Well it’s Friday noon here at Talladega and things are getting under way. The Truck series has just finished up their first practice and we are hanging out at the campsite getting the rear window in the truck replaced. We are going to head to the Sprint Cup Series practice at 1:30 today.
Anyway, on to what we are talking about today. This is the first article on shocks here on the blog so I’ll try to make this interesting for you guys. I want to make this a series of articles that start out with the basics and work up to some more technical explanations. I will try to add some pics to this post at a later date.
Today we are going to start at the very basic, and that’s how shocks are mounted on the car. I’m going to keep this circle track focused and really more modifieds and sportsman cars than anything. This year we’ve had a lot of shocks where the ball joints have hit the shock body causing the shocks to malfunction. This is restricted to mono-tube shocks like Bilstiens and Penske shocks. The root cause of this is how the shocks are mounted.
On the Fronts, you really need to take out your springs and mount the shocks especially if this car already has mounts on it. Then you need to cycle the suspension and see how close to the shocks the ball joints and spindle parts come. You should also check the clearance from the shock body to the frame. There should be a quarter of an inch around mono-tube shocks at all times. This allows for flex in the suspension components.
Some issues are caused when modified car builders want to use the smaller yellow Bilstein shocks. This makes using a larger 46mm body shock difficult, and changes should be made….as I do not recommend the smaller body shocks as they do tend to run hotter and suffer from more heat fade and wear. The changes that should be made are moving the upper shock mount in towards the engine, this gets clearance to the ball joints and spindle, but tightens clearance to the frame. When the clearance get too tight, then some of the frame can be cut near the spring pocket since the spring no longer sits in the pocket. This can save a ton of money on repairs or new shocks.
A major thing to look for that will prolong the life of your shocks is the alignment, indexing and mounting position of the shock. A shock is made to go straight in and straight out, if the centerlines of the mono-balls do not line up through its travel there will be some side loading on the mono-balls and rod bushing. This is really the only issue on the front suspensions other than having the top mount too low causing bottoming or the top mount to high which won’t let the front of the car travel up like it should. On the rear of a modified, we have alot of indexing. The alignment portion still applies, but the major factors are the indexing and mounting position. The rear suspension should also be moved up and down to look for clearance and early or late bottoming. If the shock bottoms to early such as on the RR the tire will loose traction and it cause shock or suspension failures. If a shock bottoms late, then there is the possibly on the RR that the tire will hit the frame and not have enough down travel at the same time. There are many other factors that affect this, such as birdcage shock mount heights, shock shaft lengths and shock body lengths. Typical dirt cars run 7″ fronts and 9″ rear shocks, but cars like Rayburns continue to use shocks with shorter shafts and a mixture of body lengths. Buyer Beware!
Specifically on the LR… The left rear of a 4-bar modified(or latemodel) gets a pretty good work out. You should never use a shock as a limiting device. Many guys use a chain to limit the down travel and this is our recommended option, wrap the chain with a somewhat flexible tape so that the links do not turn and shorten the down travel on you. And again you really need to make sure that there is enough up travel on this shock, if not then you will break a shock, a bolt, birdcage or chassis when it bottoms. A Bilstien shock has the threads of an 8mm nut that keeps the shaft from getting pulled out of the shock body. It will work for a while but fatigue caused by high force cycles will cause it to break, period! There are also other benefits to using a limiting chain, but we won’t get into to that. The LR needs special attention whenever you are setting up a new dirt car. Something wrong here can cause odd handling problems for a long time before it’s caught.
Hopefully this helps keep shock damage to a minimum and leads to faster lap times through consistency. You shouldn’t be damaging shocks under normal racing conditions or even rough conditions when they are setup properly.