If it is "not enough downforce to upset the balance of the car" then I would be shocked if what you are feeling is caused by the bumper at all.

 

Eh? Are you saying this front bumper is some how going to generate more rear lift? Am I missing something here? A front bumper with more elaborate integrated splitter may generate some more front downforce or reduce front lift, but it isn't really going to increase rear lift. If anything it might decrease rear lift a little bit since less air is getting under the car and making it to the rear and getting trapped. It could definitely change the balance and add more front grip, but saying it is "lifting the rear" and reducing rear grip isn't really accurate. You still have the same amount of grip in the rear as before, you just now have extra front grip.

 

The C west bumper was designed, and proven to increase front downforce. So whether I feel the downforce or not, it does provide downforce on paper. As Andrew stated, assuming no rear spoiler would offset the balance of the car, isn't accurate whatsoever.

 

basic downforce

Front end downforce by protruding the area of pressure (Splitters, extended bumpers) will cause the car to over-steer. The front end pressure will lift the rear through corners.

Rear End downforce by raising a plane for area of attack (GT Wings) will allow pressure to press the rear down; thus bringing the tires down to the ground.

Drag: Undertrays, and diffusers are meant to prevent the cause of drag. Together form clean air flow under the car and a low pressure system (A front bumper alone will not allow this) ultimately also causing downforce. Trunk link spoilers are to help clean air flow over the rear of the car assisting in less drag.

Trapping air pressure on AOA's will effectively bring the car closer to the ground, and more tire contact. This is what allows you to round corners at high speeds. Its all about grip, and reaching the lbs of pressure. This is vehicle harmonics, and understanding it is what will allow you to have a high speed straight line, and high speed corner. take a 500 lb car that produces 500 lbs of DF. then at speed generating that that DF (which it is built to do) the car can drive on ceiling.

If you want more basic info
http://www.up22.com/Aerodynamics.htm

 

I think I understand the concept of downforce, and the balance between front and rear downforce on a car. That being said, the front bumper makes absolutely no difference in the balance of a street driven car. My advan rg2 255/40/17 square setup makes the car extremely oversteer prone (much more than that bumper ever could, at every speed), and I still have no need to slap an ironing board to my trunk.