I have a 2008 Ford Expedition, short wheel base. What can I do to eliminate a bucking bronko sensation when I am towing my 2008 Nash Travel trailer on a concrete highway. This sensation doesn't happen when I am towing on a asphalt highway or when driving solo on a concrete/asphalt highways. My trailer weights 7250 lbs. and has a tongue weight of 860 lbs.,(12%). The distance between the hitch ball and rear axle of the tandum axles is 223 inches. This is less than 2x the tow vehicle wheel base of 119 inches. I have installed rubber equilizers between the tandum axle springs to no avail. I used to tow this same trailer with a Chevrolet Suburban and had no bucking sensation. I welcome any solution to this problem.

 

You havn't mentioned that you're running weight distribution bars or not. Obviously the seperations in the concrete slabs being uneven are causing the truck to porpoise up\down. If you do have the bars, perhaps add an air shock system to stiffen the rear when towing. The combo of a short wheelbase and soft springs in the rear of that expy gives it a "high seas" ride.

 

Thank you for responding so quickly. I did forget to mention that I do run with 1000lb. weight distribution bars. Also, I have antisway slide bars. This is my own oppinion, but I think the independant rear suspention has a lot to do with the problem, plus coil springs. I am surprised that other expy owners haven't experienced this kind fo problem. I will try Air shocks or air bags.

 

What tires do you have on the Ex? Load rating, max inflation pressure, running psi, etc? Under rated / under inflated tires can act like springs.

You should also check to make sure your WDH is set up properly.

 

Thank you for responding so quickly. I have had my WDH set by a business that installs hitches and they set the bars. My Ex has P265/R70 17. I have them balanced as well as the trailer tires. I am thinking of up grading to LT265/70 17 tires. They are a little stiffer. Do you think that would help?

 

Absolutely! The "P" signifies a passenger car tire. You need a "LT" tire if you are going to do any towing at all.

 

I run LT load range E tires with a max inflation pressure of 80psi. I run 60psi unloaded. If I don't air up to 80 on the rear when I tow heavy, the handling is crap.

 

Do some research and go to a reputable tire dealer. Get the right tires for what you are using the truck for. It may not fix your problem 100%, but you will feel the difference.

 

With the P(Passenger) series, you really have no sidewall to speak of, it's like riding on balloons. The LT(Light Truck) should take a good bit of the bounce out. It will increase ride harshness a little, and will most likely harm your milage as well. When I'm not towing I lower the air pressure to soften the ride some.

 

Those are very good suggestions. When I towed my 6k TT with both the '97 and '03 expy's, I ran LT's. Michelin LTX and BF Goodrich's treated me well with great mileage and handling qualities. The more weight I had in the truck the better too. 5 of us in it plus gear would compress the springs somewhat so I'm sure that helped.