rominl

iTrader: (4)

that can definitely happen, or the dealership can just reset the tpms to register the new "reference" psi.

but it's surprising to see the difference. pressure in my tires were ok here in socal one winter, we drove to norcal, and next morning all pressures said low...

allen, rule of thumb, always check pressure when it's cold, in the morning. that's always the reference. if at that time the pressure is say 36psi (or whatever your desired pressure), then that's what it is. to let pressure out, yup, nothing different from any other wheels. and on the ls460, there is no way you can tell which pressure is corresponding to which wheel

Nospinzone

As far back as I can remember (maybe the early 1960's) the car manufacturers and the tire manufacturers have always battled over recommended tire pressures. The car manufacturers want it lower so the ride is better, and the tire manufacturers want it higher so the wear is better.

As long as you inflate your tires so that they are no higher than the tire manufacturer max pressure when hot, then you are fine. You will get the best tire wear and handling characteristics. If you have to err, higher inflation is preferable to under inflation.

AceVA

If I recall (and it's been a while, I could be wrong) -- there is a hard limit built into the computer, nobody, not even the dealer, can reset the reference point below that limit, hence why so many cars were coming in when the weather got cold - I believe the hard limit isn't too terribly far off from 33psi. Lexus found it easier to just tell the dealers to (over)inflate the tires.

Speaking of tire pressures - does anyone know if the pressures on the display give any kind of indication as to what wheel position they correspond to, on the 2010 models?

rominl

iTrader: (4)

ah, good info, didn't know about that, but i think that makes sense.

i would be interested in knowing if they improved the system on 2010, though i stay a but skeptical for now

bob321

Bottom hard limit is 30. Any tire pressure of 29 or lower turns on the warning light which can Not be cleared by resetting. IIRC, even driving over an hour with the tire pressure rising above 30 would not make the warning light turn off.

jmcraney

My car doesn't work this way. When I "benchmark" at 33 PSI, my warning comes on when the display changes from 27 to 26. It is not possible to turn the warning off with the reset button. The warning is self-clearing when the pressure is returned to "near" the benchmark (31 PSI in the case of a 33 PSI benchmark) - it probably would not work very well without the hysteresis. I don't think the reset alters the benchmark for a tire that is in the alarm state but it might alter the benchmark for the other tires so it is not a good idea to be operating the reset except when you want to benchmark all tires including the spare. The reset is not intended to be used to cancel alarms and improper benchmarking can make your TPMS impotent or drive you crazy with false alarms.

In your case, we don't know at what pressure it was benchmarked so we don't know how high the pressure would need to be to turn off the warning. On my car for example, when a tire is benchmarked at 40 PSI the alarm is generated when the display changes from 32 to 31.

That is a pretty wide margin and should accommodate most temperature and permeation variations if the tires are tended to every two months.

I think most of the dealers were not well informed about how all this works - perhaps a Japanese to English translation issue - and their solution was to add more air. I operate mine at 33 PSI (cold) and never have a problem.

Johnny

^^^ What he said! My problems occurred when the dealer kept bumping up my pressures.

RGSW

I inflate the spare to 39 PSI. That way I can at least tell which one is the spare on the readout. Also, it insures I'll have plenty of air in it should I have to put it on the ground.

bob321

>>In your case, we don't know at what pressure it was benchmarked so we don't know how high the pressure would need to be to turn off the warning.

The dealer brings it home around 36-38, I lower to 33 and do a reset. Same nonsense every 5k miles

>The reset is not intended to be used to cancel alarms

When you are out in west Texas a couple hours from air - those multiple blazing yellow warning lights are just annoying.

stanatl

I checked with my SA when I got my car and they said that there was no way to know which wheel position the pressures correspond to - other than the spare which is inflated to a much higher pressure. Totally different from the 550i I had which showed a schematic of the car and each tire and changed the tire color from green (good pressure) to red (low pressure) so you could easily see which tire was causing the alarm.

rominl

iTrader: (4)

ok, so nothing has changed then even on 2010

Strad6708

I have a 2010, and I can confirm there is indeed not an indication of which reading corresponds with which tire. The manual confirms this. I have, however, figured out that the top reading must be the spare tire, because it rarely changes during driving, while all the others increase to 39 or 40.

rominl

iTrader: (4)

but later say if later on dealership rotate your tires including the spare, then it's everyone's guess

jstjohnz

I just changed tires and the dealer inflated all of them to about 38 psi, a bit higher than I like. When I let air out of the tires I did them one at a time, then checked to see which reading changed, so now I have a chart of which is which.

The order they appear is the order the sensor IDs were entered when the sensor serial numbers were programmed in.

HSVRX350

Here's a good question.

I have acquired second set of Lexus rims with tires cheap off Ebay. They came right off LS460 2010. I intend to use them as soon as they are delivered.

My question is upon installing the new set of rims with tires. Would my 07 LS460 bark with yellow lights because the computer might not recognize the other TPMS devices?