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Kirkham Motorsports

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  #1 (permalink)  
Old 01-12-2012, 07:03 AM
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Default Leafspring suspension

At least two manufacturers make available a replica of the 289 roadster, using the transverse leafspring suspension. I've spoken with techs at four alignment shops in Billings; none has any idea how to alingn a car that has no upper a-arm, front and rear. I mention shimming one or more leaves and they just shake their heads.

Those of you who have a street 289 roadster or the FIA varient with a period-correct suspension, where do you take the car to maintain the alignment? Does a sort of motorsport competition call for cars with a suspension sufficiently similar to the transverse leaf approach to sustain the needed skills? Surely there are not enough replicas in an area to assure someone on the staff knows how to align an early fifties design.

How do you guys solve this problem?
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Old 01-12-2012, 07:31 AM
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Most alignment shops these days can't even align a 64-66 Mustang where camber/caster are set by shimming the upper conrtol arm. Their heads would explode if they saw a 289 Cobra set up. Actually, many 427 Cobra replicas have a similar challenge in that the rod ends on the upper arm have to be unbolted, adjusted, and retested several times to dial in the alignment. I found a shop down the road from me with nice alignment set up and a real mechanic who not only knows how to use it, but enjoys the challenge. I also purchased a Fasttrac alignment tool and toe in bar. I've gotten pretty good at setting my own.
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Old 01-12-2012, 08:08 AM
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Default castor etc

If you own a new generation Shelby, Superformance or Riverside no problems as these have heim joints with spacers to allow easy to dial in camber and castor but if your car is not, then different length springs and / or modified lower A arms is required.Shimming does`nt change the main leafs length but would affect your ride height. You looking for more negative?
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Old 01-12-2012, 08:18 AM
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Great question:

Front:
You can adjust the camber via trunion adjustment up or down. It is also fairly common to add adjustable A-arms as that helps avoid spring length changes. Also aids in caster adjustment.

Rear:
I suggest adjustable A-arms as without you can only change the length of the spring. This also solves caster issues..... Otherwise the frame mount sets caster.

Adjustment points for 289:
A) Spring length
B) Blocks to lower off the A-pillar
C) Adjustable A-arms big plus for cast and camber
D) Trunion position (front only)

Most shops will run and hide...... There are shops scattered about but few and far between. I suggest trial and error with simple level and tire wear observations.
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Old 01-12-2012, 08:41 AM
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Sreve,

As Ross pointed out the Hi tech Automotive built cars (Superformance, Shelby [current builds] and Riverside cars) have the "Ken Miles" type lower arms which allow easier alignment.

The real key is with any specialty car you need a tech who will do more than "set the toe and ler 'er go!" A proper alignment will check several parameters and double check after a couple of bounces as things can change.
For example 60's Fords with front strut rod bushings can be set, pulled off the rack, put back on and have different settings! Why? Because if the bushings are bad they don't hold the setting, the strut rod bushings were designed to allow some "rearward compliance" to reduce road shock and when they get old they allow the strut rod to move rearward too easily. Now this is not the case on a MK II Cobra suspension but the point is the same. You can't get a proper alignment at the "$19.95 Special" shop.
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Old 01-12-2012, 09:15 AM
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Good answers guys.

I've set aside the option to purchase a 289 with the leafspring suspension. Although other considerations are still unresolved, when I purchase a 289 it will be a Kirkham hybrid: narrowed 427 chassis with a coil spring suspension. I'm willing to forego the most appreciative and knowledgable market for a slabside in favor of a car I can enjoy on terms that are important to me. I'll have fun and my son willl have one more reason to cuss the old man after I've moved on...
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Old 01-13-2012, 02:40 PM
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Steve

Probably a good choice...... Not original in respect but probably better for use in today's world.
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