Disco saggy rear springs?

[iguana]

95 disco tdi, 130k, when towing seems far more saggy at the rear than im sure it should be, are the rear springs renowned for saggging?

For replacements standard or aftermarket best?? will be used to tow a lot, but dont want daftly hard rear for car use.

Cheers

[iguana]

Cheers all, I shall investigate prices etc.