Apologies for missing the proper signoff (a danger of cross-posting!)
Also: a listmember has informed me that the new TA Pro 5 Vis arms and Axix BBs are indeed ISO tapered. He heard this directly from TA.
Adam Hammond Toronto, ON, Canada
On Mon, Apr 6, 2009 at 12:56 PM, Adam Hammond <anhammond@gmail.com> wrote:
> I posted this to the BOB list this morning, but thought CR people might be
> even keener at spotting the differences or similarities between the on- and
> off-topic TA cranks.
>
> Here is my question:
>
> I have in my possession one of the newer TA Pro 5 vis cranksets -- produced
> in 2007. I also have a TA Axix BB, which is from the same year. The BB is
> 116mm wide, which I have always heard is the correct width for TA doubles.
> This BB is completely symmetric.
>
> I ran this setup on Fuji touring bike for a few months last year to test it
> out, and everything seemed in order. There wasn't much crankarm clearance on
> either chainstay (I was using a 135mm rear end and fairly beefy chainstays),
> but things seemed more or less centred.
>
> I was testing it for the still-forthcoming custom frame I expect to arrive
> in a few months. In the meantime I've become interested in this question of
> symmetricalness. For it seems TA's older bottom brackets for Pro 5 Vis
> doubles were not symmetrical.
>
> Piece of evidence number one: this chart from Sheldon Brown's website:
>
> http://www.sheldonbrown.com/
>
> This suggests that the BB should be offset VERY slightly (1.5mm) toward the
> drive side.
>
> And this photo of a TA 344 axle (the very one specified for TA doubles in
> the above diagram) seems to show an even more significant driveside offset,
> though it is the same length as my symmetrical Axix BB: 116mm. (It may be .5
> longer...)
>
>
> http://picasaweb.google.ca/
>
> My question basically is: did TA change their cranks for the newer
> production runs to make them work with symmetrical BBs when they used to be
> designed for asymmetrical? If I were to have mounted my TA cranks onto the
> aforementioned Fuji touring bike with one of the TA 344 axles, I would have
> had one crankarm 8mm out from the chainstay, and the other smacking straight
> into it.
>
> To throw a final crankarm into the spokes: I have heard various rumours
> that the new TA production is designed for JIS spindles (and that the Axix
> BBs use JIS spindles) -- would this explain all the confusion?
>
> Confused,
>
> Adam