On a short overnight trek yesterday and today, I tried adding front panniers to the mix. The bike was fully loaded as I'm testing out how to load everything for a tour this summer where I'll need to carry more gear and food than in the past.

Usually I've carried most of my load in the rear panniers, with a handlebar bag and sometimes a tent, tarp and spare water bottles on the front rack. This time, the tent was on the rear rack and the food and camp kitchen supplies were in front.

I've tried to have the load balanced right and left.

Most of the time, it wasn't bad, but if I picked up speed the front end would start to shimmy a bit.

Any ideas what would cause this and more importantly how to prevent it? Coming down a hill and wrestling with the front of the bike is a bit unnerving to say the least.