Checkin Out That Rear

Checkin Out That Rear

There are so many rear suspension's today.

The rear we are going to talk about first is probably the most common in dirt track racing today, the four link.

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Once again we will hit some basics and in the future if we need a lil more bite on the subject we will enter some additional weight.

Understanding your four link once again starts with your chassis builder. It is so important to start out with the manufacturers setting. Keeping in mind if needed you can ask them for tweaks on the setup for the track you are going to focus on.

To steer or not to steer,more angle or less angle,less radical or more radical ? All are very good questions and can be covered at a later time. What we want to achieve here in the beginning is a basic understanding of what each bar does and the importance of a square rear end. As most have heard the chatter on lead the left side or lead the right side one would have a simple thought of , what and how would that effect the car going strait and at this point in a conversation is when you start to hear the but's and if's and a a a a a a's ! It is as if they totally forget when they come out of that turn there is a drag strip right in front of them.Lets start off with make sure your rear is square, did we say “lets make sure your rear is square “ ! All bars forward 4 Link,lower bars mostly effect corner entry and the upper bars will mostly effect corner exit. The more upward angle on top or bottom the more weight and traction you get to that corner. Keep in mind that more angle is more rear steer. As the car rolls to your outside it makes the right side bars more level and the left side bars will be at a greater angle thus wanting to send the rear of the car around. And as the may be cool to do donuts with it does very little helping you off the turn. Some roll rear steer can actually help the car going through the turns. The thing you have to keep in mind when tuning the angles of the upper bars is finding that happy medium between traction and being loose. Being that track conditions usually determine what way you go and how far from base setup it is a good idea to ask your chassis manufacturer tips for that given track that you will be running . As a rule you tend to have less angle on a bigger wider sweeping turn than say a very tight hairpin turn where you would have more angle in your 4 link bars. As a guide on a short hairpin track you would be looking at say 18 – 23 degrees. A wider more sweeping track tends to be down around 15 – 19 degrees. One thing to help with this vision is stop and think about cars back in the 1970's versus today, then you would see more cars on a short bullring track just raise there ride height and when they went to a bigger track they would lower it. Raising bars to far can lead to several things going wrong . Just some quick examples would be, topping a shock out on the left rear, bottoming a shock out on the right rear. Then you have to look at the left rear coming so far ahead that the only weight is has on it is from mechanical pressure from your bars and at this point there is probably no weight on the left rear spring at all. Then you take a look at your j-bar , with all that roll into the car now your j-bar has such a steep angle to it that your sucking the right rear so far under the car that you are not coming off the turns with any speed. A lot of older racers would say “right into the turn, left out of the turn”. They were referring to the rear wheels, having the axle adjusted correctly you would be using the right rear to get you into the turn and your left rear to get you out of the turn. Tuning the lower bars is most commonly used for corner entry. Lets say your car is loose going into the turn, you could on the right side take your lower bar and shorten it then put it in a lower hole .  

How a four-link works and general set-up and adjustments for a four bar suspension.

The Four Bar Set-up is a highly adjustable suspension that promotes traction and rear steer. When adjusted properly to track conditions and driving styles, the four link set-up can be a very effective piece .

General Guidelines

• Do not over tighten a race car. To much traction (Left Rear) will not win races.
• Adjust your chassis so you can keep the most momentum. Momentum requires less traction.
• As a general rule- Upper 4 Link bars mostly affect corner exit, while the bottom 4-Link bars mostly affect the entry.
• More angle in any bar adds more weight to that bar (traction) but also creates more rear steer.
• Too much upward angle will create to much roll steer and/or can top a shock out.
• The trick is to find a happy median between traction and roll steer.
• Bigger tracks require less upper four-link angle.
• Smaller stop-and-go tracks require more upper four-link bar angle.
• Upper bars are generally longer than lower bars to induce traction but limit rear steer.
• Raising Left Rear Bottom 4 Link bar creates more "hike up" inducing roll steer and loosening car throttle.
• Lower Left Rear Bottom 4 Link bar holds chassis on spring more inducing less roll steer therefor loosening car on throttle.

TO TIGHTEN CORNER EXIT

• Left Rear Top 4 Link Bar: Raise on chassis
• Left Rear Bottom 4 Link Bar: Lower on chassis (Reduces roll steer and holds more spring load to tighten)
• Right Rear Top 4 Link Bar: Lower on chassis
• Right Rear Bottom 4 Link Bar: Lower on chassis.

TO TIGHTEN CORNER ENTRY

• Left Rear Bottom 4 Link Bar: Lower on Chassis (More noticeable on throttle than deceleration)
• Right Rear Top 4 Link Bar: Raise on chassis
• Right Rear Bottom 4 Link Bar: Lower on chassis

TO TIGHTEN CORNER MIDDLE

• Left Rear Bottom 4 Link Bar: Lower on chassis (On throttle)
• Left Rear Top 4 Link Bar: Raise on chassis (On throttle)
• Right Rear Top 4 Link Bar: Lower on chassis

TO TIGHTEN CORNER MIDDLE/EXIT

• Right Rear Bottom 4 Link Bar: Lower on chassis

TO LOOSEN CORNER ENTRY

• Left Rear Bottom 4 Link Bar: Raise on chassis
• Right Rear Top 4 Link Bar: Lower on chassis
• Right Rear Bottom 4 Link Bar: Raise on chassis

TO LOOSEN CORNER MIDDLE

• Left Rear Top 4 Link Bar: Lower on chassis
• Right Rear Bottom 4 Link Bar: Raise on chassis

TO LOOSEN CORNER EXIT

• Left Rear Top 4 Link Bar: Lower on chassis
• Left Rear Bottom 4 Link Bar: Raise on chassis
• Right Rear Top 4 Link Bar: Raise on chassis
• Right Rear Bottom 4 Link Bar: Raise on chassis