tpms light came on

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wrote:


Thanks, Tegger.
I gathered from my experience that some speed or distance is necessary. I wonder at the devices, do they need the rotation to generate the power to send a signal? Yet the web page for the manufacturer suggests they have a device that queries them at rest. I still don't know how they get the signal to the dashboard, some form of RF I guess, bluetooth or some other frequency.

Yes, I do.

Good idea. I knew I should have put another pound or two in, to guestimate the right numbers "warm".

Ha. Takes a fair amount of pumping a hand-pump to move a car tire 1psi, and the connections often leak just about that fast.

Sure, but I assumed that three tires were good and one was lighting a sensor, and you'd think that might be visible. In my case they were all just about equally low so there was no real visible difference.

I don't grok this, why would rotational difference set off a pressure sensor, do these things cross-check each other? I can't figure why that would help.
So, do the dealers have a lot of customers with these kinds of issues?
When I next bring this car in for service, I'm going to mention the low pressure to the service manager and the front office. The only way the four wheels had the same low pressure, is if that's how they gave it to me. I do recall in the past, some guy at the dealership said they ran them low because "it gave a smoother ride". Guess he's still working there. Can't be good for the tires.
J.
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On 04/04/10 14:12, JRStern wrote:

But good for the bottom line (selling new tires). BTW, I suspect lots of owners appreciate the "smoother" ride.
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There are two kinds of TPMS. One is ABS-based (rubber valve stem), and the other is transponder-based (steel valve stem).
Transponders are incorporated into the valve stem. They work a bit like cell phones, in that they have batteries and emit a radio signal. That signal is received by the TPMS computer. Eventually, transponder batteries will go dead and need replacing. Draw on the batteries is tiny, so it will be years before they go dead. But when they do, imagine all those irate customers! Thank you, Congress.
ABS-based requires actual tire rotation to determine if one tire is low. Transponder-based does not require tire rotation. As I understand it, transponder-based systems wait a bit before deciding that there's a problem, even though they /could/ snitch immediately if they wanted to. I'm not sure why.

My Schwinn pump does about six pumps to the pound. I consider it cardiovascular exercise.
There is no appreciable leakage from the valve stem when the pump is connected to it.

Nope. No obvious visual difference until they're about 15psi low.

Rotational difference is used on ABS-based systems. ABS-based systems do not have sensors inside of each tire. Measuring and comparing rotations is the only way they have of being able to tell if a tire is low.
Transponder-based systems measure tire pressure directly, using sensors inside of each tire (and sometimes even inside the spare).

Yes. Just like EVAP.

If he said that, then he's a dummy.

Probably not. But this monkey is not too smart if he thinks he's smarter than the Honda engineers that designed your car. I'd trust the Honda guys before I trusted some goofball working for a dealership.
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Tegger

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wrote:

Must disagree. I can't tell pressure on some arbitrary tire on an arbitrary car, but I can get used to what my own tires look like properly inflated, and notice a different curve as they get low. I've had to deal with leaky tires before and had practice.

OK, I see. Sort of. Funky.

I think the logic is that Honda has to overinflate them to get the EPA mileage up, but that for a mile a gallon or two, you can get a better ride with lower inflation.
Might even be somewhat true, but even so, they overdid it.
J.
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Yup, EVERY manual says to never bleed air from a hot tire.

I've autocrossed with a lot of people who use bleed valve guages. If you're up for the ~$400 price tag.

That's the point. Not that they were "equally" low but that one may have been "too" low and the others were "just above" the limit.
But I always check mine. For exactly the two reasons you and I mention.

The sensor is actually ABS based (as opposed to the F1 sensors that really are pressure based). ABS measures the rotational speed to figure out which tire is locking up. Unless your tires, rotars, pads, pistons and master are all incredibly tuned up, one tire will lock first. Stay up late tonight (if you're in the western hemisphere) and watch one of the bought drivers in the GP of China square off a tire.

That is pure BS. Doing that introduces a huge number of safety and reliabilty issues.
A lot of drivers I AX with (including me) will sometimes chalk the tires looking for roll. Too low a pressure and too tight/fast a turn will roll a tire off the rim. I've seen it.

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On 04/15/10 12:56, Dillon Pyron wrote:

Small world, I ended up watching much of this race on SPEED last Sunday. Sorry to say, I found it fairly boring.

Haven't seen the term before, what do you mean?
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On Fri, 23 Apr 2010 06:27:42 -0400, Tony Harding

I'm gonna guess auto-cross.
Which is a combination race and scavenger hunt, or something like that.
J.
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On 04/23/10 22:31, JRStern wrote:

Thanks, I know about that (IIRC we called them gymkhanas a few decades ago), but how (or why) does one "chalk the tires"?
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wrote:

Never AX'ed, myself, but I'd wager that you just put a chalk line down the sidewall and onto the tread. Where the line gets scrubbed away, the tire's touching the pavement.
The idea would be to maximize the amount of tread remaining in contact with the road instead of getting lifted off as the sidewall rolls under.
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On 04/24/10 11:30, Tegger wrote:

Thanks.
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