I was the member that ulfnilsen referred to in previous post. Since I went self employed in 2015, I always have at least 170kg of kit for work in the boot (and often on the back seats, I know I really should buy a van as everyone on site keeps telling me) of my 63 plate TDI 170 DSG 4x4 estate and the arse end was starting to sag, to say the least, in the 108K miles / almost 8 years since it left the factory (bit like myself after 55 years on this planet :-). Got to the point where I was struggling to get over even the smallest speed bump at crawling speed without something scraping. Book ride height for the rear on standard suspension like mine is 394.1mm +/- 10mm. Fully laden ride height was less than 310mm so was sagging at least 85mm and even with the boot unloaded for the first time in at least 5 years when I was weighing the kit I carry, ride height was only 340mm, a sag of around 55mm. So decided to bite the bullet and replace rear dampers (and rubber sleeve/cover), springs (and plastic end caps), bump stops and all the consumable fixings. Local Skoda dealership kindly helped me identify the existing springs and damper by confirming the associated PR code for my car, 0YF for weight range 6 springs and 1JA for standard dampers. That was the same as ulfnilsen. He'd gone for weight range 8 springs, 3C0 511 115 AG and the original 3C0 513 049 CP damper and was pleased with the result. But as I am carrying at least another 30kg I decided to go up one step more to weight range 9 springs, 3C0 511 115 AH, again with the original damper although in my case the correct part number was 3C0 513 049 CR according to dealer. Was originally going to use OEM equivalent parts but when I had a price from a local, well respected, VW independent he would only use genuine VAG parts thanks to bad experiences in the past. Was about to go down that route when decided to see what the Skoda dealership would charge, they were actually about £20 cheaper overall thanks to the independent charging list price on parts and insisting on quoting for a minimum 3 hours work (and charging for more if he hit problems) whereas the dealer I assume quoted based on fixed book timings and so ended up cheaper despite hourly labour rates being roughly twice the independent.
20 quid is 20 quid and the independent didn't offer a courtesy car so the work was completed yesterday at Autosales Burntwood and whilst my wallet is now lighter to the tune of £718.08, it has absolutely transformed the car. Front suspension is sat at 387mm (a few mm low but still in tolerance) whilst rear is now 403mm empty (about 8mm high but still in tolerance) dropping to 369mm fully laden. That's still 16mm below the minimum book value but half the depth of the tire wall is no longer hidden in the wheel well (there's now actually a gap between the arch and tyre!) and ride height looks spot on to my eyes. And all the clanking and majority of harshness in the ride has gone despite being on 18" 40 profile tyres and still on original front suspension. I suspect it was like this when I first got the car (was a 3 month old dealer demonstrator) but the slow deterioration in ride quality in the 105K miles + 7-1/2 years I've owned the vehicle meant that I'd gotten used to the appalling ride quality as it grew to seem normal. Just wished I'd done it couple of years ago as only planning to keep it for another 12 months although they will at least now be comfortable months. Next job is 2 new rear tyres and 4-wheel alignment as the rear camber and toe-in are a mile out which coupled with the extreme loads carried and possibly my driving style when not motorway cruising (4-wheel drive means safe to boot it at every junction and roundabout, so I do, which I assumes biases the torque (and hence wear) to the rear) likely explains why rear tyres last on average just under 12k miles (compared with 24K average for same Dunlop RT Sport (and later on, Michelin Primacy 4) tyres on the front) although they don't wear particularly unevenly, usually no more than a mm variation across the width of the tyre. Anyway, attached are before and after photos, both empty and fully laden, to illustrate the transformation in ride height. I'm sure the fully laden before photo must win me a trophy for the most lowered Superb in the world :-).
Hopefully someone else will find this information useful and happy to receive PM's if anyone has any questions.