C-2 Waddle at High Speed?

[Bill S.]

Waddle is a term the Service Manuel uses to describe my issue with the 66.
I have new tires and had a alignment using a caster setting on the front driver side of 1 7/8 degrees positive and passenger side of 2 degrees. (I set it this way as Duke and Vette Brakes liked the setting)
The car does not pull braking or otherwise, BUT the front tires are "feathered" as you run your hand across them (rear are smooth)
The stability at speeds up to 55MPH is great, but from 55 to 80MPH the car waddles, as if gusts of wind were pushing it back and forth.
I was told the mid-years were noted for poor high speed stability as they tend to sit high and air rushes under them at high speeds causing a "less than stable" condition.
Opinions please....
Thanks
Bill

[Mike Cobine]

Re: C-2 Waddle at High Speed?

You are describing a host of problems.

Your condition sounds like a condition known as cupping. This can be caused by many things; misalignment, loose suspension parts, loose wheel bearings, bad shocks, poor tire balance, mismatch of front and rear alignment (front and rear fight each other), and so on.

http://www.kaltire.com/commercial/medium_truck_tires/cupping.php

Ensure all of your suspension is correct, tight, and in good condition. Frequently people have idler arms that are loose. One indication is if you have belted tires and you get severe nibbling at tar strips on old roads. The front will jump back and forth as you drive. The nature of the radial tire will often mask this and it will not be obvious.

The suspension settings are good for most roads due to the crowning of the pavement to drain water. However, if you want to travel at higher speeds, you need to align for higher speeds. Most tire stores automatically introduce uneven alignment to compensate for crowned roads, but you have to alter this for high speed use. Often the alignment person, being the paid expert, will not accept your suggestion well.

If your tires are truly feathered, where the ribs seem higher on one side than the other (like teeth on a saw), then you have "feathering" and you can see some suggestions on this here:

http://www.kaltire.com/commercial/medium_truck_tires/feather.php

One problem known back then was that the Sting Ray was an inverted airplane wing that didn't work. It created lift. The usual solution to the body design problem was to angle it nose down slightly. One inch to three inches difference from nose to tail made a big difference. This was prior to spoilers, air dams, etc. A front air dam improves handling considerably.

Restoration has caused a few problems in handling. One is that most springs are not the correct ride height. Get about 20 feet to the side of your car and stoop to where you are roughly the same level as the body line. If you can see the tops of the tires, your body is sitting too high. Originally the tires were up in the fenders but most new springs have the tires sitting further down. Compare yours to the old PR photos of the '63 found in many Corvette books.

Restoration tires are sometimes a problem. There is a reason Corvettes evolved both by owners and by Chevrolet to lower, wider tires and away from belted to radial. You could simply be beyond where your tires handle, depending on your tires, even at 70 mph.

The production Sting Ray has raced to 180 mph and the primary handling problems were lift of the front and lift of the rear. My '66 at 185 lifted the front so badly you could steer with one finger with manual steering. However, that is over 100 mph faster than you are going.

Phil Currin said his '63 coupe ('72 IMSA champ) would lift the rear so badly that he would lose traction at speed. Of course that was double your speed, so you should not be experiencing your problems if all equipment is correct.

[Duke W.]

Re: C-2 Waddle at High Speed?

C2s aren't fundamentally unstable, If fact, the coupe is quite stable in cross winds at normal speeds because the center of pressure is well aft of the center of gravity.

They do have considerable front lift at very high speed, which makes them somewhat reluctant to turn and a bit more sensitive to cross winds.

You need to do a thorough front end inspection including all the suspension bushings and steering linkage. Something is probably either worn or loose.

You did not mention camber or toe settings. Toe-in for radial tires should be about 1/16". Since modern roads have little crown I recommend zero, or as close to zero as possible cross camber and cross caster. On a normal freeway the car should track nearly straight and just slowly drift to the right.

I recommend camber in the range of zero to negative one with the low end considered a "touring" and the high end negative value as "performance".

Duke

[Michael H.]

Re: C-2 Waddle at High Speed?

Hey Bill -

Aerodynamic lift will not have a noticeable effect until well past 100 mph, so I would look at the places mentioned earlier - especially shocks.