Proper front end alignment is one of the most important factors that determines the drivability of your classic. What some people don’t know is that, depending on what you have done to the car, the stock alignment specs may not work the best if you have made modifications. For instance, late model radial tires have more grip and don’t need or like as much toe-in as original bias ply tires. In fact, too much toe-in will cause premature wear on a radial tire. Then you have other modifications like the addition of later model style power steering, which is one of the most popular modifications on any Tri-5. Power steering conversions can take advantage of much more positive caster than the original alignment specs called for. Positive caster causes a vehicle to steer harder at slow speeds and since power steering was an option in 1955-57 Chevrolet called for only +1˚ caster so they would not get complaints about hard steering. Increasing the caster causes the vehicle to track straighter on the road when you release the wheel and helps the wheel center when coming out of corners, and the addition of power steering allows you to take advantage of this. Popular power steering conversions are the bolt in 605 box, (which has been replaced with the new 500 box developed specifically for the 55-57’s), the Delphi 670 box, which is also a bolt in, and many brands of rack and pinions. Regardless of which way you go with your project, 500, Delphi or rack and pinion you will need to modify your alignment specs to get the most out of your conversion. And remember, the newer roads we drive on today are crowned in the center. So you will have your front end aligned with different camber settings on each side, -1/4˚ on the passenger side and 0˚ on the driver side. This will allow the car to not pull to the right from the crown of the road.
Photo courtesy of www.jimboehly.com
Please note that you cannot get the specs recommended above for power steering conversions with the stock upper control arms and shafts. There is an upper shaft kit available (Danchuk # 975) which allows 2 degrees of additional caster to be dialed into the front end which you will need at a minimum. Another way to go is to replace your upper control arms with ones that have and additional +5˚ of caster built in***. There are many manufacturers on the market that can supply these but remember to tell your alignment specialist that you have installed these on your car…or they just might align the additional caster out negating any benefits you would have received from installing them. Caster will in no way effect tire wear, but more than stock will allow for better stability and drivability.