GM built millions of ’67 through ’87 Chevy and GMC pickups. Their classic looks, affordability, and wide parts-availability make them a popular platform to restore and hot rod today. And now, in true Pro-Touring fashion, they can have exceptional handling capabilities and still be daily driven.
Heidts Suspension Systems released a Superide independent front suspension (IFS) and four-link/coilover rear suspension for these trucks a few years ago. The company is now in its third generation of independent rear suspension design for various other platforms, but until now, they were not offered for these pickups.
Heidts’ latest offering, the Pro-G independent rear suspension (IRS) kit, turns GM’s former workhorses into corner-hugging handlers for the street, autocross, and road-racing. There are multiple benefits to an IRS over a traditional solid-axle suspension, says Engineering Manager Jeff Dauderman.
“With a solid axle, both wheels are going to move and deflect. With IRS, one side will go up and down, and the other side is independent of it. So, it gives a better ride quality on the road.”
For high-performance driving on the track, the IRS also offers camber adjustability for greater cornering ability — something not possible with a solid axle. Also, Heidts has dialed-in more camber gain into this kit.
“As you go around a corner, it allows you to have a more-complete contact patch from the tire onto the pavement as the car or truck goes through body roll,” he says.
The Pro-G IRS also offers adjustment for toe (for an extreme example, think of walking pigeon-toed as toed-in, and duck-walking as toed-out). Adjusting the rear tires toe-in offers cornering benefits, as well.
“On a road course, this will allow you to turn into the corner later and allow you to turn out of the corner quicker. So, your average lap time is decreased, because it allows you to maintain a higher speed through the turns.”
After Ultimate Street Car racer Mark Golovin replaced the 12-bolt rearend in his 2001 Camaro with a Heidts Pro-G IRS, he dropped his lap times at GingerMan Raceway, in South Haven, Michigan, by an average of 2.5 seconds.
“He definitely beat on this one,” said Heidts Sales and Marketing Director, Scott Diedrich. “We know it handles, but we also know it holds up, which is important.”
The Pro-G IRS, which uses a Currie 9-inch center section with a wide variety of ring-and-pinion ratios, saves 40 pounds when compared to a 12-bolt rearend. But, even more important, because the center is mounted to the frame, the unsprung weight is decreased, Dauderman told us. This allows quicker response time of the suspension to react to road irregularities. A number of shock absorber options are offered, and wheel travel is up to 2-inches longer than the previous generations of IRS kits Heidts offered.
“We have our single-adjustable and double-adjustable shocks, but we’ve also partnered with Bilstein,” affirms Dauderman. “For the guys who are really performance-oriented, we’ve got triple-adjustable shocks. I’d put Bilstein right up with JRi and Penske — it’s a top-tier shock. It does very well for those who are more performance-oriented, like autocross and road-race courses.”
A top-tier upgrade, the Bilsteins include remote reservoirs. The increased fluid capacity helps lower fluid temperature, which prevents shock fade. And, they offer separate low-speed and high-speed compression adjustments.
Set Up For Track Day And Then Switch To The Street
For dual-purpose trucks, alignment of the IRS can be quickly adjusted for either set up with a few turns of the lateral-link bars. (Running a track set up on the street will result in excessive inside tire-edge wear.)
Dauderman says typical street alignment specifications call for 1 to 1-1/4 degrees of camber and zero toe. For the track, typical settings would start at -2 degrees of camber, and 1/16- to 1/8-inch of toe-in. Those are the settings used on Golovin’s Camaro, he noted.
Springs can be quickly swapped on the coilover shocks, with a 400 pound/inch spring typically used on the rear for a track day. A 250 pound/inch spring is recommended for the best ride quality on the street. The adjustable shocks can also be set for how firm of a ride is desired.
“You can dial them back down to drive on the street, and then if you want to have more performance, you can crank up the compression and rebound to stiffen-up the vehicle,” Dauderman says.
The demand for airbag IRS kits has not been great, so they will not be offered for these trucks. Besides, the new IRS rides much smoother and handles better than previous-generation kits, Dauderman says.
“It’s like riding in a brand-new car.”
Pro-G IRS Can Be Easily Installed In A Driveway In A Day
The new Pro-G IRS for GM trucks offers a couple of options. It is sold as a back-half framerail kit, or for ultimate cornering ability, as part of a complete chassis including a Superide IFS and a new boxed frame. After removing the bed, the back-half kit is designed to be installed and operational within a day’s work by the average enthusiast working in his driveway.
“The hardest part of the installation is to mark where to cut the frame,” Dauderman says. “Then, once you cut the frame off, you bolt up the IRS and everything to the cradle. Finally, you just lift it up to the frame and bolt it in.”
The kit mounts by cutting off the rear section of the frame at the original leaf spring’s front mount and lining up the holes with the new back-half kit.
“You can 100-percent bolt it in. But, I always recommend people weld it in. Once you cut your frame, you’re not going back to an original frame anyway,” he says.
The back-half kit kicks the framerails up about 8 inches in a “Z” pattern. Because of that, the bed floor will need to be raised or modified to follow this modification. Ride height, compared to a factory frame, is about 4-inches lower.
“You can put our IRS in a short-bed truck. If you have a long-bed, you can either keep it a long-bed, or you can shorten the frame into a short-bed. For $2,000 from LMC and other companies, you can buy all the sheetmetal for a short-bed truck.”
The kit is only 34 inches from the outside of one framerail to the other, and it’s easy to mount much meatier tires by modifying factory wheel tubs or mounting wider ones, Dauderman pointed out.
The Pro-G IRS kit starts at $8,900 for the standard-horsepower kit (up to 400 hp) and about $10,000 for the high-horsepower kit, which upgrades the hubs/wheel bearings from 27- to 33-splines. But, even the standard-horsepower kit is much stronger than one of the more popular factory IRS suspensions usually swapped in — the Corvette C4, with a Dana 44 center section that is much weaker than a 9-inch. The half-shafts Heidts uses are also stronger than the U-joint half shafts used in the C4 unit, Dauderman says, noting that Golovin twists its Pro-G IRS with 540 lbs-ft of torque.
The Full Monty
The majority of C10 customers who have bought a Superide frontend also opted for a Heidts four-link kit at the same time, Diedrich told us. Many of those customers have also requested an IRS. Heidts now offers a short-wheelbase frame with a number of enhancements.
“We’re hoping that because we have the full solution for the frame, enthusiasts will replace it all at one time. The frame itself isn’t that much more expensive versus buying just the front and rear together.”
The IFS sells for $4,400, and a full-frame with the IFS and IRS sells for about $22,000. It’s fully boxed and is reinforced with DOM tubing in the center. Compared to reconditioning a 50-year-old frame, boxing it, and welding in the IFS and IRS, a shop can save up to six weeks’ build time, Dauderman says.
“I don’t think there’s anything comparable to this out on the market right now. There are other IRS units, but as far as the ease of alignment, the adjustability we have with this, and ease of installation, I think we’re in the top tier of all of those categories.”
What this means is, your C10 can be a canyon carver like never before, and all it takes is a little help from Heidts Suspension Systems to make it happen.