Few things can be overlooked...
Few things can be overlooked as much as the shocks that are underneath a dirt driver's car.
I often wonder why dirt track drivers don't lose their minds, because a dirt track is never the same. Teams venture out for practice on a wet, smooth track, but by the time the feature rolls around the track is hard, dry, and usually has a few ruts in it. Keeping up with the track can be frustrating. This is why dirt drivers who keep a close eye on their shock setup and make the needed changes throughout an event will run up front.
Shocks can be one of the most overlooked pieces of the car. Here are a few basic tuning tips to help make sure you are one of those consistently at the front.
First, let's define a few terms. A basic shock will encounter two different steps as the car makes it way around a track. The first of these is compression. This is easy to understand: It is simply how easy the shock is compressed. If the shock has more compression, it will be harder to compress the shock.
The desired result of the...
The desired result of the shocks on a dirt car is to get the weight to transfer to the right side as quickly as possible and to keep that weight on the right side.
The second step a shock will enter is the rebound stage. The more rebound the shock has, the slower it will return to its normal state once the shock has been compressed. It will essentially be trying to pin that corner of the car to the track.
Another thing to consider is that most dirt series do not have a so-called shock rule. However, some Street Stock, and even Late Model classes, do have a claimer rule, although it is usually only $50 per shock. In this case it's probably best not to invest hundreds of dollars into your shock package only to have a set of them stripped from you and put on a competitor's car for $200.
The desired results of a good dirt shock setup differ greatly when compared to an asphalt shock setup. The desired result of a good asphalt shock setup is to pin the nose of the car to the ground and help prevent too much weight transfer, whereas a good dirt shock setup will assist in the weight transfer. This is especially true when the track is wet and has no grip. You want the right-side shocks to have very little compression at this point because there is no grip, or bite, in the track. The desired result is to have the weight transfer quickly to the right side and create as much traction as possible out of the right-side tires. This produces the lifting of the left-front tire that the Dirt Late Model drivers are known for.
Notice how the weight is transferred...
Notice how the weight is transferred to the right side of the car and the left-front wheel isn't even touching the ground. The shocks help produce this effect. This gives you the "sidebite" you need to get a good run coming out of the corner.
But once the track develops grip and hardens up, a shock package needs to change as well. This is what separates the dirt track stars from the everyday drivers.
"A good rule of thumb is once the track starts to harden up and slick over, you need to be dropping compression," says Dennis Wells, a shock specialist at RE Suspensions. "We tell our customers to run half the compression on the right side than they do on the left until the track hardens up."
For example, if you are running 60 pounds of air pressure inside the shocks on the right side for practice, you should be running 120 psi inside the shocks on the left side. The more psi you have in the shock, the harder it will be to compress. However, once the track develops a few ruts, hardens up, and develops a lot of bite, you should take almost all of the compression out of the shocks. A drastic change to where the shocks only have 20 or 30 psi in each shock isn't far fetched at all. This is because the track's amount of grip will produce the results you are wanting naturally. If you are battling a loose condition every time the track hardens up, this could be because your left-side shocks have way too much compression.
Some shocks have a valve stem at the top for adjusting compression, while others have a dial at the bottom of the shock for adjustments. Each time you make one turn it is known as a "click." Usually compression on Street Stock shocks is controlled by a valve stem and air pressure. Some Late Model racers run shocks with an external reservoir and a compression adjustment that can be made with a small screwdriver.
For Street Stock drivers facing...
For Street Stock drivers facing those pesky claim rules, Pro Shocks has an aftermarket adjustable shock for Street Stocks, and it only costs $69.
On the rebound side of things, it is the same principle: You do not want to run a lot of rebound on the left sides when the track is wet, because you want the weight to transfer to the right side easily. However, on the right side you might want to have a little more rebound because you want to keep the weight from transferring back to the left side of the car once you enter the straightaway. By running a lot of rebound in the right-side shocks, you can keep that weight pinned on the right side of the car.
Some shocks like this one...
Some shocks like this one have an external reservoir that fills with fluid as the shock is compressed. The reservoir also has a compression adjustment that uses the same click format mentioned previously.
RecommendationsHere are some basic changes recommended by Ohlins Shocks to improve the handling of your dirt car:
Loose In1) Decrease compression on RF
2) Decrease rebound on left sides3) Increase compression on RR
Loose Middle1) Increase compression on LF
2) Increase compression on LR
Most shocks have a mechanism...
Most shocks have a mechanism that allows adjustment of compression and rebound by simply turning a knob on the bottom of the shock. Each turn is known as a click. Ohlins Shocks recommends a 3 to 4 click change when making adjustments.
Loose Off1) Increase compression on LR
2) Decrease rebound in both fronts
Tight In1) Increase compression on RF
2) Decrease compression on LF
Tight Middle1) Increase rebound on LF
2) Increase rebound on both fronts3) Decrease compression on LR
Tight Off1) Decrease rebound on RF
2) Increase rebound on LF3) Decrease compression on LR
4) Increase compression on RR
Adjusting shocks correctly can be extremely frustrating. This is why Ohlins recommends only making small changes. If you have adjustable shocks, move them only 3 to 4 clicks. Or if you have the air pressure adjustments, adjust only 10 to 20 psi. It all comes back to keeping a steady notebook with the shock changes you have made and the track conditions that you tried them on. Make sure you test these shock combinations in your car before you race them so that you know how your car is going to respond.
For Street Stock racers who have those pesky claim rules, and who do not want to invest hundreds of dollars into each individual shock, Pro Shocks makes an adjustable Dirt Street Stock shock for only $69. This will give you the adjustability you are looking for without having to fork out the dough. These shocks are meant to replace your OEM units, but if you just want a good set of aftermarket shocks that will improve your handling, they offer the same shocks without the adjustment for only $58.
Here is a dyno sheet for a...
Here is a dyno sheet for a Dirt Late Model shock. Notice each change involved four clicks, but more importantly notice how much the rebound changes with those clicks.
That being said, if you are buying shocks, I would advise investing in a set of shocks that are adjustable. That's because, let's face it, there is only one way to learn how your car responds to different shock adjustments, and that is by trying different numbers in the shocks. You can learn what works with your car and what doesn't. It's that simple. The teams that have figured it out didn't do so by hiring an expensive shock specialist. Instead, the crew tried different adjustments and learned firsthand what works.
Make no mistake about it-there is major speed in shocks. Some teams look at shocks as band-aids and that is not the case at all. Shocks can make or break your weekend, but they can only get you so far. If your setup isn't up to par, or your engine package is lacking, then it doesn't matter how great your shocks are because you will not see marked improvement in your race program. If, however, you have every other piece in place, the right shock package might be the piece that puts you out front. And isn't that where we all want to be?