Early KVA Ford front suspension

[Marcus]

Hi All,
Looking for any owners current or past that had the old Ford Cortina front suspension set up... Trying to get the right front spring rating as my current set up is way too soft. ..Have used the extra heavy duty springs from an old Ford V6 but at 245lbs spring rating it's still way too soft... Much appreciate any info on what springs were used from anyone that had the early KVA chassis that didn't nose five under braking.
Thanks in advance for anyone taking the trouble to respond. ..
Kind regards

Marcus

 

[Mike Pass]

Hi Marcus,

I don't have a Cortina Mk3 suspension to check but here is the result of a quick calculation.
Car wheel frequency for a road car is in the range 0.5 to 1 Hertz, I have taken a rate of 0.75 for your car. I have taken the front wheel weight as being 250Kg. Putting this into the formula gives a wheel rate of 3.5 per metre which converts to a wheel rate of 310 lbs per inch.
However on the Cortina suspension the spring meets the lower arm part way along. From a drawing of the front suspension the ratio is 5.8 : 3.5 (distance from inner bearing to outer ball joint : distance from inner bearing to spring centre) as taken from the drawing.
The spring rate is therefore the wheel rate times this ratio. This works out as a spring rate of 500 lbs per inch.
To get the spring length measure the distance between the top and bottom spring mounts with the suspension set to normal ride height and add 1.1 inches to that figure. Spring O.D. as per the spring mounts or the springs you have.

Springs from here

Suspension springs for the Motorsport Industry | D Faulkner Springs LLP

www.dfaulknersprings.com

Hope this helps
Cheers
Mike

 

[Marcus]

Hi Mike....hope all good...so very kind of you to take the trouble to respond in such detail... ... Extremely helpful and I will hopefully be able to use these calculations to get this problem sorted.... All the best from me.... Cheers