Great Article On Drag Shocks
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Great Article On Drag Shocks
This is some real good materials for you newbies or those of you that have not played with your suspension yet.
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The sheer violence of a 700 HP, 3100 lbs., 10 inch tire Mustng launching off of the starting line is unequaled in almost any other form of motorsports.
The whole vehicle is in a state of "shock" at the instant that you leace the starting line. Interesting enough, not much attention is ever focused on the very important area of "shock absorbers". Sometimes this is what can separate the good runners from the really good runners.
When I ask racers what they have done to their Mustangs suspension, they mention that they have installed "90/10's in the front and 50/50's in the rear". I know for a fact that most racers spend a lot more time thinking about fuel injector size, blower pulley diameter, and a whole bunch of other things that are probably less important than shock absorber selection.
First, let's talk about the dynamics involved in the launch. And let's assume that we are running in the Street Outlaw class which requires a minimum weight of 3100 lbs. For a 302 engine, and a maximum 10 1/2" rear tire width. Our mythical Mustang has about 1750 lbs on the front tires and the other 1350 lbs on the rear tires at rest. But because we set up the suspension "right" in this particular car, at the moment of launch we might expect that for just for an instant or two, the total weight on the rear tires would be 3100 lbs, or the total weight of the vehicle. Any time a car lifts both front tires at launch, the total weight of the vehicle is on the rear tires.
Now, how many times have you seen pictures in the Mustang magazine of a Mustang leaving the line with the driver's side front tire 2 feet off the ground and the passenger side front tire 8 inches off the ground. The car looks (and is) all torqued over to one side. Rather than get into all of these unique dynamics, just remember this. When a car is torqued over like this and even though all of the vehicle weight is now on the rear tires, how evenly is the weight on both sides? On our mythical S/O Mustang we are not just looking for 3100 lbs on the rear tires, we are trying for 1550 lbs on each rear tire.
In this scenario, proper selection and understanding of the role of shock absorbers is in order.
Most OEM shocks and front struts are of the 50/50 variety. This means that the damping on the "down" stroke (compression, like when dropping into a pot hole) and the "up" stroke (rebound, as in flying over a small rise in the road) are about equal.
In drag racing, we are looking for several different criteria. The front shocks (or struts) should offer only a small resistance in letting the front of the car rise at the moment of launch. As the car leaves the starting line, this rise will allow some (or all) of the weight to transfer to the rear. As the car builds up speed the front end should come back down smoothly. At the rear, the shocks should compress and rebound evenly. It all sounds so simple.
The problem is that not only are the front and rear of the car under different loads, the left side and the right side of the car also have different loads under launch. It doesn't make sense to expect perfect weight transfer (maximum weight on the rear tires and equal weight left to right) if we don't have some way of adjusting the damping capabilities of each individual shock.
The standard and least expensive drag racing shocks have no adjustment capability. They are just 90/10 (or 70/30) in the front and 50/50 in the rear. They are better than stock and are ok for a 12 second car but are inadequate for a 10 second door slammer.
To do it right, select drag racing shocks that offer adjustments for both the compression and the rebound capabilities of the individual shocks. Good shocks allow this adjustment to be made on the car.
For the purpose of this discussion of shock absorbers I have not mentioned the importance of springs or spring rates and I don't mean to diminish their importance and proper selection. Obviously, shock absorbers and spring rates are interconnected, but for the time beign we have been concentrating on the shocks alone. Spring rates can also play an important part in assuring an even weight distribution from left to right. More compression resistance on the right rear spring seems to be the standard practive these days. This can be accomplished by using a stronger spring on the right rear or using either an air bag or rubber spring spacers between the coils.
And like anything else when it comes to adjustability, the more adjustablility available usually means that there are more potential "wrong" adjustments. When it comes to shocks for a 10 second or quicker Mustang, get good ones that have adjustablility and spend the time necessary to dial the car in at the track. If you can, use a video camera that has instant review capabilities. Take some shots from directly behind if possible and then review the tape and compare the 60 foor times.
There is just no other substitute for testing
[b][b]
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The sheer violence of a 700 HP, 3100 lbs., 10 inch tire Mustng launching off of the starting line is unequaled in almost any other form of motorsports.
The whole vehicle is in a state of "shock" at the instant that you leace the starting line. Interesting enough, not much attention is ever focused on the very important area of "shock absorbers". Sometimes this is what can separate the good runners from the really good runners.
When I ask racers what they have done to their Mustangs suspension, they mention that they have installed "90/10's in the front and 50/50's in the rear". I know for a fact that most racers spend a lot more time thinking about fuel injector size, blower pulley diameter, and a whole bunch of other things that are probably less important than shock absorber selection.
First, let's talk about the dynamics involved in the launch. And let's assume that we are running in the Street Outlaw class which requires a minimum weight of 3100 lbs. For a 302 engine, and a maximum 10 1/2" rear tire width. Our mythical Mustang has about 1750 lbs on the front tires and the other 1350 lbs on the rear tires at rest. But because we set up the suspension "right" in this particular car, at the moment of launch we might expect that for just for an instant or two, the total weight on the rear tires would be 3100 lbs, or the total weight of the vehicle. Any time a car lifts both front tires at launch, the total weight of the vehicle is on the rear tires.
Now, how many times have you seen pictures in the Mustang magazine of a Mustang leaving the line with the driver's side front tire 2 feet off the ground and the passenger side front tire 8 inches off the ground. The car looks (and is) all torqued over to one side. Rather than get into all of these unique dynamics, just remember this. When a car is torqued over like this and even though all of the vehicle weight is now on the rear tires, how evenly is the weight on both sides? On our mythical S/O Mustang we are not just looking for 3100 lbs on the rear tires, we are trying for 1550 lbs on each rear tire.
In this scenario, proper selection and understanding of the role of shock absorbers is in order.
Most OEM shocks and front struts are of the 50/50 variety. This means that the damping on the "down" stroke (compression, like when dropping into a pot hole) and the "up" stroke (rebound, as in flying over a small rise in the road) are about equal.
In drag racing, we are looking for several different criteria. The front shocks (or struts) should offer only a small resistance in letting the front of the car rise at the moment of launch. As the car leaves the starting line, this rise will allow some (or all) of the weight to transfer to the rear. As the car builds up speed the front end should come back down smoothly. At the rear, the shocks should compress and rebound evenly. It all sounds so simple.
The problem is that not only are the front and rear of the car under different loads, the left side and the right side of the car also have different loads under launch. It doesn't make sense to expect perfect weight transfer (maximum weight on the rear tires and equal weight left to right) if we don't have some way of adjusting the damping capabilities of each individual shock.
The standard and least expensive drag racing shocks have no adjustment capability. They are just 90/10 (or 70/30) in the front and 50/50 in the rear. They are better than stock and are ok for a 12 second car but are inadequate for a 10 second door slammer.
To do it right, select drag racing shocks that offer adjustments for both the compression and the rebound capabilities of the individual shocks. Good shocks allow this adjustment to be made on the car.
For the purpose of this discussion of shock absorbers I have not mentioned the importance of springs or spring rates and I don't mean to diminish their importance and proper selection. Obviously, shock absorbers and spring rates are interconnected, but for the time beign we have been concentrating on the shocks alone. Spring rates can also play an important part in assuring an even weight distribution from left to right. More compression resistance on the right rear spring seems to be the standard practive these days. This can be accomplished by using a stronger spring on the right rear or using either an air bag or rubber spring spacers between the coils.
And like anything else when it comes to adjustability, the more adjustablility available usually means that there are more potential "wrong" adjustments. When it comes to shocks for a 10 second or quicker Mustang, get good ones that have adjustablility and spend the time necessary to dial the car in at the track. If you can, use a video camera that has instant review capabilities. Take some shots from directly behind if possible and then review the tape and compare the 60 foor times.
There is just no other substitute for testing
