Steve Hoelscher
True Classic
Oh boy... this will probably need more time than I have right now to respond. I'll try to give you the basics and will follow up asap.
There are two basic applications; street car and track car. Their preferred setups are at odds and compromises often make them bad at both. I have written in the previous version of this forum extensively about this very subject. In fact, it was my Championship DSP X1/9 that launched my career in Motorsport. The car taught me a lot about vehicle dynamics and setup. It was my laboratory where I could play Dr. Frankenstein and suffer my own failures.
It all comes down to two basic components; ride frequency and roll ratio, which tend to be at odds when applying them to the two applications.
For reference I will define a few terms:
Ride frequency is the time measurement of the vehicle's ability to recover from hitting a bump. That is; the suspension/chassis's cycle time. A soft ride frequency is typically about 1 Hz (1 cycle per second) and provides for a smooth ride quality. A high frequency is over 2 or even 3 Hz (2 or 3 cycles per second).
Wheel rate is the spring rate times the suspension's motion ratio. For example: if the wheel moves 2 inches for every 1 inch of spring movement the motion ratio is 2:1. So (spring rate) x (motion ratio) = (wheel rate). The reason wheel rate is important is wheel rate is the effective spring rate for setting up the chassis.
Roll Ratio is the comparison of front and rear wheel rates. In your case the front spring is 425 lbs/in and the rear is 400 lbs/inch. Sadly, I long ago lost my spread sheet that had the X1/9 motion ratios in it and I don't remember them off the top of my head but they are pretty close (which is typical of a strut car). So we will just use spring rates for now. Given your existing spring rates your roll ratio [(Front Rate) / (Rear Rate) = Roll Ratio] 425/400 = 1.0625 I will discuss how that ratio affects the car's handling later on.
Favored Speed is the speed at which the car would have to be traveling for the front suspension and rear suspension to recover at the same point in time after hitting a bump. This is the application of ride frequency in determining ride quality. Very simply, you want the vehicle's "favored speed", the speed at which is rides most comfortably, to be a a typical cruising speed.
Center of Suspension is the point on the car's chassis, between the front and rear axles, where if you were to place a vertical load the suspension would compress the same on both ends.
More to follow.
There are two basic applications; street car and track car. Their preferred setups are at odds and compromises often make them bad at both. I have written in the previous version of this forum extensively about this very subject. In fact, it was my Championship DSP X1/9 that launched my career in Motorsport. The car taught me a lot about vehicle dynamics and setup. It was my laboratory where I could play Dr. Frankenstein and suffer my own failures.
It all comes down to two basic components; ride frequency and roll ratio, which tend to be at odds when applying them to the two applications.
For reference I will define a few terms:
Ride frequency is the time measurement of the vehicle's ability to recover from hitting a bump. That is; the suspension/chassis's cycle time. A soft ride frequency is typically about 1 Hz (1 cycle per second) and provides for a smooth ride quality. A high frequency is over 2 or even 3 Hz (2 or 3 cycles per second).
Wheel rate is the spring rate times the suspension's motion ratio. For example: if the wheel moves 2 inches for every 1 inch of spring movement the motion ratio is 2:1. So (spring rate) x (motion ratio) = (wheel rate). The reason wheel rate is important is wheel rate is the effective spring rate for setting up the chassis.
Roll Ratio is the comparison of front and rear wheel rates. In your case the front spring is 425 lbs/in and the rear is 400 lbs/inch. Sadly, I long ago lost my spread sheet that had the X1/9 motion ratios in it and I don't remember them off the top of my head but they are pretty close (which is typical of a strut car). So we will just use spring rates for now. Given your existing spring rates your roll ratio [(Front Rate) / (Rear Rate) = Roll Ratio] 425/400 = 1.0625 I will discuss how that ratio affects the car's handling later on.
Favored Speed is the speed at which the car would have to be traveling for the front suspension and rear suspension to recover at the same point in time after hitting a bump. This is the application of ride frequency in determining ride quality. Very simply, you want the vehicle's "favored speed", the speed at which is rides most comfortably, to be a a typical cruising speed.
Center of Suspension is the point on the car's chassis, between the front and rear axles, where if you were to place a vertical load the suspension would compress the same on both ends.
More to follow.