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141.99 MPH With A Trailer!

The Ultimate Tow Test!

Text By The Diesel Power Staff, Photography by The Diesel Power Staff

At one point or another, most diesel enthusiasts have towed something. Whether it’s a tractor towing a hay wagon at 5 mph, or screaming down the freeway at 80 mph with a fifth-wheel, having a trailer behind us is something we can all relate to. So we set out, nearly a year ago, to prove that diesels can tow better than anything else by breaking the current land speed record while pulling a travel trailer. Before we get into the attempt, a little history. In the ’90s, British automotive journalist Mark Walton drove a Dodge Viper pulling a travel trailer (also known as a caravan in other parts of the world) to 126.7 mph to establish a modern World Record speed. In 2002, a highly modified escort rally car bumped the record to 128.8 mph. In 2003, the record took a big jump, as the combination of a 2-mile-long South African runway, a 700hp twin-turbo Mercedes, and an aerodynamic caravan meant a 139.11-mph record.

The record had stood at 139.11 mph since then, but not for a lack of trying. The British-based TV show Top Gear tried to break the record (then at 128.8 mph) with a modified Mitsubishi EVO, only to run 125 mph before blowing up the engine. More recently, an unnamed European company attempted to break the 139-mph record with a Porsche Cayenne S Turbo, only to have its aerodynamic trailer come off the ground at speed! In the last few decades, the record had moved around from Australia to Britain to South Africa, so it’s clearly an international record—and not an easy one to break!

The Plan
We needed a plan if we were going to tow faster than anyone else on the planet—and some crazy friends to help us along the way. We found those partners in Pacific Performance Engineering (PPE) and Carson Trailer, which builds a wide range of campers, car trailers, and toy haulers. For our haul truck, PPE would be bringing The Sleepermax out of retirement. The truck already had aftermarket connecting rods and pistons to make it survive at its 744-rwhp state, but for record-breaking speeds, additional horsepower had to be on the table. To that end, the GT4094 and GT45 turbochargers were swapped out for PPE’s big compounds—mammoth GT4202 and GT55 turbochargers—along with dual wastegates to keep boost in check. A set of Exergy Engineering injectors provided 100 percent more fuel capability than stock, while a Nitrous Express (NX) dual-stage nitrous system was on hand in case we needed the extra horsepower.

For the trailer, we were understandably worried about aerodynamic stability, sway, and the trailer otherwise getting loose on us. To complicate matters further, we couldn’t use any type of sway control for the record attempt. In an effort to remain aerodynamically neutral (no lift or downforce), we chose the Carson Kalispell trailer. It was light, used a single axle (less rolling resistance), and was of 140-mph build quality. The Carson trailer was a perfect embodiment of a record-setting trailer in that it was compact (only 7½ feet wide and 10½ feet long), but it retained full amenities, including a bed, fullsize refrigerator, and kitchen appliances—all for about $10,000.

Choosing Tires
Our greatest fear during this attempt was crashing at 100-plus mph, so we spent a whole lot of time researching where the rubber meets the road. After speaking with many different manufacturers, some of which simply said “No way!” we finally settled on a set of 305/50R20 Toyo Proxes ST IIs mounted on 20x10 BMF wheels. The height of the tire would increase our overall gear ratio and give us plenty of rpm for 140-plus speeds, while the 20-inch wheel diameter would give us a smaller sidewall for more stability and a greater weight rating. Considering we’d be hustling a 7,000-pound truck along at triple-digit speeds while towing a trailer, all of these were very desirable traits. The final piece of the puzzle was speed rating, and since the Toyos are rated at 149 mph, we knew we’d be safe.

The trailer tires also had to be specially ordered, as traditional trailer tires are built for strength rather than speed and are actually only rated for 65 mph. For the trailer, we selected tires originally meant for a heavyweight sports sedan—a set of Goodyear Gatorbacks. They were rated for the speed we wanted to go, and each could support 1,477 pounds of weight.

Doing the Math
With the truck and trailer prepped, we had to make sure we could actually break the existing record, and that’s where a fair amount of math came in. While we could have lowered the truck, put on racing tires, and made numerous aerodynamic modifications to make it look like a pure race vehicle, we decided to see if we could break the existing record just as one would normally drive down the road. After all, as former Editor David Kennedy said: “Race vehicles look like a race car driver could drive them…a normal vehicle looks like anyone could drive it.”

So if we were going to eschew the aerodynamic modifications, we needed a way to figure out how much power we’d need to move our brick towing a brick through the air. For this, an online calculator ( proved very helpful. While we also used three or four other computer programs to back up the math we found on RBR’s website, the calculations said we’d need more than 1,000 rwhp to go 140 mph, based on a drag coefficient of .60 (which is bad) and a frontal area of 75 square feet (which is even worse). As it turned out, RBR’s calculator was almost dead-on.

140-mph Towing: How it Applies To You
When we first introduced the idea of high-speed towing months and months ago, we got a whole flood of letters supporting our attempt, but we also got a surprising amount of backlash. “I have no idea why you’re doing this, I just want better fuel economy,” one reader wrote. Another indicated he didn’t think anything we did would apply to him.

As it turns out, virtually everything we did to break this world record can be thought of in normal, over-the-road terms. Aerodynamic load and drag holds a direct correlation to fuel economy. Building an efficient engine is another key to both towing with power, and fuel efficiency. While our EGT limit was sufficiently higher than we’d ever recommend to anyone, there are similarities there, too. While you might not tow with nitrous, well-matched turbos (especially compounds) are very important to towing combinations. Load and speed rating of tires are a direct crossover, as is trailer tongue weight.

We didn’t just do this stuff because we could—we did it for all you readers, too. While you might not want to tow at 140 mph, everything it took to get the truck and trailer there can be directly applied to a normal, 55-mph towing effort.

By The Diesel Power Staff
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Jay Toolman
Jay Toolman

I have a hard time keep up with the traffic on the highway with my trailer because everyone drives so fast. Maybe I should take some notes from what you have done here to be able to tow a little quicker. I love camping, just not getting passed on the freeway by just about everyone.