New to the forum and appreciate all the great information. It has been very helpful to someone doing a restoration for the first time. I'm restoring a 65 FB and would like to build a Shelby GT350 replica. I have many questions, but to start I've read on some other posts about a "shelby drop" Can someone explain to me what it is, and how the mod can be done to a standard mustang suspension.
Ive drilled a lotta these holes over the years. The "drop" was actually created by Klaus Arning. It doesn't really drop the car much, about 5/8", as a side effect. The change in geometry is what you're really after. This will explain why, and how to do it:
IMO the camber setting on the Glazier/Nolan document are old school. With modern radials positive camber on these cars is a no no. If your front end parts are new, I would reduce the positive toe a little too.
No one really answered your question. I'll try.
The front tires stand practically vertical when weight is on the wheels and the steering wheel is straight.
On a stock Mustang, as the front end rises and sinks as the road undulates or in aggressive handling, the parallelogram that is created by the upper/lower control arms and the shock towers and spindles, keep the tire near vertical or tilted slightly outward at the top.
This is not optimum for performance driving as Arning and Shelby wanted. By changing the height of the upper control pivot points at the shock tower, by drilling new holes, the parallelogram is no longer a parallelogram. The goal is to do it in a way that both lowers the CG of the front of the car AND makes the bottom instead of the top of the tire goes outward as suspension compresses. This makes the contact patch of the tire remain as large as possible and improves traction and handling.
Shelby vrs Arning? Just wondering why some insist on referring to it as Arning drop? Was the Arning drop a common mod on falcons and pre-Shelby mustangs? Then Carrol Shelby made it popular by using it on Shelby cars. I doubt Carroll was the sole engineer on every asspect of the car so there has to be more to it than just Arning as the engineer....
I had the Arning drop done to my 68 Vert (200-6) in conjunction with a total rebuild of the front suspension. Handling improved tremendously. Because I went from a totally shot, loose front end that drove all over the place, to a tight, road handler all in one step, I can't say how much the Drop had to do with it. But I figured the front end was going to be gutted anyway so why not drill a couple of holes at the same time.
My measurements verified the usual 5/8 inch drop. Some people report up to an inch.
Shelby vrs Arning? Just wondering why some insist on referring to it as Arning drop? Was the Arning drop a common mod on falcons and pre-Shelby mustangs? Then Carrol Shelby made it popular by using it on Shelby cars. I doubt Carroll was the sole engineer on every asspect of the car so there has to be more to it than just Arning as the engineer....
You didn't read the link. Klaus Arning created the "drop" when he was engineering the optional Independent Rear Suspension for Ford on the Mustang. It was necessary, to make the front end geometry compatible with the IRS. The IRS was dropped due to high cost, but those involved, including some Shelby American people who had observed the IRS, realized that much of the improvement in handling was to to the simple relocation of the upper control arm, so Shelby duplicated that for the 1965 GT350. Later, in 1966, it was dropped to save time and money.
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Amateur restorer. (Well, once in a while I have been paid for it)
This is not optimum for performance driving as Arning and Shelby wanted. By changing the height of the upper control pivot points at the shock tower, by drilling new holes, the parallelogram is no longer a parallelogram. The goal is to do it in a way that both lowers the CG of the front of the car AND makes the bottom instead of the top of the tire goes outward as suspension compresses. This makes the contact patch of the tire remain as large as possible and improves traction and handling.
Actually, since the arms are not the same length, it's never a parallelogram. However, the position of the arms from the factory actually causes negative camber as the wheel extends, which reduces tire contact in turns. This gave the narrow tires the suspension was originally designed for smooth handling. But they are so primitive by today's standards no one would drive them hard. The "drop" induces the opposite effect, and as you say, keeps the tire in far better contact with the road, which in effect "radial tunes" the Mustang suspension.
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Amateur restorer. (Well, once in a while I have been paid for it)
IMO the camber setting on the Glazier/Nolan document are old school. With modern radials positive camber on these cars is a no no. If your front end parts are new, I would reduce the positive toe a little too.
Hmmm…
Shelby called for 1/8" toe, your link calls for 1/16-1/8".
Shelby calls for +2° degrees caster, your link calls for +2°-3.5°
Shelby calls for 0° camber, your link calls for -.5-0°.
Old school? I submit you are splitting hairs. The G/N link falls within the tolerances in your link.
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Amateur restorer. (Well, once in a while I have been paid for it)
Here's a good visual representation of the drop as well as the install itself (got this from the NPD site). Goes into the Shelby drop around 4:15 in the video.
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Can someone explain a "Shelby drop"
