Less Roof, No Goof: Ford builds a better Mustang
MARK VAUGHN/AUTOWEEK
Photos By Boyd Jaynes
2005 FORD MUSTANG CONVERTIBLE
ON SALE: Spring
BASE PRICE: $27,000 (est.)
POWERTRAIN: 4.0-liter, 210-hp, 240-lb-ft V6; rwd, five-speed manual
CURB WEIGHT: 3476 pounds
0 TO 60 MPH: 6.9 seconds (est.)
Why is the new Mustang convertible better than the old Mustang convertible, better in fact, than any Mustang convertible ever? There are a lot of answers to that, but it all comes down to architecture.
“This is the first time that we had an all-new platform that didn’t require compromises for our use,” said Mustang vehicle engineering manager Bob Johnston.
That’s a polite way of saying Ford finally built a Mustang to be a Mustang, instead of forcing a Mustang on something else. As you’ll recall, the previous pony car traced its roots all the way back to the Fox platform of 1978, and even then it had to perform other duties, including but not limited to holding up those “icons” of style and speed, the Fairmont and Granada. It was like asking your weed whacker to function also as a Flowbee hair trimmer, Waring blender and a snowblower. Sure, with enough engineering it could probably carry it all off, but not as well as any of those should, and you always wound up with hair in your daiquiri.
Ford designers and engineers did a lot of things right in bringing the new Mustang to market, and maybe the single most important element was building a solid chassis that would allow for a no-compromises convertible. The result is a fun, solid car that lives up to its iconic good looks.
The new Mustang platform doesn’t have to be anything but a Mustang (so far, anyway), and when engineers started to build it, they started with the assumption that it would also be a convertible.
That meant the basic structure of the car was designed to work with a minimum of reinforcement to keep it structurally sound even without a roof.
Ripping the top off a car generally sucks out about 70 percent of its torsional rigidity. That can be replaced with weight-bogging reinforcements to the floor pan, rear structure, A-pillars and windshield frames, but that’s like adding the plumbing after you’ve put in the drywall.
“Typically, convertibles are afterthoughts,” said Mark Rushbrook, Mustang vehicle dynamics manager.
While there was some stiffening to those areas on this car, that stiffening was nowhere near as much as it had been on the Fox platform convertibles. The main reinforcements to the new convertible are a big V-brace underneath in the back and a strut bar underneath joining the lower inboard suspension pickup points in front. Together those changes keep the new convertible remarkably tight.
“You’re never going to get all the cowl shake out of a convertible, but this is much better than we’ve ever been able to do before,” said Rushbrook.
Rushbrook was speaking from the passenger seat of the convertible as we sped along the contour-hugging bends of State Highway 39 in the mountains above Los Angeles. Indeed, the cowl wasn’t shaking much at all. In previous Mustang convertibles you’d hit a bump or whang into a pothole—what vehicle dynamics engineers call “an incident”—and then the waves of energy would travel back and forth through the body of the car for several long seconds, and at a fairly low frequency. Things would rattle off the dashboard, the glovebox would spring open, your glasses would bounce off the end of your nose and your date would make a mildly unhappy sound from the passenger seat. Now there is far less residual shake, for a shorter duration and at what feels like a higher frequency. In other words, it’s tight, man.
In more precise engineering terms, the body of the old convertible took 3000 lb-ft of torque to twist 1 degree. When they made this convertible, the goal was to double that figure, but they wound up exceeding it with a measure of 6500 lb-ft per degree. Granted, that doesn’t compare to a carbon fiber race tub, but it is a 117 percent improvement. Bending resistance is also up, by 25 percent.
The Mustang convertible does weigh 120 pounds more than the coupe, but even that figure is 30 pounds less than the weight penalty the old convertible paid compared with the old coupe.
Cowl shake is also reduced by a softened suspension, which you can have if you’ve got a stiff chassis. If you can get the springs to soak up the bumps before the body has to, you’ve got a more efficient package. So spring rates front and rear are reduced by 15 percent while all four shocks are softened as well. The rear stabilizer bar goes up to 20 millimeters vs. 18 millimeters to compensate for the added roll of the softer springs and shocks. The convertible’s tires are the same as the coupe—235/55ZR-17s on the V8-powered GT and 215/65R-16s on the V6-powered base model.
On the road you might notice the softer setup; it felt just a little mushier than the coupes we’ve driven. The rack-and-pinion steering feels much better connected to the road than you’d expect, given the Mustang convertibles of yore. Four-wheel discs are standard. As with any coupe/convertible choice, driving and performance purists will want the coupe, but there is far less compromise in this soft-top version.
Many other features were added to get the new ’Stang up to the competition. The top is all-new, of course. It is three layers thick, as are most tops nowadays, with an outer waterproof layer, middle sound insulation and a handsome inner liner. The basic construction consists of five bows that stack in a big Z behind the rear seats. The headliner is stiff and wide and attaches to the windshield frame with two big hand clamps. Top operation is electrohydraulic and takes 16 seconds. The rear glass is as big as they could make it, for optimum visibility, and has electric defrost standard. The Mustang also has rear quarter-windows, which, along with big side mirrors, add to all-around visibility.
The Mustang convertible weighs in 120 pounds heavier than the coupe, but it’s a price worth paying for being able to drop the top.
The side glass now slots up into rubber molding under the roof rails, a technique we first noticed on BMWs, and one also featured on the Mustang coupe. When you pull the door handle, the glass lowers before the door opens; when you close the door, the last thing the glass does is schmoosh up into the molding. That makes for a 12 percent reduction in wind noise and a 25 percent reduction in air leaking through the seals.
The rest of the Mustang doesn’t change. Power to the rear wheels comes from your choice of 4.6-liter 300-hp V8 in the GT or 4.0-liter 210-hp V6 in the base car. Five-speed manual and five-speed automatic are available in both models.
The convertible bows at the Los Angeles auto show about the time you read this and will enter showrooms in the spring, when pricing will be released. Past convertibles have made up about 30 percent of sales, and this one should settle down to that after an initial sales spike. And it will spike. After 26 years riding on the old Mustang/Fairmont/Granada, engineers were more than anxious to show what they could do with a clean-sheet-of-paper Mustang convertible.
“You’d kind of like to get it right,” said Johnston.
This time they certainly did.
MARK VAUGHN/AUTOWEEK
Photos By Boyd Jaynes
2005 FORD MUSTANG CONVERTIBLE
ON SALE: Spring
BASE PRICE: $27,000 (est.)
POWERTRAIN: 4.0-liter, 210-hp, 240-lb-ft V6; rwd, five-speed manual
CURB WEIGHT: 3476 pounds
0 TO 60 MPH: 6.9 seconds (est.)
Why is the new Mustang convertible better than the old Mustang convertible, better in fact, than any Mustang convertible ever? There are a lot of answers to that, but it all comes down to architecture.
“This is the first time that we had an all-new platform that didn’t require compromises for our use,” said Mustang vehicle engineering manager Bob Johnston.
That’s a polite way of saying Ford finally built a Mustang to be a Mustang, instead of forcing a Mustang on something else. As you’ll recall, the previous pony car traced its roots all the way back to the Fox platform of 1978, and even then it had to perform other duties, including but not limited to holding up those “icons” of style and speed, the Fairmont and Granada. It was like asking your weed whacker to function also as a Flowbee hair trimmer, Waring blender and a snowblower. Sure, with enough engineering it could probably carry it all off, but not as well as any of those should, and you always wound up with hair in your daiquiri.
Ford designers and engineers did a lot of things right in bringing the new Mustang to market, and maybe the single most important element was building a solid chassis that would allow for a no-compromises convertible. The result is a fun, solid car that lives up to its iconic good looks.
The new Mustang platform doesn’t have to be anything but a Mustang (so far, anyway), and when engineers started to build it, they started with the assumption that it would also be a convertible.
That meant the basic structure of the car was designed to work with a minimum of reinforcement to keep it structurally sound even without a roof.
Ripping the top off a car generally sucks out about 70 percent of its torsional rigidity. That can be replaced with weight-bogging reinforcements to the floor pan, rear structure, A-pillars and windshield frames, but that’s like adding the plumbing after you’ve put in the drywall.
“Typically, convertibles are afterthoughts,” said Mark Rushbrook, Mustang vehicle dynamics manager.
While there was some stiffening to those areas on this car, that stiffening was nowhere near as much as it had been on the Fox platform convertibles. The main reinforcements to the new convertible are a big V-brace underneath in the back and a strut bar underneath joining the lower inboard suspension pickup points in front. Together those changes keep the new convertible remarkably tight.
“You’re never going to get all the cowl shake out of a convertible, but this is much better than we’ve ever been able to do before,” said Rushbrook.
Rushbrook was speaking from the passenger seat of the convertible as we sped along the contour-hugging bends of State Highway 39 in the mountains above Los Angeles. Indeed, the cowl wasn’t shaking much at all. In previous Mustang convertibles you’d hit a bump or whang into a pothole—what vehicle dynamics engineers call “an incident”—and then the waves of energy would travel back and forth through the body of the car for several long seconds, and at a fairly low frequency. Things would rattle off the dashboard, the glovebox would spring open, your glasses would bounce off the end of your nose and your date would make a mildly unhappy sound from the passenger seat. Now there is far less residual shake, for a shorter duration and at what feels like a higher frequency. In other words, it’s tight, man.
In more precise engineering terms, the body of the old convertible took 3000 lb-ft of torque to twist 1 degree. When they made this convertible, the goal was to double that figure, but they wound up exceeding it with a measure of 6500 lb-ft per degree. Granted, that doesn’t compare to a carbon fiber race tub, but it is a 117 percent improvement. Bending resistance is also up, by 25 percent.
The Mustang convertible does weigh 120 pounds more than the coupe, but even that figure is 30 pounds less than the weight penalty the old convertible paid compared with the old coupe.
Cowl shake is also reduced by a softened suspension, which you can have if you’ve got a stiff chassis. If you can get the springs to soak up the bumps before the body has to, you’ve got a more efficient package. So spring rates front and rear are reduced by 15 percent while all four shocks are softened as well. The rear stabilizer bar goes up to 20 millimeters vs. 18 millimeters to compensate for the added roll of the softer springs and shocks. The convertible’s tires are the same as the coupe—235/55ZR-17s on the V8-powered GT and 215/65R-16s on the V6-powered base model.
On the road you might notice the softer setup; it felt just a little mushier than the coupes we’ve driven. The rack-and-pinion steering feels much better connected to the road than you’d expect, given the Mustang convertibles of yore. Four-wheel discs are standard. As with any coupe/convertible choice, driving and performance purists will want the coupe, but there is far less compromise in this soft-top version.
Many other features were added to get the new ’Stang up to the competition. The top is all-new, of course. It is three layers thick, as are most tops nowadays, with an outer waterproof layer, middle sound insulation and a handsome inner liner. The basic construction consists of five bows that stack in a big Z behind the rear seats. The headliner is stiff and wide and attaches to the windshield frame with two big hand clamps. Top operation is electrohydraulic and takes 16 seconds. The rear glass is as big as they could make it, for optimum visibility, and has electric defrost standard. The Mustang also has rear quarter-windows, which, along with big side mirrors, add to all-around visibility.
The Mustang convertible weighs in 120 pounds heavier than the coupe, but it’s a price worth paying for being able to drop the top.
The side glass now slots up into rubber molding under the roof rails, a technique we first noticed on BMWs, and one also featured on the Mustang coupe. When you pull the door handle, the glass lowers before the door opens; when you close the door, the last thing the glass does is schmoosh up into the molding. That makes for a 12 percent reduction in wind noise and a 25 percent reduction in air leaking through the seals.
The rest of the Mustang doesn’t change. Power to the rear wheels comes from your choice of 4.6-liter 300-hp V8 in the GT or 4.0-liter 210-hp V6 in the base car. Five-speed manual and five-speed automatic are available in both models.
The convertible bows at the Los Angeles auto show about the time you read this and will enter showrooms in the spring, when pricing will be released. Past convertibles have made up about 30 percent of sales, and this one should settle down to that after an initial sales spike. And it will spike. After 26 years riding on the old Mustang/Fairmont/Granada, engineers were more than anxious to show what they could do with a clean-sheet-of-paper Mustang convertible.
“You’d kind of like to get it right,” said Johnston.
This time they certainly did.