On Apr 25, 2006, at 3:16 PM, Mark Bulgier wrote:
>
> 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
I use a long straight edge (long piece of whatever wood is handy) and
line that up with the centerline of the stem quill, upper and lower headset, fork crown and finally upper fork leg... looking from the side. Then I measure over to the axle. Close enough is, well, close
enough, since we are just comparing dimensions between frames to get a rough idea how they measure up.
The last time I suggested to the CR list that it might be fun and informative to measure their frames for comparison purposes I just got a lot excuses why they couldn't. I was interrupting their eBay®
discussion I guess...
Chuck Schmidt South Pasadena, Southern California
.