Home Forums Articles How To's FAQ Register
Go Back   Xoutpost.com > BMW SAV Forums > X3 (E83) Forum
Fluid Motor Union
User Name
Password
Member List Premier Membership Search Today's Posts Mark Forums Read

Xoutpost server transfer and maintenance is occurring....
Xoutpost is currently undergoing a planned server migration.... stay tuned for new developments.... sincerely, the management


Reply
 
LinkBack Thread Tools Display Modes
  #21  
Old 02-15-2007, 12:35 PM
Member
 
Join Date: Oct 2006
Location: east coast
Posts: 91
martz is on a distinguished road
Your aspect ratios are fine. There are x3's that come out of the factory with 17's and the sport with 18's and others with staggered set ups , in essence +1 . Ecu has nothing to do with figuring out your tire size unless the rolling diameter is completely off, which in turn would trigger the ABS light to turn on . I am confused with your assumption that the ECU is the caused of your driveline noise .

http://www.miata.net/garage/tirecalcold.html

Did you change just the tires or did you buy a new set of wheels and tires? if so , changed back to OE's see if you get the same " driveline noise"....I think you are just getting tire noise. Dont know about the new pirellis , but they are known for tire noise. Had them years back and disliked them for that reason.

Last edited by martz; 02-15-2007 at 12:41 PM.
Reply With Quote

Sponsored Links

  #22  
Old 02-15-2007, 12:58 PM
Member
 
Join Date: Feb 2007
Location: NYC
Posts: 17
007X3 is on a distinguished road
Quote:
Originally Posted by martz
Your aspect ratios are fine. There are x3's that come out of the factory with 17's and the sport with 18's and others with staggered set ups , in essence +1 . Ecu has nothing to do with figuring out your tire size unless the rolling diameter is completely off, which in turn would trigger the ABS light to turn on . I am confused with your assumption that the ECU is the caused of your driveline noise .

http://www.miata.net/garage/tirecalcold.html

Did you change just the tires or did you buy a new set of wheels and tires? if so , changed back to OE's see if you get the same " driveline noise"....I think you are just getting tire noise. Dont know about the new pirellis , but they are known for tire noise. Had them years back and disliked them for that reason.
Not sure if you read my original post. Here it goes again.

>>>I Got an 07 sport pack and was looking to improve the handling and the look of the car. So I decided to get the 06 staggered 192M wheel option by purchasing two 18x9" rims for the rear. As some of you know in 07 they killed the 18" staggered wheel option and replaced it with a 19" staggered option. I didn't want to have 19s on my car and needed all season tires so I ordered it from the factory standard with 18x8" 192M wheels and 235/50 18 AS tires all around. Stock tires were Michelin Pilot HX MXM4 235/50 18 all around. Ride comfort with stock tires was OK even with the sport pack but handling is only so so. With noticeable body roll and a bit of unresponsiveness.


Since then I've tried three sets of tires on it. Reading great reviews from tirerack I ordered Kumho Ecsta ASX in 235/50 18 front and 255/45 18 rear per 06 Specs. Installed the tires and was very disappointed in them. The ride went to crap. Absolutely unbearable. Very harsh riding tire, Very noisy. Handling better but with such bad ride that becomes irrelevant. Also a weird driveline wine at certain engine speeds and gears and got Automatic Transmission shifting problems. The whine is not related to balancing. I thought it might be due to slightly shorter overall diameter of the tires. The stockers 235/50 18 Michelins are 27.5" OD (overall diameter) and 759 revolutions per mile. The Kumhos are 27.3" OD front and 27" OD rear. Could not find Revolutions per mile on this tire anywhere in the specs. The whine sounds like gear whine, short duration for a few seconds at a time and could be present at any given time and speed. Just from standstill or going 65 on the highway.

At first I thought it was the tires so I got a set of Michelin Pilot Sport AS in the same 235 front 255 rear sizes. After mounting them on the car the whine went away completely. The ride improved but still harsher than Pilot HX. A bit too harsh for my taste. Much quieter than Kumhos and possibly even quieter than stockers on the highway but not over bumps and expansion joints. Handling is fantastic. Feels like a different car. Response is immediate with absolute absence of body roll. What I hate about this tire is the width of the rear 255/45 18 tires. I don't know what Michelin was thinking but they decided to make 235/50 18 and 255/45 18 dimensionally identical. Meaning they are the same width. It looks weird on a 9" wide rim and looks too skinny in the back. Really kills the staggered look. They are both 27.2" OD and 762 revs per mile. Very close to stock (759 revs per mile). Less than 1/3 of a percent deviation from stock OD. Since the whine disappeared I thought to myself maybe it was the difference in diameters of the Kumhos 27.3" front, 27" rear or even a problem with the tires themselves.

Back to Michelin Pilot Sport AS. Unhappy mostly with the look of the rear tires and after getting a few complaints from rear seat passengers about ride quality I went on a new tire search. Now looking for identical or very close diameter front to rears and the ultimate in width rear tire. I came up with Pirelli P-Zero Nero MS in 245/45 18 front and 275/40 18 rear. Specs say these tires will work fine on 18x8 and 18x9 wheels respectively. They are 26.7", 26.6" OD and 780, 782 revolutions per mile front/rear. They are within 2% of the stock diameter. And I thought to myself a worn stock tire would be close to the diameter of these. So I got the tires. Which, mind you was not an easy thing to do. The 275/40 18 is on national back order. No one had these tires. Had to get them shipped from Pirelli directly after a few favors. Got them installed. From the rear the car looks fantastic. This is what the sport pack X3 should look like. Very meaty and mean look to it, though the tires seem to fill the wheel well a little less due to the smaller diameter. Driving impressions: The tire is supremely quiet. Quieter than Pilot Sport AS or the Stock Pilot HX tires. Comfort is better than Pilot Sport but maybe not as forgiving and Pilot HX. After all this is a Z rated tire and the stockers are H rated. Handling is great though responsiveness not as sharp as Pilot Sport AS. Possibly due to the wider 275 tire on the same 9" rim as the 255 Pilot Sport AS. On the Negative Side. The driveline/gear whine is back. Also the AT shifting problems are back. I think the speedometer is way off now by as much as 10MPH at 60. However I wasn't able to verify this. Maybe they are just so quiet that I think I'm going slower. After all 2% difference in size should yield only about 1.5 MPH difference going 60. Now I know for certain that changing tire size will cause all sorts of computer related problems even if it is only a very minor change.

Here is my dilemma. Can the computer be reprogrammed to compensate for tire size? Spoke to a few dealers they tell me, NO, only the factory can do that. Kind of hard to imagine the dealer can't reprogram for tire size. It is very simple to do even with basic hypertech programmer on almost all GM cars. Why would BMW only reserve that for the factory? If I'm not able to get the car reprogramed I will probably have to put my stock 235/50 18 Pilot HX MXM4 tires back on. That would be a shame, not to be able to keep the best tires for the car after spending all this money just because of dealer incompetency in reprogramming the ECU.

Anyone know how to reprogram the ECU for tire size?

I will post pictures of Michelin Pilot Sport AS and Pirelli P-Zero Nero On my car shortly.<<<
Reply With Quote
  #23  
Old 02-15-2007, 01:05 PM
Member
 
Join Date: Feb 2007
Location: NYC
Posts: 17
007X3 is on a distinguished road
Here is a copy of my post from bimmerfest.

Didn't really get a chance to take some meaningful pics of the Pirelli P-Zero Nero MS because of the recent weather but here are some pics in the meantime.

I got some comparison shots for you of the Michelin Pilot Sport AS and Pirelli P-Zero Nero MS.
Pirelli P-Zero Nero MS is in the pictures with snow. Look at the width of the rear tire This is what the Sport Pac X3 should have looked like from the factory.

Look at this picture. Can you tell which one is 255/45 18 and which one is 235/50 18. The only visible difference is wider shoulder blocks on the 255 tire which is on the right. This is my main gripe with Michelin Pilot Sport AS. As you can see from the below pictures the Tire is actually stretching outward to fit on the 18x9 rear rim.















Reply With Quote
  #24  
Old 02-15-2007, 01:50 PM
Member
 
Join Date: Oct 2006
Location: east coast
Posts: 91
martz is on a distinguished road
James Bond , oh I mean 007x3. now I know what you are after. you are trying to make the x3 look like a X5. mean and meaty.. Your Tires sizes could be over kill, you may end up messing up your transfer case.
I would revert back to the normal set up, plus it might interfere with the manufacturers warranty and in case your transfer case starts to act up which could be SOONER than you think BMW will not cover.

Last edited by martz; 02-15-2007 at 02:08 PM.
Reply With Quote
  #25  
Old 02-15-2007, 05:46 PM
JCL's Avatar
JCL JCL is offline
Premier Member
 
Join Date: Mar 2005
Location: Vancouver, Canada
Posts: 11,853
JCL will become famous soon enoughJCL will become famous soon enough
Quote:
Originally Posted by 007X3
What is this have to do with it. In my post I said there are accelerometers in the transmission among other places that always know vehicle velocity, pitch, etc... I never made mention of a rotating shaft. The transmission knows actual vehicle speed at all times. Now when the tires are rotating faster then what is programmed at given velocity due to slightly smaller tire diameter the X-Drive unit goes into default, Meaning all wheel lock. This is a soft Trouble code and does not let itself be known without a detailed scan. No dash warning lights will go off.

The point you were trying to make is that the car has no way of knowing how fast it is going other than wheel speed sensors. Thus when I stated that is has accelerometers to tell is exact speed you stated that accelerometers measure acceleration not speed. Back to my point Velocity (speed) = acceleration/time. Meaning as soon as you start moving the accelerometers report to the ECU and the ECU then computes Vehicle velocity based on acceleration/time formula. I'm not sure how intimately familiar you are to a modern automatic transmission but I can tell you with great degree of certainty that the transmission always knows exact vehicle speed, independent of wheel speed.
I tried to walk away, really I did. Sorry this is so long. I suspect that ol' MD will stick with it.

The transmission does not have accelerometers that know what vehicle speed is. I tried to explain that nicely. If you continue to believe that such parts exist, please provide a parts reference. You have now introduced the concepts of vehicle pitch but that is a different issue, that is related to the DSC control over brakes, and to a lesser extent, throttle.

The rotating shaft I refer to is the output shaft of the transmission. It is how the transmission calculates the vehicle speed. The counter calculates an expected vehicle speed from an assumed final drive ratio. It isn't complicated, it has been working that way since the forties at least (that is the oldest car I have worked on with a speedometer cable driven from the transmission output shaft). In that sense, yes, there is a different speed calculation than the ABS wheel sensors. My point that there isn't a different measurement is that the output shaft of the transmission is directly related to the wheel speed sensor (by the final drive ratio). They don't vary, they are directly proportional. Apart from the output shaft of the transmission, and the related wheel speed sensor, there is no built in speed sensor on the car.

Let's continue with your theoretical approach to vehicle speed calculation. You are saying that every time the car speeds up or slows down, the computer inputs that acceleration, calculates it over time, and comes up with a calculated speed over the ground. The car must also then filter out the forward acceleration from the three axes of acceleration it is measuring, and compute the resulting forward vector. Incredible. Just think of the error that must be introduced after a several hour drive (since the car has no way of self-correcting this acceleration/time calculation). The whole concept is mind-boggling.

We could do an easy test here. You could drive your car off a cliff. As you plummetted towards the ground, take your foot off the gas, and check your speedometer. If I am right, the speedometer will be zero. If you are right your speedometer will function as an airspeed indicator, indicating your velocity up to terminal velocity. If you want to reduce the damage potential then you can skip the cliff-jumping part. Just spin your tires in the snow. You won't go forward. Using accelerometers, the speedometer would show zero. I suspect you will find that spinning tires results in a rising speedometer reading. Let's just assume that if the transmission knows vehicle speed then that is what it is indicating on the speedometer.

I may not have worked on a modern BMW/ZF/GM automatic transmission, but I do know the inside of C3, C4 and C6 Ford transmissions, Chrysler Torqueflite 727s, and various GM models. I also know that ABS systems use an algorithm that takes inputs from four wheel speed sensors and computes a resultant average that is then compared to the delta at each wheel. It does not use a calculated wheel speed from the transmission output shaft because that is less accurate.

If you want to get back to the issue of when the transmission goes into lockup, then yes, it happens at a certain speed. That speed comes from the rotational velocity of the output shaft. We have now come full circle. Lockup doesn't relate to vehicle speed over the ground (true distance covered) as much as it relates to fluid pressure in a circuit inside the transmission valve body.

This combination of auto repair and physics discussion is lots of fun, but I don't think you are any closer to figuring out why you have a noise under your X3. Hopefully, though, you now know how the vehicle systems interact a little more.

Cheers

JCL
__________________
2007 X3 3.0si, 6 MT, Premium, White

Retired:
2008 535i, 6 MT, M Sport, Premium, Space Grey
2003 X5 3.0 Steptronic, Premium, Titanium Silver

2002 325xi 5 MT, Steel Grey
2004 Z4 3.0 Premium, Sport, SMG, Maldives Blue

Last edited by JCL; 02-15-2007 at 05:53 PM.
Reply With Quote
  #26  
Old 02-15-2007, 06:23 PM
motordavid's Avatar
RetiredBum & Semi-RenaissanceMan
 
Join Date: Mar 2005
Location: Mtns of Western NC, & SW FLA
Posts: 16,816
motordavid will become famous soon enoughmotordavid will become famous soon enough
JCL,
Very well written, as per your usual efforts!

You may be howling at the moon, however...

DblOh is on a mission; I suspect a bum tire or two
in his current batch, or was that the problem batch(es)?
I took notes and still couldn't keep the "tire test" straight.

I did not know that XDrive, transfer cases, diffs, and trannies
were so "smart"?!
BR,mD
Reply With Quote
  #27  
Old 02-16-2007, 01:52 AM
Member
 
Join Date: Feb 2007
Location: NYC
Posts: 17
007X3 is on a distinguished road
Quote:
Originally Posted by JCL
We could do an easy test here. You could drive your car off a cliff. As you plummetted towards the ground, take your foot off the gas, and check your speedometer. If I am right, the speedometer will be zero. If you are right your speedometer will function as an airspeed indicator, indicating your velocity up to terminal velocity. If you want to reduce the damage potential then you can skip the cliff-jumping part. Just spin your tires in the snow. You won't go forward. Using accelerometers, the speedometer would show zero. I suspect you will find that spinning tires results in a rising speedometer reading. Let's just assume that if the transmission knows vehicle speed then that is what it is indicating on the speedometer.
JCL
Wait a minute, I never said the speedometer is reading the transmission accelerometers output. This is your deductive reasoning at work. I wish it did. That would make things a whole lot easier and eliminate tire error. As far as computing vehicle speed with accelerometers, It isn't as complicated as you think. A $200 Gtech-pro does it with great degree of accuracy www.gtechpro.com/

I will get back to you with schematics of AT if I'm able to find what I'm looking for.
Reply With Quote
  #28  
Old 02-16-2007, 02:17 AM
JCL's Avatar
JCL JCL is offline
Premier Member
 
Join Date: Mar 2005
Location: Vancouver, Canada
Posts: 11,853
JCL will become famous soon enoughJCL will become famous soon enough
You are right, it is my deductive reasoning. I pointed out that if the transmission had accelerometers that knew the vehicle speed, it may as well tell the speedometer so they could both benefit.

I am aware of the device. It is reasonably accurate over a quarter mile. Then it must be reset.

Let me know if you find a Gtech inside your transmission.

Here is the link for the transmission speed sensor. It is item 4. There are two of them. Looks a lot like a magnetic pickup. It counts the revolutions of a shaft, and converts that into a rotational velocity. That shaft speed converts to a vehicle speed via the final drive ratio and tire diameter. Not sure of your model, but this is for the latest 3.0 X3 they had.

http://www.realoem.com/bmw/showparts...97&hg=24&fg=15
__________________
2007 X3 3.0si, 6 MT, Premium, White

Retired:
2008 535i, 6 MT, M Sport, Premium, Space Grey
2003 X5 3.0 Steptronic, Premium, Titanium Silver

2002 325xi 5 MT, Steel Grey
2004 Z4 3.0 Premium, Sport, SMG, Maldives Blue
Reply With Quote
  #29  
Old 02-16-2007, 02:55 AM
Member
 
Join Date: Feb 2007
Location: NYC
Posts: 17
007X3 is on a distinguished road
Quote:
Originally Posted by JCL
You are right, it is my deductive reasoning. I pointed out that if the transmission had accelerometers that knew the vehicle speed, it may as well tell the speedometer so they could both benefit.

I am aware of the device. It is reasonably accurate over a quarter mile. Then it must be reset.

Let me know if you find a Gtech inside your transmission.

Here is the link for the transmission speed sensor. It is item 4. There are two of them. Looks a lot like a magnetic pickup. It counts the revolutions of a shaft, and converts that into a rotational velocity. That shaft speed converts to a vehicle speed via the final drive ratio and tire diameter. Not sure of your model, but this is for the latest 3.0 X3 they had.

http://www.realoem.com/bmw/showparts...97&hg=24&fg=15

Again, I never said it didn't have a speed sensor. All I'm stating is that the ECU that is controlling Transmission, X-drive, DSC has accelerometers that tell it actual vehicle speed, lateral acceleration, yaw and pitch among other things. In fact the GM 6L50 transmission in the 07 X3 has Performance Algorithm Shifting, a transmission algorithm that looks at lateral acceleration from accelerometers, throttle, and vehicle deceleration activity to determine if the vehicle is being driven in a sporty manner. If the algorithm recognizes these conditions, it can force downshifts and hold lower gears for optimized vehicle performance.
Reply With Quote
Reply

Bookmarks

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On





All times are GMT -4. The time now is 07:29 PM.
vBulletin, Copyright 2024, Jelsoft Enterprises Ltd. SEO by vBSEO 3.6.0
© 2017 Xoutpost.com. All rights reserved. Xoutpost.com is a private enthusiast site not associated with BMW AG.
The BMW name, marks, M stripe logo, and Roundel logo as well as X3, X5 and X6 designations used in the pages of this Web Site are the property of BMW AG.
This web site is not sponsored or affiliated in any way with BMW AG or any of its subsidiaries.