[QUOTE=carfart;16600399]There's this from nooneline.blogspot.com: "The boildown is that head tube angle and fork rake work against each other in order to reach an equilibrium, a sweet spot of trail measurement (60mm, according to Don Walker). Overcompensating one because of a lack of the other is counterproductive: putting a road fork on a track bike with a steep headtube angle will make the handling less stable - the higher-rake fork reduces the trail measurement. ..."
This does not make sense. Trial is a function of 3 variables
Wheel Radius, which Soma states is 330.5 mm for the GR charts
HTA, via the sin and cosine, Soma states the HTA varies 72° to 73° for the GR
Fork Rake, which Soma holds constant at 69mm for the GR, probably to keep costs low
The Soma GR geometry charts show the trial does vary with frame size, due to the change in HTA with a constant rake
Frame Size(cm) HTA(°) Rake(mm) TRAIL(mm)
49.5 & 52 72 69 35
58 72.5 69 32
58 & above 73 69 29
The trail varies by 6mm, for Small to Medium size frames. You would need to INCREASE the Rake by 55mm to get a TRAIL of 29mm (same as the Medium frame) for the 2 Small frames, i.e a new fork.
All trails are in the "low trail' region, and less than say a Pelican at 40mm trail. It is hard to see how the handling is greatly affected due just to the HTA changes.
It is also hard to understand the "sweet spot" argument, if the trails are so close.