Replacing Mega Exo BB with Tiagra BB

bazbadger

After some research it looked like I could replace my mega exo BB (creaking away) with a Tiagra BB for my FSA Gossamer compact chainset - with the two pinch bolts on the left hand crank.

Put the new BB on ok but fitting the driveside crank is tricky as it goes through until about 1cm to go - where it needs hitting to get through the last bit. As this requires the use of a rubber mallet - not sure this is wise.

Any tips or advice on how to make it fit?

redddraggon

Whack it hard

cooper.michael1

I'm sure there was a thread on here a month or so ago, where a guy from FSA said the BB are not compatable.

redddraggon

cooper.michael1 wrote:

I'm sure there was a thread on here a month or so ago, where a guy from FSA said the BB are not compatable.

I have two gossamer chainsets running with Shimano HT2 BBs, and they are far better than the mega exo junk that came with the chainsets.

cooper.michael1

cool, it must just have been the guy from FSA flogging his own gear!

Monty Dog

Rubber mallet - OK, 4lb club hammer - not such a good idea

bazbadger

This was a response from a guy from FSA (apparently) eslewhere on the web on the issue of compatibility:

The short answer; no, the FSA K-Force Light Rd. Crank is not compatible with a Chris King bottom bracket (made to Shimano compatible dimensions). Also, the K-Force Rd. crankset will not be compatible either.

The FSA BB8200 (meant for K-Force Light) uses a 6 mm width bearing. This allows us to make the bottom bracket outside to outside dimension more narrow providing room for a wave washer. The BB8000 (meant for K-Force) does indeed use a 7 mm width bearing, yet its design does not allow for use of a Chris King bottom bracket.

However our popular alloy cranksets, the Gossamer Rd. and the Energy Rd. is compatible with the Chris King bottom bracket (made to Shimano compatible dimensions). These cranks use BB6000, this BB’s dimensions are compatible with Shimano.
Dae Oh
Full Speed Ahead

As I have a Gossamer this leads me to believe it should fit - along with the experiences of others. However, with a carbon bike (or any for that matter) I'm not sure having to hit the drive side crank with a rubber mallet to make any kind of progress for the last 20mm says to me something is not right.

I don't want to hammer it in - and then not being able to get it out again...

redddraggon

Baz, I've done it on a carbon frame and it's fine. If you are worried you could sand down the plastic seals on the BB a bit and you might fine getting the axle in a bit easier.

Anyway, once you have got the axle in, removing it and reinserting is easy the next times.

topdude

Just loosen the non drive side bearing cup a few turns. Slide the axle through and do up the cup again. This makes an allowance for very slight miss-alignment of the cups.

bazbadger

Thanks for the tips.

Managed to get the driveside carnk on through a combination of topdudes suggestion and a rubber mallet.

Turned out the creaking was not from the BB but the cassette - freewheel.... grrr

that'll teach me to through money at my bike before exhausting every other avenue...

John.T

bazbadger wrote:

Turned out the creaking was not from the BB but the cassette - freewheel.... grrr

that'll teach me to through money at my bike before exhausting every other avenue...

The BB gets blamed for every noise on the bike. It seldom is the cause.