[Classicrendezvous] Rear wheel spoke breakage, was Maillard Helicomatic question


Example: Framebuilders:Mario Confente

Date: Sat, 30 Sep 2000 21:41:14 -0400
To: Jerry & Liz Moos <moos@penn.com>, Thomas Adams <kctommy@email.MSN.COM>
From: Harvey M Sachs <sachs@erols.com>
Cc: classicrendezvous@bikelist.org
In-Reply-To: <39D653A4.CA53F197@penn.com>
References: <001801c02aaa$ea06e060$92ff2e3f@tom>
Subject: [Classicrendezvous] Rear wheel spoke breakage, was Maillard Helicomatic question

>Thomas Adams wrote:
>
> > I can't recall exactly where or from whom I heard it, but the reuptation of
> > the Helico's is that they break spokes of the freewheel side of the
> rear hub
> > with alarming regularity. Something about the hub flange being too far
> > inboard and wrongly shaped. I can't say from my own knowledge as my only
> > Helico experience was with the wheels on a Trek 720. The rear wheel had 40
> > spokes and never gave me trouble. I only stopped riding it because the
> rear
> > cogs wore out and replacements were unobtainable.

In my experience, a major contributor to right side spoke breakage is having the left flange too far outboard. I have an old Normandy HF with the left flange 11 mm (almost 1/2") further left than on the later model. (Came from my first "Ted Williams Sport Special" - Sears, with Campy derailleurs). The key here is simple: When the left flange moves outward, it increases the angle between perpendicular to the axle and the spoke. To balance the forces, and get an equivalent component of tensional forces along the axle, the right spokes have to get a lot tighter. The flatter the "cone" of the right spokes on the dished wheel, the more tension. Even a "regular" wheel can have twice the tension on right spokes as on left. It is counter-intuitive, but rear hubs should have their flanges spaced closely. In contrast to a front wheel, there is very little sideways deflection of a rear wheel unless you slide into a curb partway upright.

Incidently, that ratio of forces was the justification for the famous 42 spoke Hi-E wheel, with 14 left spokes under about the same tension as the 28 right ones.

Your myths may vary...

harvey sachs
mclean va