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gemoetry/ tyre wear


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Hello from a noobie :)

 

I have a 330cd coupe and a few questions regarding geometry and tyre wear. I hit a pot hole, so decided to get a 4 wheel alignment. It turned out my NSF had to much -ve camber. This manifested itself in slightly increased tyre wear on the inner shoulder.

 

Below is the alignment print out:

 

alignment.jpg

 

I have a few questions.

 

1) The castor after alignment is more on the right side, whereas it was much more symmetrical before alignment. Is this normal/ what effect would this have?

2) I have a little play between 12.00 and 11.00 on the steering wheel at high speed, is this due to the castor?

3) The operator reduced my toe on the front, what effect will this have?

4) Realisticly would the before NSF camber have caused more tyre wear?

5) The car had never been aligned before, and is 18 months old.... why would the castor have been out of BMW spec from the factory?

6) Is it normal to have the following wear patterns on 18" low profile tyres:

- OSF - increased wear outside shoulder (scrubbing of shoulder tread patern

- NSF - increased wear on inner shoulder (similar scrubbing of tread pattern to OSF)

7) Was the car subjected to a four wheel alignment (as per my invoice) or a full geometry check?

8) Could there be operator error using the Beissbarth aligner in terms of setting the steering wheel dead straight, or would an error in aligning the steering wheel be obvious via the system. I am paranoid tht I am steering slightly left most of the time.

 

Sorry for asking so many questions. I have read the excellent info on this site, but don't have the knowledge to relate what I read to my questions above. For example, I dont know how noticeable what looks like a small change in toe would be when translated to handling characteristics.

 

Any help is much appreciated...... thanks in advance :thumbsup_anim:

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Hi Tony.... This was a few weeks ago now, but I would say there was between half and 3/4 of a tank of fuel in the car.

 

I gather from reading other posts that the car should have been tanked, and loaded when performing the geometry. What annoys me is that the technician didn't tell me any of that, but still charged me £85 for what could have been a poor alignment.

 

If there is likely to be any problems with my current set-up, I will go back and negotiate a re-alignment with them under proper conditions. My local BMW dealer charges nearly £200 for what they call a KDS, and I have my doubts as to whether they would ensure the car was fueld and loaded. I wish there were more professionals who take the care and attention over alignment that you obviously do.

 

 

Thanks

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most bmw's need waiting to get the car at the right level to adjust, the weights we use weigh four stone each (56lb) and to get the car right we need 3 in each front footwell, 1 in each rear footwell, 1 inbetween to rear seats (on he transmittion tunnel) and one in the boot, thats a total of 40 stone or 560lb,

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Hi Tony.... This was a few weeks ago now, but I would say there was between half and 3/4 of a tank of fuel in the car.

 

I gather from reading other posts that the car should have been tanked, and loaded when performing the geometry. What annoys me is that the technician didn't tell me any of that, but still charged me £85 for what could have been a poor alignment.

 

If there is likely to be any problems with my current set-up, I will go back and negotiate a re-alignment with them under proper conditions. My local BMW dealer charges nearly £200 for what they call a KDS, and I have my doubts as to whether they would ensure the car was fueld and loaded. I wish there were more professionals who take the care and attention over alignment that you obviously do.

 

 

Thanks

In truth i feel they have done a very good job other than allowing a low fuel load to spoil the set-up. But in answer to your questions...

 

1: The castor is not directly adjustable but is influenced by other angles when adjusted... The disparity is of no concern.

2: No. Dead areas have many reasons and impossible to isolate without seeing the car.

3: Moving the toe in will reduce wear on the outsides of the tyres and help with 'turn in' response... very few would physically detect the difference.

4: Yes. The position was outside of the checking range (static) so the position would exceed all (dynamic) limits.

5: Without correct fuel loading at the time of the test we cannot comment.

6: Not normal but again there can be many reasons why.

7: Full Geometry.... Terminology differs

8: http://www.wheels-inmotion.co.uk/forum/ind...p?showtopic=118

 

Your car has very particular requirements in preparation for a Geometry that many shops fail to follow, these are..

1: Full fuel tank

2: 68kg on passenger seat

3: 68kg on drivers seat

4: 68kg on centre rear seat

5: 21kg in boot

6: Correct engine/water coolant/ gearbox/ transmission/ brake fluid levels (washer bottle not mentioned)

 

The last 1-6 would be additional charges to the £200 quoted by BMW.

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Thanks Tony and Dan. I am not sure if the car was loaded during the alignment.

 

I will check with the guys that did the work. If it turns out it wasn't loaded, would that render the current alignment useless, and mean I need to re-align?

 

One other question I have is: The NSF had about 2mm more wear on the inside shoulder when the alignment was carried out. Will the fact that the tyre had an uneaven wear have increased the -ve camber reading, thus meaning that when I put on a new set of tyres, the new camber position will be incorrect.

 

Thanks

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Thanks Tony and Dan. I am not sure if the car was loaded during the alignment.

 

I will check with the guys that did the work. If it turns out it wasn't loaded, would that render the current alignment useless, and mean I need to re-align?

 

One other question I have is: The NSF had about 2mm more wear on the inside shoulder when the alignment was carried out. Will the fact that the tyre had an uneaven wear have increased the -ve camber reading, thus meaning that when I put on a new set of tyres, the new camber position will be incorrect.

 

Thanks

The Geometry is an image in time and not necessarily the criminal? If i read thing correctly after the pot-hole the geometry was measured then corrected.. this would not explain existing tyre wear which takes many miles to become visible (normally)

I honestly say that the positions on the report are exemplary despite the low fuel load which is visible by the castor position...... nevertheless the end positions if read correctly are very good rolleyes_anim.gif Sometimes other company's other than wim can get it right..... (TFFT) ph34r_anim.gif

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Thanks Tony.

 

I ran the car for several thousand miles after the pot hole, and it was the change in tyre wear that prompted the geometry check. It wasnt a big hit, so I thought things were ok. I didn't notice any change in handling, but I am much more aware of the effects of poor geometry having spent some time looking around here.... I won't make the same mistake again, especially considering the cost of a new set of 4 tyres...... ouch.

 

I still have one remaining question. The uneaven wear will mean that the tyre wasn't sat flat on the scissor lift. As the wear increased towards the inside shoulder by about 2mm, I assume that this could have lead to the initial camber measurement showing more -ve than it actually was? This in turn will have lead to an over adjustment of camber, so that when I put new tyres on, and they sit perfectly flat, my camber will be out of spec again?

 

Or.... am I completely wrong, and the tyre wear will not effect any of the measurements...

 

Thanks..... I have learnt a lot in the past few days... rolleyes_anim.gif

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Thanks Tony.

 

I ran the car for several thousand miles after the pot hole, and it was the change in tyre wear that prompted the geometry check. It wasnt a big hit, so I thought things were ok. I didn't notice any change in handling, but I am much more aware of the effects of poor geometry having spent some time looking around here.... I won't make the same mistake again, especially considering the cost of a new set of 4 tyres...... ouch.

 

I still have one remaining question. The uneaven wear will mean that the tyre wasn't sat flat on the scissor lift. As the wear increased towards the inside shoulder by about 2mm, I assume that this could have lead to the initial camber measurement showing more -ve than it actually was? This in turn will have lead to an over adjustment of camber, so that when I put new tyres on, and they sit perfectly flat, my camber will be out of spec again?

 

Or.... am I completely wrong, and the tyre wear will not effect any of the measurements...

 

Thanks..... I have learnt a lot in the past few days... rolleyes_anim.gif

I understand your perception for tyre condition and the accuracy of the measurements during the Geometry.. Due to the same pressure we tested the difference between measuring a car with worn tyres and the same car with new tyres, the difference was negliable... 10th's of millimetres.

Static on the ramp the cameras are not aware of the forces built into the Geometry positions although the damage is visible to us... Definition between actual matter of fact positions and the complaint fortunately has a distinct division.

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Few questions of my own.

 

Why do you need to load up so much weight when the average car will just have someone in the drivers seat?

 

And wow, that's a lot of rear camber for a stock family saloon. Tony, we're winding loads more on my trackcar!!

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Few questions of my own.

 

Why do you need to load up so much weight when the average car will just have someone in the drivers seat?

 

And wow, that's a lot of rear camber for a stock family saloon. Tony, we're winding loads more on my trackcar!!

Remember i didn't design this method!!

Some (mainly) Germain manufacturers insist the Geometry is measured with the suspension loaded so accountable for most areas of wear, from this position it is reasonable to assume the range in measurement and correction is central to the overall range expected during wear within the suspension. The underlying data is for a loaded vehicle so the overlap needs to comply or the results are worthless. Just to add stupidity to this method of measurement? we also need to add a 'Spreader rod' at the front wheels to simulate rolling resistance. This is a sprung loaded pole that pushes the front wheels apart compressing the steering box/rack... But since the adjustment range is as small as .03mm (Audi) for toe then how realistic is this weighting method :blush:

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Just spoke to the operator that carried out my geometry. It turns out that there is an option on the Beissbarth system to either perform the alignment with the car loaded as BMW state, or another option to align the car by entering the ride height without having to load up the car.

 

They chose the ride heigth method. The guy I spoke to didn't seem to think that the fuel tank being half empty would be the cause in the caster being off. It is noteable that the caster was out of spec before and after alignment when compared with the target data.

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Just spoke to the operator that carried out my geometry. It turns out that there is an option on the Beissbarth system to either perform the alignment with the car loaded as BMW state, or another option to align the car by entering the ride height without having to load up the car.

 

They chose the ride heigth method. The guy I spoke to didn't seem to think that the fuel tank being half empty would be the cause in the caster being off. It is noteable that the caster was out of spec before and after alignment when compared with the target data.

The Beissbarth is able to define trim height via external trim imaging vertically but the fuel issue is longitudinal and definitely effects the position of the castor...

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