05-16-2015, 04:42 AM | #1 |
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Toe alignment in my car after curbing right front wheel
So it happened with my brand new M235i
I was in Gdansk, Poland, on a business trip and - passing an intersection at a rather high speed (traffic light was just about to change to red) - suddenly I noticed that exposed and unsecured tramway rail (renovation of crossroads) at the very last moment. The rail was sticking up so high that I decided not to drive over it (which would probably have ruined all my 4 wheels and suspension), but instead - fighting to avoid collision - hit the brakes and turned the steering wheel all the way to the left, hoping I would manage to stop in time. I was very very close to successfully avoid this unexpected obstacle, but unfortunately - jest before coming to a halt - hit the rail with my front right wheel. Still have this impact in my ears, so hard and loud it was (metal to metal)... Right after leaving the damn intersection I stopped to take a look at the damage. The only thing I could see with my naked eyes was the rim curbed on same 2 inches long area (perimetrically), but of course I was expecting the worst: loss of air (and the city of Gdansk is some 700 km away from where I live, and I have no spare), plus lots of damages to the suspension, as a minimum. So, it looked very bad... But I decided to continue driving (planning to at least get to the hotel I was staying in before all the air is gone). To my amazement, I didn't feel anything wrong in the way my car was riding and handling! No warning from my TPMS, either! Also the next day morning, my car status reported exactly the same air pressure as before the hit - so I decided to take the risk and drive back home (700 km away), so at least I could be there during repairs. On my way back home, I still didn't feel any obvious proof of damage - the ride and handling just normal, not even slightest pull to left or right, steering wheel in dead center position when following straight line, the hit tire inflation still correct... To make the story shorter: not only did I make it home safely, but on my visit to the dealer it turned out that: - the wheel wasn't even bent (bravo the 461M wheels!!!) - there was no damage to the suspension or steering parts So what I did next was of course have my dealer check alignment, again expecting the worst... But the alignment check results (attached) didn't show anything that - in my BMW dealer opinion - would warrant any repairs; not even adjustment! The only out-of-tolerance value I marked with a red rectangle in the attached b&w scan (has been printed in red on the original diagnostics printout) And the latter (toe adjustment necessity) is something I'm unsure about. The Dealer's opinion is that the slight of-of-spec- ness is not worth correcting, because - as they claim: - it's so small that probably another measurement would show the only value printed in red fall into the OK range - if they tried to correct it now, it could as well result in my car starting pulling to one direction, or the steering wheel no longer in its current (dead centered) position, etc.... However, I do suspect they were just unwilling to start the correction attempt which indeed could have taken them a number of working hours the slight toe discrepancy is not worth sacrificing. What do you guys think: should I stand up and make them at least try, or are they right it's not worth it?
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05-16-2015, 06:58 AM | #2 | |
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I would take it to an alignment shop instead... it's probably going to be more expensive to align it at the dealer anyway.... So left is toeing out -0'04 and right is toeing in 0'10 ? To me if it's out of spec, it's out of spec.... if BMW thought -0'17 would be acceptable they wouldn't have set -0.12 |
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05-16-2015, 08:00 AM | #3 |
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I totally agree with your comments, however - even with the printout before my eyes - I'm unable to tell which is the BMW's "perfect" value. IS it -0deg12'[0deg00']+0deg12' ?
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05-16-2015, 10:05 AM | #4 | |
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Wonder if they picked the right car on the computer for the alignment. Oh image is a bit blurry but ranges are: Toe: 0'09 - 0'05 Total toe: 0'10 - 0'18 Steer ahead: (-0'03) - (0'03) |
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05-16-2015, 10:14 AM | #5 | |
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The way that sheet is written, the target value is in the center bracket. You subtract the number on the left from the number in the center bracket to get the minimum spec point. You add the number on the right to the number in the center bracket to get the maximum spec point. On the sheet, "Difference" is allowed to be anywhere from -0deg12' to +0deg12', with the target value being 0deg0'. If you do the same thing with "Total", the next line down, the target value is 0deg13', with the allowed range being 0deg1' to 0deg25' (+/- 0deg12' from the target point of 0deg13').
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05-16-2015, 10:52 AM | #6 |
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I just had my car aligned yesterday, here is the printout from the dealer showing factory specified ranges... You can also see my left rear toe was out by .01deg. They centered it within range.
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05-16-2015, 02:00 PM | #7 |
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05-17-2015, 01:14 AM | #8 |
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Thanks everyone, but I still don't understand the logic behind the numbers on the attached printout. I'd also think that the left wheel is at -0deg04' and the right one at 0deg 10', but if so, why is the "difference" -0deg17'? Or the "total difference" at 0deg 07'?
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05-17-2015, 02:42 AM | #9 |
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Guys - Thank you very much for your opinions. Unfortunately my BMW service people are unable to inspire my confidence in whether they now what they are doing, and are unable to explain to me how to read and understand the individual values in the sheet they provided me with after the measurement. Therefore - before I make up my mind if I should ask them to try and adjust the toe - I have a very kind request to you: could you help me get understanding on those individual items, so that I know myself what is wrong and what should be done?
For instance: I read it that my left front wheel is at - (0 deg 04') to the left (negative toe), while the right one is at + (0 deg 10') to the left (positive toe). But if I get it right, how is it possible for the "Difference" to be at - (0 deg 17')?!! How has this been calculated? Also, I have no idea what the last item ("total difference") is, or how this one been calculated, either... I'd appreciate if you helped me understand those values, as only then will I be able to effectively discuss the current status with my BMW service and will not be at the lost position during the discussion... Of course I understand you - just like myself - may not be a specialist in this area, but am sure that an exchange of our understanding the measurement printout could help me gain more confidence. As they put it in Polish: "two minds is always more than one" Thanks for your time and Regards Piotr
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05-17-2015, 03:03 AM | #10 |
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In the article here: http://www.bimmerforums.com/forum/sh...or-your-E36-M3, I read about the influence of negative (toe out) vs. positive (toe in) values on the car's handling and steering; pls note the below excerpt from this interesting article:
"Toe-out in the front lets the car turn in nicely, but may "tramline" down the road (finding grooves and irregularities and following them). Toe-in front makes the car hard to turn and want to "push" or understeer (BTW this is what BMW recommends!). " Now: In my OP in this thread, I said I haven't noticed any change in car's behaviour in my 700 km way back home after the impact. However, when I think of it, I did after all notice one thing several times, and this has been... you guessed it, tramlining! I'm 100% positive the before the unlucky incident, my M235i didn't show a slightest tendency towards tramlining at all... Could the slight toe-out of the left font wheel (of just - 0 deg 4') be already enough to cause it? Opinions welcome!
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05-17-2015, 06:07 AM | #11 | |
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The last number (total difference at 0d07') looks like a straight sum of the left and right (-0d04' added to 0d10') with stacked tolerances in the measurement. I would guess you're looking at rounding errors due to the number of digits in the measurements. Instead of having [ 0d10' - 0d04' = 0d07' ], what you have is something like [ 0d104' - 0d037' = 0d067' ], which are all being rounded to the nearest two digits on the minutes field. Looking at it as decimal math to get rid of all the degree and minute symbols: Left is something like -3.7 being reported as -4 Right is something like 10.4 being reported as 10 The real math is: 10.4 - 3.7 = 6.7 But when the system rounds all the numbers, it reports: 10 - 4 = 7 (EDIT: Per next post) Again, it's a guess, and I have no clue where the "difference" of 0d17' is coming from.
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05-17-2015, 07:44 AM | #12 |
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Thanks for this explanation - of course rounding errors are possible, but I guess you meant displaying 10-4=7, and not as you put it 10-4=6
Did I get you right?
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05-17-2015, 08:52 AM | #13 |
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Yup, and I corrected it above. Some things you just type as you see them without thinking what the fingers are doing.
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05-18-2015, 01:34 PM | #14 |
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So I waited over the weekend (which, due to your catastrophic visions of my M235i's suspension condition was a truly devastating experience), and - first thing in the morning today - returned to my dealer asking to take another measurement, and - if it confirmed the original one - to perform adjustment...
Here it is attached; now all the theories and explanations should be even more interesting. I'm looking forward to them!
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05-18-2015, 02:04 PM | #16 |
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Have no idea... Of course I'm happier with these figures than I was over the weekend, but this instability and total lack of reproducibility makes me very uneasy
If someone can offer any theory behind this miracle, I'm all ears! Piotr
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05-18-2015, 02:16 PM | #17 |
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The range is -1.4 to 0.4 ?
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05-18-2015, 03:26 PM | #18 | |
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05-18-2015, 04:00 PM | #19 |
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05-18-2015, 04:01 PM | #20 |
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maybe there is something actually out of wack... with play on some suspension piece so it's moving and reading different depending how it sits
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05-25-2015, 04:14 AM | #22 | |
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I'm more and more suspicious towards these miraculously changed measurement results; the service people might be reluctant to spend too much time trying to get the (not-so-great, after all) toe misalignment back into specs while maintaining the dead-central steering wheel position when driving on a straight line - so they might've setup the second measurement in some "special way"; they called me over from the client's longue to the shop just to show me all correct values displayed while the cameras and stuff were all still on the vehicle.. They never could explain my questions on how it's possible for the geometry to change by itself; even the basic question remained unanswered - and it went as follows: - suppose the first ("bad") readings were somehow influenced by inadvertently knocking on the steering wheel when the mechanic was getting off the car, or anything of that sort - so in fact, the wheels we slightly off the straight position (to the left, if you take a look at my first attachment). But then, the inner's wheel angle should be greater to the left than that of the outer's (right wheel)... I'm more and more suspicious towards these miraculously changed measurement results; the service people might be reluctant to spend too much time trying to get the (not-so-great, after all) toe misalignment back into specs while maintaining the dead-central steering wheel position when driving on a straight line - so they might've setup the second measurement in some "special way"; they called me over from the client's longue to the shop just to show me all correct values displayed while the cameras and stuff were all still on the vehicle.. They never could explain my questions on how it's possible for the geometry to change by itself; even the basic question remained unanswered - and it went as follows: - suppose the first ("bad") readings were somehow influenced by inadvertently knocking on the steering wheel when the mechanic was getting off the car, or anything of that sort - so in fact, the wheels we slightly off the straight position (to the left, if you take a look at my first attachment). But then, the inner's wheel angle should be greater to the left than that of the outer's (right wheel)... Why is it still bugging me? Well, it might be auto-suggestion - but I notice a tendency for tram-lining I never noticed before the incident... What do you think?
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