Archive for the ‘Suspension and Brakes’ Category

Suspension Mounts Finally Welded In

December 6th, 2009 No comments

I have FINALLY finished welding in the rear suspension mounts. Most of it went well. On the driver’s side I blew through the frame rail and had to build it up. The result is ugly as sin, but will hold the thing in place.

Now it’s getting cold out in the garage! Harder to get motivated to go out and work on the car. Actually this project is feeling like such a long one that sometimes I have difficulty working up the motivation to go out and work on it. I know it’s on the down-hill side of it now though.

Dad and I will be working on the motor at Ray’s over the weekend of the 19th. I can’t wait to get that together and get this thing running!

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Adjusting the Koni Shocks

November 2nd, 2009 No comments

I paid a visit to Ray this past weekend, and he told me the adjustments to make on the Koni Classic shocks. Initially, I’d just put them in the middle of their range. He’d spent some development time on his car though, and determined that the appropriate adjustment for our cars would be:

Rear: 1 turn in from softest

Front: 2 turns in from softest

So what you do is push the shock all the way closed and turn CCW until it stops. That’s the limit on the soft side. Turn CW 2 for front and 1 for rear shocks.

In the rear, I was in luck, because the rear end is still down and the shocks were just hanging down. I guess what you’d do though, is just undo the bottom mounting nut and push it closed from the bottom.

In the front, I had to remove not only the top shock to shock collar fasteners, but also the shock collar nuts. I had to take out the Monte Carlo bar as well, because the tops of the shocks would not push down past rim of the Monte Carlo bar.

When I did this, it exposed a mistake that I had made when I put them in in the first place. The bottom mounts weren’t tight at all! I had tightened the bottom shock mount nuts with the top ones already tightened. Since the mounting surface on the bottom is a bit tilted, and spring-loaded, tightening the top first didn’t allow the bottom ones to sit flush with the mount surface. It gave me a false torque reading. Glad I checked that.

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Why Relocate the Control Arm?

June 27th, 2009 No comments

So, why the so called “Shelby Drop”? First, let me explain just what it is. The “drop” refers to the fact that the inboard mount point of the upper control arm is moved down. Shelby moved it down 1″,  and 1/8″ rearward. It would probably be more accurate to call it the “Arning Drop” because it was originally designed by Klaus Arning, a top suspension designer for Ford. He designed it as part of a full package for the Mustang, which included his 4 link Independent Rear Suspension design. The 4 link IRS didn’t make it into the final car, but Shelby made use of the front upper control arm positioning for the GT350. In my highly approximate picture of the stock setup, you can see why: camber_curveThe circle represents the path of motion of the outboard control arm mount point during suspension movement. You can see here that if the suspension is loaded, as in a hard turn or a bump, the control arm will move outward, pushing the top of the tire out, creating positive camber. This will make it so that the contact patch of hte tire is reduced, with just outer edge of the tire contacting the pavement.

You can imagine what happens when you move the mout point down a bit. The curve becomes more advantageous to the loaded condition. If the car is in a hard turn, it will actually be beneficial to have a bit of negative camber to maximize the contact patch of the tire.

The drop also lowers the CG a little, and reduces the leverage that the suspension has on the body, minimizing body twist. These 3 things together make for more performant handling under the stress of the track.

Why Progressive Rate Front Springs?

May 24th, 2009 No comments

I went with the progressive rate fronts, hoping to have a “best of both worlds” scenario since my car will be on the street and the track too. You really get your best handling with springs that are as soft as possible, while still resisting body roll. “Stiffer is always better” is really a myth. The function of the spring is to absorb the energy from a bump, store it, and then use it to push the wheel back down onto the road, maintaining traction. If it’s too stiff, a bump comes and the spring can’t absorb the energy – it might just pass it to the body, and the wheel then just skips along, not following the contour of the road, and therefore losing traction.

The springs should be soft enough to absorb the energy from whatever bump you go over, but stiff enough to stop too much weight transfer in a hard corner. Those things don’t really go together! Modern suspensions have ways to cope with this, but this old Mustang is not terribly sophisticated.

The soft side of the progressive rate springs is 480 lbs – just right for a firm but good ride during street driving (the original squishy stock stuff was closer to 250 I think). Under a heavy load, like  a fast corner, the suspension will compress, and the springs will hit their higher rate of 680lbs, which should give some significant push-back to resist roll and weight transfer, making for a predictable corner.

Combined with good shocks and the roller perches, the suspension should be responsive and firm.

Ideally, progressive rate suspensions are the way to go when they are properly calibrated. Is that the case here? We’ll see!

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Why Slider Mounts?

May 24th, 2009 No comments

2 reasons from what I’ve heard.

  • Traditional leaf spring shackles move along an arc. This in theory changes the rate of the spring as the rear mount point moves along this arc. Changing to the slider mount should change this rear leaf to a constant rate, which should make the rear end behavior more predictable.
  • With these springs, both the front and rear mounts have solid bushings instead of the rubber ones. This should make handling more predictable as well, allowing for less twist and deformation under load.
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Front Suspension Before and After

May 24th, 2009 No comments
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May 23rd, 2009 No comments

I’ve replaced the front brakes on the car with discs – a Baer Sport kit #1261075 . This is a 12″ rotor kit  with 2 piston PBR style calipers. The PBR calipers are a slider-style; they are the same ones that went on the ’94-’04 Mustang Cobras. This kit comes with stainless steel braided lines to the calipers, a good dual chamber master cylinder, and the lines you need to install everything.

I went through a lot of thought on this one. There are a number of ways to go with front discs on the early Mustangs. The old stock style Kelsey-Hayes discs were known for their pistons sticking, so I didn’t want to get an old one. SSBC has re-made this style and fixed that sticking problem. That’s a good way to go for street I think. You also have the option of going with a Granada conversion, but there again you have a single piston doing the work, and the sticking issue. I talked with a lot of people about different kits, and got a lot of different answers about the different ones, but the one kit I only heard positive stuff about was the Baer kit. Plus, my friend Ray has that kit on his car, and I always trust his opinion. had a great deal on it, so I went ahead and got it.

I also replaced the hard line going back to the rear, and the rear flex line with a stainless steel braided one.

Installing these front discs necessitates using a proportioning valve. I mounted that in the engine bay right near the master cylinder. I may later wish I’d mounted it in the passenger compartment, but I doubt I’ll want to be adjusting my brake bias on the fly for some time to come. I got to learn about bending and flaring tubing here. That was fun, and actually easier than I thought.

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May 23rd, 2009 No comments

Some time in 2008 I read Carroll Smith’s “Nuts, Bolts, Fasteners and Plumbing” and I reached a new level of anal about nuts and bolts. I seriously never realized how much engineering went into your average fastened joint. For anyone doing any kind of fabricating, restoration, or any work where you might have to put more stress on a joint than it was originally engineered for – I highly recommend this book! If you’re into cars, just buy all 5 of his books – you’ll want them later anyway – just get them all and be done with it. You should be able to get a decent deal at

Because of the added stress that a lot of my car is going to be under when it’s on the track, I opted to replace some of the fasteners with AN fasteners. For record-keeping, I’ll list them here:

  • Rear leaf front mount
  • Strut-rod to LCA
  • New front crossmember to LCA mount. This piece is an upgrade that I got from Delta Bay Mustang – it reproduces an upgrade that was made to the Trans-Am cars. Stock crossmembers have one bolt on each side, and it fastens the crossmember to the frame rail. This upgraded piece ties into the inboard LCA mount. This extra mount-point, perpendicular to the other mount, adds a lot of flex-resistance to the body.
  • Upper shock mount. The stock shock collar has a captive nut on the bottom. The upper shock mount sits on top of the collar, and a bolt goes down through it and into that captive nut. I’d heard that this nut sometimes strips out or falls out, and these shock mounts can fail under stress, creating a possibly dangerous situation. I knocked the captive nuts out and replaced them with AN nuts, bolts and washers.

I also replaced the shock collar-body fasteners, and the crossmember-frame rail bolts, but with new stock-style ones.

New Suspension

May 23rd, 2009 No comments

My idea with the suspension and steering (and indeed with much of the car) was to upgrade it, make it strong enough to withstand the forces that it will encounter at the track, but not to make it “modern”. At least for this first setup, I wanted to stay marginally vintage (ie: no coil-overs or rack and pinion). With a lot of help from my friend Ray, I selected a whole new suspension setup for the car.


  • Global West upper and tubular lower control arms. Uppers are relocated 1.75″ down to change the camber arc
  • Open Tracker Roller spring perches
  • Pro Motorsports progressive rate springs – 480-680
  • Koni Classic shocks (adjustable in damping)
  • 1970 Mustang Disc brake big spindles (Casting D0OA)


  • Koni Classic shocks (adjustable in damping)
  • Cobra Automotive Road Race leaf springs with slider mount
  • 1/2 upgraded U-bolts

Wheels and tires:

  • 16×8 Vintage 45 (5 spokes) with
  • 225x50x16 tires (type TBD).

I considered 245 tires, but the switch to 245 will require more rolling of the fender lips, and some tweaking of the front alignment adjustment. To do that, I’d probably want to go to the ’67+ style “vario-centric” camber adjustments. 225 should fit well and handling should be much improved with this setup.


  • Shelby style “quick-steer” idler and pitman arms. I selected the “rollerized” idler arm to reduce friction.
  • I’m not sure yet about the steering box – I may replace it later with a 16:1 version. Right now I have the old 19:1 version and I think it’s a bit sloppy.
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