The front wheels see minimal reduction in wheel speed, where the rears see a drop of 15 Hz in 30 ms.
Could this be the criteria in which the ABS determines imminent wheel lock? (At this low road speed)
Indeed there is no need for ABS to do anthing at low such low road speeds, but that does not mean it wont. It does have a mind of its own (Well that of the Bloke / Chick that wrote the software) You will know as we all do, that overlooking an unreasonable theory has the potential to come back and bite you - Hard !!!
Let's face it, both rear VSS's are showing a similar variation in frequency (one dips a tad more). Unlikely they are telling the same lies.
Could this be an issue with the adhesion of the wheel to the speed hump during such momentary suspension deflection? (Poor damping)
I am going to experiment with Tyre pressures and then see how I could increase ride height during testing.
Not Sure how Increasing Ride Height will help, unless you put new springs and shocks on it ?
If it is an adhesion issue, tyre pressures ? Lowering them would help and/or putting some weight in the back ?? Easier and quicker to achieve too.
The front ones do have the unfair advantage of an engine holding them down.