Tamdem axle conversion--road test

[bscott]

We just ended the season Tues. and pulled the boat onto our newly converted 01 Mac tandem axle trailer. The trip from Lake Granby home is only 95 miles but it requires climbing Berthoud Pass from about 8300' at Winter Park Ski area to over 10,000' and down to I-70 with three other climbs until home.

I had the shop install a slidding angle to which the axle walking beam were fixed above the frame to allow movement of the tandem axles along the frame to give me the best tongue weight. The walking beam placement was 6" aft of the original single axle location. The slider really stiffened up the frame. Surge brakes on both axles. I replaced the the original 3,500# springs for 2,500# for a better evenly weighted boat ride. The new axle is rated at 3,500#.

The original tires were Carlisle ST 215/75D-14/C1 which were 6 mos old so I bought 3 same tires from Discount Tire and balanced all 5. Aired them to 50 PSI at 5,300' alt.

Tow vehicle, 03 Jeep GC, V8, 3" lift with rear air bags aired to 6#. I forgot to air up my Jeep's rear tires so I was at my normal 35#. I usually go to 40# on a tow.

We had no idea if the balance was good but I had 9 gallons of fuel in the aft lockers and a 260# E-tec on the stern. All the typical stuff in the cabin.

Within 3 miles of the lake is a rather long down grade that I always took at about 45/50 mph in the past, but this time at 60---no sway, no nothing. My wife remarked that the Jeep rode smoother, no bucking or sway. Even with 400# on the ball, my single axle was not smooth and it did sway on this stretch of roadway.

The next big test was the downhill on Berthoud Pass to I-70, lots of swithch backs, and 8% grades with a few passing zones so cars will que up behind you if you don't do at leat 45 mph. I did have an "oh $het moment" on one hard right that the surge brakes scretched but did not lock up the wheels. Soon I forgot that I had almost 4,000# on my bumper.

I-70 during the week is like Indy--truckers going to Denver seem to be in a hurry so riding the right lane at 60 mph is like being a moving target. In the past I drove this at 55 anticipating several adult beverages at home as my "home safe" reward.

The first Digby truck passed me at about 70. In the past the boat would get pushed to the right and then get sucked back as the truck passed. This time nothing! After a few more trucks, I set the cruise to 65 and began to enjoy the ride with my wife secure enough to take a long nap.

The last part of I-70 is Mount Vernon Canyon which is a long, curvey, steep decline that trucks over 30,000# gvw are limited to the right lane @ 35 mph. At least that's what the Warning Signs say.
I have seen numerous camper trailers and semi-trucks meet their demise on this stretch and was wondering how my rig would fair. There is the original US 6-40 that I could take which is a constant 3% grade into Golden but that is now the gambling/drunkard main road to and from the gambling towns of Blackhawk and Central City so I had to decide, drunks VS out of control trucks.

Since I'm not a gambler, I went with the out of control truck crowd anticipating an interesting roller coaster ride. Boring--everything worked--surge brakes did not over power the Jeep at 50 mph, changing lanes worked, it was almost fun! When I pulled into my driveway at home I was suprised to find that the tires and wheel bearings were just warm to the touch with no grease splattering anywhere.

The reason for the tandem conversion was tire/axle redundency for anticipated long road trips into the future. I was also anticipating trading the Jeep for a longer wheelbase tow but this trip down the hill convinced me the Jeep could handle the job. Now I am thinking we might take my wifes 07 Dodge Grand Caravan to Texas next spring. Throw on a trans cooler, some air bags and hope the traction control can pull the rig up those sandy boat ramps---hello AAA.

Bob

[March]

Thank you for the report, Bob. I am thinking about that mod, too, come spring.

Careful with the Caravan. It will get the job done all right, but only marginally so. I trailered my Mac happily with a Caravan for three years (no swaying or nothing), and never had any major problem, but the engine tended to overheat on a serious upslope (+10 miles long). Had to pull to the side and wait for the engine to get back from the red. After that, no problem. Nothing unmanageable, but I feel more confident with a jeep rated for 5,500. I was also lucky NOT to have any transmission problems--a notorious weak point with Caravans. The additional transmission cooler will help, of course, but why push your luck. The plus side is, the Caravan was more economical gas-wise, but now that I have a 4 wheel drive, I wouldn't go back.