WheelCollider SuspensionSpring settings do not instantly take effect in flight.

[lo-fi]

I've been working with WheelColliders for a while now and got the hang of setting things dynamically quite well. If I set the Spring or Damper property in VAB/SPH it is carried into flight perfectly. However, if I change the values in flight they either don't take effect or there's about 30 secs delay. Setting _anything_ else (grip, distance etc.) in flight takes effect instantly.

I have a nasty feeling this is something to do with stuff going on in ModuleWheel, but I'm stumped. Calling the spring setting to the log shows it's been changed to the new value; KSP just seems to ignore it for a good while :/

        [KSPField(isPersistant = true, guiActive = true, guiActiveEditor = true, guiName = "Strength"), UI_FloatRange(minValue = 0, maxValue = 3.00f, stepIncrement = 0.2f)]
        public float SpringRate; 


        public WheelCollider mywc;
        public JointSpring thisSpring;

                foreach (WheelCollider wc in this.part.GetComponentsInChildren<WheelCollider>())
                {
                    thisSpring = wc.suspensionSpring; 
                    thisSpring.spring = SpringRate;
                    wc.suspensionSpring = thisSpring; 
                    print(wc.suspensionSpring.spring);
                }

I've tried lots of variations, not one method is more effective than the other. Even added a line in OnFixedUpdate that prints the current spring value - always reported correctly. Somethin' funny going on around here!

Can anyone shed any light? You guys have been brilliant setting me on the right path so far, though I appreciate this one may be hard to narrow down. As always, thanks in advance.