Might be a quick answer for someone?

I had my FL2 tracking checked as part of the CT (French MOT) here and was told the value was -8.5m/Km
They said the pass limit is +/-10m/Km but anything outside +/-8m/Km is worthy of note.

What the heck are these numbers in relation to 0.20degrees +/-0.20degrees, which is what I'm used to?

Is there a conversion chart somewhere (I've looked on the official French CT website).

The tyres look hunky dory by the way. Life is an uphill struggle. Only the gradient varies.

a strange unit for tracking.

Does it refer to how far the car would deviate from a straight line of 1km length ? Jules

Firstly I didn’t think wheel alignment was part of the Contrôle Technique……..
Thé alignment measurements would be in degrés/minutes……..except as Jules suggests it’s a measure of the rear axle misalignment…….if the garage is using a high tech Hunter Alignment system or similar than can measure this misalignment which will make the car ‘crab’…….i.e. pull to left or right…..if seriously misaligned…………10m/km seems a lot……
I would ask the question……has it passed the test….?
Altering the rear alignment could be a problem since spécial offset mounting bolts are used….& on an older car they could be rusted-up……
You say the tyres are wearing ok so I wouldn’t worry about it……if you have a pass….
Judging by the condition of most older cars requiring the French MOT…..it’s much less strict than UK despite being more costly…….! FL2 SD4 HSE Lux Auto MY 2012— current
D2 TD5 HSE Man MY 1999 470kmls….gone 2014 ….lovely engine..chassis rotten
D1 300TDI Man MY 1996 56kmls….gone 1999…D2 much better
Wife’s FL1 1.8P MY 2001 32kmls …gone 2007…has Mini since.

Yes Pete, wheel alignment is now part of the CT.

They drive the car over a metal plate in the floor (Remember Trakrite? Looks a bit like that to me!) and the figures appear on a TV screen, in red if a fail!

Yes, it passed the test. As the CT is only every 2 years here, I'll not worry, but I would like to understand how these "mystery french" measurements relate to what I'm used to.  Life is an uphill struggle. Only the gradient varies.

Ok Argos……test passed…..no worries but I have never seen or heard of these m/km measurements………can only imagine it’s a ‘ crabbing ‘ measurement……to check if the car is steering straight……
I’ll ask à friendly garagiste to explain…..
I have noticed Sunday afternoons in a French town quite a lot of cars ‘crab’ a bit after Sunday lunch….!
………….
Bon week-end…..Pete FL2 SD4 HSE Lux Auto MY 2012— current
D2 TD5 HSE Man MY 1999 470kmls….gone 2014 ….lovely engine..chassis rotten
D1 300TDI Man MY 1996 56kmls….gone 1999…D2 much better
Wife’s FL1 1.8P MY 2001 32kmls …gone 2007…has Mini since.

The test parameter is +/- 10 metres in 1 km. Think of this as a gradient. it’s the same as 10 metres in 1000 metres, or 1 metre in 100 metres, or 1 cm in 1 metre.

If you represent that as a triangle the opposite side is 1, the adjacent side is 100, and the angle calculates as 0.57 degrees.

So it’s the same as saying the wheel alignment tolerance is +/- 0.57 degrees.

(Which seems a fairly wide allowance as it might have to be if they use the same parameter for all cars? They are probably just trying to pick up vehicles that are wildly out on tracking - or allowing for the Sunday lunch crabbing

Similarly you could calculate it as mm of toe in/out for a given wheel radius.

So just one of many ways of expressing a tracking parameter.

Hi Dennis,
Thank you for that eloquent explanation! Finally, something in France that makes sense!
Yes, a "catchall" for cars that are way out, seems likely. I knew I should have made more effort with trigonometry at school.

I find their CT test stations a world away from the UK MOT places I've visited. They're actually not allowed to do any work on cars at all, only testing, nothing else. The argument is that they have no vested interest in failing a car in order to get the work. The downside, is that if the car fails, you have to fix it yourself off the premises. That can mean a trailer to take it away!

However, most "discrete" activities, such as moving unroadworthy cars, take place between 12 noon and 2pm, when 99.9% of the Gendarmes are to be found having lunch and half a carafe of vin rouge. The first time I saw two armed police drinking quite a bit of red wine, one of them using a tanto-bladed combat knife to cut his steak, it took me by surprise. But then you're in a foreign land, where there are new discoveries every day and in a roundabout sort of way, it all appears to work. Children sit quietly and patiently at the lunch table and everyone seems to get a handshake in the bar.

So, I'm forgiving them a bizarre method of measuring tracking, that has needed Dennis to help me understand!  Life is an uphill struggle. Only the gradient varies.

OxonPete wrote:

Judging by the condition of most older cars requiring the French MOT…..it’s much less strict than UK despite being more costly…….!

Argos69 wrote:

I find their CT test stations a world away from the UK MOT places I've visited. They're actually not allowed to do any work on cars at all, only testing, nothing else. The argument is that they have no vested interest in failing a car in order to get the work. The downside, is that if the car fails, you have to fix it yourself off the premises. That can mean a trailer to take it