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On my way home last night, I noticed a light pull to the right. Today, as I pulled out of my driveway, the tire pressure warning light was on. I pulled back in and checked my pressures. Sure enough, my front right tire was down 10 psi. After carefully driving to the gas station, I checked all of my pressures and set them properly. The pull to the right is much reduced, but not gone - I tested this in various lanes and there is a definite drift to the right. I have not hit any large potholes that I can remember.

Any ideas? Thanks!
 

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Originally posted by QSJ Ed@Aug 4 2004, 05:58 AM
On my way home last night, I noticed a light pull to the right. Today, as I pulled out of my driveway, the tire pressure warning light was on. I pulled back in and checked my pressures. Sure enough, my front right tire was down 10 psi. After carefully driving to the gas station, I checked all of my pressures and set them properly. The pull to the right is much reduced, but not gone - I tested this in various lanes and there is a definite drift to the right. I have not hit any large potholes that I can remember.

Any ideas? Thanks!
yeah definitely get that tire checked.. they are the original tires that came with your car? I've been reading about how this tire seems to get leaks in it all the time. (Bridgestone RE92).. let us know what you find out from the tire dealer.. or even the car dealer (most can check for leaks)
 

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Originally posted by QSJ Ed@Aug 4 2004, 06:58 AM
On my way home last night, I noticed a light pull to the right. Today, as I pulled out of my driveway, the tire pressure warning light was on. I pulled back in and checked my pressures. Sure enough, my front right tire was down 10 psi. After carefully driving to the gas station, I checked all of my pressures and set them properly. The pull to the right is much reduced, but not gone - I tested this in various lanes and there is a definite drift to the right. I have not hit any large potholes that I can remember.

Any ideas? Thanks!
Hmm... mine is pulling to the right too. I better check my tires when I get home tonight.
 

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remember it's not necessarily your tires. the type of steering the tC uses has a tendency to pull to either side if the road isn't perfectly flat, perfectly straight, and all in all as perfect as your state's DOT can make it.

Then again, in your case it's quite possible the tire is leaking. But for most others, if your car just occasionally pulls to either side, just remember that's the price we pay for having a sportier steering system then others
 

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Originally posted by QSJ Ed@Aug 4 2004, 07:25 AM
After a brief inspection in the parking lot I found a nail in the tread.  I guess my best course of action now is to get that plugged ASAP.  Thanks for the advice!
yeah no problem.. seems that a lot of these RE92's are getting nails and stuff.. kinda weird.. keep us updated on how it goes..
 

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Thats sweet! I'm really happy to have that feature standard in the car cuz I drive into and alleyway then into the carport on my way home. And there be lot's o nails and other crap in there. My car now has gone through 4 patch jobs just because of it and I don't even realize it til a couple days later when my wheels are saggin.
 

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Originally posted by tripeclipse@Aug 4 2004, 10:30 PM
Thats sweet! I'm really happy to have that feature standard in the car cuz I drive into and alleyway then into the carport on my way home. And there be lot's o nails and other crap in there. My car now has gone through 4 patch jobs just because of it and I don't even realize it til a couple days later when my wheels are saggin.
we need to get you some run flat tires from driving down a road like that
 

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incase anybody was wondering, i read on one of the scion forums that the way the sensor works is by checking the number of revolutions of your wheel makes (as opposed to physically measuring the pressure in the tire). i guess when the wheel revolutions are not within a certain tolerance, it will set off your tire sensor
 

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I think it's set off just when the revolutions vary amongst the tires.

IE: An increase in tire pressure due to heat won't set it off because (I'm assuming) all of your tires will increase by about the same volume and the revolutions will stay comparable, overall.

However, a decrease in one or two tires or something (like due to a blow out or a leak, etc.) will change the number of rotations the tire will make when the car travels any distance, and the warning light will go off.
 

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Wouldn't turning also vary the rotations of your wheels?
IE. if you were making a right turn, your left rear wheel would rotate more than the right rear wheel? right?
 

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Hmmm...OK good point.


I'll try to find the text where I THOUGHT I read that...maybe I was just smoking something.
 

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OK, found it. Open the Manual that was posted on this forum...its the "tirepres.pdf" file.

It says the tire pressure monitor ECU calculates the tire inflation pressure based on the signals from each speed sensor. It uses a relative wheel speed difference method (Rolling radius difference method) If this method detecs a drop in the tire inflation pressure, the tire pressure monitor ECU outputs a warning signal to the combination meter in order to warn the driver.

Says it utilizes the changes in the actual radius of the tires that result from a drop in the tire inflation pressure. When the tire inflation pressure drops, the actual radius of the tire decreases and, as a result, the wheel speed increases. The tire pressure monitor ECU compares the speed of each four wheels, and detects a drop in the tire inflation pressure from their difference.

Says this may not function properly in some circumstances:
* on slippery surfaces (guess in the cause of tire spins)
* rapid acceleration/deceleration or sharp turns is continued (I guess normal turns are OK, the system can adjust or something for it? but a long turn would signal a possible problem?
* After rotation of tires if initialization wasn't done correctly
* And other cases too

Still doesn't REALLY answer the question about the turns...can anyone more knowledgable than me (pretty much everyone) about cars explain maybe how they account for that?
 

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hey loopylady..
sure i can try to answer that question for ya..

first.. tires that are hot, or warm increase the air pressure inside the tire.. friction = heat.. heat = increased pressure..

second.. losing tire pressure is what causes you to lose control of a car, like a blow out or just a flat.. a tire that has more pressure in it, isn't enough to cause you to lose control of a car.. on some owner's manuals it says that if you drive faster than 80mph to increase the cold tire air pressure.. since air pressure can deter the effects of heat.. somewhat more than a tire that is low..

third.. there are two types of tire air pressure monitoring systems out there.. the cheapest is the one that uses the ABS (anti lock braking system) sensors to measure the tires revolutions and if the tire begins to revolve more quickly then it signals that something went wrong (loss of air pressure in a certain tire) and it illuminates the light on the dash board.. this type of system is not that accurate and it requires time for the sensors to realize that a tire is spinning faster than the others.. if you notice in the manual it says that it takes a couple miles for the system to realize what it's starting points are..

fourth.. the 2nd type of sensor is the direct sensor that has a sending unit inside the tire/wheel that wirelessly sends the actual pressures to a unit on the dash.. allowing you to monitor exact pressures..

okay with all that said.. turning the car will not cause the abs-type air pressure monitoring system to illuminate a check tires light, because it's not spinning faster for very long.. even if you drove in circles, you'd have to drive pretty fast to get the percentages that a loss of 10lbs of pressure would give.. it takes the abs type system to generate a history of more revolutions for it to realize that there is a flat..

also.. more pressure in the tire would increase the diameter of the tire and then would slow down the revolutions.. and the system isn't looking for that.. that's why to have all the pressures the same (get a nice digital gauge for this) when it's cold, and then initialize the system.. then it has a good base value of all tires being equal to monitor..

The government has mandated the direct type sensors for future vehicles.. Auto makers wants a cheaper route through the ABS.. But the government found that ABS was not quick enough in alerting the driver of a low tire.. because as most have found out it didn't realize the tire was low until 10lbs of air were lost.. a loss of 5lbs is enough to hurt a tire, if you're going fast enough.. So the next car you buy will have the type that gives you an actual number for each tire.. and they are accurate to +- 1 or 0.5 lbs of pressure..


hope this is making sense for everyone reading it so far..
 

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Yep, makes plenty of sense.

Just hope the next round of tC's don't have the new-and-improved monitoring system...that would suck for us first-round buyers. Hehe.

Thanks for the help, sciontc_mich!!!
 

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Originally posted by LoopyLady_1@Aug 6 2004, 05:54 AM
Yep, makes plenty of sense.

Just hope the next round of tC's don't have the new-and-improved monitoring system...that would suck for us first-round buyers. Hehe.

Thanks for the help, sciontc_mich!!!
hey glad to help out loopylady..

one more thing.. if you really really wanted the direct system.. www.tirerack.com sells this type of system.. couple hundred dollars.. and you get a display that tells you all of this..
 
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