I have a strong memory of my first overnighter on “Bernard” my Gilles Berthoud Adventure Touring Bike. I loaded him up the same way I had always loaded “Sky” my Rivendell Bleriot. I pushed off and on the first small down hill immediately noticed a pronounced shimmy in the front wheel. WTH?, I got off checked to see that all was attached correctly, it was. I fought the shimmy the entire day (I should note that the Bike Hermit was not on this ride with me.) The return the next day was a bit better but not much. I was crushed, thinking I had made a big mistake in buying this bike. I expressed my dismay to the Bike Hermit and his first words – “Stacy this bike has a low trail geometry, you can’t pack it the same way as you did your Rivendell”… “Oh”, I replied, “I didn’t know there was a difference between touring bikes.”
[Bike Hermit: “trail” refers to how far the center of the tire footprint on the road surface falls behind the imaginary point where the steering axis hits the road and it is a function of head tube angle, fork rake and tire size.]
One thing I have learned in the last 15 months is that Bernard performs best with the load distributed between the front and the back. He has these amazing custom Gilles Berthoud Racks that have low rails for panniers. For short trips, I don’t really want to carry 4 panniers along with my front bag so getting the weight balanced can be a challenge. On a short trip with a smaller load, I am better off with the weight being heavier in the front than the rear. Attaching panniers to the low rider rack in the front and then strapping my sleeping bag on the rear rack makes for a much smoother ride. Our recent trip to Texas I wasn’t really thinking and I had my lower rear rack but not my lower front rack so I had some challenges in getting my load balanced – I basically carried all of our food in my GB front rack bag. Then had the tent (sans poles) and my clothes in the rear panniers. Next trip I am going to go ahead and bring 4 panniers, putting the smaller ones on the rear and the larger ones on the front.
Obviously there are other design and construction details and considerations that affect how a bike handles when loaded. The type and design of racks used can affect handling too, as can the type and size and inflation pressure of tires. Most bikes billed as touring bikes should have the characteristics which will make them able to handle a load without becoming squirrely or unpredictable in handling. But every design will have its own unique nuances. Keeping in mind that an unloaded touring bike with rider aboard will have more weight on the rear wheel adds heft to the theory of biasing the added weight to the front of the bike.
The bottom line is that their are many factors which contribute to how a bike handles when carrying a rider and a passive load. That awareness means that, with some trial and error, it should be possible to optimize the load carrying setup on almost any bike.