xantia softer ride possible ?
Moderator: RichardW
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roscopervis
- Posts: 43
- Joined: 24 Mar 2002, 23:28
- Location: United Kingdom
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If it is not the spheres then maybe it is another part of the suspension set up. I know that my Xantia (Hydractive II '94 vsx) has stiffened up a lot at the rear because the trailing arm bearings need doing, and at the front as the struts need lubricating, before it was great. Perhaps this coukd be the problem.
roscopervis
I think its performing the way its designed to. The suspension moves through its height range very smoothly with no noise and the car has only done 60K. The rear of the car is a lot softer than previously and the front has more travel than previously [with the non turbo spheres fitted]. The only Xantia experience I can compare it to is a drive in an 'N' reg 2L 8v auto many years ago which was superb. I'd guess its the design of the front struts on the later TD's and or the greater weight of the TD on the front.
I know its not comparing like with like but when I do the push down front wing test on this car and my TD BX the resistance feels similar as does the travel but the two cars respond very differently. The BX bounces back immediately, overshoots a little then drops back to normal very quickly. The Xantia however does basically the same thing but noticibly slower and more controlled, the overshoot is less and the elapsed time to complete is noticibly longer. A damping difference definately but I suspect that its the combination of strut and sphere. anyway
I'm not persuing the softer ride any longer with this car, looks like I should have bought the old 2L when I had my chance.
mark_sp
I think its performing the way its designed to. The suspension moves through its height range very smoothly with no noise and the car has only done 60K. The rear of the car is a lot softer than previously and the front has more travel than previously [with the non turbo spheres fitted]. The only Xantia experience I can compare it to is a drive in an 'N' reg 2L 8v auto many years ago which was superb. I'd guess its the design of the front struts on the later TD's and or the greater weight of the TD on the front.
I know its not comparing like with like but when I do the push down front wing test on this car and my TD BX the resistance feels similar as does the travel but the two cars respond very differently. The BX bounces back immediately, overshoots a little then drops back to normal very quickly. The Xantia however does basically the same thing but noticibly slower and more controlled, the overshoot is less and the elapsed time to complete is noticibly longer. A damping difference definately but I suspect that its the combination of strut and sphere. anyway
I'm not persuing the softer ride any longer with this car, looks like I should have bought the old 2L when I had my chance.
mark_sp
Mark, I think you are right with your conclusions.
From your post, I think it's obvious that previous spheres were on lower pressure than the new ones, so the spring rates were higher, and also, the damping is higher than in BX. I coped with similar problem, unsatisfied with the harsh ride in my BX in comparison with father's GS. At the end, I fitted GS spheres, and now it's way better (my mechanic was willing to experiment, so he exchanged spheres for no charge).
It's interesting that spring rate on the front is now higher than before, since the GS spheres are 400 ccm, BX spheres 500, and the pressure is equal in both cases (55 bar). On the front the car now dives 3.5 cm instead of 4.5 cm under my weight. On the rear, spring rate is equal as before, as the sphere volume and pressure (400 ccm, 40 bar), and the car dives 8-9 cm. But the damping is obviously lower, since if you push front or rear of the car, it goes down and back much smoother than before. The reason - discs covering main bores on the spheres are almost 2 times thinner.
If you still own BX and like the ride, why don't you try fitting BX spheres to Xantia? There are only minor differences in diameter of hydraulic cylinders between BX and Xantia, so you should get similar ride.
Could you please specify volume and pressure of new spheres from AS, and your weight, so I can check how far are my formulas for calculating sphere pressure from reality?
Alex
From your post, I think it's obvious that previous spheres were on lower pressure than the new ones, so the spring rates were higher, and also, the damping is higher than in BX. I coped with similar problem, unsatisfied with the harsh ride in my BX in comparison with father's GS. At the end, I fitted GS spheres, and now it's way better (my mechanic was willing to experiment, so he exchanged spheres for no charge).
It's interesting that spring rate on the front is now higher than before, since the GS spheres are 400 ccm, BX spheres 500, and the pressure is equal in both cases (55 bar). On the front the car now dives 3.5 cm instead of 4.5 cm under my weight. On the rear, spring rate is equal as before, as the sphere volume and pressure (400 ccm, 40 bar), and the car dives 8-9 cm. But the damping is obviously lower, since if you push front or rear of the car, it goes down and back much smoother than before. The reason - discs covering main bores on the spheres are almost 2 times thinner.
If you still own BX and like the ride, why don't you try fitting BX spheres to Xantia? There are only minor differences in diameter of hydraulic cylinders between BX and Xantia, so you should get similar ride.
Could you please specify volume and pressure of new spheres from AS, and your weight, so I can check how far are my formulas for calculating sphere pressure from reality?
Alex
alexx
As I recall the spheres were all 400cc with the rears at 40 bar and the fronts at 70 bar [you can check the details on this website, the spheres are reconditioned units for the NON turbo model]. my weight is 200 pounds. Now I've driven the car for a couple of days I can tell you that there is an improvement its just that its not improved enough for my liking.
mark_sp
As I recall the spheres were all 400cc with the rears at 40 bar and the fronts at 70 bar [you can check the details on this website, the spheres are reconditioned units for the NON turbo model]. my weight is 200 pounds. Now I've driven the car for a couple of days I can tell you that there is an improvement its just that its not improved enough for my liking.
mark_sp
Thanks, Mark_SP.
Well, assuming that your and others' new/renewed spheres are on the correct pressure, it seems that my formula for calculating sphere pressure this way gives about 30% lower result than it should. In that case, there's also something wrong with Nastasic's program and Julian Marsh's spreadsheet for C5. But, it's hard to believe that all spheres mentioned in this and other topics are on too low pressure, since they are from various sources. Anyway, whatever the reason, I'll present a new formula in a week or two (three, four ...), after checking some more Xantias.
I have one more question, Mark. It's strange that rear end of your car is twice softer than before, although the sphere pressure is only 33% higher. Since your car has anti-sink, rear end should be "tested", I suppose, at least several hours after turning the engine off, when anti-sink valves are closed, and anti-sink sphere is cut off. Otherwise, rear end would be softer. Do you remember, how did you "test" it with previous and new spheres? I suppose you did the second "test" right after fitting new spheres, and in that case, can you measure the dive of rear end after the car stay overnight, to see if there's a difference (please)?
Mark_I, can you wait a little with that spreadsheet you wanted to attach, until I correct/verify that formula.
Alex
Well, assuming that your and others' new/renewed spheres are on the correct pressure, it seems that my formula for calculating sphere pressure this way gives about 30% lower result than it should. In that case, there's also something wrong with Nastasic's program and Julian Marsh's spreadsheet for C5. But, it's hard to believe that all spheres mentioned in this and other topics are on too low pressure, since they are from various sources. Anyway, whatever the reason, I'll present a new formula in a week or two (three, four ...), after checking some more Xantias.
I have one more question, Mark. It's strange that rear end of your car is twice softer than before, although the sphere pressure is only 33% higher. Since your car has anti-sink, rear end should be "tested", I suppose, at least several hours after turning the engine off, when anti-sink valves are closed, and anti-sink sphere is cut off. Otherwise, rear end would be softer. Do you remember, how did you "test" it with previous and new spheres? I suppose you did the second "test" right after fitting new spheres, and in that case, can you measure the dive of rear end after the car stay overnight, to see if there's a difference (please)?
Mark_I, can you wait a little with that spreadsheet you wanted to attach, until I correct/verify that formula.
Alex
Alexx
I did all the tests with car on level ground with the handbrake on and the engine idling. I've checked again this evening now that the spheres have been in use for a few days and the results are the same.
I also re-tested the front with the handbrake off [rear wheel chocked] just to see if it made a difference, it didn't.
The push down tests are a bit crude and inconsistent so I'm not sure how seriously you should take them but good luck with the calcs.
mark_sp
I did all the tests with car on level ground with the handbrake on and the engine idling. I've checked again this evening now that the spheres have been in use for a few days and the results are the same.
I also re-tested the front with the handbrake off [rear wheel chocked] just to see if it made a difference, it didn't.
The push down tests are a bit crude and inconsistent so I'm not sure how seriously you should take them but good luck with the calcs.
mark_sp
Thank's, Mark.
I've test driven one Xantia MkII 1.8 16V today and also checked how much it dive. On the front bumper, it was almost ok, about 2.5 cm (450 ccm/50 bar spheres). On the rear bumper, interesting thing happened. Before turning the engine on, rear end dived only 1 cm under my weight (400 ccm/30 bar spheres), so obviously, spheres were on low pressure (the car was up - anti-sink worked). After we started the engine, it was different: at first, it also dived about 1 cm, but after 5-6 second, it gradually dived further, about 3 cm in total. So, obviously, anti-sink sphere can also be checked this way, as I thought: if there's no difference, it's flat.
Of course, you can't expect this method to be very precise, but it's enough as quick check.
I've test driven one Xantia MkII 1.8 16V today and also checked how much it dive. On the front bumper, it was almost ok, about 2.5 cm (450 ccm/50 bar spheres). On the rear bumper, interesting thing happened. Before turning the engine on, rear end dived only 1 cm under my weight (400 ccm/30 bar spheres), so obviously, spheres were on low pressure (the car was up - anti-sink worked). After we started the engine, it was different: at first, it also dived about 1 cm, but after 5-6 second, it gradually dived further, about 3 cm in total. So, obviously, anti-sink sphere can also be checked this way, as I thought: if there's no difference, it's flat.
Of course, you can't expect this method to be very precise, but it's enough as quick check.