BMW KDS Geometry Alignment.....,

[Palmo]

Tony,

 

Yesterday evening I sent you a PM on the Omega Owners Forum, after reading several of your previous posts there, which has led me here. I'm looking for your expert advice!

 

Below is a copy of the PM I sent to you.

 

I own a BMW 525d (3.0d) M-Sport, 2007 LCI model. I have owned this car from new (April 2007). Since day 1, I have experienced considerable 'instability in cross winds'. I have complained numerous times to BMW and never managed to get anywhere. However, the car remains very stable in calm conditions and handles very well otherwise. Therefore this problem only rears it's head on breezy - windy days.

 

To cut a long story short, yesterday I manged to get a local BMW Dealership to carry out a full KDS Geometry Alignment with agreement from BMW UK under warranty - even though the car has now done 33k miles (due to the problem existing from day 1). In addition to this 'instability in cross winds' issue, I also suffer from uneven tyre wear.

 

The results are as follows:

 

Tyres

The car is fitted with the optional 172 M 19" 'staggered' wheel set-up.

 

Front tyres (245 / 35 / 19) are original and have covered = 33k miles (always run with 2.1 bar of pressure - specified by BMW).

 

Rear tyres (275 / 30 / 19) were replaced at 19k miles and have covered = 14k miles (always run with 2.5 bar of pressure - specified by BMW).

 

Tyre Depths

Inner / Middle / Outer (all in mm)

 

Right Hand Front: 3 / 4 / 2 (Note: the Outer shoulder on this tyre is worn 'smooth')

Left Hand Front: 2 / 5 / 3

Left Hand Rear: 2 / 3 / 4 (Note: the Inner edge of the original tyre was worn smooth, this second tyre is wearing the same).

Right Hand Rear: 3 / 3 / 4

 

Alignment Results

Attached below are the actual alignment figures – including before & after. Sorry but my scanner is not currently working so I have taken a picture - not sure if you will be able to read this?

 

 

Conclusions

What strikes me from this is as follows:

 

1. The Right Rear Toe was out and has been corrected.

2. The SAI is out of Spec and HAS NOT been adjusted - I believe this is not directly adjustable? If I'm reading this correctly this is almost 1 Degree out of spec on both sides? Could this be the cause of uneven tyre wear on the front and the instability in cross winds? If so, why is the car so stable in 'normal' 'calm' conditions?

3. No target data is present for the Caster, so I don't know if this is within spec?

 

I would really appreciate your thoughts on this. Is there anything that can be done to correct the SAI back into spec? For the record, I have owned the car from brand new (it literally had 3 or 4 miles on the clock) and it has not been involved in any accidents.

 

Thanks in advance - your time on this is appreciated.

 

Martin

[Tony]

The instability is normally associated with suspension or anti-roll bars although it's odd she drives ok in good weather?

 

The SAI is a concern since the cars weight is placed incorrectly at the tyres footprint, what was their opinion of the SAI? also is the car on runflats?

[Palmo]

The instability is normally associated with suspension or anti-roll bars although it's odd she drives ok in good weather?

 

The SAI is a concern since the cars weight is placed incorrectly at the tyres footprint, what was their opinion of the SAI? also is the car on runflats?

 

The car definitely drives 'perfect' in calm 'everyday' weather conditions - I'm an experienced driver and have had a host of performance vehicles in the past. It drastically changes however when there is a cross wind (not too bad with a head on wind). A number of people have driven the car with me present and experienced this (although there are never the right weather conditions when I go to my delaers to demonstrate), including my dad who has been a motor mechanic for over 35 years - he is not an alignment specialist though. He has checked the car over on a ramp, and there is nothing visibly wrong i.e nothing clearly bent or hanging off. The car is exceptionally well looked after with NO kerbing (not one mark on the 19" wheels) and never been in any accidents.

 

The tyres are NOT runflats. I have the optional 172M 19" alloy wheel upgrade fitted from new, which uses conventional rubber - I have the OEM Continental Sport Contact 2's fitted both front & Rear in a 'staggered' configuration.

 

The dealer tried to tell me that the SAI wasn't an issue and sort of passed it off as normal, saying this was more an issue on certain BMW models - but not a problem on mine? Whilst this is virtually even on each side, if I'm reading things correctly (I'm no expert) it is however, almost a full deg below the min tolerance?

 

Also, on the sheet the Caster Target data is not specified, so whilst I can see the values are different from side to side, I can't see if these figures are within spec?

 

What is your general view of the set-up? I would really value your comments as this is driving me crazy - especially on a car I paid the best part of £40k only 18 months ago, with this problem being present from day one. I intend to go back and push further but need to understand what I'm talking about. Why would the SAI be so far out?

 

Thanks very much for your time.

 

Martin

[Tony]

The disparity between the castors is not an issue.... normally when the fields are missing it means the operator needs to input data like body height during the setup.

 

The SAI is to high in position which means it's low figuratively, it's position when the camber value is removed shows the included angle, this in turn suggests where the cars weight is placed at the tyre.

 

Incorrect SAI can be due the suspension changes but i would have thought the KDS has the lower cars values so i suspect your results even for the lower car are incorrect. The best way to test this is to borrow some OEM (not optional) wheels and test drive the car.

[Palmo]

The disparity between the castors is not an issue.... normally when the fields are missing it means the operator needs to input data like body height during the setup.

 

The SAI is to high in position which means it's low figuratively, it's position when the camber value is removed shows the included angle, this in turn suggests where the cars weight is placed at the tyre.

 

Incorrect SAI can be due the suspension changes but i would have thought the KDS has the lower cars values so i suspect your results even for the lower car are incorrect. The best way to test this is to borrow some OEM (not optional) wheels and test drive the car.

 

When you say the results for the lower car are incorrect, do you mean that the alignment figures printed on the sheet are incorrect, or that these figures are printed accurately, but the car has been set-up to the wrong spec? Or simply that they have measured the setting's incorrectly?

 

Wouldn't fitting OEM Wheels cause other problems that may then cloud the issue, as the OEM wheels will have runflat tyres, which mine don't? My wheels are OEM, but were an optional upgrade. Do you think the car maybe set-up for the standard wheels and not my upgraded wheels?

 

For what it's worth, at the top of the printout, it does refer to my vehicle as follows - which is all correct:

BMW: 5 series - E60 (2002 - ): All Rear Wheel Drive Models: without AFS (Active Front Steering): Sport Suspension (with lower ride-height): 19" Wheels.

[Tony]

The runflat and the suspension is a package, fundamentally the suspension is downgraded to accommodate the harsh RFT sidewall. I've had owners who want to replace their RFT's with normal tyres but i cannot unless they also change the suspension.

 

I think we may have hit the nail on the head regarding your complaint!!

[Palmo]

The runflat and the suspension is a package, fundamentally the suspension is downgraded to accommodate the harsh RFT sidewall. I've had owners who want to replace their RFT's with normal tyres but i cannot unless they also change the suspension.

 

I think we may have hit the nail on the head regarding your complaint!!

 

OK.....I understand what you're saying here, but the majority of M-Sport cars (all fitted with BMW's sports suspension) are specced with the optional 'upgraded' 19" wheels. Surely BMW aren't allowing a car to be specced with a wheel / suspension combination that are not correctly matched?

 

I initially wondered if the 5 series (or at least the M-Sport version) had an inherent aerodynamic design flaw as others have complained about similar issues to mine. However, of those that have complained about similar issues, there appears to be no pattern: some are SE models - fitted with 'standard' suspension and runflat tyres of 17", others are M-Sport Cars (sports suspension) with either the 18" runflat's or 19" non-runflat's like mine.

 

A good few months ago I drove across the M62 (one of the highest motorway summits in England). My car was terrible as it was very windy - anything above 55-60mph was almost undriveable, certainly keeping the car in the lane was very difficult. Later that evening, I exchanged posts with another guy on a BMW forum, who by pure chance had driven the same road, on the same day, in the same direction about 20 minutes behind me. He said his car hardly moved. His car was of identical spec to mine (including wheels / tyres) except his was the more powerful 535d engine (same basic engine just with twin tubo's & automatic gearbox). Both cars were also within 2 months of build date.

 

This has therefore all led me to believe there must be a specific issue with my particular car (and indeed those cars that experience this problem) rather than a generic problem. Do you not think the SAI reading could be causing this then? Is there anything else contained within the alignment figures which is a cause for concern.

 

I must thank-you very much for your time spent today on this!

[Tony]

The SAI position can cause handling problems but this will be constant...... Other than that the Geometry report looks fine.

 

Since you are a member of the BMW forum you would probably know more than me regarding wheel/ suspension packages but i would still be inclined to check your suspension is not meant for "normal" tyres.

 

In the past i have called dealers and asked if i can fit normal tyres on certain BMW's and the answer has always been "NO".

[Palmo]

The SAI position can cause handling problems but this will be constant...... Other than that the Geometry report looks fine.

 

Since you are a member of the BMW forum you would probably know more than me regarding wheel/ suspension packages but i would still be inclined to check your suspension is not meant for "normal" tyres.

 

In the past i have called dealers and asked if i can fit normal tyres on certain BMW's and the answer has always been "NO".

 

Well thank-you very much for you comments - they are greatly appreciated.

 

On the fitting of 'normal' tyres on a run-flat model - that is BMW's standard response - 'no'. In reality, many 5 series owners have fitted normal rubber to their originally equipped run-flat tyre model. I think all of the reports I have ever read (without exception) have said that the car has been transformed, with improved grip, much better ride quality and so on.... it's almost become the 'first mod'. When I bought my car I wasn't sure which wheel / tyre combination to go with, there was an overwhelming steer on the forums towards 19" non runflats which I think was an excellent choice (apart from the M5, my wheel option is the only non-runflat choice), excellent handling, very good ride quality (which amazed me) and very little tram-lining considering the size of the tyres.

 

My only issue has been this cross wind instability.......Thanks again!

[Tony]

The tyre type if tested by other members can be removed from the equation then, obviously i have to be very cautious in this area.

 

I've been contacted by another very well respected company about your problem and out of sight we have a "solution" in theory, we're still swapping final arguments but tomorrow i hope to offer a absolute reason why the problem is confined to windy weather.

[CIH]

This is all very fascinating. Out of interest, was the wheel packagae a factory or dealer-fit option ?

[Tony]

This is all very fascinating. Out of interest, was the wheel packagae a factory or dealer-fit option ?

 

It was an optional package reading the original post.

[CIH]

so, factory fit ?

[Tony]

so, factory fit ?

 

Yeah.... staggered and not RFT?

[CIH]

Seems odd SAI would show as out of spec but consistant across the axle. Like the Golf I did a few weeks ago.

And the different max. steering angles ? Though, when I've tried that I've often found the target can be obscured from the camera and have had to abandon that spcific procedure.

 

Eitherway, be interesting to see what WIM+Friends have theorised.

[Tony]

Seems odd SAI would show as out of spec but consistant across the axle. Like the Golf I did a few weeks ago.

And the different max. steering angles ? Though, when I've tried that I've often found the target can be obscured from the camera and have had to abandon that spcific procedure.

 

Eitherway, be interesting to see what WIM+Friends have theorised.

 

The lock procedure on the Hunter is pants...... For TOOT stop the lock at 20d (outer wheel) it works better.

 

Friend on this topic is pro-drive accredited so i have the "big boys" on the topic now

[Palmo]

The tyre type if tested by other members can be removed from the equation then, obviously i have to be very cautious in this area.

 

I've been contacted by another very well respected company about your problem and out of sight we have a "solution" in theory, we're still swapping final arguments but tomorrow i hope to offer a absolute reason why the problem is confined to windy weather.

 

Tony,

The tyre type is indeed tested world wide by other members - one of the regular forums I go on is international. I'm fairly sure this is not a runflat vrs non runflat tyre issue. In reality, I know that my car would benefit from having a set of new tyres, as these are worn unevenly and past their best. However, I know for a fact that these being worn aren't the cause of the instability as it has done this from day 1 - even with brand new tyres, when driven in the right (or wrong) conditions. I will be investing in new tyres in the near future.

 

In response to your second comment above - WOW - THANKS GUYS - for the taking the time and effort to be so helpful! It really is appreciated - in a later post you say your friend is 'Pro-Drive accredited' - it's getting serious focus now. Out of interets and digressing a moment - my previous car was a Subaru Impreza, with loads of Pro-Drive goodies, inc. group N / fast road geometry settings done by a very well respected outfit in the Scooby World. It handled amazing!

 

Anyway back on topic.....this problem is so annoying as the car is so awesome most of the time, just really let down when driven in windy conditions. Granted, this is not everyday - far from it, but enough to spoil the experience, especially when having to drive from one end of the country to the other - which I often do, and the weather is poor!

 

I have also just become aware of another interesting fact. A fellow member of another forum who has a very similar aged / specced car to mine has just posted his alignment results that were done back in Feb 08 by another BMW Dealer. They are very similar across the board to mine! And wait for it..............you can probably guess where this is going..........his SAI is out of spec and virtually identical to mine! My SAI figures are - Left: 13 Deg, 31' Right: 13 Deg, 32'. His are - Left: 13 Deg, 33' Right: 13 Deg 27'. Both are against the target setting of 14 Deg, 59' on both sides! Unfortunately he doesn't directly say in his post if he suffers from instability in wind, but does complain that he is not impressed with his handling. I have just replied, specifically asking him to comment on his stability in wind! I will update when he responds.

 

CamInHead,

For the record I can confirm that the tyre / wheel combination is indeed a factory fit option and NOT dealer fit. This is an upgrade option and is very popular on current M-Sport models as it replaces the dreaded runflats with non-runflats - the only non-runflat option available on the 5 series other than the M5 itself. See pictures below of my car to see the wheels I'm talking about - you will have seen these on the road no doubt!

 

 

Just listening to the weather outside and it seems quite blustery - interesting as I am due to go out in the car first thing in the morning. This maybe the first opportunity to drive the car in wind since having the geometry set-up done, although in reality all they altered was the Right Rear Toe (back into Spec). I'm not expecting this to have made much difference, but you never know.

 

Thanks again folks - this is really helping me!

[Palmo]

The tyre type if tested by other members can be removed from the equation then, obviously i have to be very cautious in this area.

 

I've been contacted by another very well respected company about your problem and out of sight we have a "solution" in theory, we're still swapping final arguments but tomorrow i hope to offer a absolute reason why the problem is confined to windy weather.

 

Any update Tony?

[Tony]

The tyre type if tested by other members can be removed from the equation then, obviously i have to be very cautious in this area.

 

I've been contacted by another very well respected company about your problem and out of sight we have a "solution" in theory, we're still swapping final arguments but tomorrow i hope to offer a absolute reason why the problem is confined to windy weather.

 

Any update Tony?

 

Kind of.... Below is the key email extracts from my friend and myself

...................................

My friend>

You'll find that it's mainly caused by the large tyre size differential between the front and the rear axles.

 

The lateral stability of a rolling pneumatic tyre is ultimately a function of the rubber surface area on the floor, and reduces quickly with increased wheel speed.

 

So at motorway speeds all four tyres are getting low on lateral stability but rears will still have considerably more stability left in reserve than the front axle.

 

If you picture a situation where the cross wind is stronger than the front axles lateral stability a gust will push the front axle across the road surface, but because of the tyre size imbalance the rears will still have enough stability available to stay put on the road surface.

 

The net effect is that a yawing moment is put onto the car by the wind rather than just blowing the car neatly sideways in an even fashion. And it's this unrequested and unexpected YAW that he's finding disconcerting, and rightly so in my opinion.

 

My advice would be to balance the tyre widths front and rear, which ever way he can.

...................................

Myself>

Your explanation makes perfect sense although this wasn't a thought i had, my only problem is that most high end marques have a front/ rear tyre stagger without problems, or is it the case that on these cars the Geo is calibrated to compensate for the pneumatic disparity.

..................................

My friend>

From my experience every car I've ever driven with a staggered set-up has experienced this problem to a varying degree, there are other factors like aerodynamics that obviously play a massive part as well but I bet the main route of this problem is the large stagger.

....................................

Myself>

I'm nervous suggesting a wider front tyre because the wheels are staggered as well, could this really be his problem since cars like Lotus/ Porsche and alike all have staggered tyres?

.....................................

My friend>

I'm afraid so, both the Porsche and Lotus have very slight profiles and rearward weight distributions so they are inherently far more stable at speed by design than a slab sided 50/50 distribution uber cruiser.

 

Obviously he's backed him self into a corner with his rim choice but good advise is still good advice, even if it does mean he does need to re-think the rims.

.....................................

Back to me> In addition to this the Continental tyre is know to have a high pneumatic slip angle, or in other words a floppy sidewall.

[CIH]

Would chaning tyre brands help alleviate the syptoms ?

 

Tony, are you sure the wheels are staggered ? I was surprised, recently, to find an MGF has symmetrical wheels despite different tyre sizes.

[Tony]

Would chaning tyre brands help alleviate the syptoms ?

 

Tony, are you sure the wheels are staggered ? I was surprised, recently, to find an MGF has symmetrical wheels despite different tyre sizes.

 

Yes to some degree.... A tyre like Bridgestone would have less pneumatic slip angle.

[Mark H.]

My MR2 blows across the road in heavy winds .

[Tony]

My MR2 blows across the road in heavy winds .

 

The tyre stagger conflict may apply to the MR2 as well.

[Mark H.]

You can feel the front get blown around a ft+ across the road. Not ideal when that means entering another lane.

 

My car has Falken zeix 512, the rears are 912 as they don't make the 512 anymore and they needed replacing. It moved across with the 512's front and rear though.

[Tony]

You can feel the front get blown around a ft+ across the road. Not ideal when that means entering another lane.

 

My car has Falken zeix 512, the rears are 912 as they don't make the 512 anymore and they needed replacing. It moved across with the 512's front and rear though.

 

The complaint boarders three very powerful areas in chassis dynamics, namely dynamic indexing, tyre saturation limits and Geometry calibration.

 

The holy grail is to address a "doable" solution that fits the purse.... Fundermentally the index is a done deal so the saturation fails into sight via the calibration but not without consequence and that consequence will be tyre wear.