My 6 months old RL has all 4 tires P235/55R17 whereas it should be P245/50R17.
Any reason why previous owner may have preferred P235 over P245?

 

When I bought my last set of tires, the sales guy told me that 245/50/17 was an unusual size and that they didn't stock that size at any of their stores (Discount Tire).

I had to wait a few days for the tires to be delivered, so maybe the previous owner didn't want to wait? That's my best guess.

 

I did that on purpose once. The selection of tires in the RL's size was so limited, I went down a width because I wanted to put General Altimax's on it. It didn't work out horribly, but one got slightly out of round in a severe heat wave summer, and tire overload could have been a contributing factor. No way to know for sure.

 

I think 245 on RL might be overkill, also as previous mentioned the tire selection in stock size is very limited. I have a set of snow in the size of 225/55/17. The diameter is almost identical to stock size and the load rating on the tires is more than sufficient for the weight of the car. The diameter on 235/55/17 is larger than stock so your speedo will be slightly off.

 

Price.

It's not unusual for people to choose slightly different tyre size based on cost.