I’ve finally gotten around to buying some modern rubber for my ’66 Impala. For the time I’ve owned the car I have only run with the skinny, reproduction, bias plys. Even though I like the stock look it isn’t exactly a pleasure to drive. So, for general putting around, I’m going with 275/50R17’s front and rear. Decent size rubber and they are very close to the factory tire height of 28”. Question is, what alignment specs to use with the radials?

The factory specs for the bias plys, from the original service manual, are as follows:

Caster = Positive ¼* +/- ½*
Camber = Positive ¼* +/- ½*
Toe In (total) = 1/8” to ¼”
Steering Axis Inclination (like I have any idea that that one means, or if it’s even adjustable) = 7 ½* +/- ½*

Last time I had the car aligned on modern equipment all the specs from their computer were listed in decimal instead of fractions. Those specs are as follows:

Caster = + 0.3* to + 1.3*
Camber = - 0.3* to + 0.8*
Toe In = + 0.13* to + 0.25*

Cross Caster = - 0.5 to + 0.5
Cross Camber = - 0.5 to + 0.5
Total Toe = + 0.25 to + 0.50

What would like help with is determining what specs to use with the radials that will provide decent road manners, while not having too horrible an effect on the bias plys when I need to use them.

Any suggestions from your alignment gurus?

Many thanks,

Dan

these are just guesses..
in most cars, you want as much caster as you can get- of course, if you don't have power steering you might not want so much since it will make it harder to steer at low speeds.
camber should be pretty much straight up- maybe tip the top in a degree or so.
and toe maybe 1/16"-1/8" in.

Radials like more + caster as a rule. If I were doign it I`d try to get +4* caster and still get a little - camber if I could. You may be limited by how much adj you have available. If memory serves from a `65 Impala conv. I aligned a year or so ago (it`s on the photos page on our website) the lower arms have adj. on the onboard side. I used those to get a little - camber and then shimmed the back side of the upper arms to get more + caster. I think that car ended up at -1/4* camber and +4* caster with an extra .5* cross caster to compensate for road crown. It was a big improvement,the car tracked straighter and handled better. The extra caster gives the steering more road feel and auto centering too. The customer was a very happy camper. :) Mark SC&C

Thanks Derrik. The car does have PS so low speed effort isn't an issue.

Mark, correct on the adjustment point inboard on the lower control arm. Since I'm an alignment dufus, you are suggesting:

Camber = as many degrees as possible(?) left and right
Caster = +4 degrees left and right
Cross caster = .5 degrees

How about toe and cross camber?

Or, even easier for this dufus to follow, let play fill in the blanks:

Camber = _________
Caster = __________
Toe = ____________
Cross Camber = __________
Cross Caster = ___________
Total Toe = _____________

The 6 items above were pulled directly from the print out I got from the last alignment.

Thanks much for the help and education.

Dan

Left camber +1/4, right camber 0, left caster +2-1/2, right caster +2-3/4, toe +1/8''. If you give it a lot of caster it will steer great going straight but you may get tire squeel when turning sharp. The higher the caster the more toe out in turns and camber change you will have. These specs will work fine.

Too much adjustment on the strut-rod on the lower will twist the lower control arm bushing, which can be a real problem if you're using poly bushings... they bind regardless, but pulling the lower too far forward will make it worse.

I'd aim for 0.25* neg camber, and as much positive caster as possible with the lower arm straight... then pull the lower forward with the strut-rod only as much as needed to get 4*+ caster, then re-adjust camber as needed to keep 0.25* negative, and go with 1/16" toe in.

Thanks again for the feedback Man, Derek.

Completely understand what you are saying about the lower control arm binding. I'm using stock rubber bushings everywhere in the suspension.

I just want to make sure I have some numbers to take with me when I request a "custom" alignment.

All information is appreciated.

Dan