How to Achieve Proper Geometry on Your C-10 Rear Suspension
The rear trailing arm suspension is definitely one of the best features of mid-year C-10 trucks manufactured from 1963-72. Similar setups are still in use today on many larger model automobiles by many manufacturers; it’s also the go-to choice for NASCAR. Trailing arm suspension has proved to be a wonderful platform for cars and trucks. Known for its excellent stability when cornering while offering a smooth ride, GMs choice to use the system was clear during the company’s heyday.
As time went on, though, the cost of raw materials began to climb, and the trailing arm suspension met its demise once it became too expensive to produce. With the new ’73 model makeover, the decision was made to revert to the profitable leaf spring rear setup. Now, just like every engineered item in this world, there is always room for improvements or refinements. As engineers like to say, the trailing arm suspension that General Motors produced was good, but it wasn’t great.
By far the biggest mistake GM engineers made in the ‘60s was the shock placement on the trailing arm suspension. But who knew that these trucks were going to be pushed to the limits of performance driving. No Limit found the cure by relocating the shocks outboard rather than inboard of the frame. Your C-10 will become more stable in the turns, and by moving the shocks behind the axle, they complement the ride quality because they can control wheel hop. After we got our hands on No Limit’s kit, we took off the old shocks and the lower mounts by removing the U-bolt nuts.
Stop and think about it for a second. What makes a trailing arm suspension work so well is simple geometry: A triangle formation of arms or link bars is used to gain stability, where the front of the main link bars mount at a front cross member relatively close together then spread out towards the rear at a wide angle directed at each of the tires on both sides. A rear link, or panhard bar, is used behind the axle to help control lateral movement while still offering a good range of vertical motion.
On the passenger side of the axle, the lower shock mount shares duty with the panhard bar bracket that we coined the shark fin for obvious reasons. The shark fin and the panhard mounting plate are slid in place through the U-bolt on top of the trailing arm before the arm and the lower shock bracket/axle pad are installed and snugged down.
What complements this triangle of links is where a set of coil springs supports the weight of the frame. Placement of the springs is key to having a steadfast system with inertia control. Mounting the spring to the lower arms, just outside of the frame, allows for a sturdy and secure base no matter the coil springs’ weight rating. This gives the vehicle’s occupants a better ride, provides the driver with cornering confidence, plus it adds more traction, as well.
A set of shock studs is bolted to the lower shock bracket to create a space for the shock’s mounting eye to rest. Then the upper shock mount is bolted to the frame. If this setup looks familiar, you have a great memory, because this kit can be purchased for a stock frame application. No Limit recommends this system for use with its new back half long to short conversion.
No Limit’s panhard kit is a clean and simple way to attain proper geometry, allowing for a tighter more stable feeling while maintaining control under heavy cornering. The frame mount is bolted in place through the fame on the outside and underside of the driver’s frame rail, whereas the fixed end of the thick gauge mild steel tube is fixed to the bracket located on the axle plate.
These were all the great things that GM campaigned about the Chevy trucks throughout the ‘60s: 1963-72 Chevy trucks came equipped with trailing arm rear suspension, while the GMC brand had leaf springs. What the designers of those trucks never dreamed was that 45 years later people would view these trucks as performance vehicles, not workhorses. So why were they so bad, and what can the modern enthusiast do to cure the plague of problems that exists with the Chevy trailing arms? In search of answers, we looked into the way that No Limit Engineering outfits its new long-bed to short-bed conversion frame kit that we featured in our October issue (“Some Assembly Required,” Oct. 2012, pg. 30). Let’s take a look at the changes and how the kit is installed.
The adjustable end of the bar attaches to the frame bracket underneath the rail where you have a few choices on mounting points. We chose the center, or neutral, setting which is perfect for all around driving. Why is this bar so special compared to the factory? The answer is in the frame mounts’ placement. A longer bar reduces body roll and creates more traction.
To round out the install, the shocks are installed by sliding shock’s eyes over the bottom bracket first. Repeat with the supplied bolt and nut on the top. Here’s another example where this kit works so much better than the stock setup: Moving the shocks outboard reduces body roll, and placing them behind the axle enhances ride quality. Some of you reading this may be wondering why the shock is set at an angle, or why it’s so long. It’s a tradeoff to help tune the weight distribution, allowing for a smooth ride while combating wheel hop. The length of the shock also allows from a wider range of compression and rebound characteristics making a mid-level performance shock work like a much more expensive adjustable shock.
No Limit Engineering
455 South D St.
San Bernardino CA 92401
Text and Photos by Marcel Venable