111mm BB?

[Brucey]

I think a lot of the problems occur when the original BB wears out and an identical replacement is difficult or impossible to source. The generally held (and IMHO, misleading) view that 'barring ISO and JIS the tapers are all very similar' is OK -within limits- when fitting new cranks and BBs together, but with used cranks the situation is very different; they almost invariably have 'accomodated' to the old BB taper shape.

CJ has reported loosening with an ISO FAG BB on an older TA crank, and this mirrors my experience too. IIRC 'old' TA spindles had a taper that was shorter and fatter than many modern ISOs. What I think may happen is that the 'new' taper really only makes good contact at the narrow un-accomodated 'toe' end and the joint isn't firm at the 'heel' of the taper. So it comes loose. Eventually this arrangement might settle down in use with repeated retorquing but it is also likely that it could damage the crank instead.

I was hoping that some folk with digital verniers and a bunch of new (or old) BB spindles might take it into their heads to do some measurements to add to those I've taken so that we can have the makings of a useful database. Adding the dimensions of the flats would help too.

Anyone keen?

cheers

[CREPELLO]

IIRC 'old' TA spindles had a taper that was shorter and fatter than many modern ISOs. What I think may happen is that the 'new' taper really only makes good contact at the narrow un-accomodated 'toe' end and the joint isn't firm at the 'heel' of the taper. So it comes loose. Eventually this arrangement might settle down in use with repeated retorquing but it is also likely that it could damage the crank instead

I'm baffled by this observation. As I understand, the taper on JIS and ISO is at the same angle, just that the JIS taper is shorter and fatter than the ISO. Could there really have been two ISO standards? Anything's possible I guess. As I've previously mentioned, I fitted a ISO Campag crank onto a JIS 107mm BB, which produced a chainline the same as for a 110mm ISO BB (IIRC).

I was hoping that some folk with digital verniers and a bunch of new (or old) BB spindles might take it into their heads to do some measurements to add to those I've taken so that we can have the makings of a useful database. Adding the dimensions of the flats would help too.

Anyone keen?

Sounds like a great idea, although I could only contribute the usual UNxx suspects myself (and I'd have to buy a digital caliper). How would you produce a meaningful measurement of the flats, they're being bevelled at the edges? I suppose that taking the actual width measurements of the taper equals the width of the flats, no? The bevelled edges need to be discounted in the measurements I would have thought.

[Brucey]

my recollection -which could be faulty so bear with me- is that one or other (or possibly both) the 60s-70's 'stronglight 49D' and 'TA cyclotouriste' cranksets used a shorter fatter taper that was later discontinued. Both these cranksets also used a different crank extractor thread, too.

When the revised stronglight 99 (one of the first ISO tapers? ) came out it wouldn't fit on an 'old' stronglight BB IIRC and TA cranks wouldn't fit a stronglight 99 BB very well either.

Maybe my recollection is wrong; it has to be over 25 years since I've messed with these parts; all I have in my box of bits is an old (stronglight I think) spindle that has short fat (vs ISO) tapers on it.

If anyone else can clarify I would be grateful.

Re the measurements; see my earlier post re proposed 13-OS measurement. The flats are easily measured for 'width of the flat bit' -since this is what touches the crank- ideally at each end of the taper.

cheers

[Mick F]

I have my Veloce BB of course, and my Stronglight 651 (late 1980s) available.

The 651 is on Barbarella, I'll get off my bum shortly and whip off the LH crank and measure it.

I'll be back on here later.
Just had lunch apres a 30mile jaunt on the bike and I'm still wearing my cycling kit.

[Mick F]

Here we go.
It would seem that there is ISO and there is ISO.

Campag Veloce 16.8mm
Stronglight 651 15.3mm

These measurements are from the very end of the spindles to the inner end of the flat bit of the taper.
The tapers don't just "taper off" there is a definite "end" to them and the measurements were easy.

I wonder how long JIS tapers are?

[BigG]

my recollection -which could be faulty so bear with me- is that one or other (or possibly both) the 60s-70's 'stronglight 49D' and 'TA cyclotouriste' cranksets used a shorter fatter taper that was later discontinued. Both these cranksets also used a different crank extractor thread, too.

When the revised stronglight 99 (one of the first ISO tapers? ) came out it wouldn't fit on an 'old' stronglight BB IIRC and TA cranks wouldn't fit a stronglight 99 BB very well either.

Maybe my recollection is wrong; it has to be over 25 years since I've messed with these parts; all I have in my box of bits is an old (stronglight I think) spindle that has short fat (vs ISO) tapers on it.

If anyone else can clarify I would be grateful.

Re the measurements; see my earlier post re proposed 13-OS measurement. The flats are easily measured for 'width of the flat bit' -since this is what touches the crank- ideally at each end of the taper.

cheers

I don't think that this can be correct. I still use a Stronglight 49A (the same as the 49D but steel, not alloy) and this fits modern Shimano UN53 axles without problems. No doubt the chain line varies a little compared with the original axles (about 1960), but this does not seem to matter.

[Brucey]

Thanks for that, but if so, its using a JIS axle then, not an ISO which means it is using a shorter fatter spindle.... ....doesn't it...?

BTW how close does the axle come to 'bottoming' i.e. close to the end of the taper when you take the bolt off?

cheers

[PW]

My memory of TA Cyclotouriste is the same as Brucey's. In fact I trashed one before I learned better, by fitting the wrong B/B which only gripped the inboard end of the crank taper hole. Colin could find out, his chainset expert at Spa still sells the parts.