I have front pannier racks on my Bike Friday Pocket Llama , and 'Season Tikit' .. and use the front bag support foe luggage on my Brompton M3L...



FWIW a Porteur bike was a bike designed especially around quickly getting bundles of the latest edition of French newspapers to the news Agent's Kiosk

around the cities like Paris..

Having a lower trail helped the bike handle well and quickly with a front rack carrying several heavy bundles of newspapers..






....
Basically since the 2 lines that make up trail , on the ground, cross each other above the ground, If the 2 input factors remain the same..
Head tube axis and fork offset, axle plumb line ..
with a smaller diameter wheel, that crossing point is closer to the ground and so trail must be less..





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