I have 235/55R18 tires on my new NX sport. The dealer put 37 PSI in all tires. The door indicates all tires should be 32 PSI. Car tires great, but might be a little bouncy. Being new, hard to compare to anything. Did the dealer over inflate? Should I put what is indicated on the car? Thanks.

 

Mine were the same, as were many of those who hang out here. I reduced mine to 33 PSI, which noticeably improved the ride. Probably lost an MPG or two as well, but such is life.

 

Overinflation of tires is a common practice across all Lexus dealers. Even their loaner cars are high.

32 psi is recommended. You can go 2-3 psi below or above if you like depending on your comfort (less PSI) vs MPG (higher PSI) preference.

 

I am set at 33 and when driving at 60MPH they go to 36-7PSI and the ride is good
When I picked up from dealer they were set at 40PSI and up to 48 while driving and it was too much, creating a very rought ride

 

I set mine to 32 on cold tires as recommended on the door. The TPMS was showing 32 was too low. Tried resetting the system but the low pressure alert was still present. Had to up mine to 35. Anyone else experience this? Or know a fix?

 

This isn't normal. Sounds like a visit to the dealer may be in store for you. 32 PSI cold pressure is the target PSI on stock tires.

 

It's possible that your gauge is off and you were setting the pressure too low.

 

Ok, yeah I thought that was weird. The dealer had my tires set at 42, which is crazy. I'll get them to check it out.

 

If I am not mistaken, the manual states 41 psi if you are going to go over 160kmh. So thats what I have been putting into my tires...

 

Oh no, that doesn't make any sense. At that speed, in hot weather, 41 psi (cold pressure) could hit 50-51 psi which is typically the max pressure a tire can handle and can blow out!

Please double check your manual and be safe!

 

I'll double check the manual tonight and post here...

But thanks for the concern bro...

 

Thanks for all the great feedback on this question. I brought my tires down to 33 according to my tire gauge. Much softer side. When I checked the cars dash screen that shows the tire pressure, it shows 34 in all. I'll assume the car's dash numbers are more accurate that my digital tire gauge. Also, why do Lexus dealers put so much pressure in the tires? Why do they see that as a positive?

 

The pressure in the tires seems to vary a lot between driving conditions. On a 58F morning, I can see 33psi in the tires and will get it up to 35psi by the time I get to work, but when its 80F in the afternoon it will be 37psi and will get to 39psi by the time I get home.

I think its the size of the tire, and the shear amount of rubber that causes so much variation in the pressure.

Honestly, I'm leaving it where it is. The ride is smooth and my tires are too new to show any type of wear that will allow me to adjust.

 

After putting back to 32psi, I find the ride much better. It does vary with temps lately with the hot weather....usually goes up to 35psi.

 

No, assume your guages are more accurate, specially if you are reading cold temp at rest when the car has been in the shade.

The TPMS sensors are inside the tires and are more affected by the internal air temperature. Also, there is no way to know the error margin for that particular sensor. Using an external guage to measure at cold temperature at rest in the shade and then using another one to confirm is the best way to ensure you have an accurate reading. If those 2 reading happen to coincide with the TPMS reading, then all the better. In my 2IS, I had one sensor on one of the tires that was off by 2psi. I know the tire was inflated properly, but it always read 2psi higher than it was. I mentally adjusted it every time I checked. Plus, I didn't have TPMS sensors in the winter wheels. so 5 months of the year my check tire light was on.