C2 rear suspension articulation

[Doug W.]

Help me understand! I am new to the corvette hobby and currently refurbishing the entire rear suspension on a 65 coupe and I cannot grasp how a solidly mounted 1/2 shaft to an articulating trailing arm combination can work without applying a severe preload to the rear wheel bearings. It appears to me that the design makes the 1/2 shaft also serves as a another suspension link along with the torque rod to stabilize side to side movement of the trailing arm and maintain wheel alignment at the expense of the load on the wheel bearings, u joints and differential yokes. Is this true or am I missing something?

[Joe L.]

Re: C2 rear suspension articulation

Help me understand! I am new to the corvette hobby and currently refurbishing the entire rear suspension on a 65 coupe and I cannot grasp how a solidly mounted 1/2 shaft to an articulating trailing arm combination can work without applying a severe preload to the rear wheel bearings. It appears to me that the design makes the 1/2 shaft also serves as a another suspension link along with the torque rod to stabilize side to side movement of the trailing arm and maintain wheel alignment at the expense of the load on the wheel bearings, u joints and differential yokes. Is this true or am I missing something?

Doug-----


The rear suspension design of C2 and C3 Corvettes DOES include the use of the half shaft as a suspension link. There's no doubt about that and GM has never indicated anything to the contrary.

I don't know that the design places severe preload on the rear wheel bearings. However, it definitely places severe load on the u-joints and the yoke axles. That's the reason that these often need to be replaced.

[Duke W.]

Re: C2 rear suspension articulation

It's called a "three-link suspension" - two lateral links, one of which is the halfshaft, and a trailing link. It was first used by Colin Chapman on a formula car in the early sixties. The rear wheel bearings see slightly more load that the fronts, but only because of greater weight due to a small static rear bias and increasing rear bias with increasing occupant and cargo load. The wheel bearings on both ends see both static weight and cornering loads.

The u-joints do see greater load than in a driveshaft application, but they are considerably larger than the driveshaft u-joints and the axle u-joints are shared with some medium duty truck driveshafts.

I don't think the axial load on the u-joints decreases life. The outboard u-joints are typically the first to go, and I think the primary cause is usually water intrusion that washes out the grease leading to rapid wear.

The C2/3 rear suspension has some issues - primarily lots of toe and camber change through the range of travel. It also has poor anti-squat characteristics. A free body in space has what is called six degrees of freedom, and any position and attitude can be represented by x, y, and z coordinates and an angle about each of the three axes. Ideally, we want the rear tire to have only one degree of freedom - pure up and down movement, and this implies five links.

Modern Corvettes and purpose built race cars all have two a-arms plus a steering tie rod in front and fixed toe control link at the rear. An a-arm effectively acts as two links, so there are five links on each end. No one has come up with a better suspension architecture than this.

BTW, the C4 rear suspension also uses the half-shaft as a suspension member with four additional locating links, so it's technically a five-link, but it's a compromise because using the half shaft as a suspension link limits the roll center height selection to a range that is less than ideal. The C5 was the first Corvette to have a true five-link suspension that didn't involve the half shaft as a suspension member - two a-arms and a toe control link.

One of the reasons I bought a new Mercedes 190E when they were first available in the US in 1984 was the five link rear suspension, and in this case it was five independent links. At the time it was the most sophisticated automotive suspension in the world, and it certainly showed in the way the car rode and handled. I liked that little four-cylinder 190 so much that I bought a six cylinder version when they became available a few years later, and I still own it.

A three link suspension similar to the C2/3 was also used on the second generation Corvair, and despite the three-link suspension's faults, it was a vast improvement over Dr. Porsche's swing axle design (used on the first generation Corvair) that is probably the most devilish rear suspension architecture ever devised.

Duke

[John D.]

Re: C2 rear suspension articulation

I believe there was an SAE paper written by Zora back in the day that explained his thinking on the C2 rear suspension

[Michael W.]

Re: C2 rear suspension articulation

Here's the paper

http://www.web-cars.com/corvette/1963_SAE-paper.php?page=0

the suspension stuff is on page 4 onwards.

[Doug W.]

Re: C2 rear suspension articulation

Ah, It is all much clearer now. Thanks to all for sharing your knowledge and understanding of this suspension design. Your years of passion and expertise in this hobby are invaluable to many of us.