Hope Road BB spacers

[Feanor]

Hi,

I have here a new Hope road BB.
It is supplied with 2 x 1mm spacers.

The instructions simply tell you to 'determine if they are required', with no guidance on how to determine this.
http://www.hopetech.com/webtop/modules/_repository/documents/RoadBBinstructions.pdf

The original existing Shimano BB has no spacers.
I can't see why the hope unit would be a different length or something odd.

ETA: Just had the vaguest load of waffle from Hope's tech support!
"Uhh, well, you can use them if you like. Like a washer.  Uh, yes it will push the chain line out by 1mm, but that's OK.  No, you don't have to use them, you can install the BB like the Shimano original.  Un, no, there's no actual real benefit from using them."

But no explanation of why or when I'd actually *want* to use them.
I could imagine they could be used to fine-tune the chain-line, but that's about all I can think of.

So what are the spacers for?

[greenmeansgo]

I'll have punt on this one. The Shimano equivalent BBs come with spacers which are required for a 68mm BB shell, but aren't for a 73mm shell. You can play around with the arrangement of spacers to adjust chain line slightly if required (usually 2 on one side and one on the other as I recall). The pdf just shows two 1mm spacers, so it looks like something is different about the fit. It talks about the bearings fitting straight on the crank.

What I'd do is try it with the spacers first - does the crank axle go through far enough to clamp the NDS crank onto the spindle? If so then you need the spacers. If not then take them out so that you have full contact on the splines. Check that you can adjust the bearings correctly now. You might "bottom out" against the edge of the BB spindle if you don't use the spacers when they're required (I would suppose). Closely examine the Hope and Shimano BB cups for differences in dimensions that would affect the installation.

In summary, if you install it one way and can't find a problem with how things work, then it's probably good enough!

[Feanor]

And the answer is in:
You use the washers.

The Hope external cup is 1mm thinner than the Shimano one:


P1000612 by Ron Lowe, on Flickr

The 1mm washer brings it up to the same thickness, so that once screwed fully home into the BB shell, the bearing faces are the same distance apart as with the Shimano originals:


P1000613 by Ron Lowe, on Flickr

( sorry about the poor focus on that one! )

[frankly frankie]

So the Hopes are offering you a lower Q factor if you can assemble everything without the spline bottoming out.  Or you might be able to use just one spacer, or you can alter the chain line by using both on one side or the other.

I must say I'm not usually a fan of Hope stuff but I do like that extra depth of thread there - very sensible!

[Tewdric]

I'll have punt on this one. The Shimano equivalent BBs come with spacers which are required for a 68mm BB shell, but aren't for a 73mm shell.

That's the MTB ones only - not the road ones. 

For MTB BBs you use 2 spacers on the right and one on the left with a 68mm shell, and just one on the right for a 73mm shell.

[greenmeansgo]

That's the MTB ones only - not the road ones. 

For MTB BBs you use 2 spacers on the right and one on the left with a 68mm shell, and just one on the right for a 73mm shell.

Oh, my bad. I've only experience of the MTB chainsets/BBs.

How do the road ones work then?