Took a trip up to see some friends on the Wirral at the weekend and took the P38. Not long after setting off there was a request from the passenger seat to keep it below 60mph, as her seat was wobbling.
We've had this before with the offroad wheels/tyres fitted and I've always put it down to poor balancing of the tyres and the fact that the steel wheels aren't hub-centric, like the alloys are. With the offroad set fitted I can also feel the wobble in my seat and the steering wheel and it gets worse the faster you go - which hasn't been a problem as our offroad trips are reasonably local and on rural roads so high speeds aren't really encountered. However, it's always 100% gone upon refitting the road set.
This weekend, my girlfriend said that the wobble was really bad in her seat but I could barely feel a thing through the steering wheel or through my own seat - which I found odd. If the car was shaking I'd expect to feel through the whole car and if she hadn't mentioned it I'm not sure I'd have noticed anything at all. It also seemed to come and go, and came in at different speeds throughout the journey. Sometimes 70mph was fine and sometimes she'd report the wobble as low as 50mph.
When fitting the wheels before the trip I made sure that the directional treads were all pointing the right way and I set the tyre pressures according to the handbook (28psi front, 38psi rear). The wheels were torqued to 80lbs ft while still in the air and doing each nut in a star pattern. The only difference on one wheel was a missing locking wheel nut cover. They were re-checked on arrival and everything was as it should be.
The wheels are the OEM 18" wheels (Hurricane style, I think), powdercoated grey and wearing 255/55 R18 tyres of a brand I've never heard of before buying this car.
I don't think the missing wheel nut cover would cause such wobbling and I'm hesitant to suspect the tyres, even though they're an unknown brand, as they've previously been fine and have sat in the garage since they were last used.
Any suggestions?
In other news, I somehow managed to get 28mpg (and climbing) showing on the screen between Uppingham and Leicester before hitting Friday afternoon traffic all the way north :(
Factoring in the traffic and including a period of 20 minutes sat not moving at all, we reached our destination showing 20.0 - which I was pleasantly surprised by.