Hi all,
Further to "Comfort Spheres", I'm about to get 6 new spheres for my 1991 XM V6 SEI. Ideally I'd like to get more of a "CX quality" ride from it, so I'm toying with the idea of using slightly different spheres to achieve this.
Couple of basic questions:
Does higher sphere pressure give a firmer or softer ride, all other factors (volume and damper orifice size) being equal? Can anyone give a definitive answer on this one?
I've noted the warnings about "comfort" spheres and how they affect handling.
What effect would putting Estate rear CENTRE sphere on (500cc/40bar) as opposed to standard hatch (400cc/50bar) have? In theory, the larger volume should have more "give" under normal driving, but wouldn't affect sport mode when the centre spheres are cut out of the system. But what about the lesser pressure of the estate sphere? How will that affect ride?
Also, replacing front (400/50/0.6) V6 spheres with (400/55/0.7) 2.0 version; effectively similar to comfort spheres I guess.
Any suggestions?
Cheers,
PaulE
Toowoomba, Qld
Tweaking suspension
Moderator: RichardW
-
Jon
Hi Paul
The Xm V6 used 50bar front spheres, and the 2.0 has 55's.In both cases the Volume is 400 (i.e. sphere height of 130mm)."Comfort" spheres are 75bar with a 400 volume.Thus higher sphere pressure does give a softer ride (CX's all used 75 bar front spheres), although of course this is also controlled by damper size (I do not have the damper size of comfort spheres I'm afraid but the XM V6 had a 0.60 damper and the 2.0 had a 0.70). To my way of thinking the comfort spheres are just a bit too soft for V6 models unless you want a real floating ride (and lots of roll).
At the rear all the V6/2.1td/2.0 saloon spheres are all the same at 30 bar, 400 volume with a 0.50 damper. "Comfort" spheres being 40 bar pressure.
So I reckon the way to go is fit 2.0 front spheres to give a slighter softer ride, and leave the back alone, anyone else got any thoughts on this (Alexx?)
As regards using the Estate centre rear on a saloon, I would imagine this would have the effct of slightly stiffening things up due to the lower pressure.
Anyone?
The Xm V6 used 50bar front spheres, and the 2.0 has 55's.In both cases the Volume is 400 (i.e. sphere height of 130mm)."Comfort" spheres are 75bar with a 400 volume.Thus higher sphere pressure does give a softer ride (CX's all used 75 bar front spheres), although of course this is also controlled by damper size (I do not have the damper size of comfort spheres I'm afraid but the XM V6 had a 0.60 damper and the 2.0 had a 0.70). To my way of thinking the comfort spheres are just a bit too soft for V6 models unless you want a real floating ride (and lots of roll).
At the rear all the V6/2.1td/2.0 saloon spheres are all the same at 30 bar, 400 volume with a 0.50 damper. "Comfort" spheres being 40 bar pressure.
So I reckon the way to go is fit 2.0 front spheres to give a slighter softer ride, and leave the back alone, anyone else got any thoughts on this (Alexx?)
As regards using the Estate centre rear on a saloon, I would imagine this would have the effct of slightly stiffening things up due to the lower pressure.
Anyone?
Unfortunately, I didn't have the opportunity to drive a Hydractive XM, so it's hard for me to suggest 'better spheres' for it (I drove 3 hydractive Xantias and was a bit disappointed with the ride, but XM suspension is differently tuned).
Anyway, higher the product volume x pressure, softer the sphere. But, this affects mainly longer waves on the road, resulting in lower vertical accelerations during the drive and more pleasant 'eigen frequency' of the car (ideally about 1 cycle per sec).
Behaviour on the shorter and sharper bumps depends mainly on the damper valves. If the damping is too high, the ride is harsh and suspension is loud. If it's too low, the car floats too much and the roadholding is bad.
Replacing 400/50/0.6 front spheres with 400/55/0.7 might give some improvement on sharper bumps, but I don't think there will be a big difference (it depends whether disc valves on the spheres are also different). Other possibility is to refill the same corner spheres to higher pressure - 60-75 bar front, 40-45 bar rear - this will improve the things on longer waves. But, you can't make XM riding like a CX, unless you fit CX spheres and eliminate the whole hydractive system, which is not a very good idea, I think.
Anyway, higher the product volume x pressure, softer the sphere. But, this affects mainly longer waves on the road, resulting in lower vertical accelerations during the drive and more pleasant 'eigen frequency' of the car (ideally about 1 cycle per sec).
Behaviour on the shorter and sharper bumps depends mainly on the damper valves. If the damping is too high, the ride is harsh and suspension is loud. If it's too low, the car floats too much and the roadholding is bad.
Replacing 400/50/0.6 front spheres with 400/55/0.7 might give some improvement on sharper bumps, but I don't think there will be a big difference (it depends whether disc valves on the spheres are also different). Other possibility is to refill the same corner spheres to higher pressure - 60-75 bar front, 40-45 bar rear - this will improve the things on longer waves. But, you can't make XM riding like a CX, unless you fit CX spheres and eliminate the whole hydractive system, which is not a very good idea, I think.
<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>
If it's too low, the car floats too much and the roadholding is bad.
Replacing 400/50/0.6 front spheres with 400/55/0.7 might give some improvement on sharper bumps, but I don't think there will be a big difference (it depends whether disc valves on the spheres are also different). Other possibility is to refill the same corner spheres to higher pressure - 60-75 bar front, 40-45 bar rear - this will improve the things on longer waves. But, you can't make XM riding like a CX, unless you fit CX spheres and eliminate the whole hydractive system, which is not a very good idea, I think.
<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">
Agreed alexx and then it could end up like the one I spoke about where I had a BX 16V "tailwagging" under brakes.[:0][:0]
Alan S [B)]
If it's too low, the car floats too much and the roadholding is bad.
Replacing 400/50/0.6 front spheres with 400/55/0.7 might give some improvement on sharper bumps, but I don't think there will be a big difference (it depends whether disc valves on the spheres are also different). Other possibility is to refill the same corner spheres to higher pressure - 60-75 bar front, 40-45 bar rear - this will improve the things on longer waves. But, you can't make XM riding like a CX, unless you fit CX spheres and eliminate the whole hydractive system, which is not a very good idea, I think.
<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">
Agreed alexx and then it could end up like the one I spoke about where I had a BX 16V "tailwagging" under brakes.[:0][:0]
Alan S [B)]
French car day? Now you tell me!![:)]
Got to work unfortunately.
Points noted on spheres though.
Think I'll go with 2.0 on front, as they aren't too radical.
Out with the calculator on the back ones. I'm getting the spheres from Andyspares, as even with freight, they're much cheaper than here.
Cheers all,
PaulE
Got to work unfortunately.
Points noted on spheres though.
Think I'll go with 2.0 on front, as they aren't too radical.
Out with the calculator on the back ones. I'm getting the spheres from Andyspares, as even with freight, they're much cheaper than here.
Cheers all,
PaulE