Drive side crank clearance

[bikenut2010]

Ok 1049 strada super record cranks fitted to 115 mm ITA BB, small chainring clipping the chain stay; sounds like they'd been fitted to a JIS BB and opened the taper so sliding onto the ISO BB spindle too far? OR need a spacer to move the drive side cranks outboard ( anyone have ITA BB spacers? ) OR clout a dent in the chain stay ( sounds risky!)

any advice/tips?


:shock:

 

[hamster]

Tapers do wear and spread with time. However, it might be worth reversing the BB (possible with ITA as the threads are both RH) in case it's asymmetric and you can use it your advantage. IIRC some Campag BBs were, but I cannot recall which off the top of my head.

As the taper angle is identical IIRC, it might be worth fitting them onto a JIS BB to see if they fit decently. If they just rest on the first 4mm then you know it's not a goer.

 

[bikenut2010]

Tapers do wear and spread with time. However, it might be worth reversing the BB (possible with ITA as the threads are both RH) in case it's asymmetric and you can use it your advantage. IIRC some Campag BBs were, but I cannot recall which off the top of my head.

As the taper angle is identical is identical IIRC, it might be worth fitting them onto a JIS BB to see if they fit decently. If they just rest on the first 4mm then you know it's not a goer.

Thank you!

 

[gfk_velo]

Re:

Worth noting (more in passing as it's not strictly relevant to the OPs problem) that the Campag BBs of that era were not true ISO - the tapers themselves are a fraction longer than a true ISO so you have to be careful about mounting 1049s to a straight ISO BB, especially if you think they have been spread - as you can end up with (especially the LH) crank migrating so far up the taper that it comes up against the scalloped shoulder of the taper - we've seen plenty of vintage cranks crack due to this problem, including one of my own, I'm sorry to say :-(

For a short while in the fixie-hipster boom a few years ago we also had a succession of the current Pista cranks coming in to us cracked, having been fitted to 111 ISO BBs because the Campag Pista BB is not well enough sealed for road use (naturally, that's not what it was made for) ...

I think if the tapers *have* been spread to that point in this case there's a danger of the fixing bolt bottoming out anyway - looked at logically, there would normally be something of the order of a couple of mm clearance on a non-indented stay between inner ring and chainstay and the axle should come through the crank, post tightening down to within ~3 mm of the base of the crank bolt recess - so if the crank is migrating up the taper to the extent it appears to be, bottom-out is a risk.

I'd be tempted to strip everything out of the frame and do a dry assembly of the crank to the BB axle off the bike and have a look from the back to see how far up the taper the crank is coming, check to see how close you are to bottoming out when the crank bolt is undone then figure out what to do from there.

It's likely teaching gran'ma to suck eggs, I know, but given that the BB axle is assymetrical, you do have the axle in the BB the right way round? Stranger things have happened!

Depending on which "fixed" BB cup you have in, there were both thick-wall and thin-wall variations for some years - you could possibly use a thin wall if you can lay your hand on one and that's not what's in there already ...

I've got a Royce 119 mm BB in one of my vintage bikes with a 1049 chainset to get around a broadly similar issue - the chainline isn't *great* but like the OP I was wary of squeezing an indent into the chainstay (I am a framebuilder and still didn't fancy the risk!) so that may be an option you might want to look at. It depends how determined you are to stay "all original".

You'd have to hunt around but OMAS, Rino and I think Galli all did BBs with adjustable chainline back in the day, all of which, IIRC, worked OK with 1049 cranks - so one of them might provide an option too.

 

[Midlife]

Blimey I wish I could type like that being born in the 50's

It's usually down to suck it and see around that era, there was such a mix of things going on that the "rules" got a bit bent. The shortened rear stays plus the trend to not flattening the chainstay meant a longer axle. Then there was the safety issues about front mechs trickling down.

The black GS axles of the era saved our skins a few times

Shaun

 

[gfk_velo]

Blimey I wish I could type like that being born in the 50's

Well, I was born in the early 60s
Part of what I do for Campag is writing technical advice for users so I have just got used to trying to make sure I don't miss anything - don't want to be liable for a rear derailleur going into the spokes because of missing something out that I thought was "obvious", or anything of that nature!

It's usually down to suck it and see around that era, there was such a mix of things going on that the "rules" got a bit bent. The shortened rear stays plus the trend to not flattening the chainstay meant a longer axle. Then there was the safety issues about front mechs trickling down.

The black GS axles of the era saved our skins a few times

Shaun

Yes, absolutely.

In some ways it's easier now where the rules are rather more "the rules" ... back then, before true standardisation (and before ambulance-chasing bloody lawyers, too), we all had to be & could afford to be a good deal more creative!

 

[bikenut2010]

Thanks! very informative! Actually the BB is not asymmetric , it's a standard campy sealed cartridge type...a pair of later (Mirage?) cranks sit on it fine...I guess the hunt is on for a BB that works or ditch the rather lovely 1049 cranks...PS This is a buddy's bike I'm try to help with; all the sage advice well appreciated!!

 

[gfk_velo]

Thanks! very informative! Actually the BB is not asymmetric , it's a standard campy sealed cartridge type...a pair of later (Mirage?) cranks sit on it fine...I guess the hunt is on for a BB that works or ditch the rather lovely 1049 cranks...PS This is a buddy's bike I'm try to help with; all the sage advice well appreciated!!

Ah, therein lies your problem, the 1049s used an assymetric axle.

That the Mirage cranks sit on it OK doesn't really signify ... They should as if the BB is contemporary with the cranks, they were designed to work together & post-date Campag's adoption of the ISO BB taper standard on all but the Pista chainset(for as long as they continued to use square taper anyway).

So, the correct axle is going to depend a bit on what front mech you are using ... But there are plenty of period BBs out there if you know where to look.

If you can send / post an image of the front mech, I can check the axle spec you need. I'd rather not rely on memory!

 

[Midlife]

All my bikes have asymmetric axles apart from my 2012 Basso

Shaun

 

[gfk_velo]

There is a good table, from a past copy of Record News here:

https://www.flickr.com/photos/stronglig ... 05/detail/

Reference the "Technical Support 1982" document, which gives axle dimensions and compatibilities.
There is also one in Sutherlands Handbook for Cycle Mechanics vol. 6 which is reliable.