We've discussed this before, but the French nominal 14 x 1.25 and the Engli sh nominal 9/16 x 20 TPI are extremely close. In practice, the pitch dif ference is insignificant, and the only difference that matters is that the English thread diameter is slightly larger. Most French pedals will actu ally thread fairly well into English cranks. They will be slightly loose , but not nearly as loose as some accounts lead one to believe. In fact, one can almost always use French pedals in an English crank as long as one is careful to keep them well tightened. Conversely, many English pedals can be installed in French cranks without formally retapping the cranks. Essentially, using noticeably, but not massively, more force, one can i n effect retap French cranks just by installing English pedals. Again, m any accounts greatly exaggerate the difficulty of doing this. Indeed, I suspect that thousands of French cranks in the couple of decades since they ceased to be widely available have been retapped in this way by teenage bi ke shop employees who did not even know they were doing it and who never ev en heard of French thread. Ignorance is bliss.
A few years ago TA actually sold pedals whose thread dimensions more or les s split the difference between French and English, and which TA claimed to be suitable for either type of crank. I have a couple of pairs. On an English crank they were just slightly loose, but still quite usable. On French cranks they required a bit of extra force to install. And what T A did by design, Lyotard did accidentially. I like Lyotard pedals a lot, particularly the Berthets, but they are famous for the wide variation in t hread dimensions, to the point that French and English thread for them are only statistical concepts. On average, French threaded Lyotards are smal ler diameter than English ones, but only just. I'm still convinced that Emerson's (or was Thoreau's?) quote that "Consistency is the demon of littl e minds." was stolen from some French philospher.
Regards,
Jerry Moos
Big Spring, Texas, USA
From: John Betmanis <johnb@oxford.net> Subject: Re: Re[2]: [CR]Loose pedal threads To: "Classic Rendezvous" <classicrendezvous@bikelist.org> Date: Thursday, November 13, 2008, 5:32 PM
At 05:05 PM 13/11/2008 -0500, Dmitry Yaitskov wrote:
>Sorry, I should have made this clear(er): I have two pairs of Chater
>Lea pedals, they both (or rather, all four of them) fit those cranks
>(also Chater Lea) similarly. Both those pedals fit another English
>threaded crank normally. And I have a TA French-threaded crank that
>these pedals do NOT fit. Also, I don't know but I assume that French
>threading has a different TPI, doesn't it? (If it does then
>French-threaded pedals probably won't go all the way into
>English-threaded cranks even if they have smaller diameter, no?)
Both French and English threads are close in diameter and pitch, which makes it possible to easily tap out French cranks to 9/16 x 20, but Sutherland's doesn't say anything about doing the opposite, which is why I thought a French tap (or pedal) would be sloppy in an English crank.
In your case I suspect it's just a tolerance problem. Even if the pedals were tightened to where they felt solid, they might still rock under load, loosening or causing damage. I think a weak grade of Loctite, like 222, would prevent this from happening.
John Betmanis
Woodstock, Ontario
Canada