BB30

[Valbrona]

I thought I would ask ye olde venerable square taper brigade about BB30. If I were to ask this on a younger persons forum I might get laughed off it.

For anyone not familiar with BB30, you get an assembly each side of the BB shell essentially comprising a cartridge bearing and a bearing seal. However, on the NDS you also get a wave washer that tightens up the bearings as you put torque in the system - the wave washer eventually occupying about 2mm of space on the bit of the axle that sticks out of the NDS.

Now I'll be jiggered, but after lots of measuring the LH pedal seems to sit a couple of mm's more outboard than the RH pedal, and one can only put this down to the presence of the wave washer.

Surely Cannondale when they designed BB30 couldn't have got this so wrong. Or maybe they think it doesn't matter if one pedal sits a couple of mm's further outboard than the other. Or maybe my measuring is out.

Any thoughts?

Thanks.

[Brucey]

the wave washer (and its long travel) may well be a Band-Aid fix for problems that might have arisen (without the same tolerance) in testing. The '2mm offset' will vary with exactly how the frame has been made.... and 2mm isn't a big deal; there are plenty of cranks that have been (and still are) offset far worse than that.

cheers

[reohn2]

2mm that's some kind of tolerance to work to with pedal offset,would anyone notice?
I reckon within 5mm is acceptable.

[Valbrona]

I guess ~2mm doesn't much matter with all the pedal float we have these days.

[Eyebrox]

And should the BB give you problems, as many have because of the precise frame tolerances required, fit a Praxis Works converter. Unfortunately you also need an external bearing BB and new cranks to go with it. It cost me £140 to sort.

[Valbrona]

Started off with a Wheels Mfg converter allowing me to run a regular 24mm crank. Now in the process of fitting a BB30 crankset in what is a BB30 shell.

[Manc33]

...wave washer eventually occupying about 2mm of space...

Sorry to reply to an old thread but the problem seems to be that the 68mm version of the Praxis Works bottom bracket adapter is only to be used with road Hollowtech 2 cranks.

Shame they say this as a footnote at the end of all the raving about how amazing it is.

So amazing that on a 68mm bottom bracket shell on a MTB you cannot fit a MTB crankset to it because:

"Sorry , 68mm can only be used with road cranks . Cannot be spaced. STAFF" - Evans Cycles

"Note: 68 mm for road crank only. It cannot be spaced for use with MTB crank like a traditional threaded BB" - SJS

"68mm MTB frames shells not supported by this BB." - praxiscycles.com

Because... why?

The spindle on the HT2 crank won't reach through?

Is that what they mean by "cannot be spaced"?

It seems that road bottom bracket cups end up at 90mm wide, while a MTB setup ends up at 88mm wide (regardless of 68mm/73mm shells).

So on a MTB with a MTB crankset (HT2) and a 68mm shell, there isn't a solution on the market like the Praxis and the Praxis itself cannot be used, apparently.

The Praxis is totally different to any other fix and is well known as the only properly working method. As far as I know all the other methods rely on pressing something in and it holding there with Loctite. Unless there's a lip of something over the BB shell, anything will just "walk" to the side when fitted IMO.

Of course Praxis do make a 73mm version of their adapter for MTB frames with a 73mm shell and this one can be used with a MTB crankset. Thing is my shell is 68mm not 73mm.

Praxis should make four different types not just two:

68mm for road
73mm for road
68mm for MTB
73mm for MTB

All of those FRAME combinations exist, although a road frame with a 73mm shell might be rare(?), I bet they do exist.

Far less rare is a MTB with a 68mm shell so why is there no bottom bracket adapter for that?!

Instead Praxis make only two, a "68mm for road" and a "73mm for MTB", so if your MTB shell is 68mm you're stuck and can't use a MTB crank on it.

I have no idea if there's a Hollowtech 2 road crank available with 44-32-22 chainrings but I have never seen one. Even then the crank arms (because it is a road chainset) will be 5mm too close to the chainstays and it will rub, so it still wouldn't work even with the right size chainrings.

All I can think is some sort of converter to make a 68mm BB shell become a 73mm BB shell, yeah right.

I'm pretty much at the point of just giving up with it now.

[recordacefromnew]

...wave washer eventually occupying about 2mm of space...

Sorry to reply to an old thread but the problem seems to be that the 68mm version of the Praxis Works bottom bracket adapter is only to be used with road Hollowtech 2 cranks.

Shame they say this as a footnote at the end of all the raving about how amazing it is.

So amazing that on a 68mm bottom bracket shell on a MTB you cannot fit a MTB crankset to it because:

"Sorry , 68mm can only be used with road cranks . Cannot be spaced. STAFF" - Evans Cycles

"Note: 68 mm for road crank only. It cannot be spaced for use with MTB crank like a traditional threaded BB" - SJS

"68mm MTB frames shells not supported by this BB." - praxiscycles.com

Because... why?

The spindle on the HT2 crank won't reach through?

Is that what they mean by "cannot be spaced"?

It seems that road bottom bracket cups end up at 90mm wide, while a MTB setup ends up at 88mm wide (regardless of 68mm/73mm shells).

So on a MTB with a MTB crankset (HT2) and a 68mm shell, there isn't a solution on the market like the Praxis and the Praxis itself cannot be used, apparently.
.......
.......
I'm pretty much at the point of just giving up with it now.

I think it is the other way round. HT2 mtb spindles are longer than road ones, which is why despite HT2 cups are nearly (but not exactly) the same size and interchangeable, mtb cranks might need some or all the 3x 2.5mm spacers between the cups and the bb shell, depending on whether the shell is 68mm or 73mm, and/or whether a chainguard or e-type fd is used etc.

A kludge (well some say bb30 is a kludge itself... ) is to introduce spacers between the praxis cups and the cranks. This is what e.g. wheelmanufacturing's SPC kit http://www.swinnertoncycles.co.uk/components-c169/bottom-bracket-c172/spares-c175/spare-wmfg-bb30-68-73mm-bb-shim-p9266, as in http://wheelsmfg.com/tech/PDF/BB30-PF30_install.pdf, does.

It is probably preferable to introducing 30mm ID spacers between the praxis bb cups and the bb shell, because of the way the praxis expansion sleeve works.

[Manc33]

I think it is the other way round. HT2 mtb spindles are longer than road ones, which is why despite HT2 cups are nearly (but not exactly) the same size and interchangeable, mtb cranks might need some or all the 3x 2.5mm spacers between the cups and the bb shell, depending on whether the shell is 68mm or 73mm, and/or whether a chainguard or e-type fd is used etc.

If MTB spindles are longer, what do the shops selling the Praxis mean by "Cannot be spaced"

Got this from elsewhere:

For BB: The only difference between road and MTB Hollowtech BB's are the inner dust shield between the two threaded cups. The MTB version is wider, since MTB's generally have wider BB shells (73mm). The MTB BB also includes three spacers (two driveside, one nondriveside) for narrow (68mm) shells. All 72mm (he means 73mm?!) shells use one spacer (driveside). You can interchange road and MTB Hollowtech BB's as long as you have the appropriate inner dust cover (just reuse your old one) and applicable shims (for MTB only).

For crankset: The real difference is the spindle length. The MTB cranksets have a wider spindle (he means longer!) for wider BB shell. Rather than make different models for narrow and wide BB shells, they just shim the BB cups out on 68mm shells (cheaper/easier). To fit a MTB crank on a road bike (probably 68mm shell), you need to shim the BB.

If MTB spindles are longer... I wonder why the Praxis can't be shimmed.

"Cannot be spaced" - when every 73mm MTB crank thats a HT2 setup has spacers!

What makes the Praxis not able to have spacers?

Surely the point of a Praxis is that it comes out a the ends like a HT2 BB?

It might be something that voids the warranty if it is put next to the BB but is can be done, so they just say it can't be done, like removing the bearings from them voids it but how else are you going to replace them, by spending £60 on a bottom bracket again? I don't think so Charlie!

Another post elsewhere repeating about how it cannot be spaced but not explaining why that would be:

We do not make a Conversion BB for 68mm MTB frames.

Our 68mm is made for the 68mm Shimano Road cranks.
Our 73mm is made for the 73mm Shimano MTB cranks.

You can't put the Shimano MTB crank on our 68mm as our BB is not designed to be spaced.
In the NOTES tab we have a bullet point on this
• 68mm can only be used with road cranks. Cannot be spaced.

Not "designed" to be, but it can be done though right?

[gloomyandy]

I'm pretty sure that it simply won't work. Look at how it is constructed. When you screw the DS half into the NDS part it is designed to expand the inner sleeve and hence make a good mechanical tight fit with the internal bearing BB30 face. If you add spaces then three things will happen:
* The collet will be in a different place than it is designed to be so the expansion area may not be in the correct place.
* When you tighten up the DS half it will not screw as far into the NDS sleeve/collet this will almost certainly mean that the collet will not expand by the required amount resulting in a poor fit.
* There will be fewer threads engaged in the screw which may result in the threads failing if you try to tighten the two halves to compensate for not have the expansion part of the bracket holding the assembly in place.

So it seems to me that there is a very good chance you will end up with a creaking bottom bracket, certainly not one that fits well.

[recordacefromnew]

I'm pretty sure that it simply won't work. Look at how it is constructed. When you screw the DS half into the NDS part it is designed to expand the inner sleeve and hence make a good mechanical tight fit with the internal bearing BB30 face. If you add spaces then three things will happen:
* The collet will be in a different place than it is designed to be so the expansion area may not be in the correct place.
* When you tighten up the DS half it will not screw as far into the NDS sleeve/collet this will almost certainly mean that the collet will not expand by the required amount resulting in a poor fit.
* There will be fewer threads engaged in the screw which may result in the threads failing if you try to tighten the two halves to compensate for not have the expansion part of the bracket holding the assembly in place.

So it seems to me that there is a very good chance you will end up with a creaking bottom bracket, certainly not one that fits well.

I presume you are talking about the option of introducing spacers (OD c42mm) between the praxis cups and the bb shell. If so one should get the praxis cups designed for 73mm shell - which would/should ameliorate most if not all your concerns.

Nevertheless, as I mentioned above, it is probably preferable to introduce spacers (ID 24mm) between the cups and the cranks - this option should have little, if any, impact on the function of the praxis cups, and certainly no impact on their installation.

But of course both are kludges. In fact although the praxis system seems better than a press-fit, I suspect the solidity/alignment is still no better than a traditional threadless cartridge bb, let alone a traditional bsa threaded cartridge bb.

[gloomyandy]

I'm not sure if the 73mm version would work well in a 68mm bottom bracket. Using this version (along with spacers) would almost certainly put the expansion part of the collet in the wrong place (too far out from the normal bearing position), unless praxis recommend this solution I'd not use it. I agree that using external spacers may be the a better solution. Personally I'd just use a BB30 crankset and have done with it.

[Manc33]

Yes I always mean putting 24mm ID spacers in there between cups and cranks.

From what I can tell, this setup would just work like a stem on a fork steerer - set a preload on the bearings by gently tightening up the crank with that proprietary plastic tool thing (Shimano TL-FC16) to stop it wiggling, then clamp the crank onto it at normal crank tightness, voila... what's the problem with having spacers outside the cups, in this case? The crank wouldn't be able to crush the bearings and the spacers would be there to stop it wiggling.

Or yes, have a BB30 and creaking.

Its not even creaking that gets me on BB30 its the fact that the cups aren't even screwed in and where they are "glued" (?) in its about a 10mm surface area at the edges of the BB shell

Imagine being on a motorbike, in a car or on a plane that was Loctite'd together... you'd say get me off this plane and put me on one bolted together please. I feel the same about bottom brackets.

Wheels Manufacturing also make a Praxis style adapter, I wonder if they allow use on a 68mm MTB setup.