Harley-Davidson Inc. has unveiled its largest product development project ever: eight redesigned cruiser motorcycles for 2018, including bikes that have been a mainstay of the Milwaukee-based company for decades.

Harley says the new Softail models, available this fall, come with the most powerful engine ever offered on its cruisers.

The new bikes, aimed at Harley's 115th anniversary year, are being rolled out as manufacturers of cruiser and touring motorcycles have seen a decline in U.S. sales.

Harley has a 10-year goal of attracting several million more customers, which is important as baby boomers age out of riding.

The company says a massive amount of research and testing went into the makeover of some of its best-known motorcycles, including the Heritage Classic.

“The new Softail models are the result of the most extensive research and development program in the company’s history,” said Paul James, product portfolio manager.

Harley’s Softail and Dyna product lines, as riders have known them, are gone.

“It’s now one platform for them all,” James said.

There's a "new frame, new chassis, new suspension, new metal. New everything, really," he said.

As part of the research, Harley-Davidson says it interviewed more than 3,000 riders for their views on cruisers — a versatile style of bike with a relaxed riding position, suitable for long-distance riding but more nimble than a big touring motorcycle.

“We were literally in people’s homes and garages, talking with them about their motorcycles,” James said.

The eight new bikes — Fat Boy, Heritage Classic, Low Rider, Softail Slim, Deluxe, Breakout, Fat Bob and Street Bob — have an all-new chassis and suspension system that Harley says delivers a much better ride.

The bikes are powered by a specially configured version of the Milwaukee Eight engine Harley introduced a year ago for its touring motorcycles. The company says the 107 cubic inch version of that engine provides 10% quicker acceleration, from 0-60 mph, than the High Output Twin Cam 103 engine on previous models.

Four of the new Softails — Fat Bob, Fat Boy, Breakout and Heritage Classic — are available with a more powerful 114 cubic inch Milwaukee Eight.

Up to 35 pounds lighter than 2017 models, Harley says all eight bikes have an improved power-to-weight ratio for quicker acceleration, better braking and handling.

“Every component of the bikes had a weight-reduction target, and we rigidly monitored it through the program,” said Ben Wright, chief engineer for the Softail redesign program.

"Every little bit of weight savings counted."

The company gave the bikes a healthy dose of classic cruiser looks — some of it vintage 1950s — while incorporating modern features such as anti-lock brakes, LED lighting, a digital instrument screen, keyless ignition, a USB charge port, mono-shock rear suspension and lockable saddlebags.

Some of the new Softails have a dark, muted finish, while the Deluxe and Low Rider models glisten with chrome.

The new Heritage Classic has a darker, more sinister appearance.

Remake is 'massive undertaking'

The last time Harley-Davidson did a makeover of the Softail lineup was in 1999 for model-year 2000.

Harley says its largest product development project until this announcement was the Rushmore line of touring motorcycles unveiled in August 2013.

Eight models were retooled under Rushmore, including the venerable Electra Glide Ultra Classic.

Harley says the Softail redesign was even bigger and more complex, including roughly 300 parts and accessories created specifically for the new bikes.

“It was a massive undertaking, a complete redesign from the ground up of our cruiser portfolio,” James said.

Tuesday, Harley unveiled model-year 2018 motorcycles — not including 115th anniversary models coming later — at its annual dealership meeting in Los Angeles.

The 2018 Softails will be available, in limited quantities, at dealerships as early as this week.

Bikes begin in product development center

Motorcycle design involves generous portions of engineering and emotional appeal.

The Willie G. Davidson Product Development Center, in Wauwatosa, is where Harley has designed motorcycles for the last 20 years.

The center’s tall glass windows have motorized shades to keep prying eyes from getting even a glimpse of bikes that might not be released to the public for several years, if ever.

The styling department has a 1950s-vintage Harley FL, one of the company's most famous bikes, that designers turn to for inspiration.

“We want to make sure that our motorcycles speak to some of our key DNA,” said Brad Richards, vice president of styling and design.

“That motorcycle (the 1950 FL) in particular really does show some of the bones that we were trying to capture with the new Softail platform,” Richards said.

The product development center has "mood boards" in the studio to communicate the emotional side of the designers' work.

There's a sound chamber, approximately 60 feet by 60 feet, with wedges on the walls to simulate an outdoors acoustic environment.

The wedges are filled with 50,000 pounds of fiberglass. The entire room, weighing nearly 3 million pounds, rests on 61 pneumatic mounts that isolate the room from any vibrations from adjacent laboratories.

There's also a "structures lab" that can simulate a lifetime of real-world customer road damage in only a few weeks.

New models are still put through hundreds of thousands of road-test miles, but lab testing speeds up the process.

Not that riding a motorcycle all day long on a test track wouldn’t be a lot of fun.

But “we can get results more repeatedly without beating riders up on the track in the Arizona heat,” said Ev Paddock, test lab manager.