Outboard b/b bearings and chain alignment

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George
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Outboard b/b bearings and chain alignment

Post by George » 28 May 2013 15:19

A month or so back, I went all new-fangled on my summer bike, and fitted a new Campag chainset of the PowerTorque type, plus the matching outboard cups and bearings. It all went together easily enough and seems to be a nice smooth-running, stiff arrangement compared to the old-fashioned set-up with its inboard bearings and square-section axle.

However ...

The chain rings are significantly further to the right than before, meaning that the chain alignment is, well ... crap. Even on the granny ring, dead straight is achieved only when the chain is to the right of the mid-point in the block, and when I'm on bottom sprocket, the chain is at a silly angle and makes a lot of noise. This can't be efficient or good for component life expectancy.

This leaves me rather frustrated, but also rather puzzled. When looking at frame specs on websites, I've never noticed mention of new frames having narrower bottom bracket shells than was normal 5 years ago. But, unless that's the case, surely everyone with one of these Campag chainsets is riding around with crap chain alignment, like mine? And, if it is the case that you can get a sensible chain alignment only if you have a frame that's got a narrow b/b shell, surely Campag and/or the shops should say to prospective buyers "only suitable for ..." ? But I looked at chainsets on several shops' sites before buying and saw no such warning.

As it is, I've got a set-up that I've spent >£200 on, and am not entirely happy with, but can't easily return, because the issue wasn't apparent to me until I'd fitted the equipment and ridden on it.

Have I missed something embarrassingly fundamental here?

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dweben
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Post by dweben » 28 May 2013 18:22

Not sure about campag (brr roadie stuff) but my new Whyte frame uses a BB30 setup which does have a narrower bottom bracket width which my normal Shimano XT setup wouldn't fit with. It would end up a) the opposite of yours and b) the left pedal would stick out a mile! I have an adapter built into my bottom bracket to offset my standard BB24 crank to the correct measurements of the BB30 frame.

Sounds like your outboard stuff is maybe built to take a narrower bb into account really same as BB30.

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John Sanderson
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Re: Outboard b/b bearings and chain alignment

Post by John Sanderson » 29 May 2013 17:17

George wrote:When looking at frame specs on websites, I've never noticed mention of new frames having narrower bottom bracket shells than was normal 5 years ago....

....But I looked at chainsets on several shops' sites before buying and saw no such warning.
I'm a big fan of sourcing parts online, so hesitate before saying this, but... shopping at the LBS would have probably avoided this fate!

I did wonder if i'd end up with a 'wrong width' BB when I replaced the drive train on my bike with parts i'd sourced online, so checked it was all going to match before I fitted it.... My situation was slightly different though - I was more concerned i'd inadvertantly buy MTB rather than road parts - which I think have a different width - rather than get wrong spec road parts...
It's all about the bike.

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George
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Post by George » 30 May 2013 21:29

Thanks for the feedback, both, which is interesting.

However, no one has yet actually said anything to confirm that your average road bike does actually have a narrower bb shell than 5 years ago. And I can't say that I've ever heard/read that that is the case. So I'm really still in the dark. Because either that is the case (and I'm embarrassingly ignorant and many on-line shops are not providing the info they should), or it isn't (and the design of Campag's chainsets is crap).

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Post by Pedlo Mudguardo » 30 May 2013 21:38

Hi George,

I use Campag Power Torque and Ultra Torque on my bikes. Both systems seem to work really well with no chain line issues. In fact it's possible to use both extremes of gears without a problem. As far as I'm aware most road bikes have a 68mm bottom bracket shell and have done for some years.
The only other variable I can think of is the position of the cassette on the rear wheel and wether the wheel is properly dished.

All of my cranks are double are you using a triple ?

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Post by pprince3145 » 31 May 2013 07:38

Odd.

Wheel dish won't affect it as the hub is in a fixed position in relation to the frame, dishing will affect the rim alignment, not the cassette.

My first check would be measuring your chain line and try and find out via Campag tech docs to see if its correct or not.

Assuming it is and your chainrings are too far out next I would see if your Bb shell needs facing or not if you have an alloy or steel frame of course.

Other than that its a head-scratcher for sure
Cult Racing...better than Rock Racing
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John Sanderson
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Post by John Sanderson » 31 May 2013 08:34

George wrote:Thanks for the feedback, both, which is interesting.

However, no one has yet actually said anything to confirm that your average road bike does actually have a narrower bb shell than 5 years ago. And I can't say that I've ever heard/read that that is the case. So I'm really still in the dark. Because either that is the case (and I'm embarrassingly ignorant and many on-line shops are not providing the info they should), or it isn't (and the design of Campag's chainsets is crap).
A quick Google turned up this: http://www.bikeradar.com/gear/article/c ... ets-36660/ and also this http://sheldonbrown.com/bbsize.html

I've also seen mention somewhere in the quick search of some Campag having a 5mm offset for some models.

I'd guess your problem is less about the bb width and more about the spindle and /or spider design? Unless the spindle is actually slopping side to side in the bearings the BB shell must be the correct width?
It's all about the bike.

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George
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Post by George » 31 May 2013 10:03

Those are really helpful responses. I'll do some research along the lines suggested. (But not now!)

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George
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Post by George » 17 Jun 2013 15:30

After doing some internet research, I think I may have the explanation. As some of you may have guessed, the explanation is that I'm an idiot.

Having watched an assembly video that anyone sensible would have watched before assembling the crankset, I now understand that the crankset is boxed with a 3mm shim slotted on to the RH crank assembly. Although the shim arrives with the RH crank, you are supposed to remove it and slot it on to the LH side of the BB when you put the whole lot together. Idiots who get the stuff out of the box and assemble it 'as is' end up with everything 3mm too far to the right.

All I have to do now is buy some more tools to dismantle the whole bloody thing (you can't take it apart without their special tools, apparently) and reassemble it with the shim on the other side and normality should be restored.

My friends, be warned by me: if all else fails, read the instructions!

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George
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Post by George » 17 Jun 2013 15:39

I may sue Campag. They say "Final assembly must be carefully performed in order to avoid an accident, personal injury or death." But nowhere does it say that I need to be careful in order to avoid making myself look like a plonker in a public in internet forum.

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George
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Post by George » 17 Jun 2013 16:29

Image

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Grogz
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Post by Grogz » 17 Jun 2013 16:38

George wrote:Image
Someone must have one you could borrow? Nic or Chris H maybe?

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George
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Post by George » 17 Jun 2013 17:43

Thanks for the suggestion, Greg. Ideally, however, I'd like an at-home solution, otherwise I've got to drive into B'ham and back twice each time I want to take the crank off. Step 1 is therefore some judicious use of a rubber mallet. If that doesn't work, I'll take up your suggestion in the short term while also looking round for a cheaper (e.g. 2nd hand/copy) tool in the long term. After all, it's hard to do a thorough clean without taking the cranks off; I would usually do that about once a year.

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Post by laurence_cooley » 17 Jun 2013 17:54

The Park Tool tool (which is actually two tools - CBP-3 and CBP-5) looks to be cheaper, if not exactly cheap.

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Post by John Sanderson » 02 Jul 2013 09:16

George wrote:Image
Ouch!!!
It's all about the bike.

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