[Dan Case]

Eye Center Free Chamber
To Eye Center Camber
(inches) (inches)
Front
AC COBRA CHASSIS INSTRUCTION BOOK 39.250 3.250
Shelby Automobiles, Inc. January 2005 37.000 Not Available

Rear
AC COBRA CHASSIS INSTRUCTION BOOK 41.000 5.313
Shelby Automobiles, Inc. January 2005 39.500 Not Available

Notice: How much different eye to eye the two sources are. This was the case with all sources of replacement parts too. I do not have their messages anymore but I believe the current owners of AC Cars offered these same eye to eye dimensions as the original chassis manual but the gage was thicker (and very expensive!!!!).

The average leaf thickness front (several cars measured) is 3/16” (0.188 - 0.190 actual). This gage is for practical purposes obsolete. There is no gage taper, the leaves are constant, as constant as the hot roll process can make, gage end to end.

The average leaf thickness rear (several cars measured) is 7/32” (0.218 – 0.221 actual) There is no gage taper, the leaves are constant, as constant as the hot roll process can make, gage end to end.

I did a lot or research, hours a day for weeks, on original leaf springs. I had help from several other owners in various parts of the country that have cars in some stage of restoration. I had multiple contacts with AC Cars, Shelby Automotive, Motorsports International, and my fellow owners.

I am grateful several owners took time from the activities to remove their springs and make measurements. One pair of people even made a fixture to hold the whole spring assemblies out horizontal for measurement with large calipers. I dismantled my springs and used a 4X4 section and clamps to flatten the springs against my steel work bench. All my measurements were multiple readings made starting completely over at least twice (multiple days, multiple set ups, five readings each minimum, all measurements averaged).

Some things became clear.

1) The eye to eye dimensions in the AC COBRA CHASSIS INSTRUCTION BOOK (AC) are for the two main leaves while they are still straight prior to heat treating into an arc or finished leaves held out flat along their top surface tangent to the rolled ends afterwards.

2) All the front springs (or rear springs) measured were very consistent in eye to eye centers except CSX2551 (which I am working on). CSX2551 had a longer set of front main leaves, perhaps Dragon Snake length as they are reported to have special longer front springs. The front camber on CSX2551 made it look like an old tractor.

3) It was very common for the center clamp bolt (runs through the middle to hold leaves together) to be considerably off center. This surprised us. We had assumed you could center the bolt in the clearance hole in the spring tower and you would have even side to side control arm (the springs being the upper control arms) length. Not true. One spring was found to be 0.120” off center, not good for an alignment gage. Range found was exactly in center to 0.120 off center. This confounded me enough to gather tools to measure the location of the clearance holes in CSX2551’s spring towers. After much work I got five sets of measurements and averaged them. The average offset for each was 0.000”, at least they were in the center. They must have been jigged for drilling as getting that accuracy on a fabricated weldment otherwise would be tough.

4) No two front (or rear springs), comparing one car to another, still had the exact same free camber or exactly matched AC. This is probably due to each individual chassis’ use history. The variance was not large.

Specific dimensions of leave width and width at ends were they fit into their uprights depends on what the dimensions are of the mating parts. Wear also is important. About 1991 I had exact copies of the Vandervill brand thrust washers made in 660 bronze bearing material except for thickness, I had parts made nominal, in +0.005, and in +0.010 so I could fit to eliminate slop due to wear or process variation.