Monday, March 11, 2013

Revolution!-Trucks Invade the Optima Batteries Ultimate Street Car Invitational

Autocross definitely owes at least some of its popularity and success to the pro touring movement, which has become a huge influence on truck owners. But to be honest, I think the car guys that claim to have started the movement really stole it from the truck guys.

Yes, autocross events are full of pro touring-style cars that are usually classic automobiles built to handle like modern sports cars, and are capable of being driven from coast to coast without any problems. While most of the car guys won’t admit it, I feel that the pro touring movement took its winning play right out of the truck owner’s handbook. For decades truck owners have been modifying everything under the sun on their rides to increase performance, drivability and reliability.

One manufacturer has developed an event that offers an outlet to the world’s finest automotive minds, an event that offers a level playing field to the best vehicles. I’m talking about Optima Batteries Ultimate Street Car Invitational, or OUSCI for short. Last year marked the fifth running of the event that is held at Spring Mountain raceway in Pahrump, Nevada, the Saturday following the last day of the SEMA Show.

There are two ways to get your car in the event: win your way in by finishing on top at one of the approved qualifying events, usually a Good guys or an American Street Car series event, or be lucky enough to get a “golden ticket” from one of the Optima representatives who walk the isles at the SEMA Show.

Each year, 60 vehicles get the invite to come out and battle in these five categories: Street Driving/Open Road/Rally Competition, Autocross, Acceleration/Braking, 2.5-mile Road Course and Performance/Design Competition. This is center stage to drivers, builders and SEMA manufacturers, because the “put up or shut up” theme runs rampant throughout the pits.

Historically, trucks have been the underdog at all autocross events, because of their design. This has made the car the undisputed contender as far as putting together a successful program that will allow someone to go out and win races. However, 2012 brought many changes to the autocross and pro touring world, because the truck guys have been doing their homework. Autocross trucks are fast trucks and consistently ran at the top throughout the year at many of the Goodguys and ASCS events.

Validation of that success came in the form of official invites to the OUSCI. While some of the truck guys qualified in early with a win at a previous event, others had to sweat things out as they walked the halls of SEMA with their fingers crossed for a shot at receiving the coveted Golden Ticket.

This year more trucks were added to the competitors list than ever before. I hate to spoil the big surprise, but the winning vehicle wasn’t a truck, the car guys were victorious once again, but the big story of the event was that trucks held more than just their own. All five truck competitors finished in the top 25 out of more than 50 competitors, proving to the world that trucks can perform just as well, if not better than their counterparts with back seats.

Let’s take a look at the lineup.

Curt Hill
1972 Chevrolet Blazer
Finished 23rd
406 Dart SBC 500-plus-hp
Porterbuilt suspension
12-bolt differential with 3:73 gears
13-inch brakes, Intro wheels

Built at Hills Rod and Custom in Pleasant Hills, CA, shop owner Curt Hill talked long time friend Brett Alworth into allowing him to drive this awesome Blazer at the 2012 event. Although Curt himself was new to autocross, he showed the fresh build no mercy as he pushed the Blazer to its limit in all five events. He brings new meaning to “drive it like you stole it,” and a few times I don’t know who was more nervous, Brett watching Curt slide the thing around the first turn time after time on the road course, or Curt trying to keep it straight and on the track.  I guess it’s a good thing that Brett is friends with an awesome mechanic!

Rob Macgregor
1969 Chevrolet C-10
Finished 15th
LS 500-plus-hp
No Limit Engineering one-off chassis
Quick-change rear differential with floater hubs
Wilwood Wide Five brakes, custom wheels

This truck has had a target on its back since it debuted in April 2012 at the Del Mar Nationals. Owner/driver Rob Macgregor and his crew at No Limit Engineering built the truck, known to many of its followers as Hellboy.  Numerous wins have put the truck on top, and it’s the 2012 Goodguys truck class champ. There was some controversy that surrounded Rob and the ’69 C-10, including the big East coast/West coast rivalry with fellow OUSCI competitor the Summers and Sons team with their Saturday Night Special C-10. Rob had his work cut out to quiet the rumors that Hellboy wasn’t street worthy. He put everything them rest when he jumped in the truck at the SEMA show floor and drove the 100 miles to Pahrump with the radio blaring as the fuel mileage held in at around 22 mpg! Any time you mix exceptional handling with great ride quality, plus a low stance and big horsepower, you’ll be a winner, and that’s been No Limit’s goal since the beginning.

Phil Gerber
1970 Chevrolet C-10
Finished 12th
LS 700-plus-hp
Roadster Shop Fast Track chassis
Afco billet coil-overs
Wilwood brakes, Forgeline wheels

During one of the Goodguys events this past summer, someone asked me  what business the Roadster Shop had building a truck to go out and beat on, which I thought was kind of funny. I said, “Do you always phrase your questions with the answer first? Maybe you should go on Jeopardy!” Simply put, yes, it’s bad. Yes, it’s fast, and yes, it’s a truck. If the name isn’t familiar, or you think that the shop only builds roadsters, then think again. Phil Gerber and the guys at the Roadster Shop mean business, and want to go fast—real fast. This truck is another one that has stirred the pot on the Goodguys circuit because it has been beating up the top car and truck contenders since its debut mid-season last year. After they worked out the bugs in the truck from the previous season, they pulled it apart to paint and shine it up enough to be featured in the Optima Batteries booth at the 2012 SEMA Show.

Chris Smith
1967 Chevrolet C-10
Finished 16th
383 SBC 500-plus-hp
No Limit Engineering Wide Ride suspension
Ride Tech Shockwaves
Moser-equipped rear differential
Wilwood brakes, Forgeline wheels

Back in 1999 when Mike and Chris Smith opened up a shop in Tiffin, Ohio, events like the OUSCI were around to allow shops just Like Smitty’s Custom Automotive showcase their talents in fit and finish, but also in performance. Through hard work and by providing excellent service, their shop has grown to 7,500 square feet and now employs seven craftsmen specializing in building show cars and trucks while having a great time. This year, the guys made the trek out from Ohio with this beautiful ’67 small window C-10 to show everyone that even a truck that’s on air and can lay out, will out corner even the best of them. Show-winning fit and finish is nothing new to these guys, as they’ve had some success in the show car world, including an Autorama Great 8 pick back in 2010, however Chris made sure that nobody called the C-10 a trailer queen at Pahrump because he drove it hard all day. Watch for this truck at an event later this year; the shop has big plans for this one.

Brad Coomer
1970 Chevrolet C-10
Finished 24th
LS 500-plus-hp
No Limit Engineering Wide Ride suspension
Ride Tech coil-overs
Quick-change rear differential with floater hubs
Wilwood Wide Five brakes, Custom wheels

There must be something in the water in the Midwest because everybody from that area is involved in some kind of racing. With that said, the name Trent Summers might be familiar to you if you frequent the Goodguys autocross circuit. Trent is the operations coordinator for all of the events. Watching everybody run their stuff time and time again gave Trent the itch to join in the fun and show some of the car guys a thing or two about how to tune a vehicle’s suspension. But with Trent running the show how would he be able to pull double duty? Enter Brad Coomer, who can be found over at the Summers and Sons compound every now and then and has been more than happy to not only lend his expertise on building this ‘70 C-10 named the Saturday Night Special, but also to show the truck and its competitors no mercy as he did in Columbus last July where he drove the SNS to the win and an invite to the 2012 OUSCI.

Needless to say, trucks will continue to make a huge impression on the car guys for many years to come. One advantage that we truck guys still have over cars is the fact that no matter how fast they think they are, girls still love trucks more!

Text and Photos by Marcel Venable

Tuesday, February 26, 2013

Air vs. Static: Battle of the Springs

Aftermarket Suspension Systems Explained

Compiled by Marcel Venable

There’s an ongoing debate about which suspension system is the better choice for classic or late model trucks. Similar debates or conspiracy theories also exist, including Chevy vs. Ford, Coke vs. Pepsi, and if the U.S. really put a man on the moon. Nevertheless, we wanted to get to the bottom of the suspension dilemma, so we sought opinions from manufacturers of modern day aftermarket suspensions. Let’s start with the basics.

Most customized trucks are the product of an independent front suspension system that includes some type of control-arm-over-spring combination. Yes, there are other types, like I-beam and torsion bar styles, but most aftermarket performance-based systems manufactured today are targeted to enhance the control-arm-over-spring units found in most trucks.

Starting from that foundation, let’s focus on the modern era of GM-based trucks beginning with the 1967-72 model to the current model GM truck platform. Why GM? Well it’s simple, for most of its 40-year span the principles of this style have remained generally the same. Plus, this type of suspension is close to that of most performance automobiles; many of the manufacturers of these units share what they’ve learned from vehicle to vehicle. Sure, most of the theory is correct, however just because it walks, talks and looks like a duck doesn’t always mean it’s a duck. First you must look at the components and their functions. Understanding how this style works will help you form a better conclusion based on what or how you what to drive your truck.

The IFS or independent front suspension theory is simple, both wheels travel at a different rate based on road conditions and on a vertical and/or lateral force. A coil spring is located under the frame on both sides that carries the weight of the vehicle while maintaining the ride height, and to an extent, reflects vertical and lateral force. A shock absorber assists the coil spring to control vertical and lateral forces. Steering or control of the vehicle is guided by the other components, such as the control arms, spindles and the steering linkage. These are partnered with other items, such as an anti-sway bar and the shock absorbers.  

We all know that GM setup its truck suspension to haul heavy loads and fit an oversized tire with a ton of sidewall to handle more weight than automobiles. Simply put, trucks are naturally handicapped with a higher center of gravity, an undesirable stance and huge amounts of body roll or sway. So how do you change a truck into a ‘Vette? It’s geometry, my friends, geometry

First, it’s necessary to change the ride height, which will alter the center of gravity and reduce the exchange of weight transferred laterally while cornering. There are many ways of doing this and is where the debate begins.

Option One: Lowered Coil Springs and Spindles

These components are the simplest as well as the most affordable way to change ride height. Simply install a shorter coil spring along with a corrected spindle. Changing just one component won’t ensure the best handling and drivability, and as a matter of fact, will create all kinds of problems with wheel and tire alignment, making the vehicle almost impossible to drive at highway speeds. It’s a good idea when changing coil spring height to include some type of partner component, like a spindle to maintain proper geometry, if you plan to make a drastic ride height change. 

So what are some of the effects from just changing only one of the components? An increase in negative camber is the first that comes to mind. Too much is never a good thing. Having too much negative camber can cause horrible tire wear. The fix is to bundle the items together creating a balanced system that will help maintain proper geometry at a lowered ride height. Another method is changing both the upper and lower control arms. They’ve been engineered to maintain the factory geometry of the coil spring and spindle geometry, so changing them will alter a truck’s ride height. For anything more than a 2-inch drop up front, shorter shocks are a must. Many companies offer specific shocks tailor made for lowered trucks.

Option Two: Airbags
First, the term “airbag” isn’t the proper term for this component. As a matter of fact, an airbag is really a pnuematic spring. They were developed to allow drivers to change spring rates using compressed air, thereby adjusting a vehicle’s ride height based on heavier loads. Air springs are common equipment on most tractor-trailers, buses, trains and even luxury automobiles. In recent years, customizers have co-opted their use on their own projects.

While most of us love the look of a truck hugging the pavement, there are trade-offs to consider. Unfortunately, a truck that’s extremely low will have very little suspension travel, so to get any kind of ground clearance you have to raise the truck to a safe ride height. The same person might install an air suspension as a way to clear large diameter tire and wheel combos. To do this they have to overinflate the springs to avoid rubbing the tires on the fenders, resulting in a harsher ride. Finding a balance is paramount, and mounting locations can be changed to help gain more lift and/or better ride at lower levels.

So does this mean they’re only good for hauling weight? No, as a matter of fact, when the proper components are matched, air springs offer the user exceptional handling and stability, regardless of load. This means that you can maintain the same ride height no matter how much weight is added. How? Because the operator has the ability to add air pressure to the ‘bag, which will change the spring weight rating based on air pressure, thereby creating a progressive spring. In most cases, the driver can control air pressure through the use of an in-cab valve controller. Some manufacturer’s systems can be preset, and even electronically monitored via computer with a leveling system. When paired with a corrected geometry system (control arms and ‘bag mounts), you can experience close to a perfect balance between ride quality and handling characteristics. Lowered shocks are a must for a proper ride because the airbag only acts as a spring replacement; a shock is still needed to control rebound. The proper combination can result in a low ride that rivals any luxury car.

If space is limited, the application may call for a ShockWave, which is simply a combination of an air spring and a shock absorber. The advantages are easier mounting, more tire clearance, a better working angle for the shock and the air spring, as well as the inclusion of a high quality billet adjustable racing shock.

Option Three: Coil-overs

A pair of coil-over shocks shares many similarities with the ShockWave system. It’s a combination of an adjustable shock absorber, surrounded by a metal-wound coil spring. One of the advantages of installing a pair of coil-overs has a lot to do with space, just like it does with the Shock Waves; however, they send more positive feedback to the driver at higher speed.

They are adjustable, but not on the fly like an air spring. Based on the vehicle’s ride height and/or suspension travel, the operator can choose a spring based on the coil spring’s weight rating. The stiffer the spring the more vertical and lateral resistance is created to control more of the force that’s generated by vehicle weight during high speed cornering. This makes them ideal for use in a racing applications, but does this mean that’s all they’re good for? No, but knowledge is power, so understanding more about your truck’s suspension makes a huge difference. For example, having an idea of how much weight is being distributed on all four tires will allow you to get closer to choosing the proper coil springs. This is what is referred to as “corner weight,” and it’s vital to making the proper selection of coil spring. Coil-overs allow some ride height adjustability, but they’re limited to the shock’s travel parameters. A good rule of thumb is to pair coil-overs with the correct suspension components, like corrected control arms.

What’s the verdict? It’s difficult to say for sure. Only you can answer that question because you’re the one who will be driving your own truck. Be sure to weigh all of the options before you make your decision.

We will leave you with this advice, though, to crush any myths. Maintaining proper geometry is the right way to set up your truck’s suspension no matter which spring you choose to install. Also, airbags and coil-overs aren’t just for trailer queens and race cars. When paired with the proper components, they’ll make your truck handle just as well if not better than most sports cars for a fraction of the cost.





Cando Specialties

Chris Alston Chassisworks

DJM Suspension



KP Components

McGaughy’s Suspension

No Limit Engineering


Romic Billet Shocks

Slam Specialties

Tuesday, February 12, 2013

Spinnin’ Gears

All About the Fab 9-Inch from Currie Enterprises

When deciding to increase your truck’s tire size, there is a major component that needs to be addressed to maintain the engine’s torque, horsepower and fuel economy. Increasing your truck’s tire diameter will affect the engine RPM, which affects torque and power. When changing your rear tire’s diameter from smaller to larger or vise-a-versa, it will not affect the rear end differential gear ratio. The only way you can change the rear end gear ratio is to physically change the ring & pinion gear set. Changing tire diameter only affects the ratio of the driveline.

Hot To Figure Gear Ratio and Tire Rotation

It is amazing that only two components can make a dramatic effect on drivability and fuel mileage as the ring & pinion gears in a vehicles differential. The smaller the gear ratio the faster the vehicle will accelerate. There is a trade off, when running a smaller gear ratio the engines rpm will increase and fuel mileage will decrease. When deciding which gear ratio will be best for your application, the first thing is to determine what gear ratio does the your truck have currently have.

You can figure your gear ratio without having to remove the rear-end differential. Using a floor jack place it under the rear differential jack the differential up until the rear tires are off the ground. Always place jack stands underneath the frame rails safety precaution. Place a piece of tape at the 12:00 o’clock position on the tire sidewall. Then crawl underneath the truck and place a piece of tape on the driveshaft at the 6:00 o’clock position. Put the transmission in neutral. Crawl underneath the truck and rotate the driveshaft until the tire completes one full revolution. Count the amount of time the driveshaft rotated to equal on full revolution of the tire.

3 ½ rotations of driveshaft = 3.56
3 ¾ rotations of driveshaft = 3.73
4      rotations of driveshaft = 4.10

How to figure ring & pinion gear ratio:
Divide the number of teeth on the ring gear by the number of teeth on the pinion gear.

37 teeth on the rear gear
9 teeth on the pinion gear
37 / 9 = 4.11 gear ratio

The higher the gear ratio means more torque and power, but less fuel efficiency.

Engine RPM x Tire Diameter = MPH
2200 RPM x 33” dia. = 72.60 MPH

Recommended Engine RPM @ 65-70 MPH Highway Speed
V6: 2,000 – 3,200 RPM
Small Block: 1,800 – 2,800 RPM
Big Block: 1,800 – 2,600 RPM
Diesel: 1,600 – 2,800 RPM

We approached the folks at Currie Enterprises in Corona, California to checkout their FAB 9 differential axle housing. The FAB 9 diff/axle housing features a 3/16-inch thick Hi-Form 50 steel plate body, a 3/8-inch thick third member mounting face surface, with 3-inch diameter axle tubes. The FAB 9 differential axle houses is unique with the first bend of the housing was centered with the centerline of the axle tube. Inside the housing are welded bulkheads that interlink the face, body and inner ends of the axle tubes are fused together as one unit. The FAB 9 differential was designed to incase traditional Ford 9-inch internal components. The FAB 9 design and construction contributes to increased, strength and durability. It also looks cool and is bulletproof at the same time.

The Eaton Detroit Truetrac is a fully automatic limited-slip differential that works with helica gears instead of clutches or cones. The Truetrac eliminates and parts that would wear and requires no special limited slip lubricant or additive.

As with a conventional differential, the Truetrac side gears are interconnected by pinion gear, which allow one wheel to slow down or speed up as required. Truetrac gears have spiral teeth, and the pinions are mounted in pockets in the case.

Torque flows through the differential’s ring gear and the Truetrac case drives the pinions. Torque then flows to the side gears and to the axles. The side gears are also in mesh with each other side to side and in turns, one side will speed up and the other will slow down. Just like an open differential. Because there are no clutches to release first, the differential action is smooth and quiet. When there is a difference in traction side to side, the Truetrac uses resistance of pressure angles between the teeth of the side and pinion gears, as well as thrust forces of the pinion in their pockets in the case, to provide the “braking” action needed to transfer torque from the low to the high traction axle.

With large wheels comes the need for better stopping power using a 9-inch housing kit from Wilwood. It features larger 14-inch diameter rotors that are cross drilled and slotted for cooling and 4-piston calipers, the multiple pistons mean better and more responsive braking.

Follow along as we documented the construction of a Currie FAB 9 diff/axle housing, 31-spline axles. The installation of a Motive Gear Ring & Pinion 3.73 gear set, with an Eaton Detroit Truetrac and Wilwood disc brakes.


Currie Enterprises
 (714) 528-6957

Eaton Detroit Truetrac
(800) 328-3850

Motive Gear
 (800) 934-2727

Wilwood High-Performance Disk Brakes

Text by Bob Ryder
Photos by Jason Mulligan

The 3-inch diameter axle tube inner surface were chucked up in the lathe and machined to accept the fitment of the axle housing/outer bearing race flange.

The axle housing/outer bearing race flange was checked for proper fitment.

A 9-inch differential housing was bolted to the Currie FAB 9 body to eliminate any movement while the axle tubes are welded to the body.

The axle housing/outer bearing race flange was then pressed into the Currie FAB 9 axle housing.

The axle housing was measured to make sure it was the correct distance from the Currie FAB 9 body to the outer bearing race flange outside surface.

After double-checking the distance from the Currie FAB 9 body to the outer bearing race flange surface, the axle housing was tack welded to the Currie FAB 9 body.

The outer bearing race flange was tack welded to the 3-inch diameter axle housing.

The axle was inserted, chucked up and steadied with a tailstock. Then, the individual splines 31 in total were cut horizontally into the axle by the milling machine’s cutter.

The axle’s hub face surface was machined straight, true and perpendicular, to the axle’s centerline.

The major internal components of the 3rd member of the differential include the Motive Gear ring and pinion gear set with a ratio of 3.73 Currie 3rd member and the Eaton Detroit Truetrac unit with inner axle bearings.

After pressing on the inner axle housing to the Eaton Detroit Trucktrac unit, the Motive Gear, ring gear was aligned with the Tructrac unit. Ruben then threaded and torqued the bolts to 89 ft-lbs. in a criss-cross pattern to properly seat the ring gear.

After the pinion bearing was pressed onto the pinion shaft, the Motive Gear pinion gear was slid into the pinion support bearing housing.

Gasket synch was applied to the third member housing face surface then the gasket was carefully applied.

Gonzalo lowered and aligned the pinion gear and support bearing housing onto the third member.

An air gun was used to snug up the pinion support bearing housing bolts. Then torqued to 60 ft-lbs.

The Motive Gear ring gear and Eaton Detroit Truetrac unit was then laid onto the bearing carriers of the third member housing.

Gonzalo installed bearing carrier caps then inserted the cap bolts that were torqued to their proper specs.

A very important procedure when assembling a differential third member is setting the ring and pinion gears backlash. The gears backlash is the adjustment that meshes the ring and pinion gear together. To tight and the gears will wear out setting the mesh to loose and it can cause failure in the gear set. A depth gauge was mounted on the third member housing. The plunger was set on the ring gear surface the ring and pinion were then rocked back and forth watching the play between the two on the dial indicator. The optimum tolerance to look for is, .004 of variation, it was checked on three different locations around the ring gear surface for consistency.  The lateral adjustments were made by, tightening or loosening the side adjusting rings. The dial indicator was between .008-.012 so we were good.

To check the gear mesh pattern, a thin coat of gear compound paste was applied to the ring gear teeth surface. A drill-motor was attached to the pinion shaft. The pinion gear was rotated using the drill-motor, which in turn rotated the ring gear after a couple rotations an impression or pattern was left in the paste on the ring gear. By moving the pinion gear in or out would adjust the gear mesh pattern.

The side adjusting rings were adjusted to find the optimum gear-meshing pattern.

After the gear backlash and meshing pattern were dialed-in the cap bolts were torqued to their specs.

The pinion gear seal and cap were slid onto the pinion shaft followed by the pinion yoke that was slid onto the pinion shaft splines.

An air impact gun was used to tighten the pinion gear shaft gland nut securing the pinion yoke.

To secure the third-member onto the differential housing, mounting studs were threaded into the housing and tightened.

Sealant was applied to the housing surface. Then the gasket was installed and sandwiched between another layer of sealant too prevent from leaks.

The third-member was carefully lowered and aligned over the studs, then placed onto the differential housing.

Using Nyloc nuts to secure the third-member to the Currie FAB 9 differential housing, Gonzalo used a torque wrench to tighten the Nyloc nuts to their torque specs.

Wilwood offers this Explorer style internal drum parking brake, with their Wilwood disc brake kit.

The Wilwood disc brake cross-drilled/ball milled/vented rotor was secured to the Wilwood hat by hand weaving the safety wire.

The Wilwood 14-inch rotor and hat assembly was slid over the axle wheel studs.

The Wilwood 4-piston calipers were slide over the rotors then fitted with their semi-metallic brake pads for optimum stopping power.

A socket and Allen wrench were used to secure the disc brake pads detainment bar.

The Wilwood disc brake assembly will deliver excellent stopping power after installing the larger wheels and tires.

A picture is worth a thousand words.

Tire Dia./Engine rpm/Gear Ratio Chart is very helpful to figure engine rpm.