I had STRs for a week and they were downright dangerous. Exactly the symptoms you're describing.
Wheel size has an effect too. The bigger the wheel the more sensitive to tyres the p38 seems to be.
How do you test the steering damper .
Gotta aggree with yer there Guy ,,,,,, when I changed me wheels to 19's (Even with Scorpions fitted) they "Tramlined" like fook ....
& BEFORE Tony or J posts up ....... YEAH I KNOW there actually ARE fookin TRAM LINES up the main street in Fleetwood ... but that was EVEN WORSE!!!!
pirrelli on front nexon on rear new steering damper fitted was like this before i changed rear pirellies for nexon
Size? Original rims or aftermarket? The bigger the rims the more likely the Rangie is to tramline. Also performs best on OEM rims (ok cue all those with 22" drugdealer blingsta rims to rush in and announce how wonderful their Rangies road handling is!!)
You really need 4 matching tyres on a P38, balanced, and correct tyre pressures - this is critical in P38s - STs were the best, no longer available and STRs are not the same. Zeros all round do just fine on my Rangie, others have found Goodyear tyres handle well.