[CR] Measuring fork rake (offset) [was:The mighty PX-10 ]

(Example: Framebuilding:Tubing)

Subject: [CR] Measuring fork rake (offset) [was:The mighty PX-10 ]
Content-class: urn:content-classes:message
Date: Tue, 25 Apr 2006 15:16:50 -0700
Thread-Topic: [CR] Measuring fork rake (offset) [was:The mighty PX-10 ]
Thread-Index: AcZorCG5EixsDUyqTXiC4nP8piM80wABvWeQ
From: "Mark Bulgier" <Mark@bulgier.net>
To: "classicrendezvous Bike List" <classicrendezvous@bikelist.org>


Chuck "why not ride a Masi" Schmidt wrote:
> Measuring fork rake (offset)??? Straight edge alongside the fork
> centerline and a ruler (scale) from the edge to the axle center.

I'd like to add that you need to measure from the steering axis, which often enough is not the center of the fork blade. Forks can be bent, or quite often were simply brazed at a slight angle originally. The steering axis is defined by the headset bearings - so make sure your straight edge is laid alongside the centers of the upper and lower HS cups. Measure perpendicular to the straight edge, not parallel to the ground. Do this on the right side of the bike, because QR cones are easier to see the center of, than the lever side

Holding the straight edge right along the steering axis is difficult to do precisely, especially on small frames where the cups being closer together magnifies any error, out where the rake is measured. So just accept that whatever number you get is approximate. You should be able to get to the nearest half-centimeter though, which is good enough - it's hard to tell the ride difference with rake differences smaller than that anyway.

VAR made a tool to measure not only rake, but trail as well. Yes you can calculate it, but the VAR tool measured it directly - clever.

Mark Bulgier
Seattle WA USA