Fork trail question
 

Hi all,
after a crash I have to replace my forks but the bike shop says there are no new ones available and they want to take one from a demo bike and fit it to mine. My caad12 is size 50 with a trail of 63 mm, offset 45 mm, head tube angle is 72, the demo bike is size 56, with a trail of 56mm, same offset, head tube angle is 73.1. Does it make sense to take the fork from the bigger bike? How will it affect the handling of my bike? From my limited understanding fork trail has a big impact on handling, will it be twitchy and unstable or slow ?
thanks in advance

If the crown to axle length is the same or very close, it will handle identically. Trail is affected by Head Tube Angle and Fork Offset. In your case the bike is the same, so HTA doesn't change. The offset on the new fork is the same as your old fork. It's essentially an identical swap. The crown to axle length may vary by a few millimeters, but this will affect trail less than a millimeter.

Manufacturers usually use the same fork over the range of sizes, so it will be an identical replacement. The important factors are the axle to crown height and the fork offset, which are the same in this case. As Taras has already said, the trail number is a result of the head tube angle and the fork offset. The difference in trail, that you are seeing on the chart, is due to the different head tube angles of the frames in question.