2021 Ram 1500 TRX
Patrick Rall's picture

One Simple Reason Why the Ram TRX Only Goes 118

Many people are hung up on the fact that the 2021 Ram 1500 TRX will “only” go 118 miles per hour, but this relatively low top speed is due to the fact that off-road tires don’t have the high speed ratings of on-road tires and the automaker can’t offer a vehicle with a top speed that is higher than the speed rating of the tires.
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When FCA introduced the 2021 Ram 1500 TRX earlier this month, the performance truck market finally had the Hellcat-powered pickup that they had been expecting. It has the look of the concept complete with the optional bed-mounted spare tire carrier and the rollover bar. It has more interior gadgets than any truck on the market, including other Ram 1500 models and, of course, it has the supercharged Hemi.

With 702 horsepower and 650 lb-ft of torque, the Ram TRX packs the monster power that we had all hoped for, allowing it to offer impressive acceleration numbers for a huge off-road truck. It will sprint to 60 in the mid-4-second range and 100 in the mid-10-second range, while covering the quarter mile in the high 12s. The power and acceleration numbers are better than any truck on the market today and the TRX is also faster than any truck on the market today with a top speed of 118 miles per hour. However, some people expected this half-ton pickup to offer an insane top speed similar to that of the Jeep Trackhawk and Durango Hellcat, both of which will hit 180.

Some of the critics can’t comprehend how a truck with over 700 horsepower will only go 118, but it isn’t an issue of the Ram 1500 TRX not being able to go faster. It is electronically limited based on the speed rating of the tires, which is required by law.

Speed Ratings on Tires
Every tire sold in the United States has a speed rating, which is the highest speed at which the tire can safely operate. The faster a vehicle is moving, the more outward forces are being applied to the tire. High performance tires are engineered to withstand the extreme forces created at high speed, as well as the heat that is created by friction on the road at high speeds.

2021 Ram 1500 TRX

For example, the Pirelli PZero tires that come from the factory on the Dodge Challenger and Charger SRT Hellcat have a (Y) speed rating, which means that they are rated for speeds in excess of 186 miles per hour. Both of those cars are capable of going over 200 miles per hour, so they need the highest speed rating available. The 2018 Challenger Demon reached buyers with Nitto NT05R drag radial tires which have a W speed rating. Tires in the W class are limited to 168 miles per hour, so by law, Dodge had to electronically limit the top speed of the 9-second muscle car to just 168 miles per hour. This was the only option, as there is no 18-inch drag radial tire on the market with a higher speed rating.

The same issue is affecting the 2021 Ram 1500 TRX. There are no DOT-approved (street legal) tires that offer the off-road grip needed by this monstrous pickup with a higher speed rating. As a result, the 702-horsepower super-truck is limited by the T speed rating of 118 miles per hour of the Goodyear tires.

Ram TRX Could Be Much Faster
While the 2021 Ram 1500 TRX is electronically limited to 118 miles per hour due to the speed rating of the tires, it really could go much faster with a few fairly simple modifications. First and foremost, if a TRX owner wants to go well beyond 118 miles per hour, they need to buy tires that are intended to go very fast on paved roads. For example, a TRX owner could start by buying 20-inch wheels that would work with a set of Jeep Trackhawk P295/45ZR20 Pirelli PZero tires, which have a speed rating of 186 miles per hour.

2021 Ram 1500 TRX

Next, the electronic speed limiter would need to be removed by a tuning shop. This would entail buying an unlocked PCM (or having the factory PCM unlocked), followed by some tuning magic that removes the speed governor. Keep in mind that going this tuning route to raise the top speed wouldn’t necessarily mean that the TRX was getting more power, but that would be an option while it is at the tuner as well.

One the 2021 Ram 1500 TRX was fitted with tires with a higher speed rating and a tuner has removed the speed limiter, we expect that this 702-horsepower half-ton will go well beyond 118 miles per hour. How far beyond? We aren’t really sure. According to FCA, the Trackhawk has a curb weight of roughly 5,400 pounds and the TRX weighs right around a thousand pounds more. The Trackhawk will go 180 with the same engine and transmission as the Ram 1500, but the truck weighs more and is less aerodynamic. When we factor in the added weight and the reduced aerodynamics, we would guess that the TRX will still get to 150 or more on a long pull, but we don’t know how much faster it would go with the added weight and such.

2021 Ram 1500 TRX

Fortunately, we can bet that at least one 2021 Ram 1500 TRX owner will install on-road performance tires, tune-out the electronic speed limiter and see how fast it will really go. All we know for sure is that it will definitely go well beyond 118 miles per hour.


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