I bought my 3rd generation GS450h a year ago, everything fine. Decided to check the tyre pressures. Tried to take the large valve caps off - they were METAL - and were absolutely impossible to shift. I put some large grips on them, but due to an electrochemical reaction the caps were fused to the threaded shank of the valve. Tried hammering, penetrating oil, old Coke, heating, cooling - no way would they unscrew.
Took the car to tyre shops - they too couldn't shift even a single cap, all warned that if any more force was used, the valve might burst wide open.
So I used a Dremel hi-speed cutting tool and sheared off the valve caps as carefully as humanly possible, but so bad was the fusion that, while I did cut the caps and prise them off in pieces, there was damage to the threaded shanks below, making topping up air pressure difficult-to-impossible.
I found the sensor part number - Pacific PMV-107K = Lexus 42607-50010 of the damaged ones still inside, and ordered 4 s/hand ones, original equipment and identical-looking to the ones being junked.
I thought there'll be no further hassles. Wrong.
I now have to find someone with the kit to add the 4 valve and transmitter ID codes to the car's computer. My Bluedriver ODBC-II scan tool (bought for about $100 from the States) can't do it.
No way do I take this to a Lexus main dealer, they charge an arm and a leg and a half, plus they manage to introduce new problems. I buy Lexus in spite of the dealership quality, not because of them.
What hope do I have of finding an independent tyre shop with the right ODBC kit to make the change?
I believe the only choice for this would be fit 235/45/18 (same size as S4 GS 450h on 8Jx18" wheels) to keep any accuracy to your speedometer, although it will still show you going faster than you are as the overall diameter will have increased compared to the standard set up. A 225/45/18 tyre size is virtually the same overall diameter against 245/40/18 but I'm not sure they would wide enough to fit an 8J rim (happy to be told different). If you go for the 7.5Jx17" wheels with 225/50/17 tyres the overall diameter is also virtually the same as you would expect. I would also suggest that if you choose to alter the size of tyre on your 18" wheels you might fall foul of your insurance company as anything other than 245/40/18 is not a standard size for the S3 GS 450h. If you fitted the 17" wheels with 225/50/17 tyres this would not be an issue as these are a standard size that were fitted to some models.