Low Speed Tech
Low speed nose, this is a term we often use to describe a condition in a shock that has been altered to perform different. Low speed is a force generated by the shock when the shock is moving at a slower shaft speed generally between 0 and 3 inches per second. This is the force range where the shock will control the car at its best. Low speed can be built in two ways, 1st by reducing free bleed and adding high speed, which is the way most shock builders will do it because it is easy and fast, the 2nd way is by changing free bleed in a controlled way without increasing the high speed to a level in which the car is ridged. A standard off the shelf shock will have a good amount of bleed in it, this will allow the shock to move in and out easily and also allow the race car to process bumps in the track very well. The standard shock runs a ratio of high speed to low speed of about 6 to 8 percent. When changing the amount low speed to increase it to 15 percent the nose or low speed must be altered in a way that the bleed circuit reduces the amount of oil that can flow through it without increasing the high to much. Most people don’t do this because it is difficult to accomplish, but it leaves the shock in a way that allows the car to make grip in the slick better. Sometimes nose is confused with zero force, the dyno sheet below shows low speed nose but not zero force, because it is not the type of chart that shows it and we will discuss it later in a different article. Zero force is good but in an overall shock like the right front, less zero force will run better in more conditions than one with a large amount.
On the chart below is two shocks, both are 9 rebound and 1 compression shocks and as you can see there is a difference in low speed nose between the two shocks. The added rate at 3 inches on the red run will increase the ability to control the car when the race track slows down and this is what we call low speed or nose on a shock. When we add nose to a BSB shock we do it on a standard piston by changing the amount of free bleed while maintaining a good number of zero force to allow the tire to make grip. Always remember to ask your shock guy to give you bleed for grip and forward traction and to reduce the amount of zero force in the shock.
The blue box between the blue and red line at 3 inches is the difference in nose on these shocks. The red line shock with hold the car down better and both are a 9 valve shock based on a BSB valving chart.
9-1 Dyno Run