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Complete 69 Plymouth Valiant Suspension Upgrade

If You Think There Might Be More To Performance Than Just Racing In A Straight Line, Then Follow Along On This Mopar A-Body's ...

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Disc Brake Conversion
Right Stuff Detailing makes a simple yet effective disc brake conversion for the early A-Body cars that bolts on with very little effort. The kit comes with the spindles and is also shipped with new upper control arms to accommodate the different ball joint, which we didn't need with the Hotchkis tubular arms. The Right Stuff kit comes with all the necessary components, including new wheel bearings, seals, 11-inch rotors, loaded factory-style iron calipers, caliper brackets, stainless hoses, clips, and even an adjustable proportioning valve. The best part was that the company was able to ship these parts to us very quickly. And since most of these parts are kept in stock, you can expect to get the same quick service we enjoyed. The prices listed in the parts list reflect the cost savings of not needing the stock upper control arm and the additional cost of the powdercoated calipers and drilled rotors.

Rolling Stock
The key to making any car handle to its ultimate potential is to create the best symmetry between the suspension and the tires. A great set of tires and wheels will fare poorly with a lame suspension, while even the best suspension components are limited if used with ancient tires. We did a little measuring and discovered that we could actually fit a 275/40ZR17 tire under the back of this little Mopar, so the call went out to General Tire for a set of Exclaim UHP hoops, including a slightly smaller 245/40ZR17 for the front. We chose the General tires for their great handling qualities and affordability. We could have gone with much stickier tires, but that would have been more costly and reduced tread life. The General Exclaim UHPs offer a treadwear rating of 380 (which means they're relatively long-lasting tires) along with an A traction rating. Best of all, the entire set was just less than $550.00.

The next challenge was to fit those tires under the car with no interference. Unfortunately, we couldn't be sure until installing the front and rear suspension conversions and disc brakes. This left us very little time, but Curtis Speed Wheels came through with a set of 17x8-inch cast center Vintage wheels with a very specific 5.5-inch backspacing front and rear that positioned the tires perfectly inside the wheelwells. Ideally, the 275 rear tires should be mounted on a 9.5- to 10-inch-wide wheel, but the next step up with the Vintage wheels is 10 inches, which would probably have rubbed, requiring expensive sheetmetal surgery, so we decided on the more conservative 8-inch wheel width. We want to especially thank Mark Curtis for helping us out on very short notice with a set of outstanding-looking wheels.

Track Testing
The sad part about this story is that you can't get behind the wheel of the car to experience the difference for yourself. The next best thing is to test the car to evaluate the difference. Anyone who has ever driven a drag-oriented car knows that the combination of tall ride height, flexible sidewall rear tires, and soft shock valving does nothing to inspire confidence in the corners. Frankly, we expected the skinny front tires to produce a skidpad number just ahead of a Conestoga wagon, but a 0.71 g is commendable. Adding the Hotchkis suspension, Flaming River steering box, and General UHP tires put the A-Body on track. More so than that was Shannon's enthusiastic response after the initial testing: "It's a completely different car now-wow!" We also have to give props to the Flaming River steering box with its much quicker ratio. Even Hudson's enthusiastic testimony and the superior test numbers don't convey just how massively different the car feels after the conversion. You just have to experience it for yourself.

  SKIDPAD 600-FOOT SLALOM
(G's) (AVERAGE MPH)
Original 0.71 55.3
Hotchkis conversion 0.85 63.0

Alignment Specs
Hotchkis decided to dial a slightly more aggressive front alignment into the A-Body for maximum grip. While this worked well, negative camber settings of more than 1 degree will eventually generate excessive inboard tire wear. We've included a second set of street alignment settings that will still allow the front suspension to improve handling but without undue tire wear.

  CAMBER CASTER TOE-IN
  (DEGREES) (DEGREES) (INCHES)
TRACK -2.5 to -3.0 + 8 1/16 to 0
STREET -1.0 to -1.5 +6 to +7 1/16

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8 comments
John Lenau
John Lenau

I enjoy many different kinds of racing, but nothing better than a straight line

Ronnie Richardson
Ronnie Richardson

Youre my favorite mag and Ive been reading a long time. I still like straight lines better. HAPPY THANKSGIVING.

Jerry Justice
Jerry Justice

let's go play in the dirt happy thanks giving guys and gals

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