Pro-Touring Explained: Where It Came From, What It Takes, How It Differs From Pro Street

For most of the muscle car's history, the measure was the quarter mile. Pro-touring changed the question. A pro-touring car keeps the classic body and adds modern suspension, brakes, tires and drivetrain so it can carve corners, stop hard and cover long distances, with the stated goal of matching or beating modern performance cars. These cars are built to be driven, on the street, on road courses, at autocross and on long road trips.

Where it came from

The style grew out of flat-out road events such as the One Lap of America and the Silver State Classic. Street Machine credits RJ Gottlieb's 1969 Camaro, 'Big Red,' at the 1988 Silver State Classic as an early example of the modern approach, and notes that Australian builders were running similar cars in the late 1980s and early 1990s before anyone had a name for them.

The name itself is most often credited to Mark Stielow, a GM engineer, and Jeff Smith, then the technical editor of Car Craft. Stielow's white 1969 Camaro, known as 'Tri-Tip,' ran the One Lap of America in 1993, and coverage of that car helped put the idea in front of enthusiasts. Accounts differ on exactly when the term was coined: the Audrain Automobile Museum says the early 1990s, while other accounts place it later in the decade. Stielow also built 'Red Witch,' a 1967 Camaro put together while he worked at Summit Racing, which his Lateral-g biography says was Hot Rod magazine's 1996 Car of the Year.

His 1969 Camaro 'Mule' is the car many builders point to as the template. Built over 24 months from 2001 to 2003 as a test bed for his ideas, it took its name from the development mules Stielow knew from GM, and Popular Hot Rodding ran a long series of technical stories on it starting in July 2001. At a time when most such cars still used leaf springs and a solid axle, Stielow gave it a four-link rear with adjustable coilovers and reworked the front suspension with rack-and-pinion steering. Its original engine was a lightweight, fuel-injected 400 cubic inch small-block making more than 540 hp on pump gas. The Mule is now in the Audrain collection, which describes it as the beginning of the pro-touring industry. Stielow later co-wrote the book Pro Touring Engineering Performance with Will Handzel, published in 2011.

The formula

There is no rulebook, but the hardware falls into five groups. Each one addresses a different limit of a car designed in the 1960s around bias-ply tires and drum brakes.

Suspension geometry

This is the heart of the style. Up front, builders replace or rework the factory geometry with layouts designed around modern tires, typically pairing coilover shocks with rack-and-pinion steering. Complete bolt-in front subframes exist for popular platforms such as the first-generation Camaro. In the rear, a multi-link setup such as a four-link replaces the leaf springs to locate the axle more precisely. Stielow's Mule used exactly that combination. Adjustable shocks let the same car be set up softer for the street or firmer for the track.

Brakes

Pro-touring cars stop on modern big brake kits. For a 1967 to 1969 Camaro, Baer's Pro+ front kit, for example, uses 14 inch two-piece slotted and drilled rotors with six-piston fixed calipers and is designed to fit most 18 inch or larger wheels. That wheel requirement is why brake and wheel choices are made together.

Wheels and tires

Wide, sticky radials on large-diameter wheels are the visual signature, but their job is grip at all four corners. Competition sets limits on how far that goes: the Optima Ultimate Street Car Invitational, one of the premier venues for these cars, requires tires with a treadwear rating of at least 200, which keeps entrants on street tires rather than slicks.

Drivetrain

Modern fuel-injected V8s such as GM's LS family or Ford's Coyote, paired with overdrive transmissions, provide the power, drivability and highway manners the style needs. The aim is an engine that will run hard on a road course and then idle in traffic on the drive home.

Comfort

Because these cars are meant to be driven, many carry the amenities of a new car: climate control, supportive seats, modern gauges and a sound system. That overlap is why pro-touring and restomod get used interchangeably. The difference is emphasis. A restomod can be built entirely around comfort and reliability; a pro-touring car is built around performance, especially handling and braking.

Pro-touring versus pro street

Pro street was the defining muscle car look of the 1980s, and it points the opposite way. A pro street car, also called a back half or tubbed car, is built to imitate a Pro Stock drag car while staying street-legal with a full interior. The usual ingredients are a heavily modified V8, a narrowed rear axle with oversized rear tires tucked inside the wheel wells, and often a roll cage and wheelie bars. Jalopnik describes the style as show-oriented, with massive rear tires and superchargers, and impractical for everyday driving.

• Goal: pro street is about straight-line acceleration and drag-strip attitude; pro-touring is about turning, braking and covering distance.
• Tires: pro street concentrates tire width at the rear; pro-touring runs wide, grippy tires at all four corners.
• Chassis: pro street cuts the back of the car for tubs and a narrowed axle; pro-touring reworks geometry front and rear for grip and control.
• Use: pro street cars mostly live at shows; pro-touring cars are expected to be driven hard, on track and on the road to get there.

If you are planning a pro-touring build, spend on the chassis first. Power is easy to buy in this era. A car that can use it through a corner, and stop from speed lap after lap, is the hard part, and it is the whole point of the style.