Recommend me a bottom bracket...

[citoyen]

WTF is Samox?

Never heard of them before, but apparently that's the brand of the chainset and BB on my MTB. The BB is knackered and needs replacing...

It's a Shimano Hollowtech II style external threaded BB, and in the middle it's marked 68/70.

A Tiagra BB would be a suitable replacement, wouldn't it?

[bludger]

I don't know about compatibility but if it is compatible, spend the money and get an ultegra one. I had a tiagra one and it was in bits within a year.

[citoyen]

The one thing that makes me wary of getting an Ultegra BB is that I don't have a clue where my adapter is for the BB spanner...

Aside from that, the reason the current BB is knackered is riding the bike through wet and muddy woods over the winter, so I'm not sure a more expensive BB would necessarily last any longer. I know they claim to be "sealed" but...

That said, even the Ultegra BB is available for less than £20 so it's hardly going to break the bank.

[grams]

The external width of HT BBs is different for road and MTB cranks. You can’t mix them - well you can, but it requires getting creative with spacers and the tube in the middle doesn’t fit.

The MTB style normally has at least one spacer twixt the frame and the cups.

[citoyen]

Yes, I would assume the MTB has 73mm(?) BB shell, but the fact that the old BB is marked 68/70 made me think it was probably a road size.

Yes, I should actually measure it... but it's bedtime, so I'm not going out to the garage now. Will do that in the morning.

And yes, there was indeed a spacer between the drive side cup and the frame.

I kind of know all this shit, but I was thrown a bit because Samox isn't a brand I'm familiar with, so I'm wondering if there are compatibility issues I need to be aware of (not least because I've had trouble mixing and matching Shimano and FSA components in the past).

I guess I should probably also measure the diameter of the crank spindle, though I am assuming it's 24mm.

[Brucey]

I was going to mention the potential mismatch ( a la FSA and Shimano) but you are all over it anyway.  IIRC shimano BB spindles are 24.00mm and FSA ones are a gnat's over this.  You need a micrometer or a good set of verniers to measure the difference. A good dodge can be to use old, (slightly worn) top hat bushes with a shimano BB and a FSA spindle.

FWIW Samox are a brand that manufacturers use to save a few quid on the bike spec. IIRC currently there is a recall out on samox cranksets fitted on Genesis Day One models which are two or three years old. 'Risk of breakage' apparently.   The affect ones are square taper type but even so I'd examine yours carefully before bothering to buy a BB to suit it.

cheers

[citoyen]

FWIW Samox are a brand that manufacturers use to save a few quid on the bike spec.

I suspected as much. It's an odd mix of components on the bike, obviously built to a price point, some blingy bits, but cheap'n'nasty tyres etc. Doesn't surprise me they would save on the cranks.

Thanks for the info.

I've measured up and the spindle seems to be as close to exactly 24mm as my callipers will measure. Was going to order the Deore BB52 but Chainreaction had the Saint BB80 for only a couple of quid more so I've taken a punt on that...

[Hot Flatus]

Odds on that it is Shimano standard.

FSA (Fucking Shite Arsecrap) couldnt even agree a standard amongst themselves.

[citoyen]

Odds on that it is Shimano standard.

Yep. If anyone's still interested, the new BB arrived a couple of hours ago and I decided to fit it straight away with the idea of going out for a ride later when I finish work. The crank spindle was a very snug fit but didn't require excessive force to insert, so I would say that's pretty much spot on.

As I was finishing the job, it started raining... chiz! Oh well, that's perfect weather for riding the trails through the woods, isn't it?