Changed suspension - have questions

I changed my stock 91 suspension as follows:

15mm front and 25 mm rear Ichiba spacers on 15/16 OEM wheels.
98 oem dampers mounted with Tein S-Tech springs.

So the car is a bit lower and stance a bit wider.
The rear camber is more negative than the 93 factory settings due to the lowering springs.

The result:
The ride feels softer than with the stock 91 dampers/springs.
The car seems to be leaning more in turns.
It also feels less stable while cornering over bumps.

I'm not a track person nor a particularly fast driver.
Could use some comments from those knowledgeable about suspensions.

Were the 98 dampers new when bought? Not sure if the tein type s springs are progressive or linear but assuming their stiffer than stock 91 springs the only thing is the dampers.

Sduff@Composites said:

Were the 98 dampers new when bought? Not sure if the tein type s springs are progressive or linear but assuming their stiffer than stock 91 springs the only thing is the dampers.

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Stephen, the 98 dampers had 35k miles on them, no leaks.
I believe the Tein S-Tech are progressive.
Do you think the progressive rate on the Tein is different from the oem springs?
I've used this page from Dali for some data:
http://www.daliracing.com/v666-5/catalog/suspension/more_springs_matrix.cfm

from that chart you have taken a step down in performance..the tein springs have lower weight ratings(softer) esp the front.Why not just use the oem springs with bilstein dampers.

docjohn said:

from that chart you have taken a step down in performance..the tein springs have lower weight ratings(softer) esp the front.Why not just use the oem springs with bilstein dampers.

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Doc
The chart says my 91 oem springs were 170 lb/in front and 220 lb/in rear.
The Tein S-Tech are 224 lb/in front and 246 lb/in rear.
Doesn't that mean the Tein are firmer?

JD Cross said:

Doc
The chart says my 91 oem springs were 170 lb/in front and 220 lb/in rear.
The Tein S-Tech are 224 lb/in front and 246 lb/in rear.
Doesn't that mean the Tein are firmer?

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yikes you are right..I don't know what the hell I was looking at..maybe the fact that you mentioned 98 dampers got me wacked up....if body roll bothers you get a thicker frot swaybar....or try bilstein shocks with the tein.

No idea... Just test this and tell us what you think.

Remove the spacers and ride exactly like you did before with with just the suspension setup changed. I doubt the spacers have anything to do with it but who knows. The slightly wider stance could be throwing you off and be the cause of what you feel?

I never like buying used shocks. I agree with Sduff - remove the spacers and report your findings. I also agree I don't think the spacers are the problem and would bet on old, worn out shocks.

As I think I mentioned before, according to the NSX Wiki, the NSX-T suspension is softer than the Coupe suspension. From what I remember, I'm pretty sure you bought 1998 NSX-T struts.

http://www.nsxprime.com/wiki/Model_Information
"The NSX-T also has different suspension rates than the coupe. At low rates of wheel travel, T front rebound and compression rates are 7% softer. At higher rates, T rebound is 21% softer, compression is 32% softer. At high rates, T rebound is 15% softer, compression is 21% softer. Rear suspension varies similarly..."

Hapa88 said:

As I think I mentioned before, according to the NSX Wiki, the NSX-T suspension is softer than the Coupe suspension. From what I remember, I'm pretty sure you bought 1998 NSX-T struts.

http://www.nsxprime.com/wiki/Model_Information
"The NSX-T also has different suspension rates than the coupe. At low rates of wheel travel, T front rebound and compression rates are 7% softer. At higher rates, T rebound is 21% softer, compression is 32% softer. At high rates, T rebound is 15% softer, compression is 21% softer. Rear suspension varies similarly..."

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Adrian
According to the Wiki here: http://www.nsxprime.com/wiki/Suspension the 97 dampers appear to be firmer than the 91 dampers.
Which one do you think is correct?
Or am I reading it wrong?

JD, you said this back in June. What's changed?

JD Cross said:

The 98 T- dampers and Tein S-Tech springs are on now.
The car is about 1" lower which looks better.
It feels like T dampers have a firmer compression rate compared to the 91 OEM dampers, likely because they are rated for a slightly heavier car.
The springs are slightly firmer too.
The car feels tighter all round and the ride is not tooth rattling.
I think this is a good low cost suspension refresh.

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Anyway, I did more research and for the 1995 NSX-T Car & Driver said "Suspension gets slightly softer", but in 2002 it also notes a suspension revision.
http://blog.caranddriver.com/origin...gined-supercar-for-the-price-of-a-new-accord/

Other websites agree, while others point to the suspension page you mentioned.

I really don't know now JD, can you expand on why in June you felt it was stiffer and now it feels softer?

Hapa88 said:

JD, you said this back in June. What's changed?
Anyway, I did more research and for the 1995 NSX-T Car & Driver said "Suspension gets slightly softer", but in 2002 it also notes a suspension revision.
http://blog.caranddriver.com/origin...gined-supercar-for-the-price-of-a-new-accord/
Other websites agree, while others point to the suspension page you mentioned.
I really don't know now JD, can you expand on why in June you felt it was stiffer and now it feels softer?

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Adrian
I've been driving the car more spirited lately and now it feels softer supporting your data on the 95 on softer suspension
Reflecting on my earlier comments I'm thinking the only thing that's changed is I'm 67 and it's all in my head :smile:
Thanks for your patience and help
Jim

Adrian
I may have another point of view on the suspension
I've added 25 mm to the length of the rear suspension member with the wheel spacer.
This effectively increases the length of the lever acting against the resistance of the spring.
I don't have the length of the lower suspension arm but let's say it's 16 " from where it bolts to the frame to the wheels studs.
That's about 400 mm stock
By adding a 25 mm spacer I've increased the length of the lever to 425 mm which increases the force exerted by the moving wheel by over 5 %.
This would explain the suspension feeling softer as the spring would be compressed more by wheel motion.

Does this make sense?

It does but widening the track width increases the distance between the tires contact patch and the center of gravity which has the effect of reducing body roll.

Another thing to consider is driving the car harder will make the car move around more than taking it easy.

stuntman said:

It does but widening the track width increases the distance between the tires contact patch and the center of gravity which has the effect of reducing body roll.

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Why isn't body roll a function of the vertical distance between the center of gravity and the roll center (and thus not dependent on track width)? No doubt increased track width minimizes weight transfer because an equivalent weight transfer creates a larger torque about the longitudinal axis, but that seems unrelated to the motion between the sprung and unsprung sections.

Reducing weight transfer reduces body roll. The question becomes whether the reduction in weight transfer and body roll overcomes the increased leverage on the spring.

Edit - As you know any change in a single aspect of suspension has many secondary effects to the rest of the system. For example, increasing weight transfer with a stiffer swaybar or raising the roll center will both reduce roll, and that goes against what I just said.

Holding everything constant, increasing the track width should decrease body roll because as the wheels get further apart, it creates a larger moment arm resisting roll for the same wheel rate. It all depends on the geometry of the suspension since sometimes increasing track width ends up hurting your motion ratio and reducing your wheel rates, so you might end up loosing what you gain. But ignoring that - for the same wheel rate you will get less roll on the car with a wider track.

For the OP, I believe the loss in motion ratio will be much smaller than the gain you get from track width in terms of roll stiffness. I would therefore think that you would still get a reduction in roll even if the motion ratio got worse with increased track.


Now if you look at the whole picture for the OP, he lowered his car (lowering the CG and RC), changed the spring rate (increased), increased the track width, different dampers (which could be the issue with not enough low speed damping), and drove his car harder (which alone could be what he's feeling, on top of that everything he did should increase the cornering ability and peak lateral acceleration of his car).

Stating something does not make it true.

The body roll should remain constant with spacers. That same compression of the springs is balanced by a lower weight transfer than before because of the increased track width.

Draw a force diagram. Track width has no effect on body roll other than a change in roll center and that change, it seems to me, should be very small.

The vertical compliance will likely increase due to the change in suspension geometry.

Edit: It occurs to me that the effect of tire compliance on the roll stiffness will change with track width, exactly as Billy suggests. But in a road car, I imagine tire compliance is a relatively small contribution to body roll as compared to suspension compliance.