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Kirkham Motorsports

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Old 01-27-2023, 12:05 PM
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Default Steering arms

Does anyone know on an original 427 car are the steering arms the same as a 289 arm with a bend put into it? thanks
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Old 01-27-2023, 06:35 PM
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Original coil spring arms are bent whereas leaf spring arms are straight.
Larry

Edit: I should add thats in basic terms of production based cars. Some leaf spring comp cars had a bend in the steering arms, similar to later Cobra 427 arms to clear alloy wheels and bigger/wider tires.
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Old 01-27-2023, 08:15 PM
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But are they the same arms and they just bend the 427 arms or are they cast with the bend in them?
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Old 01-27-2023, 08:58 PM
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Quote:
Originally Posted by feadam View Post
But are they the same arms and they just bend the 427 arms or are they cast with the bend in them?
I don't know for sure as I don't study coil spring cars. That said, early modifications done by Shelby to fit comp car wheels were most likely bent in house. By the time the Cobra 427 came about, I'd say the steering arms were made with a bend at AC Cars or by their subcontractors according to plan.

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Old 01-27-2023, 09:11 PM
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Are the casting arms the same for 427 and 289 cars?
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Old 01-27-2023, 10:57 PM
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Quote:
Originally Posted by feadam View Post
Are the casting arms the same for 427 and 289 cars?
I don't think they're cast, rather forged. The set I have are forged.
I believe they're the same arms other than that though.

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Old 01-28-2023, 08:34 AM
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The 427 cars reportedly had an entirely new coil over independent suspension designed by Bob Negstad and Klaus Arnig at Ford in Detroit prior to fabrication at AC Cars in England. The suspension used a lot of Arnig's then new, patented and soon to be patented, IRS design theory including his anti dive and anti-squat technology. While I have never seen the two cars' steering arms side by side, I would be surprised to discover they were the same.
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Last edited by eschaider; 01-28-2023 at 10:20 AM.. Reason: Klaus instead of Claus
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Old 01-28-2023, 09:31 AM
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That is why the Bump Steer was so atrocious on both models....
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Old 01-28-2023, 10:18 AM
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I agree Morris. I don't understand if they didn't consider it important, didn't know about it (I doubt that), chose to, or had to shortcut the design process, or what? The only thing for certain is the bump steer was impressively poor — and with a clean sheet of paper, at the design stage, it would have been easy to do right.
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Old 01-28-2023, 10:43 AM
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Borrowing a photo from David Kirkhams thread on rebuilding an original 427 suspension, this shows the steering arm and upright. Note the bend in the steering arm. The lower portion of the upright looks very similar if not the same as the leaf spring counterpart. The upper portion is different to accommodate the ball joint. Mounting points on the arm look the same as well.

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Old 01-28-2023, 10:46 AM
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Another from the same thread showing the steering arm bolted to the upright.
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Old 01-28-2023, 12:24 PM
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When the steering arms were designed for Cobras CS 2030 (prototype rack and pinion steering car in RHD) and then CSX2126 (first production rack and pinion steering car in LHD that was the prototype for Ford electrical and cooling system components) onward, they were for street Cobras with 5.5” wide wire wheels and narrow widths of treads for standard and optional tires made with relatively hard compound(s) tires.

All early racing Cobras started off as street car chassis. I do not believe that the steering arms, forged in a straight ahead pattern for rack and pinion steering cars, and tie rod ends had any clearance problems as long as 6” wide magnesium sprint car wheels (a.k.a. kidney bean wheels or in the 1960s sometimes called coin slot wheels) made by Halibrand Engineering were used.

As soon as Shelby American started using any pattern of magnesium wheels made by Halibrand in 6.5” width an interference with tie rod ends and insides of front wheels cropped up. The amount of interference depended on the exact wheel casting pattern used (there were several in the slotted hole sprint wheels and six spoke sprint wheel designs) and how each batch of wheels was machined. Not every version of 6.5” six spoke (a.k.a. called FIA wheels even though they were used in all forms of racing Cobra participated in and the only version made with the F.I.A. in mind was the 8.5” inch rears where 8.5” rear wheels was allowed). I have no idea how many different 1963-65 casting patterns Ted Halibrand’s company had for the 6.5” wide six spoke wheels but I test fit five (5) different versions of factory racing wheel in 6.5” width on our red car one Saturday and every version had a different back spacing and every one had a slightly different amount of tie rod end clearance. I think that I have figured out a possible reason for so many versions of six spoke 6.5” wheels was perhaps that the designs and the sizes of front brake calipers in Cobras were changed a few times. Example: I have a pair of front wheels used in racing on CSX2009 decades ago and they will not clear the stock front brake calipers of cars CSX2165 and later without some kind of modification to something. I suspect that each time Cobra front brake caliper designs were changed Halibrand had to come up with a new pattern and machining patterns to make front wheels to fit. It was not until the 1965 version of the six spoke front wheel that new wheels worked with any Cobra’s front brake calipers including the large racing aluminum ones allowed in experimental or modified classes or in F.I.A. events.

For early rack and pinion steering Cobras, in all 6.5” wide front magnesium wheel cases it seems Shelby American heated steering arms and added bends to them to clear the back sides of magnesium wheels while they had new chassis partially dismantled for conversion into race cars. I believe but have no proof that A.C. modified the steering arms for the chassis specially ordered as race cars starting with the wide rear wings (A.C. Cars description, a.k.a. in later years cut back door cars) cars.

Enter what we call 427 Cobras. When the CSX30xx chassis were built at A.C. they had steering arms bent into gentle curves very much like that last racing Cobras. The first wheels for CSX30xx cars were left over 1965 type six spoke pattern wheels in 6.5” width. Soon the COBRA II 7.5” wide front wheels became available and then a clearance problem apparently cropped up. If you see pictures of an unrestored as built CSX30xx car with 7.5” COBRA II front wheels the rubber dust boots of the AP Lockheed tie rod ends are probably being distorted and rubbed by the magnesium wheels. The fix at some point for a retro rework for CSX30xx cars was to bend the arms some more.

Somewhere in the CSX3101-CSX3200 contract, and perhaps from the start but I do not know, A.C. put more significant bends in the steering arms and that created a better gap between steering tie rod ends and backs of 7.5” wide front wheels.

Very few "Cobra" related subjects are simple ones.

And then there were things that owners did post production to adapt all kinds of magnesium wheels in all kinds of widths up to 8.5" (that I have seen, perhaps wider) to the fronts of Cobras and 427 Cobras. I have seen seriously modified steering arms.
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Last edited by Dan Case; 01-28-2023 at 12:52 PM.. Reason: add material
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Old 01-28-2023, 12:41 PM
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Reason I ask question is I bought a set of steering arms for a 427 car but they are straight. So I guessed that they are all (for 289 &427are the same) and the 427 arms are just bent with a 30 degrees bend.
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Old 01-28-2023, 02:24 PM
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Same
Bend them
Unless your running super skinny rims.
HTM111 bent
AC1085 bent, Some Later cars with 16” wheels not all were done.
Goldie bent ....... 289 progress........ To review buggy spring arms with big brake and FIA wheels.
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Old 01-28-2023, 03:34 PM
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Do you know if it’s about a 30 degree bend?
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Old 01-28-2023, 03:54 PM
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Look at my thread. Basically shows steps. As to angle Dunno it works though.
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Old 01-29-2023, 03:15 PM
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Did you get your steering arms from cobra racing or are they original?
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Old 01-30-2023, 01:54 PM
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Comp arms and street arms also have different brake caliper mounting bolt hole spacing and different brake caliper offsets. The comp arms are not interchangeable with street arms. BTW caliper bolt hole spacing is also different on the rear uprights between street car and comp car.
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Old 01-30-2023, 06:56 PM
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Tom
Do you know the degree bend in the 427 arms
Thanks adam
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Old 01-30-2023, 07:46 PM
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The more you bend the arms the more anti-Akerman percentage you get.
My suggestion is to bend the steering arms the minimum amount to clear the rim.
This assumes of course your steering arms are not cast and the material can be safely bent that far.

More info on Akerman:

https://www.racecar-engineering.com/...ring-geometry/

https://www.vehicledynamicsinternati...behaviour.html
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