A friend of mine has a 2006 Cadillac XLR and he is looking for new wheels. He would like to get 19" and have few questions. Does he need different air pressure sensors or are they same for 18" and 19"? What tire size would he need in a 19" to keep the same height as the 18", whats the actual bolt pattern and offset?

Any help will be greatly appreciated.

He can use the same sensors. No issues there.

As for the size. He will want to try and keep the same overall diameter of the wheel. So if he has a 235/50/18 and wants to go to a 19" then he would run something like a 235/45/19... Just an example.

As for the bolt pattern, it is a 5x120. I dont recall the offsets off the top of my head.... Sorry.

Thanks,

Dr. Design
D3 Cadillac

A friend of mine has a 2006 Cadillac XLR and he is looking for new wheels. He would like to get 19" and have few questions. Does he need different air pressure sensors or are they same for 18" and 19"? What tire size would he need in a 19" to keep the same height as the 18", whats the actual bolt pattern and offset?

Any help will be greatly appreciated.

Offset is 61 mm.

CC :seeya

I have found the 'smaller aspect tires' (20/22/24) require more air pressure. Can the 'car's requirements' be changed ? Thanks

I have found the 'smaller aspect tires' (20/22/24) require more air pressure. Can the 'car's requirements' be changed ? Thanks

If you want to be very keen, you can set tire pressures with a touchless thermometer. This is much easier with an assistant who stays outside the car.

Drive the car until tires etc. are fully warmed up, say 10 miles. Now, drive the car in your 'usual' style, for at least 0.5 mile, 1 mile is better. Return to your assistant (who is in a safe place off the road yes?), and they measure the tire temperatures in three places across the width of each tire. This needs to be done quickly, before they cool down. Write all 12 readings down!

When the tire pressures are correct, each of the three readings across the width of the tire tread will be the same.

Assuming correct alignment, then if the center reading is higher than the inner and outer edge readings, the pressure is too high. If the center is lower than the two edge readings, you guessed it, the pressure is too low.

Now, if the inner edge and outer edge readings are different, the camber might be out. The temperature is higher on the edge carrying the greater load and if the inner edge of the tire tread is a little hotter than the outer edge then that is probably a good thing, a tad of additional negative camber helps the car to turn in better. This is more of an issue on front (steering) wheels than rear wheels. It is very unusual to run positive camber on modern cars (top leaning outwards).

If there is a slight difference between inner and outer temperatures, workout the average of the two for the correct center reading.

Set new pressures and repeat. Front and rear pressures might be different, but left and right should be the same. If you are getting wildly different results suspect the thermometer. Also, the tires on each axle need to be the same type (and should really be the same in all four positions).

Having done this, and waited for the tires to cool down (overnight), what readings do you have? Drive the car and feel for harshness over bumps. If you have set a pressure much below the recommended value ask why? It would suggest that something has gone wrong with the procedure and running low pressures in your tires is not a safe thing to do.

If higher, is the feel harsh (feel every bump and ridge)? If yes, then too hard perhaps. Now on a wet day make sure you still have enough grip. Tires set too hard will lose grip in the wet very quickly, so be careful.

As with any advice like this, use it at your own discretion, this advice is supplied without any warranty express or implied.

Regards