The TriVette 3 Wheel Car – Breaking All The Rules

Trivette 3 Wheel Car

When a country has its oil price go up over four times (America 1973, Oil went from $3 a barrel to $12) and the government starts talking about a fuel tax, people begin thinking outside of the box.  Bob Keyes was one of those people and he saw an opportunity to produce a 3-Wheel Car (Trike) to combat the problem. The Trivette Trike delivered four times the fuel economy of an average American car with an increase in handling and performance.

Bob Keyes was no backyard inventor. He was a physicist with many years of experience in the Aerospace and Defense Business, who worked on anything from flight simulators to assembly line robots. And, he was determined to give the world a new fuel-efficient vehicle. So, the idea of TriVette was born.

Why A Two Seater Car?

He found statistics showing that 93 percent of all vehicles (at least on California freeways) had only one occupant, the driver.  So that's a one and a half ton vehicle on average carrying around only 90kg person. Not much efficiency there.  Not much efficiency there.

Bob realised that the car’s cost had to be low due to massive inflation and the current recession. It also had to be very efficient due to the fuel shortage. It had to be practical, reliable and the parts had to be cheap and readily available.

Bob Keyes looked into 4-wheels, 3-wheels, and 2-wheels configurations. The vehicle had to be light with a low center of gravity and it needed to be protected from the weather and other traffic.

[TriVette Trike Front]

[TriVette Trike Side]

This analysis led to the selection of a 3-wheel, single front tire configuration as the optimum choice. This choice offers perfect opportunities for low weight, excellent aerodynamics, excellent handling and performance, and modest production costs. The TriVette was designed as a vehicle that was optimized to comfortably carry only the driver most of the time, in a fully enclosed, all weather vehicle with heater and optional air conditioning.

That was exactly what was needed to create a fuel-efficient commuter vehicle. A second seat is provided for the occasional passenger, or as a place for luggage, groceries, etc. The TriVette is classified as a motorcycle under American State and Federal laws.

Personally, I love the front view and the top view.  The side view however looks like a ladies shoe.  In the Vigillante Trike (see down below) he overcomes this look and the car has an all round good feel about it.

What Running Gear Did The TriVette Trike Use?

Most of the TriVettes used powertrains and other components from the Fiat 850's of the late 1960's/early 1970's. These were excellent powertrains that provided spirited performance and extremely good fuel economy.  In a 520kg vehicle the trike typically got 4.7 litres per 100km in heavy city traffic and 3.60 litres per 100km on the highway. Also, because of their light weight and excellent balance, they were a lot of fun to drive.  O-100 kmh speed was around 9 seconds.

[TriVette Trike Rear]

[TriVette Frame]

[TriVette Trike Side]

TriVette’s aerodynamics generate large down forces, hence the stability increases with speed. The vehicle’s center of gravity is low and close to the two rear tires, which helps to handle transverse cornering loads. When it gets to the physics, it is similar to the weight and balance proportions used when designing light aircraft.

How Did The TriVette Trike Handle?

In short, better than a Porsche 911s.  Road Test magazine tested a TriVette and published an article in the January, 1976 issue. Their numbers show that the TriVette reached .77 lateral "g" on the skidpad using Goodrich T/A street tires. Comparison with other vehicles in the review chart attached to the article shows that the TriVette actually out cornered a Corvette of that time by 10%!

It also out cornered an Alfa Romeo Alfetta GT, a BMW 530i, a Fiat X1/9, a Lotus Elite, and a Porsche 911S.  That is pretty spectacular handling for a 3-wheeled vehicle, which many people consider to be inherently unstable. Later testing by the Department of Transportation in 1980 determined that the TriVette had a theoretical tip-over limit of 1.28 lateral "g", or a .5 lateral "g" safety margin over what the tires could deliver. That means the TriVette will slide long before it reaches the tip-over limit. It also had the quickest transient response that they had tested.

[TriVette Trike Painted]

[TriVette Trike Blue]

Many previous 3-wheel vehicle designs have typically been oriented toward very low performance applications. Their physics were not suitable for high performance applications, but the TriVette demonstrated that with the proper physics, 3-wheeled vehicles can be designed to have excellent handling. This is also what made them so quick and agile and fun to drive in traffic. Also, the aerodynamics generated large down forces, so the stability increased as the speeds increased. The physics of high performance 3-wheeled vehicles requires that the center of gravity needs to be close to the two tires that can handle transverse cornering loads.

The height of the center of gravity must also be kept low to control transverse weight transfer during cornering, as well as fore/aft weight transfer during acceleration and braking. The physics is similar to the careful weight and balance calculations that must be used when designing light aircraft. Also, like in light aircraft design, the highly variable loads of fuel and a passenger must be located close to the center of gravity so they will have minimal effect on the handling as those loads vary.

Why Select A DELTA Configuration For The TriVette Trike?

The primary reasons for selecting the delta (single front tire, two rear tire) configuration for the TriVette (vs. the single rear, two front tire configuration or Tadpole) are improved performance and handling. During maximum acceleration, weight is transferred off the front tire and on to the rear drive tires. That increases the percentage of the total vehicle weight on the drive tires, and increases the maximum acceleration capability. The Turbo TriVettes had enough thrust that they could momentarily jerk the front tire off the ground, but careful weight and balance calculations ensured that it could not be held off the ground. Sufficient weight remained on the front tire to provide steering control during maximum acceleration. This provides nearly the acceleration capability of an all-wheel drive design, but without the cost, complexity, power consumption, and weight of all-wheel drive.

[TriVette Trike Model]

[TriVette Trike Body Form]

[TriVette Trike Frame]

During maximum braking, weight is transferred from the rear tires to the front tire. At maximum braking, the TriVette ends up with approximately 1/3 of the weight on each tire. Again, the height of the center of gravity, the fore/aft location of the center of gravity, the wheelbase, and other factors are carefully calculated to achieve this result. Even in a full lockup stop on wet or slick pavement in a corner, the TriVette will not spin. That's because more than half of the braking is still being done by the rear tires behind the center of gravity, so the vehicle is in a dynamically stable position. The TriVette will out-brake even high performance conventional vehicles, particularly on slick surfaces.

This design also allows a very light static loading on the single front tire, so a very quick 12 to 1 ratio can be used without power steering--again, saving cost, complexity, power consumption and weight. The forces are so light that it can be turned easily with a small steering wheel at rest for parking and requires only two fingers to steer on the freeway. This design also makes possible a front suspension design that has no bump steer, and one which can turn sharply enough to provide a very small turning circles with a long wheel base.

The long wheel base provides an excellent ride for the driver, who sits in the middle of the wheelbase. It also provides excellent high speed stability. The long wheelbase does not cost anything in transient response, however, because of the very low mass on the front end and the very quick steering ratio. In fact, the front tire literally goes wherever you point it, even at the limit of adhesion on a skidpad. The transient response of the front end is so quick that it is easy, even for a novice, to stay ahead of the back end where most of the mass is concentrated. The physics of the TriVette design result in a very stable, quick and nimble handling vehicle.

[TriVette Trike Happy Customer]

[TriVette Trike Happy Customer]

[TriVette Trike Happy Customer]

With this kind of handling, it was not surprising that customers began ordering TriVettes with stronger motors. The company produced some Turbo TriVettes with approximately 220 horsepower turbo motors. The weight was still 1,140 pounds. This results in a street legal vehicle with 5.2 pounds per horsepower, or about 1/2 of that for a Corvette or other high-performance street vehicle. These vehicles would run 0 to 60 mph in 3.5 seconds and would run the 1/4 mile in 10.4 seconds at 140 mph. Stability and directional control at 140 mph was phenomenal.

All Hail The Vigillante Trike

This all led Bob Keyes to deciding to make a third incarnation of the TriVette and he called it the Vigillante (with two Ls). This was to be a race car built for the road and he knew that since he had the physics correct he could achieve absolute phenomenal performance.

(Excerpt from Vigillante Site 2006)

[Vigillante Trike Front]

[Vigillante Trike Roof Open]

[Vigillante Trike Top]

The Vigillante™ ("Vig™") is a third generation design vehicle that began with the TriVette™ in 1974. As with the TriVette, the Vig is designed as a vehicle that is optimized primarily for the driver (the same as a regular motorcycle). Like the TriVette, it also has a rear seat for the occasional passenger or luggage. The Vig carries the physics of the TriVette to the level of the ultimate street machine. The Vig is the quickest, fastest, meanest street legal production vehicle in the world. And, it is an American designed and built exotic.

The Vig is designed and hand-built just like a formula race car. It uses a very light weight aluminum, honeycomb, foam, and composite tub. The body work is a composite of aircraft fiberglass, Kevlar and carbon fiber in an epoxy matrix. The front and rear tubular steel subframes are extremely light weight. The suspension links are tubes with rod ends. The wheels are competition aluminum alloy. Everything is designed to be race car light and strong. The result is a street legal exotic that weighs under 1,500 pounds. That's 50 pounds lighter than an Indy car. Yet, the Vig runs small block Chevy motors up to 700 horsepower.  That's about the same horsepower to weight ratio as an Indy Car. Imagine driving an Indy car on the street!

Here's what the Vig will do with a high performance street motor and high performance street tires:

  • 0 to 60 mph in 3.0 seconds
  • The 1/4 mile in under 10 seconds at over 150 mph
  • 1 "g" cornering
  • Top speed over 200 mph
  • 60 to 0 mph braking in 120 feet


[Vigillante Trike Roof Open]

[Vigillante Trike 350 Small Block]

[Vigillante Trike]

Like the TriVette, the Vig uses tandem seating. This provides a long, narrow, aerodynamic body shape like a jet fighter. It also places the driver in the center of the vehicle and provides the driver with the fantastic feel and visibility of driving a formula car on the street. The driver can see out both sides equally well without having to look around a passenger, and driving in the middle of the lane makes left and right hand corners symmetrical, like in a formula car.

Optional fully enclosed or formula car open tops are available, or it can be driven as a completely open vehicle. Optional heater and air conditioner are available. These are not installed as standard items because they add weight. The instrument panel displays seven analog gauges, all fully visible from the driver position without interference from the quick-release steering wheel.

The height of the dash and the height and reach of the steering column assembly can be adjusted to fit each individual driver. The steering wheel height can be adjusted relative to the dash assembly. The driver's seat can be attached to an optional integral roll bar safety cell that can be adjusted many ways to fit each driver. This roll bar safety cell is equipped with a full lap belt and shoulder harness. The shift lever is a fully gated B & M ProStick to give positive control over upshifts, and to eliminate any possibility of a missed shift.

[Vigillante Trike Drawings]

[Vigillante Trike Close Up Side]

A racing fuel cell is incorporated into the passenger seat. Both the passenger and the fuel cell are located near the center of gravity so variations in loads will have minimal effect on the handling.

Weight and balance calculations are done so that 95% of the total vehicle weight is on the rear drive tires at maximum acceleration, with only 5% on the front tire to provide steering control. The Vig is carefully designed so it can not do sustained "wheelies"; that would reduce the acceleration capabilities. This provides virtually the same acceleration capability as an all-wheel-drive design, but without the weight, cost and complexity.

This is very similar to the way dragsters are designed. During maximum braking, approximately 1/3 of the total vehicle weight is on each tire. Since more than 1/2 of the total braking force is being done behind the center of gravity, the vehicle is dynamically stable and will not spin, even if all the wheels are locked up on a slick surface in a corner. The braking is absolutely phenomenal. There is no need for features like anti-lock braking when the weight and balance are correctly designed.

At the end of the day the Vigillante has solved some of the issues that we had with the TriVette.

I think it looks better from all angles, especially the side.  I like the roof design better and the entry and exit ability provided by the new canopy.  Finally I think that if we are going to be building alternative vehicles they should do something besides just look different.  In this case Bob Keyes totally nailed the performance.  When I build my Trike, it will blow cars away, be comfortable inside, look great and be economical when I am not thrashing it.

I feel this is a car that needs to be made again.  I believe I would very much like to drive one and most probably love to own it.  Keep Triking.