Another tyre pressure question… Van is a T6 T32 Kombi, 2WD, 200hp with DSG.
OEM tyres are awful 215/60 R17C 104/102 (commercial tyres). VW recommended pressures are 57/48 psi F/R unladen and 58/58 psi laden. I can’t find a load/pressure chart for these commercial tyres but the narrow pressure range for the rear (only 10 psi) implies the rear is about 80% loaded in an empty van. That makes no sense; another post said rear axle load on an empty T32 is only c. 45% of max. That makes sense, so why 48 psi for an onloaded van?
I think kerb weight for my unloaded van (just 2 people & diesel) is about 2,200 kg, assuming c. 1,450 kg front / 750 kg rear. ‘Loaded’ for my typical usage is around 2,800 kg, assuming c. 1,500 kg front, 1,300 kg rear.
I am swapping to 235/55 R18 V 104s. The ETRTO load inflation tables for these tyres would put the pressures at around 33/22 psi F/R unladen (22 psi minimum recommended) and 33/29 psi laden. That seems crazy low. Am I missing something?
If I use the maximum design axle load to set the loaded pressure (1710/1720 kg F/R), ETRTO tables give 41 psi F/R. If I then subtract 550 kg from the rear (275 kg per tyre) for the unloaded case, would equate to 26 psi. In summary, 41/41 psi F/R for the laden case and 41/26 psi for unladen. Small cars like Ford Fiestas have a large pressure differential on the rear for loaded vs unloaded, so that makes sense to me for an empty van.
Thanks for any thoughts or advice.