

[AndreZA]

Dont know much about these things but the guys at morningside cycles changed my internal bb to external one and I still have the same FSA crank.

 

 

 

 

I would love to see how they did that. With internal BBs the axle is build into the BB and with external BBs the axle is build into the cranks.

[Guest Big H]

Go and look here to see why it would be impossible to convert a internal BB/crank setup to a external BB/Crank setup.

If it has been done like claimed above we would like some pics above!!!!!!

 

http://www.shimano.com.au/media/techdocs/content/cycle/EV/bikecomponents/FC/EV-FC-M660-2790B_v1_m56577569830672023.pdf

[SURFER]

I would also like to see the pic's

[chuck]

In theory if your spline axle has the correct length and diameter (highly unlikely) you could try and remove the axle form the sealed cartridge and use it in the external BB but there are other issues that you will have to deal with like lateral movement.

[Guest Big H]

..... why would you remove the axle from a perfectly new external bearing crankset just to fit your old cranks?????..... sounds dumb!!!!!!

[dts29]

ill get some pics up tonight, but with my little knowledge. The bb used to sit inside the frame and it looked like the first pic in OP. The new one looks like the second pic, sitting "outside" of the frame.

[chuck]

 

..... why would you remove the axle from a perfectly new external bearing crankset just to fit your old cranks?????..... sounds dumb!!!!!!

 

Actually not so dumb if you read the post properly. Remove the splined axle from the internal BB (old one).  You cannot remove the axle from an external BB crank without an angle grinder which is...yes you guess it, dumb.

 

Anyway this is just theory since going to all this trouble just to use a splined crank set cannot be worth the trouble. Much easier and cheaper I would imagine just to install an external BB with crank.