John, He is correct about the fretting wear, but I'm not certain what he is saying in that section exactly, but it may be that as mentioned earlier in the discussion, roller bearings are MUCH better at carrying the loads seen by the front fork.
Jon MSE at GIT Crate Marietta, GA
-----Original Message----- From: classicrendezvous-bounces@bikelist.org [mailto:classicrendezvous-bounces@bikelist.org] On Behalf Of John Hurley Sent: Tuesday, November 24, 2009 10:05 AM To: classicrendezvous@bikelist.org Subject: [CR] Brinelling, False Brinelling, Fretting
Stimulated by the thread on headset brinelling, a quick internet search turned up a lot of information, including this interesting article:
http://en.wikipedia.org/
True brinelling is impact damage, in which the race material is pushed aside to form a crater around the ball bearing, without any loss of material. False brinelling has a similar appearance to the naked eye, but the mechanism is fretting, which involves wear and loss of material, with or without corrosion.
The following paragraph, however, I couldn't quite follow, and wondered if someone could comment or clarify:
"Until recently, bicycle headsets tended to suffer from false brinelling in the "straight ahead" steering positions, due to small movements caused by flexing of the fork. Good modern headsets incorporate a plain bearing to accommodate this flexing, leaving the ball race to provide pure rotational movement."
The writer may have ventured out onto thin ice here.
John Hurley
Austin, Texas, USA