Lennart Sorth
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« on: September 27, 2008, 10:40:00 pm » |
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Unfortunately I don't think anybody have the technical specs of the suspension,- spring "k" values, shock absorber parameters etc. If I'm wrong, PLEASE let me know.
My new springs and shockabsorbers have resulted in the rear being too soft, and the car can bottom out quite easily. A bloody nuissence as I had requested to get a *replacement* setup, as I had no intention of fiddling about with suspension settings - all I wanted was lower springs so the rear came down where it belongs, and then modern shosckabsorbers. period.
(Unfortunately you cannot get modern absorbers unless you get them "adjustable", which I requested to have adjusted once-and-for-all to "Murena standard" values.)
Initially I thought the problem was that the springs were too soft, but I have come to the conclusion that it only is the shockabsorbers that are different.
My left one is either set way too soft, or has failed already(!) - the right one feels right. The left actually bounces when I let it go, - the right just comes back up and stops, - so the left absorber is either set to *very* low absorbtion, or has failed already (?!)
Now for some measurements: --------------------------------------
The rideheight, as measured at the top of the rear wheel-arc on my car is slightly different right/left with nobody sitting in the car.
Left: 602mm right: 610mm
This may however be caused by the body having been fitted by a French worker on a monday morning, so it is more interesting to look at the compression:
When I put my weight (84kg) on each corner, they compress to:
Left: 584mm right: 594mm
ie compression is : Left: 18mm Right: 16mm
However, I only have one Murena, so I would urge all owners weighing approx 84kg (however many stones and pebbles that amounts to) to measure the compression when you sit on the rear corner of the car.
Please also say if its 1.6/2.2 and the year.
If you don't match the 84kg then find somebody who does :-) Alternatively we could establish a concensus on a Murena driver weight, and I could re-do my measurement.
/Lennart
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Anders Dinsen
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« Reply #8 on: October 01, 2008, 01:58:28 pm » |
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My new springs and shockabsorbers have resulted in the rear being too soft I had felt that exactly the same happened when I fitted my "GAZ" suspension. I have tried to adjust the dampers, but I have the feeling that its the springs that are a bit too soft. THe problem can of course be both the springs and the dampers, but it's possible to eliminate one or the other by some simple checks. The key is to remember that the springs handle mostly static loads, the dampers only dynamic loads. With fixed spring positions like what we have on the standard rear shocks or KONI's, you will notice that the car sits too low if the spring is damaged. I had this problem, and it was due to surface corrosion on the spring. With adjustable springs like those you have on the rear GAZ shocks, you will have to do a "load test" like the one proposed by Lennart: Put X kg in the car and measure how much it compresses - then compare with a known good car. When Lennarts car "bottoms out" over bumpy roads, but it okay on the load test, the problem is definitely not the spring, but the damper: This is the kind of dynamic loads that the shock absorber should handle by adding some "stiffness" to the suspension. Is this common on the GAZ shocks? Michal runs these too AFAIR, and he's a very happy owner. - Anders
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1982 Talbot Matra Murena 2.2 prep 142 (under restoration) 2017 BMW i3 "Charged Professional" 94Ah 2024 VW id.buzz Pro
Used to own: 2001 Renault Matra Grand Espace "The Race" V6 24v 1997 Renault Matra Espace 2.0 8V 1987 Renault Matra Espace J11 2.2
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Lennart Sorth
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« Reply #11 on: October 02, 2008, 10:22:39 am » |
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My main issue is excessive "body roll"..
We have to remember the car is a 1980 design (I'm sure you do). Modern sporty cars have beefy antiroll bars to keep them horizontal through bends, but I don't think that per default give you better handling, as it sort of defies the purpose of independent suspension. Did you know that the Ariel Atom actually doesn't have any antiroll bars at all ? - for that car, its all about having a low center of gravity, which makes it corner completely flat. So maybe you should cut the roof off your car (just kidding) However, having felt the weight of the rear hatch when I replaced the gasstruts, we could easily save a lot of high-placed weight by replacing it with perspex or similar. /Lennart
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Anders Dinsen
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« Reply #13 on: October 02, 2008, 12:27:48 pm » |
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Did you know that the Ariel Atom actually doesn't have any antiroll bars at all ? Ultima doesn't have antiroll bars either ![Cool](http://www.matrasport.dk/forum/Smileys/default/cool.gif) Anti roll bars are primarily for tuning grip during cornering between front and rear, not to prevent the car from rolling. They do it by transferring load diagnoally through the chassis on the car. I remember that Mr.Dinsens car had a more firm poise even on standard springs/dampers
And that was even with my old front shocks, which came off Roy's silver car - i.e. they were 25 years old and had coveret a lot of kilometers. Lennart had a ride with those as well. I have since replaced them with new ones, and the grip on the front has improved by a little, especially (of course) on uneven surfaces. I have a bit better feeling of confidence with the car. Tery 'direct' steering pattern of the Murena makes it noticable on the steering wheel: Slippery contact on the front wheels is felt by the steering getting lighter. Heavier steering during cornering is an indication that I'm safe to go faster ![Cheesy](http://www.matrasport.dk/forum/Smileys/default/cheesy.gif)
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1982 Talbot Matra Murena 2.2 prep 142 (under restoration) 2017 BMW i3 "Charged Professional" 94Ah 2024 VW id.buzz Pro
Used to own: 2001 Renault Matra Grand Espace "The Race" V6 24v 1997 Renault Matra Espace 2.0 8V 1987 Renault Matra Espace J11 2.2
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