Okay so I have:
1x Specialized Allez.
1x Tiagra Cranks HT2(no BB)
1x Shimano MTB HT2 BB.
I want to replace the Square Taper cranks for the HT2s. Is it case of taking out Square taper BB and cranks off and putting the HT2 in?
I heard that if I take the plastic tube from between the two cups then it will fit the frame...is this true? Will everything be spaced okay?
Or should I just stop being a tight arse and buy a Road BB from Rose?
From memory, Hope use a shorter spacer(which can be left out, as you say), and a 1.5mm spacer either side instead of a combination of 3x 2.5mm spacers to fit their MTB cups on a 68mm road frame.
it wont work. MTB cups are wider and you'll have a fitting/chainline issues.
And that'd be the reason for using 3mm worth of spacers instead of 7.5mm worth 
he doesn't have a Hope BB coatesy. It's Shimano.
As said, Shimano MTB cups are slightly wider than the road ones, so even if you leave out the central sleeve it will still be too wide for your roadie cranks. You can do it for an emergency fix but the common sense solution is just to buy a dedicated road BB PGreen.
As for Hope, the MTB cups are the same as their road cups. The only difference is the width of the central sleeve (MTB is wider, as you run three spacers whereas with the road BB you don't run any). You can therefore swap the cups between road and MTB by just buying a different central sleeve.
Right, overall width of Shimano and Hope BBs are nominally the same, and both have 7.5mm of spacers on a 68mm shell, therefore if you can use Hope cups with two 1mm(not 1.5mm as I thought they were) spacers to obtain the correct width, then surely it follows that you can do the same with Shimano cups.
Currently running a Tiagra HTII bottom bracket with the middle sleeve from an old LX one on my hardtail.
It hasn't exploded and killed me or anything yet 
so conversely you should be able to run an MTB one in a road frame without the sleeve (or with a road sleeve if you have it).
I think the road cups were maybe 0.5/1mm narrower than the MTB ones, but in an HTII set-up there is a bit of leeway with the way the cranks attach.
Or just buy a road one...... Tiagra BB on CRC .......at £11.99 it's cheaper than Rose Bikes when you include postage.
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