Bracket Drag Racing Basics
Rear Suspension
When it comes to the Rear Suspension, you have a few different choices. You maybe able to keep your original Suspension and just Modify it for better Traction, or if you plan on going all out, with a lot of extra Horsepower, then you may want to put in a whole Rear Sub-Frame Assembly with a 4-link setup. Only Experts or very good Mechanics should try to Install the whole Sub-Frame Assembly, as they have to be placed in the Body perfectly and Welded with Precision. If they are not put in Correctly the Vehicle may not go down the Track Straight and, or if not Welded in Correctly, could be a disaster waiting to happen.
As far as using your Original Suspension goes, Whether you have Leaf Springs or Coil Springs, you can replace them with Heavy Duty Springs that are available. You can also install Ladder Bars or Traction Bars. When buying Traction Bars, buy High Quality units, the cheaper designs have a tendency of breaking under hard launches. Good Traction Bars for Leaf Springs, are the ones that the U-Bolts that hold your Axel Housing in place, go thru. You should use new U-Bolts when using this style of Traction Bar. You should have no more than about a ½ inch distance between the top of the Rubber Snubber and the Spring Eye. This is where the Rubber Bushings goes in the end of the Spring. While on the Subject of these Rubber Spring bushings, they can be replaced with harder ones that will also help with Traction. There are many Great Traction Devises on the market today, shop around.
Always use a high quality Shock Absorber on the Rear of your Race Vehicle. You can get Coil Over Shocks that are Ideal for Racing, most are Adjustable. You can also get special Racing Adjustable Shocks. I would not recommend using Air Shocks on any Drag Race Vehicle although, I am sure it is done.
Back to the 4-Link Setup. This is the best setup for Traction and is used in most Drag Racing Vehicles. You can modify your existing Body to accommodate a 4-Link setup, but it would be wiser and probably better to just have the whole Rear Sub-Frame Assembly welded in, and at the same time have the Body fit with a set of Wheel Tubs, so you can use much Wider and Taller Tires (Slicks). The 4-Link setup is totally adjustable and can be tailored to your Vehicle easily for the best Traction. It utilizes Coil-Over Adjustable Shocks also. A Sub-Frame Assembly is available for most any Vehicle out there, except front wheel drive cars.
The Rear-ends, or Differentials that stand the test of Time and Racing are the Dana 60, and the Ford 9”. The Ford 9” design is desired as you can change a center section with a different set of gears in a matter of Minutes. There are many Manufactures that make Heavy Duty Items for the 9” Ford Units. Changing the gears in a Dana 60 is a lot more difficult and time consuming. The Chrysler 8 ¾” unit is very similar to the Ford Units. Then there is the Quick Change Units. Quick Change Units have a Ring and Pinion like most rear ends, but the way you change gears is with a smaller set of gears that can be changed very quickly from the rear of the Vehicle. There are many units available and you should shop around for the best setup for you.
For Drag Racing you will want a Detroit Locker unit, Posi Unit, or more preferable is a Spool. A Spool locks the Axels together so both Axels turn at the same speed. This way the Race Vehicle will go down the Track Straight. Most stock rear-ends have what is called an open rear-end, (an open rear-end uses Spider Gears) to turn the Axels. An open rear-end is made for everyday driving. It is made so that the Vehicle can go around corners without wearing tires out or breaking the rear-end. The reason these units are not good for Racing, is because Power will go to the tire that has less Traction and then you will have that one tire spinning Freely while the other tire does not do anything. Never Weld Spider Gears together for better Traction as this is not allowed in Drag Racing. The Spool takes place of Spider gears. You should never use a Mini Spool for Drag Racing either although it is done. The reason is, that the use of a Mini spool puts all your Horsepower, on a ¾” Steel Shaft in your Rear-end, and in most cases will not hold up long.
You can use any Differential you want, but if it has C-Clips that hold the Axels in place, these will have to be modified with C-Clip Eliminators, this is a safety rule at most Drag Strips. C-Clip Axels are used in most GM Products.
As far as Gears (Ring and Pinion Gears) for the Rear-ends, you can get Gears for Ford, Chrysler, and GM Rear-ends, in a wide variety of Gear Ratios. The Rear-end Gears (Ring and Pinion Gears) are one of the most important Items in your Race Vehicle and should not be Taken Lightly. Setting up Gears in your Gear Case should be done by an expert. If not Setup correctly, you can ruin a New set of gears in a few feet of Driving. I have seen it done. A Set of Gears set up by an expert can last a very long time, but should be checked regularly, and that depends on the how hard they are Raced.
You can get Gears in almost any Ratio, 2.71-1 to 7.33-1. These numbers represent the number of times the Pinion or Driveshaft will turn, per one turn of the Ring Gear, Axels and Tires. In a 3.50-1 Gear set, the Pinion or Driveshaft, would turn 3 ½ times to one revolution of the Axel and Tire.
The reason you would want to go to a Lower gear (high number) is because it would take less Horsepower to turn the tires over. Meaning more Horsepower to the Track, to turn Bigger Tires over. A 2.71-1 Gear is Great at Daytona, but not at the Drag Strip. The Gear set you need for your Race Vehicle will depend on a lot of different things. It depends if you going to Race 1/8 Mile or ¼ Mile, it will also make a difference as to what Transmission you are going to use, what size Tire you use, Even how much Horsepower you are going to put out.
There are special Gears made for Drag Racing, they are softer thank the ones used in Circle track racing. That way they can take more abuse and not break as easily.
Anytime you use a Spool, you are supposed to use Aftermarket Axels. Meaning Axels that were Manufactured by a company that makes Axels for Racing. These are Superior to Stock units. I would stay away from anything under 30 Spline Axels. Make sure you get the right spool to go with your Axels, or Axels to go with your Spool. Axels and spools come in many different Spline configurations. There 26, 28, 30, 31, 33, 35, and 40 Spline Units, so you have to make sure you have the right Axels for the right Rear-end. If you contact an Axel Manufacturer, they can custom make axels for you, any length and any spline you need.
Another Part of the Rear-end you will want of high quality would be the Pinion Yoke. This Yoke is mounted to the Pinion Gear and connects the Rear-end Gears to the Driveshaft via Universal Joint. You can get Aftermarket Yokes that are nearly indestructible, as well as the Carrier and Bearing Retainer. You can obtain them all in high quality lightweight Aluminum. They will set you back quite a bit, but Gears are not cheap either. This is one of those places I was talking about that your Vehicle is no stronger that it’s weakest part. Don’t let a cheap part, cheat you out of a Race or Championship.
Universal Joints is one place that can put you on a trailer real quick. Make sure you buy high quality Universal Joints and use top quality Locking components, like a U-Joint Girdle.
When it comes to Drive Shafts, make sure you have one built by a good company that has of years experience. Make sure you have it balanced as this is one of the fastest moving parts you will have and it will be turning right next to you or under you. If it breaks, it will do damage and not to just the car. That is why you have to use a Drive Shaft Safety Loop. Stop and think of how fast that shaft is going to turn, You have a ring and pinion with a Gear Ratio of 4.11-1, a pretty standard performance gear. Your Drive Shaft is turning 4 times faster than your tires, now how fast are your tires turning at 100 MPH? Just something to think about. If your Transmission has a final drive of 1-1 and your motor is turning 8000 RPM the Drive Shaft is turning at 8000 RPM also. If you have overdrive it will be going even faster.
