Philes' Forum by Vic Lucariello

Hello, Bimmerphiles! This month I continue my 'few comments' on trailering.

Last column, I suggested that you consider more than the tow vehicle manufacture r's published towing capacity when choosing a tow vehicle. I forgot to mention an important factor. Carefully review how the manufacturer defines towing capability. You will probably find that the rated tow capability includes the weight of the loaded trailer plus the weight of passengers and cargo in the tow vehicle itself. This would mean, for example, if you wanted to pull a trailer which weighed [loaded] 5000 lb. [typical for a steel open trailer carrying an E30 or E36 Bimmer], and you carried 1000 lb. of cargo and passengers, the required tow capability would be 6000 lb., not 5000.

Remember, too, that the tow capability will likely be affected by the transmission you choose, with automatics typically rated higher than manuals on light-duty vehicles. I think this is because the manufacturers are concerned about clutch life in the manuals. The consensus seems to be that automatics are preferred for towing. [I wouldn't know about this as I don't know how to drive an automatic.] If you do choose an automatic, I recommend an additional transmission oil cooler, which may already be included in the manufacturer's towing package.

The so-called 'tow package' is a must in my opinion. Typically included are:

1. Increased capacity alternator and battery.
2. Increased capacity cooling system.
3. Modified electrical power distribution with isolation fuses and relays for the trailer electrics.
4. Additional automatic transmission oil cooler. Most slush boxes come with an oil cooler mounted inside the radiator. The two package sometimes adds an oil-to-air cooler in front of the radiator or A/C condenser.
5. Wiring for the trailer electrics, including a heavy-duty, 7-pin connector.
6. Hitch receiver bolted to vehicle frame.
7. Heavy-duty turn and hazard lamp flashers.
8. Engine oil cooler.

On the trailer itself, some options you should get are:

1. Dual axle electric brakes. Some trailers have single-axle brakes as standard equipment. Some aluminum trailers come with hydraulic surge brakes. Despite all their problems, I think the electrics are superior.
2. Break-away kit with safety chains. The kit comprises a small 12-volt battery and a break-away switch which are supposed to activate the trailer brakes, and keep the trailer behind you, in the event of a failure of the hitch ball or trailer coupler. The safety chains are supposed to keep the trailer attached to the tow vehicle in the event of a similar failure.
3. Removable fender so you can open the driver door while on the trailer. Just remember to remove the fender before you drive onto the trailer. DUH!!
4. Back-up lights.
5. Extended ramps. If your trailer is available with ramps which slide into position for loading /unloading, get them. Ask Big Al about the time he grabbed one of my trailer ramps, which don't have this feature, and helped me put them in position.
6. Load-distributing hitch. [Especially if you use a SUV for towing. Heavier duty vehicles are less likely to need this.] As the name implies, a load-distributing hitch [AKA: load-equalizing], takes some of the trailer tongue weight [the weight you would measure at the trailer coupler] from the tow vehicle's rear axle and adds the load to the vehicle's front axle and the trailer axles. This allows you to increase the percentage of tongue weight [typical recommendation is about 10% of the loaded trailer weight] and increase the highway speed stability of the rig.
7. Anti-sway control. [Again, especially if you use a SUV] This is basically a friction-type dampener which helps to reduce trailer sway and oscillation, especially under 'pucker' conditions when you are trying to avoid that ciucione who just cut you off!

Finally, I recommend you do a quick brake test on your electric brakes whenever you use the trailer after it has been sitting a while. It only takes a few minutes and counts as 'quality time' with your spouse or children.

First, check that your break-away battery is fully charged. On the rechargeable batteries, you should measure a terminal voltage of 12.6 volts. Next, plug the trailer connector into the tow vehicle and jack up one side of the unloaded trailer so that both wheels are off the ground. Check that both wheels rotate freely and give them a shake to check for loose bearings. Now, unplug the trigger cable from the break-away switch, and you shouldn't be able to turn either wheel more than 1/2 turn before it locks. Replace the trigger cable in the break-away switch, and have your assistant apply the trailer brakes via the manual switch on the brake controller in the tow vehicle. Again, the wheels should lock. Repeat for the other side.

This quick test establishes that all 4 trailer brakes, the controller, and the break-away system are operating. The test is very worthwhile. Ask me how I know this!

Anyone wishing to contribute to Philes' Forum should contact me via the info on the masthead. I'm interested in tech tips, repair /maintenance questions and/or tips, dealer horror stories, product evaluations, etc. Please call before 8 PM, and if you leave a message, PLEASE INCLUDE A PHONE NUMBER WHERE I CAN REACH YOU ON WEEKDAYS. Also, please be patient, I try to return every phone call, but it sometimes takes a while. If you don't hear back from me within a few days, please call again. The best way to contact me is via e-mail.

Copyright 1999 - V.M. Lucariello, PE