Hi Garth,
I've built a few frames and hundreds of wheels, and I can tell you
definitively that heavier guys break axles with regularity. It starts with a
bent axle, then if you take the wheel out of the bike and put it back in, (it
will be in a different relative position) and it gets bent again, you are
essentially bending the axle at the root of a thread (stress riser) just
inboard the cone. If you do that a few times, the heat treated(?) CrMo axle
breaks. A machinist friend of mine tells me he knows someone who makes
connecting rod bolts for grand prix engines, using high zoot steel alloy
bolts, heat treating the bolts and then rolling threads. It seems backwards
(in terms of economy) but it produces light, strong bolts that are VERY
expensive. The same technology applied to Campy hubs would probably mean
$100+ axle that wouldn't bend and break for a 200lb rider. If he makes some,
I'll buy a few!
I've broken axles on narrow six speed wheels and sevens are worse. That said,
I'm also fairly light on my wheels in terms of technique. The best wheels I
ever had were sew up 28s with an early aero rim. I could ride them up and
down curbs (unweighting the wheels) and down the shallow steps at the north
end of the Golden Gate Bridge without ever damaging the rims. Axles were a
problem just hitting pot holes. If you've been doing well all these years,
don't gain weight!
Stevan Thomas
Alameda, CA