Suggestions for softer Koni coil over springs on MKIV

[AdamIsAdam]

Hi,
I've got a new-to-me MKIV that I LOVE. What I hate are my NY roads! I don't generally shy away from stiff suspensions, but this car is so stiff that when I go over bumps, especially those "speed bump" type expansions in the road, it launches the car (and its occupants) into the air. I'm mostly worried about that happening mid-turn one day.

It looks like the Koni coil-overs come with 500# up front and 350# in the rear of my solid-axle 3-link. When I use ridetech's online calculator (https://www.ridetech.com/tech/spring-rate-calculator/), it's calling for about 275# up front and 225# out back (using their database for weights, not my actual car's weights yet).

My question to you is do you have known combinations that you can recommend as a good starting point? The car is mostly street driven. I LOVE the ride height. I don't know how much travel the wheels have and wonder if that's part of the reason for such a stiff spring from the factory.

Oh, and the car's steering is pretty twitchy, bordering on oversteer. It's got power steering, 17" Nitto NT01's (245 up front and 315 out back) and I have been running them at 19psi all around.

The engine is a 347 with a T5 and 3.55 gears in the solid rear as I said above.

Thanks in advance for any help.

Pics for attention...

[frankeeski]

Go with a quality spring from Eibach or one of the other manufacturers, quality matters. I ended up with #425 on the front of my own MK3 with #250's in the rear for the solid axle. I've used this same combination on numerous customer cars, primarily used for street driving. Firm, but not too firm. You may also find that 19 PSI is still a couple lbs to much in the rear with 315's. Best to used a laser thermometer measuring across the thread width immediately after a drive. You want an even reading across the width. If it's hotter in the center of the tire, you're running too much pressure. Adjust accordingly.

[AdamIsAdam]

Go with a quality spring from Eibach or one of the other manufacturers, quality matters. I ended up with #425 on the front of my own MK3 with #250's in the rear for the solid axle. I've used this same combination on numerous customer cars, primarily used for street driving. Firm, but not too firm. You may also find that 19 PSI is still a couple lbs to much in the rear with 315's. Best to used a laser thermometer measuring across the thread width immediately after a drive. You want an even reading across the width. If it's hotter in the center of the tire, you're running too much pressure. Adjust accordingly.

EXACTLY the type of specific advice I was looking for. A proven combination I can use as a starting point.

Is your experience with this combination with a big block or small block? My car is a 347 with very little options in terms of weight. power steering, manual brakes, no wipers, no heat, 17" wheels, etc.

So these?

https://eibach.com/us/i-551-eibach-coilover-spring.html
https://eibach.com/us/i-485-eibach-coilover-spring.html


It's been a long time since I built a suspension (30+ years) and those were not coilovers. Question: when making a change like this, as I understand it, I can maintain the same ride height I have now despite the softer springs so I can still clear my neighborhood speed bumps, but will I potentially have issues more often of bottoming out over big bumps? (I guess that's what the bump-stops are for ;) ) Is that more of an issue in a FFR Cobra - tire hitting inner fenders for example?