Openion.. Hunter result included

[suj999]

Hello,

 

Just had my car tested for laser alignment (Hunter), the garage said the rear Toe is out and can be fixed for £100. The front camber can't be adjusted by them, but its not much so don't worry about it.

 

My mate had a look at the data sheet and said its really not worth getting adjusted now as they are not so far off the mark. So I have left it without paying to have the rear toe adjusted.

 

Openions any one? Should I have the front camber looked at somewhere else?

 

Car is a BMW F10 520D

 

[Tony]

The NSF camber would be an issue to me if the cars pulling left?....... Did they put any ballast in the car, it should be around 150kg.

[suj999]

The car is pulling to the left ever so slightly.. Hence why I took it in.

 

But they said they were only able to adjust the rear toe, would the rear toe that's slightly out make the car pull to the left? The guy in the shop said uneven tire wear, but nothing about pulling left or right.

 

Regarding the font camber, they said with these BMWs some short of part needs changing and the camber itself can't be adjusted? Is this true?

 

They didn't use any weight, but I believe a large size technician was in the driver seat during the test.

[suj999]

Ohh forgot to add.. The front left has a Piralli run flat (7mm), all the others have Goodyear runflats, (6mm front, 4mm is both back sets)

 

Would this odd tire cause the pull? As I bought the car like this, I'm thinking there was uneven wear on the NSF that's why it's got a Piralli and all the others have slightly older tires.

[Tony]

First up the BMW target datum needs the suspension to be pre-loaded so in truth the data they acquired ( without ballast ) is redundant. The disparity at the front still exists but the true value displayed is fictitious.

 

To explain BMW require the cars suspension to be loaded at a designated hight meaning it's position is central to "bump and droop". call this a mean average or a realistic template that covers most owners driving environment.

 

In view of this error the rear toe positions are not in question and certainly cannot make the car pull!

 

As it stands and without absolute true values the front camber looks like this \  \ between the wheels. Camber is a "conical force" or let's say a compressive force. At the moment the compression isn't balanced so there's a "push" to the left.

 

BMW offer correction upper arms with a range of +- 30' depending on the complaint. Your only option is to replace the NSF upper arm for a -30' adjuster.

 

In truth there's a bend on the NSF so a more complete printout displaying the KPI/ SAI position would confirm this and if found true by triangulation it would have been a much cheaper option than buying a new upper arm.

 

In addition on the Hunter machine the "ballast" details and target height are displayed during the set-up process. If you feel the need to question the workmanship then this display cannot be denied if they don't have any ballast! 

[NickT]

On my wife's Vectra C, the rear toe is dependent on the height between the centre of the wheel and the upmost wheel arch, but aim to have half a tank of fuel and the ballast to do a correct geometry test. On the car of the previous post above, if the reading should have been taken with 70kg per front seat as ballast (for example) would it affect the front camber/ toe/ sai if the ballast was mainly over the drivers seat?

[Tony]

Loading the ballast needs exact placement NSF/ OSF and boot. A collection of maybe 170kg has a massive effect on the camber reading and in turn the front/ rear toe and due to a change in the cars sprung rake the castor position.

 

Question could be had about the drivers weight? Well yes but where do we stop? How about the fuel load or washer bottle level ( two gallons in some ) Abiding to some simple parameters is the best starting point. Modify the car then that's another story but not end of days.

[NickT]

I'm trying to ascertain and understand the reading above if the measuring range above is actual correct for this car, considering it is not pre loaded with the correct ballast, yet the driver was sat in the car. I'm trying to visualise the camber reading with just the driver in compared to the ideal result, and how it would affect the nearside camber and overall front toe readings.

[NickT]

Ie would the front camber readings above be reversed of the driver had sat in the passenger seat.

 

On another note, I wonder why Hunter just don't set defaults in tier software to always enable run out compensation and to always include the 3rd angles. ...

[suj999]

Thanks for all the advice.

I'm not sure if I want to go back to that place and ask for more details..

 

Seeing as I only had the car for a month, I am tempted to wait and see what the tyre wear is like. The pull to the left is there but it's very minor.

 

The NSF upper arm replacement isn't cheap is it? Having a quick look on the net range of £400-£550 being mentioned.

 

Would you advice against driving it like this to see if the tyre wear / driving is affected before getting any mechanical work done?

Or should I go to a different place to have it inspected properly? (Not sure what kpi/sai is). Any advice for places in Essex / east London?

 

Thanks again for all the advice.

[NickT]

Try swapping the front wheels over and see if the pull goes to the right

[Tony]

Thanks for all the advice.

I'm not sure if I want to go back to that place and ask for more details..

 

Seeing as I only had the car for a month, I am tempted to wait and see what the tyre wear is like. The pull to the left is there but it's very minor.

 

The NSF upper arm replacement isn't cheap is it? Having a quick look on the net range of £400-£550 being mentioned.

 

Would you advice against driving it like this to see if the tyre wear / driving is affected before getting any mechanical work done?

Or should I go to a different place to have it inspected properly? (Not sure what kpi/sai is). Any advice for places in Essex / east London?

 

Thanks again for all the advice.

 

 

A positive camber position is less destructive ( within reason ) than a negative camber...... There's a few deciding factors to consider.... One would be the severity of the pull but there is a way to reduce the effect with a little bit of cheating..... Let's say the OEM tyre pressure is 30psi, then you could add 2psi ( no more ) to the NSF tyre and remove 2psi ( no less ) to the OSF tyre. By doing so the rolling circumference will have an off-side bias, or push shall we say.

 

Next point is the turning reply. If during a left turn the steering is lazy to return then that could be dangerous, so that's something you need to access. The right hand turn should be fine.

 

The fact the car wasn't ballasted means the actual positive camber position is not as bad as displayed but.... And there always has to be a but, the imbalance between the front cambers will remain, this is called "cross camber".

 

Historically the incorrect NSF camber position is due to a bend in the lower control arm. The fact the position is positive reads odd to most but hitting a pothole whilst on a lock can allow the camber curve radii to thrust away from the natural compression points and bend the neck of the control arm. Had they have bothered to measure the KPI/ SAI < same angle different terminology, then the reading would have confirmed a bend in the lower arm.

 

To explain KPI/ SAI, it's King Pin Inclination and Steering Axis Inclination. Both refer to the angle of the pin in the lower control arm ball joint, hence the reason if the angle had been measured then i/ we could say with confidence if the arm is bent.

[Tony]

I'm trying to ascertain and understand the reading above if the measuring range above is actual correct for this car, considering it is not pre loaded with the correct ballast, yet the driver was sat in the car. I'm trying to visualise the camber reading with just the driver in compared to the ideal result, and how it would affect the nearside camber and overall front toe readings.

 

Adding ballast or the driver would still allow the cross-camber bias to remain and that's the issue. But you have some good points i need to explain.

 

The front camber position with the addition of the driver tends to lean the NSF camber toward negative so a transverse shift. The front toe should remain the same "static" but has a fluid migration during the suspensions transitions ( bump/ droop ) the actual amount of transition depends on the suspensions condition and of course the condition of the bushings. 

[suj999]

Thanks for the advice, will try the tyre presure option.

 

Also will change the front tyres around to see if it makes a different as one is Goodyear and the other is Pirali.