1999 Subaru Impreza Owner's Manual - Page 228

The tongue load can be adjusted by proper distribution of the load in the trailer. Never load the trailer with more weight in the back than the front; approximately 60 percent of the trailer load should be in the front and approximately 40 percent in the rear. Also, distribute the load as evenly as possible on both the left and right sides. To check both GVWR and GAWR and to confirm that the total weight and weight distribution are within safe driving limits, you should have your vehicle and trailer weighed at a commercial weighing station. Be sure that all cargo is firmly secured to prevent a change in weight distribution while driving. J Trailer hitches WARNING Never drill the frame or under-body of your vehicle to install a commercial trailer hitch. If you do, dangerous exhaust gas, water or mud may enter into the passenger compartment through the drilled hole. Exhaust gas contains carbon monoxide, a colorless and odorless gas which is dangerous, or even lethal, if inhaled. Also, drilling the frame or under-body of your vehicle could cause deterioration of strength of your vehicle and cause corrosion around the drilled hole. D Do not modify the vehicle exhaust system, brake system, or other system when installing a hitch or other trailer towing equipment. D Adequate size trailer brakes are required when the trailer and its cargo exceed 700 lbs (318 kg) total weight. Choose a proper hitch for your vehicle and trailer. SUBARU does not offer accessory trailer hitches. Consult with a professional hitch supplier to assist you in choosing an appropriate hitch for your vehicle. Be sure to follow all of the hitch manufacturer's instructions for installation and use. CAUTION 7-46