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Some basic education about wheel alignment on C1 and C2 Corvettes by Joe Fisher
Joe (Plaidside) and I have worked up some basic information regarding common terms used in discussing and performing front-end wheel alignment of first and second generation Corvettes. Joe’s info is not intended to be an exhaustive guide on how to align your C1 or C2 Corvette though we do include some information from the ST-12 - 1953-1962 Corvette Servicing Guide. Rather, the intent is to explain the terms and concepts involved in what we hope is a simple straight-forward manner. We appreciate helpful suggestions from JohnZ along the way as we prepared the documents! Brief commentary from Duke Williams (SWCDuke) in an earlier CF thread is also included.
Two PDF files are attached. The C1 document is for the early cars and the “shimmed control arms” document is oriented toward the C2’s though it is applicable to most cars using shimmed control arms in the front suspension. We hope you find this info of use for your private reference collection; especially those of you who are new to these great old cars.
Cheers!
Joe (Plaidside) and I have worked up some basic information regarding common terms used in discussing and performing front-end wheel alignment of first and second generation Corvettes. Joe’s info is not intended to be an exhaustive guide on how to align your C1 or C2 Corvette though we do include some information from the ST-12 - 1953-1962 Corvette Servicing Guide. Rather, the intent is to explain the terms and concepts involved in what we hope is a simple straight-forward manner. We appreciate helpful suggestions from JohnZ along the way as we prepared the documents! Brief commentary from Duke Williams (SWCDuke) in an earlier CF thread is also included.
Two PDF files are attached. The C1 document is for the early cars and the “shimmed control arms” document is oriented toward the C2’s though it is applicable to most cars using shimmed control arms in the front suspension. We hope you find this info of use for your private reference collection; especially those of you who are new to these great old cars.
Cheers!
I think the descriptions of positive and negative caster in figure 4 of the attachments are backwards. Doesn't positive caster increase the self-centering of the wheels? The bicycle wheel analogy seems wrong. Am I missing something?
I think the descriptions of positive and negative caster in figure 4 of the attachments are backwards. Doesn't positive caster increase the self-centering of the wheels? The bicycle wheel analogy seems wrong. Am I missing something?
Figure four is correct if the bicycle wheel is traveling forward from right side of diagram to left side. The further out in front of the steering pivot point you put the axle the more positive caster and thus the more self centering effect.
Figure four is correct if the bicycle wheel is traveling forward from right side of diagram to left side. The further out in front of the steering pivot point you put the axle the more positive caster and thus the more self centering effect.
I disagree.
The further forward the axle is, and thus the tire contact point, the greater the tendency to turn away from the direction of travel.
Try this: get a bicycle on a level surface. Straighten everything up, and holding it by the seat, push it forward. You won't go very far before it veers off course and does not recenter itself. In fact, it gets farther off course as it goes. It has NEGATIVE caster.
I disagree.
The further forward the axle is, and thus the tire contact point, the greater the tendency to turn away from the direction of travel.
Try this: get a bicycle on a level surface. Straighten everything up, and holding it by the seat, push it forward. You won't go very far before it veers off course and does not recenter itself. In fact, it gets farther off course as it goes. It has NEGATIVE caster.
No, I don't think so. See Post #8.
Also read Fred Puhn's "How to Make Your Car Handle" and Carrol Smith's book "Prepare to Win".
My four years of automotive training goes back to the mid 70's which included front end alignments. What was taught then remains the same today. Positive caster will cause the wheels to return to center on their own when coming out of a turn once you let go of the steering wheel. Zero caster will not. Negative caster causes the wheels to track or follow the direction the vehicle is already traveling.
Per the 1963 Corvette Shop Manual. "...The correct caster angle or positive backward tilt should be 1 3/4 degrees =/-1/2 degree."
Maybe we are all thinking the same thing, ie. a backward tilt (upper pivot to the rear of the lower pivot) is positive caster.
I have a rather basic question regarding my 64. I recently had my first alignment after frame off, but discovered my steering wheel hub may not be in the proper position (for the directional release to work correctly) and may need to be rotated such that my steering wheel will now be out of alignment when driving straight. So if I correct my steering wheel hub, how do I then adjust the steering so the wheel is looking right when driving straight without affecting my fresh alignment? Is it possible?
Per the 1963 Corvette Shop Manual. "...The correct caster angle or positive backward tilt should be 1 3/4 degrees =/-1/2 degree."
Maybe we are all thinking the same thing, ie. a backward tilt (upper pivot to the rear of the lower pivot) is positive caster.
That description sounds like positive caster to me. The rake on motorcycle front forks is positive caster as well to again keep the front wheel pointing straight unless or until the rider induces a turn.
I was always told that Toe In is measured at the rim edge (not the tire).
And when I check my more modern vehicles that use "degree measured" Toe In, my Toe Plate agrees with that (if I try to verify the Toe by measuring at the tire tread surface, the Toe In is that much larger). Note that my Toe Plates measure at the rim surface, not the less accurate tire bulge surface).
The ST-12 and most sources do not indicate where Toe is measured, and most of us assume it is at the tire tread........
And I agree it is Positive Caster, otherwise the tire will try to flip around to the rear (to follow).
Thanks for the articles!
Plasticman
Last edited by Plasticman; 07-22-2016 at 05:57 PM.
Been aligning cars since 1983 on different types of equipment. Not the sharpest tool in the drawer, but I can get it done and know the terminology. Sorry, Dave, but you are backwards. Positive caster is having the kingpins or ball-joints canted at a backward slant. So there is a forward rake of the knuckle. Think chopper motorcycle. Negative caster is the opposite. Try pushing that bicycle with the handlebars flipped around and the fork backwards.....it'll fall over even sooner. That's negative caster. Negative or O caster was used back in the day at slower speeds so manual steering cars steered easier. Later cars travelling at higher speeds on radial tires with power assisted steering used more caster...sometimes 2 or 3 degrees. Hell, look at any Mercedes turning it's wheels in a parking lot....almost 10 degrees of caster, you can see it with your eye. Great for high speed stability. For plasticman, toe is the difference in track between the front and rear of the front tires. From the same point on each tire, you measure the distance on the front of the tires, and on the back of the tires, going across. IF the front distance is less, you are toed in. If the distance is the same, you have zero toe. If the front distance is more, you are toed out....like a duck. Very basic stuff.
My original confusion is from where the red lines in figure 4 are drawn. I think, in both cases, the line should be vertical since that is the axis of rotation. Therefore, the caster wheel has positive caster and the bicycle wheel has negative caster.
07-21-2016, 12:20 PM
Some basic education about wheel alignment on C1 and C2 Corvettes by Joe Fisher
