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Spacers for external Bottom Bracket cups

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Spacers for external Bottom Bracket cups

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flag roxovanos
Posted: May 22, 2012 at 16:25 Quote
I just installed a brand new set of Shimano DXR cranks onto an SE Stout 2011 (68mm shell), with Acros ceramic cups, but WITH NO SPACERS.

Initially I went with the guideline of using just one 2.5mm spacer on the drive side, but there wasn't enough axle sticking out through the other end for me to clasp my crank arm to. So I ditched all the spacers and now the cups are resting up against the frame's BB shell.

I was just having a look at my work today, and it suddenly crossed my mind that having metal rubbing up against metal, isn't the best idea in the world, and without a shadow of doubt, it would be sweeter to have one 2.5mm spacer either side of the BB shell to cusion the cups against the metal of the frame. Plus you could tighten it up harder and the plastic spacer would compress a micrometer or two, saving both metals either side from damage.

What do you think?

With something like a Saint crank, the axle is longer than the DXRs, so I have the option for doing this. But I had no choice with the DXRS.
flag Yeroon
Posted: May 23, 2012 at 15:05 Quote
Why do you see the cup against frame as a bad thing? Its like 99% of other fasteners on your bicycle. It shouldn't be getting damaged, provided theres a friction reducing substance between the cup and frame, ie grease. You'll get a more even and consistent torque and the deepest cup engagement the way you have it.
I'd take it your way over having spacers every time. Less stuff to install/misplace when service time comes around too.

Yeroon
flag roxovanos
Posted: May 23, 2012 at 15:12 Quote
Yeroon wrote:
Why do you see the cup against frame as a bad thing? Its like 99% of other fasteners on your bicycle. It shouldn't be getting damaged, provided theres a friction reducing substance between the cup and frame, ie grease. You'll get a more even and consistent torque and the deepest cup engagement the way you have it.
I'd take it your way over having spacers every time. Less stuff to install/misplace when service time comes around too.

Yeroon

I dunno.... Yeah you're right, definitely a deeper screw-in, but only 2.5mm more than with a spacer. How deep is the cup, like 12mm maybe? About that...

It's just a gut feeling/common sense that's telling me to put the spacers back on, one either side....Like for cushioning....PLUS you're making the whole bottom axle unit 5mm wider. Not sure if wider is better or not.

I dunno, it's just a gut feeling. Think of it this way, it's like choosing which side of the Park Tool hammer to hit a metal object with, the rubber side or the metal side. Kinda like that...
flag Yeroon
Posted: May 23, 2012 at 15:23 Quote
You'd be widening the bb interface and narrowing it at the crank arm/spindle interface, which is going to be the weaker one to begin with.
The spacers are only needed to get the chainline correct and the axle width right for the different bb widths. If you get it perfect without it, don't go making it more complicated then it is.
If you really want to do it your way, find the thin stainless shims from centerlock caps. Gives you the thought of saving your frame and won't widen the bb width by anything worth caring about. 20mm axle centerlock uses bb cup tool. Not that those are going to be easy to find.

Its not common sense to make things worse AND more complicated. Leave it alone, and go ride.

Yeroon
flag roxovanos
Posted: May 23, 2012 at 15:35 Quote
LOL. I took it for a maiden voyage two days ago, and the replacement upgrade from the stock garbage cranks/pedals, to the new Shimano DXR set up was phenomenal. Even the added 5mm crank arm length was really noticeable.... Okay, I cleaned and re-greased the chain, plus had a brand new Raceface 34T single-ring installed into the setup..... But it was like I was being rocket-propelled or something, when I was riding.

There's something very very satisfying about doing upgrades, I think. It's kinda like fun noticing the improvement. I mean it wouldn't be any fun starting out with 'the best bike in the world' coz you'd never experience the joy of having anything better, kinda thing.

But......Unfortunately, this joy was very shortlived, and I smashed the right pedal into the ground and I went flying into the handlebars, onto my gut.

Don't you just hate it when something like that spoils the fun....Especially with brand new kit. Real downer, man. Real downer.

I guess that's what got me thinking about this BB cup dilemma in the first place....The shock from the impact of the accident (the pedal smashing into the ground). The idea is that, with the spacers, any damage to the spacer and you just chuck'em and replace them. Any damage to a frame's BB, and that's it.... You got to buy a new frame.
flag iffy
Posted: May 24, 2012 at 8:09 Quote
roxovanos wrote:
LOL. I took it for a maiden voyage two days ago, and the replacement upgrade from the stock garbage cranks/pedals, to the new Shimano DXR set up was phenomenal. Even the added 5mm crank arm length was really noticeable.... Okay, I cleaned and re-greased the chain, plus had a brand new Raceface 34T single-ring installed into the setup..... But it was like I was being rocket-propelled or something, when I was riding.

There's something very very satisfying about doing upgrades, I think. It's kinda like fun noticing the improvement. I mean it wouldn't be any fun starting out with 'the best bike in the world' coz you'd never experience the joy of having anything better, kinda thing.

But......Unfortunately, this joy was very shortlived, and I smashed the right pedal into the ground and I went flying into the handlebars, onto my gut.

Don't you just hate it when something like that spoils the fun....Especially with brand new kit. Real downer, man. Real downer.

I guess that's what got me thinking about this BB cup dilemma in the first place....The shock from the impact of the accident (the pedal smashing into the ground). The idea is that, with the spacers, any damage to the spacer and you just chuck'em and replace them. Any damage to a frame's BB, and that's it.... You got to buy a new frame.

yepBeer
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