DJDiggler Posted May 18, 2016 Report Share Posted May 18, 2016 Kind of an oddball issue here, hope someone can help me! Been trying to google for answers and it is infuriating as I just get results about tpms and rotating your tires... not my issue! I recently recieved my new 20" rims for the journey and was somewhat/incredibly surprised to find the valve stem mounts on the INSIDE edge of the wheel... and no it's not a drilling mistake, (which was my panicked/horrified thought at first), this is how they were designed according to the manufacturer and all the pictures I found online. So I figured, whatever, there is a ton of room and no clearance issues for the stem to be pointing in but my shop indicated there might be an issue with the tpms sensors. Because they are mounting on the opposite side of the rim they will be oriented "backwards" ie rotating in the opposite direction they would normally be. Will this confuse the computer or cause issues? I think the sensors are made to rotate in either direction but I'm not sure about how the computer detects the sensor positions. The worst I can think of is the computer will swap sides left to right. Any thoughts appreciated! Quote Link to comment Share on other sites More sharing options...
bramfrank Posted May 18, 2016 Report Share Posted May 18, 2016 Does your tire shop believe that if you do a four wheel cross rotation, that they'd have to remove the tires that changed sides, rotate the sensors, remount the tires and rebalance them? Makes you wonder.As to which wheel is sensed where? In the olden days of 10 and more years ago you used to have a 'learning magnet' to teach the car which wheel was where. On modern Chrysler vehicles there are three antennas - they are used to determine which sensor is closest to each of three wheels and the last is the one that isn't as close. Quote Link to comment Share on other sites More sharing options...
Journeyman425 Posted May 18, 2016 Report Share Posted May 18, 2016 The sensors are omnidirectional. The system is engineered as such so the tires can be rotated without having to re-train the sensors to determine their position on the vehicle. dhh3 and jkeaton 2 Quote Link to comment Share on other sites More sharing options...
dhh3 Posted May 18, 2016 Report Share Posted May 18, 2016 It seems to me that the inside and outside of the wheels are rotating in the same direction at any given time. Quote Link to comment Share on other sites More sharing options...
bramfrank Posted May 18, 2016 Report Share Posted May 18, 2016 The concern was that if they were on the outside, not only would they be 'backwards', which is ridiculous, but that they might be too far from the pickup. Quote Link to comment Share on other sites More sharing options...
DJDiggler Posted May 18, 2016 Author Report Share Posted May 18, 2016 It seems to me that the inside and outside of the wheels are rotating in the same direction at any given time. Yep but from the sensor's perspective when it is on the drivers side normally it will be rotating to the right... Swap it to the inside lip and it will be rotating to the left, (like it would mounted normally on the passanger side). Obviously the sensor can go either way but will the system get "confused" with the sensors rotation swaped. Aparently they had issues with this on a couple cars... A porshe and a honda, (cant remember exactly), and it took a lot of back and forth with the tpms supplier to figure it out. They make rim bands to mount the sensor in the proper position but would like to avoid that if possible. Quote Link to comment Share on other sites More sharing options...
bramfrank Posted May 18, 2016 Report Share Posted May 18, 2016 The simple fact is that the sensor has no idea which direction it is spinning - acceleration and deceleration impact on perceived direction, but the sensor could only tell which by integrating it with change in outward force, but to what purpose?. It is only centrifugal force that activates these devices and at fixed speeds the entire moment of force is directly outward from the hub of the wheel. Quote Link to comment Share on other sites More sharing options...
dhh3 Posted May 18, 2016 Report Share Posted May 18, 2016 If the TPMS is mounted on the inside of the driver's side wheel (as if it were mounted on the passenger side) they are both rotating in the same direction. I do not get where you believe that they are rotating in opposite directions. Quote Link to comment Share on other sites More sharing options...
DJDiggler Posted May 18, 2016 Author Report Share Posted May 18, 2016 Sorry guys mabye I just suck at explaining it my shop just talked to bartec tpms supply and they say it will work but the computer will just get mixed up and swap sides as I suspected... If it indicates a low tire on the left front it will actually be the right front. It might sound crazy but aparently its something to do with how the system works. I have the option of just installing them as is or getting a rim band and orienting them properly so it reads correctly. I dont want a band so when I finally get them installed I will update whether or not it actually does swap sides! dhh3 1 Quote Link to comment Share on other sites More sharing options...
DJDiggler Posted May 18, 2016 Author Report Share Posted May 18, 2016 (edited) Actually modren tpms units have several advanced sensors and take several readings From Wikipedia: https://en.m.wikipedia.org/wiki/Direct_TPMS "The TPM sensors currently fitted to high volume production cars worldwide are battery-powered, self-contained units which periodically measure tire pressure, and often temperature and acceleration... The pressure, temperature and acceleration sensors generate analog signals which are converted to their digital equivalents using analog to digital converters. The acceleration sensor measures the centrifugal force generated when the wheel rotates. This force is proportional to the rotational speed. The acceleration sensor may be a simple switch rather than an analog transducer." Not sure how the system uses rotational direction from the sensor but apparently it does... Well I'll find out for sure if it does soon. Edited May 18, 2016 by DJDiggler dhh3 1 Quote Link to comment Share on other sites More sharing options...
bramfrank Posted May 18, 2016 Report Share Posted May 18, 2016 It can figure out whether you are accelerating (outward force increasing) or decelerating (outward force decreasing) and whether you are going one way or the other, based on rotational force vectors - they can imply whether it is forward or backward based on how large the outward forces are and in what rotational direction the acceleration was . . . of course they can get all of that and a lot more right from the speedometer circuit. Pressure is a no-brainer and the temperature value could be used to compensate for the pressure reading based on a Boyle's Law calculation which in turn suggests you'd always be displaying the 'cold tire pressure value' as calculated, based on the real value.But the one in the DJ is just a dumb sensor and it outputs in 1 psi steps - it isn't particularly accurate, either. Quote Link to comment Share on other sites More sharing options...
bramfrank Posted May 18, 2016 Report Share Posted May 18, 2016 As to the comment about centrifugal force being hogwash . . . . THAT is hogwash. The reason you got the update as quickly as you did was either because the sensor was sending it's once per hour transmission, or the act of changing tire pressure ALSO wakes up the sensor. Tire pressure doesn't change fast enough (or reliably enough) in the minute or so after starting to roll to wake up the sensor. Quote Link to comment Share on other sites More sharing options...
OhareFred Posted May 18, 2016 Report Share Posted May 18, 2016 Not to hijack the thread, but this is about tpms.... On my 09 the low tire idiot light came on ( no advanced dash, thats all I gots). I checked each tire, none are low. It went away for a few days but now as soon as I turn the car on it get the "ding" and the idiot light stays on. No low tires. Now my question, please dont laugh too hard, is there a battery that needs changing or do I need all new sensors? I got the car July of 08, so its almost 8 years old (jeeze, time for a new car!) Anyone know for sure?? Quote Link to comment Share on other sites More sharing options...
OhareFred Posted May 18, 2016 Report Share Posted May 18, 2016 Thanks animal! I know Costco by me had some kinda sign about them, I'll have to look into it tomorrow. Of course not covered under my extended warranty and Im sure the dealer will b big $$$$. Quote Link to comment Share on other sites More sharing options...
jkeaton Posted May 18, 2016 Report Share Posted May 18, 2016 Thanks animal! I know Costco by me had some kinda sign about them, I'll have to look into it tomorrow. Of course not covered under my extended warranty and Im sure the dealer will b big $$$$. Most tire places now make you get a "TPMS rebuild kit" when you buy new tires from them. I assume it's either replacing the batteries or replacing the unit so they don't have to deal with people coming back when the light comes on after getting new tires. At least discount tire does. Quote Link to comment Share on other sites More sharing options...
OhareFred Posted May 18, 2016 Report Share Posted May 18, 2016 Cool, thanks for the info. I'll check at Just tires, etc. Thanks for the help guys! dhh3 1 Quote Link to comment Share on other sites More sharing options...
OhareFred Posted May 19, 2016 Report Share Posted May 19, 2016 Well, upon further review, after rechecking my MaxiCare lifetime coverage, THEY ARE COVERED! Yes it will cost $100 deductable but they are $35 each aftermarket, not installed. Also I found out a repair I paid for should also have been covered (heater hose assembly, was about $480). I'll be calling my dealer tomorrow... Animal Mother, jkeaton and dhh3 3 Quote Link to comment Share on other sites More sharing options...
jkeaton Posted May 19, 2016 Report Share Posted May 19, 2016 Well, upon further review, after rechecking my MaxiCare lifetime coverage, THEY ARE COVERED! Yes it will cost $100 deductable but they are $35 each aftermarket, not installed. Also I found out a repair I paid for should also have been covered (heater hose assembly, was about $480). I'll be calling my dealer tomorrow... Good sleuthing brother. Good luck! Glad I got that maxcare warranty. OhareFred and dhh3 2 Quote Link to comment Share on other sites More sharing options...
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