C-Record BB compatibility

S

Simon Masterson

Old School Hero
Hi all, I have a set of C-Record v2 (that's what I think they are, anyway) pista cranks that I bought last year for a retro TT build I'm doing soon. I haven't used anything from this group previously and have read in a couple of places that the ISO tapers are slightly different - can anyone enlighten me on this? I have a Chorus double from the early 90s that has worked fine with several different ISO BBs.

Will I be able to build up with a modern cartridge BB, or do I need to buy a C-Record era BB? I know which I'd rather use...

Thanks for any help.
 
As far as I understand it, the older Campag taper is neither ISO nor JIS. Provided it fits well onto the taper of the BB and doesn't bottom out on the end you should be fine.
 
C-Record post-dates all the proprietary taper chicanery that existed in the early Eighties: they take an ISO BB.

In fact, there is now no difference between ISO and JIS tapers: both tapers are 2° and the square at the end of the taper measures 12.7mm.

The difference is that ISO BB have a 1mm x 45° chamfer at the end of the taper, so a JIS BB of the same nominal length as an ISO BB will actually be 2mm longer: Record Pista take an 111mm ISO BB, so you'd want a 109mm JIS BB for the same chainline.

FWIW (if you're going to race it) a cup & cone BB will be faster than a cartridge on account of the bearing drag.

And if you're chasing a low Q-factor (Record have that going for them), Shimano 7400 on 103mm beats Record. I've got a Royce 102mm to try on my TT bike, but I think the lump hammer will have to come out again: I had to dent the chainstay with 103mm and a 56t ring...
 
ScillySuffolk":arixrg4i said:
C-Record post-dates all the proprietary taper chicanery that existed in the early Eighties: they take an ISO BB.

In fact, there is now no difference between ISO and JIS tapers: both tapers are 2° and the square at the end of the taper measures 12.7mm.

The difference is that ISO BB have a 1mm x 45° chamfer at the end of the taper, so a JIS BB of the same nominal length as an ISO BB will actually be 2mm longer: Record Pista take an 111mm ISO BB, so you'd want a 109mm JIS BB for the same chainline.

FWIW (if you're going to race it) a cup & cone BB will be faster than a cartridge on account of the bearing drag.

And if you're chasing a low Q-factor (Record have that going for them), Shimano 7400 on 103mm beats Record. I've got a Royce 102mm to try on my TT bike, but I think the lump hammer will have to come out again: I had to dent the chainstay with 103mm and a 56t ring...
Click to expand...

Brilliant, thanks.

If I'm completely honest, I mainly bought the cranks out of a love of shiny Campag, and though I do intend to race this bike, it will have drop bars (and no tri bars), and non-aero wheels, so I'm not chasing every last second - I'm thinking of having some fun with it on spocos and hillys, as my 'serious' TT machine is fixed.

As regards Q-factor, I'm sure I read somewhere that Ian Cammish used to use the axle length intended for triples (115.5?) to give better clearance, and there was that incident with Boardman when he couldn't engage top gear - any thoughts on doing that?
 
You're welcome.

A "classic" class bike: fair play and fair enough!

I can't see the benefit in more clearance: enough is enough and if you're fixed, changing gear isn't a concern.

What's the OLD? If it isn't 120mm then you might encounter issues but crank length and chainring size also comes into play.

Mine is a former track pursuit frame and my cranks are 150mm, but it was the size of the ring that meant the hammer had to come out.
 
You might find that the crank, spider, chainring, chainring bolts or any combination thereof foul the chainstay then.

But if you're using [cough] variable gears [cough], then you can afford to increase the BB: the difference between track and road chainline (typical, outer ring) is 4mm, so that gives you a range of 111mm to 119mm BB to play with.

Or get the hammer out: https://www.lfgss.com/comments/12836846/
 
Simon Masterson":2xqyrlhp said:
Top man, thanks for all the answers. Now I just need to get the frame back from Mercian so I can try some BBs in it...
Click to expand...

So you won't be using a lump hammer then !!!!!
 
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