Braking would cause shimmy from the warped disks, but it also puts more weight on the nosewheel, which could be the cause of the shimmy.  So even with perfectly straight brakes, you still add some forces to the nosewheel when braking.  When we apply brakes at high speed right after touchdown we always have full aft stick to keep the weight off the nosewheel, but when we slow to about 30 KIAS we lose elevator authority and the full aft stick has little effect.

 

I landed recently with two people in the front seats and only 20 gals of fuel, just a couple bags in the back and got the gently shimmy when braking.  It went away as soon as I let off the brakes.  My ES is close to the forward CG limit with that loading.

 

Flying home from Oshkosh, I was heavy, three people, baggage compartment to the roof with another bag in the fourth seat, CG further aft than I've ever had it.  I could tell by the sensitivity of the trim among other things.  No shimmy at all.

 

I think the weight on the nosewheel is a contributing factor.

 

Mike Easley