Re: [CR] Brinelling, False Brinelling, Fretting

(Example: Framebuilders:Cecil Behringer)

Date: Tue, 24 Nov 2009 16:25:33 +0100
From: "M-gineering" <>
Cc: <>
References: <249DDD9704676C49AE6169AE3D2D9F4ECDB91E@Exchange-SVR>
In-Reply-To: <249DDD9704676C49AE6169AE3D2D9F4ECDB91E@Exchange-SVR>
Subject: Re: [CR] Brinelling, False Brinelling, Fretting

John Hurley wrote:
> Stimulated by the thread on headset brinelling, a quick internet search
> turned up a lot of information, including this interesting article:
> 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.
> Shimano headsets have inserts with a curved exterior which allow some self alignment. This is supposed to take care of all the load bearing on only a few bearings when the steerer flexes

-- mvg

Marten Gerritsen
Kiel Windeweer