|11-20-2009, 02:53 PM||#1|
Drives: 2012 GTR
Join Date: Sep 2009
Tire pressure monitor & wheels help!
Does anybody know how the tire pressure monitor system works on European spec M3's (or all if there is no difference)?
The reason I ask is because if I were to put aftermarket wheels (manufactured in the US) on a European M3, would those have to be prepared for the tire pressure monitor or something?
(Remember, if there IS a difference with the monitor system, mine is a European M!)
|11-22-2009, 10:20 AM||#2|
Automotive Industry Insider
Drives: Lemans Blue M3
Join Date: Aug 2007
Allow me to explain WHY...
The U.S-spec M3's uses a direct tire pressure monitoring systems (TPMS) which requires the use of physical TPMS sensors mounted inside each wheel. The U.S. Department of Transportation (D.O.T.) mandated this provision as standard equipment for every passenger car and light-truck sold in the United States after September 2007. The D.O.T criteria for TPMS module fitemnt, is that the vehicle must have only four wheels (no dually trucks or motorcycles), and the vehicles curb weight is less than 10,000 lbs. Direct TPMS sensor modules wirelessly relay the tire pressure back to a TPMS receiver mounted in the car. (433 mHz signal)
There are two different styles of TPMS sensors for a direct system:
1) A valve-mounted TPMS module (pictured above)
2) A strap-mounted TPMS module (fastened around the outer barrel of the wheel)
Note: ALL BMW U.S.-spec direct TPMS system-equipped vehicles use the valve mounted type.
The only time you'll see a strap-mounted TPMS module on a wheel...is when the aftermarket wheel manufacturer dropped the ball, by not engineering this provision into the final wheel design blueprint.
Now in your case...
Euro-spec M3's use an entirely different TPMS system, to detect a tire that is going flat.
It's based on the rpm feedback received from your wheel speed sensors. (ABS)
If your tire starts to lose air pressure, it's rotational speed will increase slightly.
For example...if your right front tire pressure is low (at 25 psi), it will spin faster than the left front tire (at 35 psi). The ABS wheel speed sensors will recognize the difference in the two wheel speeds, and it will trigger a TPMS low-pressure warning chime. (along with a light on the dash)
This indirect TPMS system "knows" what tire rotational speed is acceptable, and what speed is not. That's because the entire TPMS system is CALIBRATED at the factory, based on the O.D. of the factory OEM tire sizes. (that are fitted to the car on the assembly line)
This indirect TPMS system, does not require the use of actual TPMS modules inside the tires to monitor your tire pressure.
All Euro-spec E09/92/93 M3's use this indirect TPMS system. (including Canada)
For the record...
Our U.S-spec'd E46 M3's (2001-2006) actually used the same indirect TPMS method, before D.O.T. forced the switch to the hardware-based direct TPMS modules in 2007.
BTW: Not all wheels will be compatible with valve-mounted BMW TPMS modules. (Euro-spec M3 OEM wheels for example) The size of the sensor shouldn't be a problem for most aftemarket wheels, but if the valve hole is in the middle of the wheel's barrel (or it's too small), then the valve-mounted sensor will not fit properly.
Every wheel manufacturer should be aware of the issue (if they actually know what the hell they're doing), and they should be making most their BMW fitment wheels TPMS-compatible.
When you buy aftermarket wheels, it's important to RESET the TPMS monitoring system...if your new aftermarket tires are not EXACTLY the same O.D. as the stock tires that came on the car from the factory.
This is also something the manufacturer or vendor should tell you PRIOR to mounting the wheels on the car. (many vendors don't even know this)
To be perfectly blunt here...
I'm not sure what aftermarket wheel brand you have decided to purchase, but...the fact that you had to ask us this kind of question on the forum is a very bad sign.
The company/vendor you paid thousands of dollars to...should have explained all this to you already.
This type of tire/wheel fitment information is neither proprietary, nor difficult to obtain. It simply requires a keen knowledge of how all these things are inter-related.
Any competent wheel manufacturer or vendor (who sells any wheel products internationally), should already know this information. That information should have been forwarded to you by now (to calm any fears that you might have regarding a potential 'TPMS problem') once your wheel purchase was confirmed.
As far as I'm concerned, this is a clearly poor customer service.
I wouldn't have a whole lot of faith in a manufacturer (or vendor) that could not give me a straight-forward answer to this very basic wheel fitemnt question.
I pride myself on being able to give my local clients all the information they need in order to make the good fitment decisions regarding their wheel and tire choices. Not every wheel shop (especially online vendors) have the breath of knowledge required to dole out competent recommendations. That is a HUGE problem from what I have on these forums. (not just here, but on the net in general)
Many of the members here seem to think wheel/tire fitments are "easy".
Well, that's very naive, and it diminishes the efforts and knowledge of those who have acquired the necessary training and experience in regards to wheel & tire fitments. Tire and wheel fitment success stories are not a "happy accident". They are the direct result of a competent wheel and tire fitment professional who KNOWS what will or won't work for a given application. (before anything is even bolted to the car)
That person should always be able to explain to the client (in detail) exactly WHY certain requests will not work on a given application.
And in the the case of extreme fitments...what modifications would be required to avoid any issues that may lead to possible damage of their clients car.
A responsible vendor WILL say no to some off-the-wall fitment request (that simply won't work for a legitimate reason), even if the customer gets pissed and chooses to walk away.
It's very important to have some core STANDARDS that can not and will not be violated under any circumstances.
Given the wheel & tire fitment limitations with any vehicle, it's important to seek out the knowledgeable vendors here who can help you safely navigate all these issues...so you can simply enjoy you aftermarket wheels. (with no drama)
Unfortunately, there aren't very many vendors like that on this site. (who are actually looking out for the customers best interest!)
There's a wide variety of tire & wheel fitment options on the market today.
You have new wheel brands popping up out of Miami and Socal on a weekly basis now. None of them have impressed me very much at all. They produce marginal quality products, with cookie-cutter wheel designs that all look the same. (knock off designs from their competitor right down the street in most case)
It's takes a tremendous amount work and dedication to stay on top of all that, so you can always provide your clients the best fitment advice. (based on the most accurate information available)
Sorry for the very long and drawn-out post ///FCB, but this kind of thing really bothers me.
The best is yet to come...
|11-22-2009, 02:01 PM||#3|
Drives: 2012 GTR
Join Date: Sep 2009
Hey Lemans_Blue_M, that was exactly what I wanted to know and with a 100% detailed explanation!!!
Its amazing how you manage to gather, keep and remember so much precise info about these topics
I heard the ABS thing before but was very unsure if, for example BMW's used the same system. I'll explain where my confusion came from. On a Benz S class I've had a small issue with the tire pressure monitor once factory wheels were switched to winter tires. The car was imported from the US but the winter wheels package was not purchased in the US, so the car's computer constantly showed tire pressure error. I figured out the pressure monitor was on the wheels and got confused between the ABS thing because...my daily drive is a VW group car purchased here in Spain, and once I changed the wheels on that one, there was no problem at all, and those come without any special sensor on the wheels because they are from a European brand...
So the answer as you said then is the difference of US vs Euro spec monitor system, I previously thought that the difference was simply that perhaps the more "expensive" and more complex cars such as a Mercedes or BMW use a different tire pressure system but I was wrong I'm gonna keep that in mind from now on!!!
thanks for the good reply and I'm sure its gonna be useful for someone else in the future!!
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