Rear Suspension/Wheel/Tyre Problem

[Len]

My Mk 3 is on standard suspension but has 17x8 alloys with 215/40 tyres
Now I dont have any problems at the front, but have noticed recently that if I have a load in the back,
passengers or heavy load that at times it bottoms out and the inner edge of the bumper and arch trims scrub the wearing face of the tyre! Now this appears to be only one side, the offside.
When I bought the car it had had new shocks and since then have done about 17k miles so that shouldnt be a factor. Also last year for MOT (June) had the rear bushes done.

So I'm looking for ideas/opinions folks!

My guess atm is springs.
But it could just be that tyres/wheel offset is wrong for the car???

[HARDCOR3]

maybee it's the width of the rim, i've got 17x7.5's with 205x40x17's and they are fine 5 up and the cars fairly low...

[Len]

Yea i know been thinking that too! But if thats the case why am I not getting problems at the front?

I do have a set of 17x7 alloys that I am gonna swap those tyres onto. Mainly because those 17x8's badly need a refurb!!! Those 215's are very stretched across the 17x8's