Catalin,
Since I don't have experiences in suspension tuning, I think I'm not competent to give you advices about that, but here are some hits anyway.
From various internet sources, it seems that damper bump/rebound ratio for street cars is mostly between 1:2 and 1:2.5, so maybe it's not very good idea to go higher. Ratio up to 1:5 is used for rally races on really bad surfaces, while for races on very smooth surfaces it's close to 1:1.
Also, here are some rules:
- harder front roll-bar = more understeer
- harder front springs = more understeer
- higher bump/rebound ratio of front dampers = more understeer
- harder rear roll-bar = more oversteer
- harder rear springs = more oversteer
- higher bump/rebound ratio of rear dampers = more oversteer
As a rough guide about springs, Alfa 156 dives about 1.5 cm on the front bumper, and about 3 cm on the rear bumper, under my 70 kg. If you are driving mostly on rough roads, I think harder springs would do more harm than good.
Since you have thick rear roll-bar and stiff rear 'springs', I think that's the reason for oversteering on bad road. First, I would try increasing pressure in rear spheres. Front springs should be 1.5-2 times stiffer than rear, because they take more weight. If you decide to modify the dampers, try using higher bump/rebound ratio on the front than on the rear. Maybe 1:2.5 on the front and 1:1.7 on the rear. But, bear in mind that I'm just guessing here.
Anyway, the result of your experiment is questionable. Don't forget that it's not easy to get better results than the factory. They are developing this suspension for several decades, so you'll also need plenty of time. Good luck!
Spheres & roadholding
Moderator: RichardW
<blockquote id="quote"><font size="1" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by alexx</i>
I used translator on http://babelfish.altavista.com/ - this link was posted by Catalin. It's not perfect, but it's better than nothing.
<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">
Alex and Alan,
VERY impressive. As you say, the translation isn't perfect. But it's not bad for about 2 microseconds of hard work!!!
Now to read at my leisure.
Thanks for all this thread - I've found it most interesting.
I'd still like to soften my Xantia but it does look too hard. Probably best to leave well alone.
JohnW
I used translator on http://babelfish.altavista.com/ - this link was posted by Catalin. It's not perfect, but it's better than nothing.
<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">
Alex and Alan,
VERY impressive. As you say, the translation isn't perfect. But it's not bad for about 2 microseconds of hard work!!!
Now to read at my leisure.
Thanks for all this thread - I've found it most interesting.
I'd still like to soften my Xantia but it does look too hard. Probably best to leave well alone.
JohnW
Update on the sphere dismanteling:
The one I dismantled last WE was not a 16v one although sold like one as it had 30 stamped on it!
The OE part has 2 bound discs (~0.5mm) and 4 rebound (~0.9mm). Also, the damper on the latter does NOT press out, it's made as one piece then welded to the sphere.
Now I finally know what's wrong with my back damping, I had wrong "16v" spheres fitted!
The one I dismantled last WE was not a 16v one although sold like one as it had 30 stamped on it!
The OE part has 2 bound discs (~0.5mm) and 4 rebound (~0.9mm). Also, the damper on the latter does NOT press out, it's made as one piece then welded to the sphere.
Now I finally know what's wrong with my back damping, I had wrong "16v" spheres fitted!
Aha!
Obviously, it's easy to mix the sphere type. I think I had a similar problem with my BX16 with rear spheres. Finally, after 5 years of uncomfortable drive, I replaced spheres with GS-spheres and finally enjoying the ride. On Jpn site, rear damper is specified as 4U/4U, but I'm quite sure rebound damper was 4A, since the whole package was almost 2 times thicker than on GS sphere (3U/3U), near 1 mm.
If someone has flat Xatia sphere (non-HA) and enough time to dismantle it, report what's in.
Obviously, it's easy to mix the sphere type. I think I had a similar problem with my BX16 with rear spheres. Finally, after 5 years of uncomfortable drive, I replaced spheres with GS-spheres and finally enjoying the ride. On Jpn site, rear damper is specified as 4U/4U, but I'm quite sure rebound damper was 4A, since the whole package was almost 2 times thicker than on GS sphere (3U/3U), near 1 mm.
If someone has flat Xatia sphere (non-HA) and enough time to dismantle it, report what's in.