Err there is not that much a Computer can do to help you with alignment on a standard Murena really.....
Only thing you can easily adjust is the "Toe in and Toe out" of the front wheels with the track rods. Never been near a computer for this myself, most tyre fitting shops in the U.K. have a portable alignment gauge that they do this with.
The other item on the front that is adjustable is the "Camber" which you adjust by adding or removing the "Camber Shims" between the upper suspension arm bracket assembly. Castor is fixed.
Actually that is not true Graham. The castor can be adjusted too, because if you take out or add more shims to the front or rear top wishbone fastening then it will move the top ball joint forwards or backwards and therefore adjust the castor angle! Actually it is not just the number of shims, since there are three different thicknesses of shims, so it it the total thickness that is important. You must take out (or add) the same thickness of shims at the front and back fastening of the top wishbone if you want to adjust the camber and not disturb the castor.
There is absolutely nothing that can be adjusted on the rear of the car except tyre pressure!
Correct, but the rear tracking should always be checked because if something is bent or worn it could be incorrect.
As for the front ride height, this can easily be taken up and down by the nut on the end of the lever which goes to the spline on the end of the Torsion bar part of the front suspension. Measure this with a Tape Measure from the ground to the lower edge of the front wing above the wheel and make adjustments accordingly.
Correct the front ride height can be adjusted up or down normally... but in this case I'm very much doubtful he will ever get anything satisfactory, as I've already explained to him owing to the wheel and tyres that have been fitted previously. So that you can see the problem, these are what are fitted to his 1.6 Murena:
Front: 205/45ZR16 tyres on 7.5Jx16 wheels
Rear: 225/40ZR16 tyres on 9.0Jx16 wheels
These may look good cosmetically, put they are really too big for a Murena, particularly a 1.6 which doesn't have as much power or cornering potential, and I wouldn't want to drive or corner fast on them without a lot of careful testing, as they have altered the carefully designed Matra set up outside the correct parameters.
Now I did a calculation on these and the front is riding 16mm higher than the rear! So the car has a 'nose up' stance which is bad for aerodynamics as well as upsetting all the carefully designed suspension set up done by Matra Automobiles to produce a superb handling car.
His front tyres will
raise the front ride height compared to the original Murena 1.6 175/70HR13 tyres by 8 mm. They would also be much closer to the front wheel arch and therefore there will be a more limited amount you can lower the front on the torsion bar setting. Since the wheels are 7.5" wide, which are strictly a little too wide for 205 width tyres, I suspect the offset is incorrect with more to the outside also altering the contact patch centre of the tyres and again generally upsetting the way the car was designed.
His rear tyres will
lower the rear ride height compared to the original Murena 1.6 195/70HR13 tyres by 8 mm. Again the wheels are much too wide for those 225 width tyres, and certainly the offset must be incorrect otherwise the inside edges would foul the semi-trailing arms. The front tyres could have been put on 6.5" and the rear tyres on 7" wide rims. The greater offset will put a torque twist on the bearings and therefore the hubs and semi-trailing arms, as the contact patch is again outside of the original design spec.
The rear ride height on a standard Murena is non-adjustable. If you want to adjust the rear ride height you would have to invest in new Coil Over Shock Absorbers with Adjustable Spring Platforms.
I suspect though that you just have worn dampers front and rear and that the rear springs have all sunk with age?
You would replace both sides of the car for this as standard practice.
Cheers, Graham
P.S. Read the article from Roy's Website (as stated in my posting)
To sum up, I'm sorry but you simply can't truly diagnose any faults with this cars suspension with those inappropriate wheels and tyres! Ideally you would put a set of original wheels and tyres on it first, whether that is the 70 profiles on 13" steel wheels or the 60 profile tyres on the 14" alloys, but if you use a set of alloys with 60 profile tyres, then you need to lower the front torsion bar setting to allow for the fact that even those 195/60HR14 rear tyres lowered the rear ride height and produced an incorrect front to rear ride height, which Matra forgot to allow for! This is all explained in my article, where I strongly recommend using 55 profile 14" tyres on the front to bring the ride heights back to the original design specification.
A final point is that the Murena appears to have been designed to suit French roads with their, at times, heavily cambered surfaces. In the U.K. where we drive on the left and any road camber is the opposite of French roads, I found when my car was brand new, that it would drift slowly into the kerb if you didn't pay attention to keep it straight. So working in the trade with access to all the right equipment, I double checked all the suspension was correctly set as per the design spec. It was, so I live with that slight drift. However, whenever I took the car to France, which I have done now on various occasions, I found that the car tracks perfectly straight and I can take my hands off the wheel, even at 130 kph, and it runs perfectly straight!
Roy
P.S. as for the garage that can't do any checks because 'the computer doesn't know the car', that just proves how pathetic some mechanics and their understanding is now - if a computer can't tell them, then they have no idea! Rubbish! Even if I didn't have the actual spec. for any vehicle, I could still check it out fully, see what readings I got, and know if it was about right or something was patently wrong.
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