I was told recently that if you add a couple degrees of toe-in when you have your front end aligned it will help remove some of the wander and improve road feel. Is there any truth to this?

 

Where does one hear all these tall tales?

Duke

 

Toe in isn't measured in degrees - but in inches, usually sixteenths of an inch. I suspect he meant to say that increasing caster by several degrees will tend to reduce wandering (which is true) - but it's hard to tell from the statement. Increasing toe in more than a couple sixteenths will just scrub your tirethread, although it may slightly improve the response of initial turn-in to a turn - but not something that's recommended.

 

Ken - hope you don't mind my tagging on your thread re alignment -

Dan/Duke - Like Ken - I also have a 66. I alternate between two sets of wheel/tire combinations- factory original steel with stock bias tires and original Knock Offs with radials. If I get the alignment set for the steel wheels - would I then have to get another alignment when I run the KO's ?

 

I'll bite. Here's what an old alignment man told me years ago, and I believe it to be true.

In the C2 era, all cars had bias ply tires. The bias ply's called for a certain amount of TOTAL toe in... 1/8 to 3/16 inch as I recall.

After 73?, all Corvettes came with radial tires. The specs for alignment for radial tires called for LESS toe in.

Somewhere along the line, the published alignment specs used for all C2's and C3's changed to the "radial" spec.

If you drive your Corvette with bias ply tires using a radial tire "toe spec", it will wander...find ruts in the road....twitchy steering, etc. I guarantee this to be true from personal experience.

The cure is to align your front end to the "old" original bias ply spec. With the small amount that all of us drive these cars, the "scuff" of the radials isn't really a factor.

Heck, I'll be dead or in the nursing home before I wear out a set of radials on any of my Corvettes. Chuck

 

This might be a little off the subject but I've been playing around with my "Gran Turismo" Playstation game using the C-2 Vette. Every single aspect of the suspension, drivetrain and tires can be changed and you can learn a lot about how those changes affect the car's handling. SWCDuke's recommendations seem to work the best.
If you haven't tried this game, it's worth a look. It's a fantastic learning tool.

 

No, changing wheels/tires does not affect camber or caster even if the wheel offset is different. Since toe is measured at the outside diameter of the tire, a change in tire diameter will affect toe, but it would be tough to measure the difference if the diameters are within an inch or two.

Many modern car toe specs are ispecified in degrees rather than inches, and there is an easy why to convert using a couple of geometric principals.

1. The length of arc subtended by a small angle is equal to the radius of the arc times the angle of the arc in radians, and for small angles the arc and secant length are very nearly the same. The secant is the straight line between the angle at the specified radius, which lies inside the arc and is very slightly shorter. The secant is what we are actually measuring for toe.

2. 360 degrees = 2pi radians

On a Corvette with radial tires the "ideal" toe in is about 1/32" per wheel, which would measure 1/16" between both tires

Toe in angle = (.031/13.5)(360/2pi) = 0.13 deg. per wheel

This can then be linearly interpolated for different toe in measurements. If the toe in per wheel was 1/16", the toe angle would be 0.26 degree. If you're a fan of Henry the Navigator you will want to convert these decimal degrees to arc minutes and arc seconds to aid your navigation of the world. Fortunately most alignment specs are now specified in decimal degrees, not arc minutes and arc seconds.

If you run radial tires for driving and have a set of bias plys for show and judging, set the toe-in for radials - about 1/32" per wheel, rather than the larger value recommended for bias plys (see your service manual). There's no need to change toe-in all the time, particularly if you don't drive much on the bias plys.

Duke

 

Duke - Absolutley perfect info - exactly what I needed to know - many thanks

 

Duke, I have to respectfully disagree with you.

The original specs for 63-66 call for a toe in of 7/32 to 11/32. The 67 calls for 3/16 to 5/16.

Beginning in 73, with the advent of radial tires, the specs changed to 3/32 to 5/32. This is the spec that most alignment shops use.

SO...there was much more "total toe in" used with the old bias ply tires.

Setting a car that you drive on bias ply tires to the radial tire spec will cause the wandering, jumping out of ruts, etc.

When I've driven my 63 and 69 on radial tires, with a "radial" alignment, the cars drive fine. When I put my bias ply "repro" tires on, keeping the radial alignment, the cars are scary to drive. They're all over the road.

Changing the alignment to the old spec for bias ply tires completely changes the steering characteristics of the car. They drive perfectly on bias ply tires, like they used to 40 years ago. Chuck

 

I don't know what you disagree with. I made the distinction that bias ply toe-in values are greater than what is usually specified for radials.

I believe the question was what to do if you have both radials and bias tires on different wheels that you swap back and forth, and my answer was to use radial tire toe-in values if you do most of your driving on the radials and only use the bias plys for shows and judging.

In 1968 when I installed a set of 205HR-15 Pirelli Cinturato radials that replaced the 6.70-15 Michelin X radials that I installed in 1964, the Pirelli Pocket Guide I got (and still have) discussed the differing toe-in requirements for radial tires. They recommended 5/64". I just rounded that to 1/16" and that's the total toe-in value I shoot for on most of my cars.

Over the years I've experimented with various toe-in and even toe-out values on most of my cars, and with the exception of my Cosworth Vega where I run a little toe-out, all the others appears to steer and handle best with minimum toe-in - about 1/16" total or 1/32" per wheel.

Duke