Volvo C70 2.5T Coupè 1998 Suspension Comfort Problem

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I bought ZF SACHS MADE IN GERMANY shock absorbers with original boxes and codes and hologram quality, ordered from Germany. Good driving dynamics (but so was the original Volvo Sachs with over 200,000km). comfort remained poor. KYB springs with part number same as original Volvo springs, no difference.

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I attach pictures of my shocks absorbers (front + rear).
I show one shocks absorbers for axle.

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Originally Posted by SteveSarre

On your 205/55 R16 Dunlop Sport tyres what is the air pressure?

Steve

Volvo label on side of door say: 2.2bar front and rear (for light load).
I try 2.2, 2.5, 3.0bar, but not change comfort. Suspension not have travel and not have stop.

Now as my previous message i have Sachs Made in Germany shock absorbers with some code of original Volvo Sahs 1998, and Kyb springs mark as equivalent code of original Volvo.
Handling? Perfect (but too with old shock and springs)
Comfort? Poor (as old shock and springs)

Solution:

1

If i'll buy Shock absorbers and springs of C70 Cabriolet Comfort Chassis?

My C70 is Coupe with Dynamic Chassis (Coupe not exist with Comfort Chassis)

2

If i'll buy Koni Special Active Shock Absorbers and leave actual KYB springs?

Goal: dramatically improve comfort.

[tony209]

That is the chassis set up I have on my T5 cabriolet, koni special active shocks and KYB springs, it works really well although the front is still a bit too firm with the KYB springs. KYB front springs are 442mm compared to 460mm stock(dynamic) and rears are 400mm compared to 430 stock. I removed the KYB rear springs because they are too low and make the front very light - so light I had to lower the pressure in the tyres. With the KYB springs on the front and standard height springs on the rear, the front is too low and probably the reason why the ryde is too firm. When the weather improves, I'm going to put the correct height dynamic springs back on the front and see what the ride is like.

I can highly recommend the koni active shocks, it's just a mater of getting the right springs. I have had a chat with a KYB engineer, he was a bit surprised (and concerned) to hear that the KYB rear springs effect the ride height of the front! I think the KYB rears would have been better if they were 410 - 420mm

A big problem with the C70 is the front is too heavy and therefor requires a stiff spring. I have a P2 V70 and the ride is superb, it's a very similar set up to the P80 but it's a lot lighter at the front, aluminium bonnet and battery moved to the rear. Also, it looks like Volvo tilted the engine slightly to the rear shifting some weight off the front axle.

What size wheel do you have? These cars were designed to have 16" rims, a larged wheel diameter and lower profile tyres will give a firmer ride.

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The space between the tire and the wheel arch is currently quite large. I don't think the KYB have lowered the set-up, quite the contrary! However, I will purchase the Koni Special Active. At the time of replacement together with the mechanic we will measure the total height of the original Volvo Dynamic Chassis and KYB springs. How can I assess if the original springs (which I have removed and kept) were still good or worn out? The original Volvo springs had about 220.00km.

[tony209]

These are the KYB springs I have:-
RC5923 rear 400mm (stock 430mm)
RA3789 front 442mm (stock 460mm)

These springs are recommended for both the coupe and the cabriolet. I removed the KYB rears because the ride was too firm, although the lower rear ride height improved rear visibility!

I fitted Suplex 38100 springs at the rear as these are the the original stock length (430mm).

With the KYB springs on the front and the Suplex on the rear, the ride height at the front is at least 18mm lower than factory and possibly more than that due to more weight being transferred to the front.

Below is a comparison of the Suplex rear spring (left) and the KYB rear spring - if I still have the original Volvo rear spring, I'll take a comparison picture but I can assure you that the Suplex and the Volvo are the same length.

When I swap the KYB fronts, I will take a comparison picture with the Volvo original dynamic (brown) spring.

I don't know what the spring lengths are for the factory lowered dynamic springs but I would suspect that KYB used those figures.

Regarding the Koni special active shocks, they do say that they are not suitable for lowered ride height, not sure if this includes factory lowered or just refers to aftermarket lowering.

If you decide to buy the Koni shocks, I would suggest you buy the fronts first, I didn't find any difference in fitting the rears and even Koni suggest that you can fit the fronts only.

I still thing the biggest problem with the C70 regarding the firm ride is due to the high weight at the front. The car was designed by TWR (Ian Callum) but I think they were limited to what they could change with the P80 chassis.

The P2 V70 (Y2 chassis) is much lighter, front tyre pressures are 31psi compared to 35psi on the C70. The P2 chassis is so well sorted that when I changed from 15" wheels with 195/65 tyres to 17" wheels and 225/45 tyres, there was no difference in ride quality.

[EgilsSilins]

Hi Tony209 and others!
I hope that everything ended up good with spring replacement.

At the moment I am at the same situation and I am still wondering what springs do I have to install at rear for the best possible performance. Basing on your posts looks like 430mm (Sachs) is much better than KYB/Lesjofors 400mm springs.
I will not replace the rear shocks, just springs.

Could you tell me how the replacement ended up, please?
I would appreciate if you could share picture with new springs installed at rear end.

Thanks!

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My coil springs:

front: KYB RA3789 442mm (data from KYB website)

rear: KYB RC5923 400mm (data from KYB website)

Comfort? Poor. But i guess the guilty is from Sachs Shock Absorbers.

I have the old original Volvo springs front and rear. If i want i can reinstall it. But comfort not is different with KYB instead Volvo OEM.

[EgilsSilins]

Thanks!
Could you tell me what the distance is at front and rear with KYB springs measuring between wheel center and wheel arch.

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In next days i'll take misure from center hub to upper height of arc.

About comfort of C70 i have an idea:

A friend of mine did me a favor a few days ago: he tested a Volvo C70 I in Canada to see the level of comfort. He told me it was super soft. Softer than its XC70 III. So now try to get photos of the trim code shown on the plate near the battery compartment. Then they proceeded to order springs + shock absorbers + any bump stops and original Volvo Canada supports specific to that set-up. I need to make the C70 I a comfortable car.