Class Structure: Shocks, Springs, Tires and Wheels

Class Structure: How Can “Stockers” Be So Quick?

Part 2: Shocks, Springs, Tires and Wheels

In the past, we’ve taken a close look at what makes a legal Stock Eliminator car tick. They’re certainly much quicker than they have any right to be – no secret. Some of the well-scienced parts include shocks and springs, along with wheels, tires and rear end assemblies. For a closer look, check out the following:

 

Shocks & Springs: Shocks and springs are the forgotten pieces of the drag race suspension puzzle. Unfortunately, shocks and to some degree springs are the most critical pieces in the racecar chassis package. If you check carefully, you’ll find the quickest drag cars are those with very well sorted suspension systems. After “stiction” is resolved, you can then think about shocks and springs. Now, some of you might be offended by this, but there’s no free lunch when it comes to these components. Buy the best hardware your budget will allow. As an example, some of the very best shock absorbers are built by Penske Racing Shocks. Period. These shock absorbers are hand built for the application. They can be purchased in many formats, but the most exotic drag race “dampers” are technically three-way adjustable (bump, rebound and nitrogen charge). With these shocks, there is no limit in terms of valving. In simple terms, whatever you want, it can be built. And once it’s built, and you’re not satisfied with the valving, you have the option of either sending the shock back for a revalve or you can revalve it yourself (using Penske components).

Class Structure: Shocks, Springs, Tires and Wheels
Shocks that you can adjust are important. Honestly, these common Strange Engineering adjustable jobs are more entry level than some found on Stockers. You’d be surprised at the sophistication here.

Aside from correct valving, another reason high quality shocks are important is consistency. In simple terms, the accuracy of these components (coupled with the incredible build quality) allow the car to repeat from round to round. Yes, high-end shocks are expensive, but unless you abuse them or crash, they can outlast the car. What if you don’t have the money to buy good shocks? From this perspective, buying cheap shocks is like buying worn out, used slicks. It’s false economy. Instead of chrome plating parts or painting your racecar in a rainbow of candy colors, spend the cash on high quality shocks. This is something we can’t stress enough: The right shock absorbers are the absolute key in making the car work.

Class Structure: Shocks, Springs, Tires and Wheels
There are a lot of different springs out there (some labeled for drag race use). The smart chassis builders and racers have springs custom wound for the specific application. The reason is that every car is different. That’s why scaling a racecar is important.

As far as springs are concerned, the best Stockers out there don’t use store bought springs. Instead, they’re custom wound for the application (or in the case of leafs, custom built). To get the right spring, the car must be completed first, and then (in ready-to-race trim), it’s “scaled.” This practice involves the use of four wheel electronic scales to determine the corner weights of the car. Only then can the correct spring rate be calculated. Yes, it might be cheaper (although not necessarily) and far easier to buy ready-made springs. No, store bought springs don’t work as well. Close doesn’t count when you’re dealing with springs.

Class Structure: Shocks, Springs, Tires and Wheels
On a traditional leaf spring Stocker, it’s no secret split leaf mono leafs such as the Cal Tracs examples (top) are popular. They’re available in different ride heights too.

 

Tires & Wheels: Any well-versed Stock Eliminator racer will tell you flat out that radial slicks are the way to go on automatic cars. It’s a huge story, but suffice to say, on 99% of the automatic cars out there, radials are quicker and more consistent. One thing you will find on a quick and consistent Stocker is rubber that isn’t dead. This might mean changing slicks more often (buying tires more frequently), but it’s a small price to pay for performance. On the nose, roll out is king. The bigger the tire, the better.

Class Structure: Shocks, Springs, Tires and Wheels
Peeling out weight from wheels and tires is something else you’ll see on most Stock Eliminator cars. A lot of stock racers spend a lot of time working on unsprung weight.

When it comes to wheels, light is right. And the lighter the wheel, the quicker the car will go (and the more consistent it will be). This has been documented by others, and we’ve also done some testing with light weight wheels. Although it’s beyond the scope of this article, we can assure you there is definitely ET lurking in your rolling stock (approximately 1/10 between “heavy” aluminum wheels and flyweight jobs). When shopping for wheels, do your homework. Some advertised weights are a bit on the “optimistic” side. Others aren’t. We went to the trouble of weighing wheels, and here’s a hint: The smaller the rear wheel backspace (within a given line of wheels), the lighter the weight.

Class Structure: Shocks, Springs, Tires and Wheels
Right now, Hoosier seems to be the tire of choice with many stock class racers (part of it has to do with the fact that all three of the Factory Stock cars – COPO, Drag Pack and Cobra Jet – are supplied with them). Bottom line here is, even tire weight is important.

 

Rear Axle & Driveline: Rear axle and driveline hardware? No big deal, right? Wrong. In a Stocker, if you want to fly, you have to really think about unsprung weight and rotational weight. Yours truly (and friends) have done substantial testing on the effects of removing weight from driveline components. Everything from lightweight axles to metal matrix (aluminum composite) driveshafts have been tested. The conclusion? The less weight you have to turn (from a rotating component perspective), the quicker the car will be. It’s also interesting to note that a car with lightweight driveline hardware also repeats with more accuracy than one with heavyweight pieces.

On a similar note, if you can take weight out of any piece in the driveline which is unsprung (which includes the tires, wheels, brakes, rear axle and half the weight of the suspension links, drive shaft, springs and shocks) when compared to sprung weight (the rest of the car), the car will hook better. Why? Simple. Less unsprung weight makes life far easier on the shocks (remember – anything you can do to make the shocks more efficient makes for better traction).

What about reliability? It might be better than you think. Our old pal and chassis builder, Mike Pustelny (MPR, Almont, Michigan), has used Mark Williams aluminum spools, lightened ring gears and rifle drilled axles with lightened flanges for years on his old Super Stock cars. Even after a year of abuse, the axle splines in both the spool and on the axles look as good as the day they were installed. There’s no question Mark Williams pieces are top notch, but they’re also reliable and they fit. Which is no small dilemma when it comes to rear axle hardware.

 

Fuel Delivery System: Don’t discount the fuel delivery system as a source of performance in a car such as a Stocker. This is another area where we’ve done considerable testing. Believe it or not, a single four-barrel Stocker may just place more demand on a fuel pump and a fuel delivery system than an old school carbureted Pro Stock car. Here’s the reason: A car with a small fuel bowl capacity (your typical Stocker) can run out of fuel quickly. Meanwhile, those old Pro cars of yesteryear had double the bowl capacity of a Stocker (or quadruple the capacity, depending upon the carb in the Stocker). A Stocker needs instant results from the fuel delivery system. The philosophy here is to pump as much clean, un-aerated fuel (and this is a key) to the front of the car as possible. Because of this, many “slower” cars respond very well to monster pro style fuel pumps.

Class Structure: Shocks, Springs, Tires and Wheels
Fuel cells are legal. This setup includes an integral high capacity fuel pump. Note the plumbing. It’s all lightweight, large diameter hose, and no hard-90-degree hose ends are used (all are bent tube or straight).

Another thing to consider in the fuel delivery system is the need for correct hose and, especially, hose ends. Tight 90° bends should be eliminated. Why? That’s easy: The flow in a tight bend (usually a forged 90° adapter fitting) is rotten in comparison to a straight or bent tube fitting. On a carbureted application, fuel volume is critical. That’s why a hard running Stocker will often carry -10 AN hose from the pump to the regulator. When it comes to EFI applications, pressure reigns supreme. These cars will usually have a -8 AN fuel feed line coupled with a similar -8 AN return system from the regulator. By the way, all of this fuel system information applies directly to a bracket car – fast or slow.

That’s a wrap for this issue. Next time around we’ll look at the engine, transmission, converter and other pieces in a Stock Eliminator car. They might be less “stock” than you might have guessed. Watch for it!

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