[CR] Cranks and BCD, old + new

(Example: Component Manufacturers:Chater-Lea)

From: "Kai Hilbertz" <khilbertz@googlemail.com>
To: Mark Stonich <mark@bikesmithdesign.com>, Classic Rendezvous <classicrendezvous@bikelist.org>
In-Reply-To: <E1LQw88-0003ud-4S@elasmtp-scoter.atl.sa.earthlink.net>
Date: Sun, 25 Jan 2009 16:01:16 +0100
References:
Cc: nicbordeaux <nicbordeaux@yahoo.fr>
Subject: [CR] Cranks and BCD, old + new


Jan. 25, 09 - old subject line: "Re: [CR] The Alex Singer on French Ebay"

Hello Mark + List, cc George + Nick,

thanks for your post, I'm quite familiar with the TA Pro 5 Vis, commonly called Cyclotouriste.

Regarding the discussion with Jan, we ended the thread with two e- mails off list. Despite Nick's boxing analogy, I hope no blood was spilled. Please note that I've put a new subject line in this e-mail, even though it's a reply, because A) Jan wanted to end the previous thread, and B) I'm trying to answer your question, and perhaps start a new thread which doesn't directly relate to Alex Singer.

When Jan referred to a "compact double" in his posts, both George and I thought he was referring to a relatively modern compact crank, most of which have a BCD of 110 mm. Now a 110 only goes down to 33 teeth (more on that later), so I was wondering about the 48/32 Jan referred to. Assuming five arms (rather than four or three), either this was a typo, or he was using something with a smaller BCD, such as a 94. If he was using a 94 BCD crank, 32 would be an unusual choice, since most folks go down to 30 or 29 teeth on a double. Turns he is using a smaller BCD, but a vintage six arm crank, namely the aforementioned TA Pro 5 Vis.

Hillary says the Stronglight 49D was introduced in 1936, and according to Joel Metz, the Pro 5 Vis were introduced in 1963. In that period, there were no better touring cranks. Many bicyclists still like them today for their low width (Q-factor), gearing flexibility, and of course for the fact that they're period correct on many vintage bikes.

However, their small BCD of 50.4 leads to a fair amount of flexing in larger rings. As Peter White puts it; "Also, the bolt circle is tiny, even for the outer chainring. This allows the outer ring to flex easily to the outside during upshifts, and in time, the gap between the ring and the arm becomes even smaller. As the gap between the outer and middle ring increases, the chain ends up falling between the two. When I was installing the Pro 5 Vis regularly on high end touring bikes in the 1970s, I rarely used outer rings larger than 46 teeth for that reason." That's the reason I don't use them, but as always, YMMV. Use whatever makes you happy.

I'm an architect and engineer by training, though I no longer work in that field, and I like stiff, forged one-piece cranks with five arms. Like many List members, I wrench a bit (to avoid the dreaded term "tinker"). Over the years, I've primarily used cranks with a BCD of 144, 130, 122, 110, 94, 74, 58 + 56. I don't do much with the Pro 5 Vis anymore, and I've never personally used an 86 BCD like the Stronglight 99, but that's just me. Back in the 70's, I loved Campagnolo but wasn't happy with the 36 tooth low of the stock triple. So I made a custom triple with a Gipiemme 30 tooth low, it has 54-42-30. Ironically, it was 170mm, and I discovered longer crank arms soon afterwards, so I ended up almost never using it. I've still got it today, it'll be up for sale soon. To clean house, I intend to put all of my non-110/74/56 BCD stuff on eBay, just haven't found the time.

As has been noted by Sheldon + Hillary, gearing is influenced not just by chainring, cog, and wheel selection, but also by crank arm length. I ended up mostly riding 185mm cranks, doubles and triples, so it's generally been TA for me. I mostly use Zephyrs, along with Vegas(180mm) and Carminas. The latter two aren't one-piece but hey, what you gonna do? But then crank arm length would probably constitute a whole 'nother thread, and I would like to return to your BCD question.

As far as I know, Campagnolo never made anything smaller than 42 teeth for their NR/SR cranksets, but TA did. I've still got a vintage, not modern, 41 tooth TA chainring for Campagnolo, it's eBay bound. TA also made and makes 38 tooth chainrings for 130 BCD Shimano-style cranks, and of course they make a 33 tooth chainring for 110 BCD, I own several. On doubles, I mostly use 50-33 or 48-33. Like the 41/144 + 38/130 BCD rings, 33's have to be relatively thin to fit the spider. Peter White sells them for around 50 bucks.

Your sign-off "28-42 compact double with a 14-28 FW" was interesting. I checked the archives, my questions to the List concern what kind of cranks and gearing other folks are using on their vintage and KOF bikes: 1. What BCD do YOU like, i.e. are most folks riding (Campagnolo) 144 and/or (TA+Stronglight) 50.4, or is there a sizeable minority of others? 122 anyone? Or do we have lots of collectors with almost as many BCD's as bikes? 2. Are almost all using vintage cranks, or do other heretics besides George and myself also use classical style but post '83 cranks like TA Zephyrs, Sugino compacts etc? (Hope that question is OK, Dale) 3. Do we have mostly racers and randonneurs with doubles, or a bunch of triples as well? What gearing do YOU like?

Greets

Kai Hilbertz Munich, Germany

On 25.01.2009, at 04:58, Mark Stonich wrote:
> At 1/24/2009 07:37 PM +0100, Kai Hilbertz wrote:
>> Hello Jan, cc List,
>>
>> do you personally prefer 48/32, as stated? That would mean a BCD of
>> 94
>> (or smaller), and then you could go smaller with the inner chainring.
>> Or were you referring to 48/33 or 48/34 with a BCD of 110? What do
>> you
>> use in the rear?
>
> Kai,
> With the TA Cyclotouriste a 26t inner ring on a double is possible.
> With the 86mm Stronglight 99 a 28t inner ring on a double is possible.
> I imagine the constructeurs were making whatever they needed.
>
> Have you ever seen a 33t 110mm bcd ring? I haven't.
>
> Mark "28-42 compact double with a 14-28 FW" Stonich;
> Minneapolis, Minnesota USA