I am overhauling my entire suspension on my 1985 XJ6, and trying to figure out which shocks to buy.

So far, I have:
*Installed new upper shock bushing mounts (front)
*Installed poly steering rack bushings
*Installed larger/stiffer front swaybar with poly bushings (bar and end-link)
*Installed new front outer tie rod ends
*Replaced large and small radius arm mounts on IRS

In the near future, I am going to:
*Install poly upper and lower control arm bushings (already bought them)
*Replace IRS-to-chassis mounts (HD mounts from SNG Barratt)
*Install King Springs lowering springs, which are slightly stiffer and will drop ride height about 1-1.25" (already bought them)
*Replace any other wear-and-tear items as necessary (ball joints, inner tie rod end, etc)
*Install 17x8" wheels and summer tires

The car has an LS1 engine and 4L80E 4-speed automatic trans. I also have a supercharger from a Cadillac CTS-V that I'll put on this winter. After it's all said and done, the car is going to be back to its stock curb weight but with A LOT more power.

I have never driven a car with aftermarket Bilstein or Koni shocks. I know the Knoi shocks are adjustable, but must be removed from the car for adjustment. Given my modifications, you probably already guessed it - I am looking for a sporty ride that will perform well while being pushed, yet not beat me up during normal driving.

So, any experience with the Koni or Bilstein shocks? The Bilstein shocks are already expensive, but the Koni shocks are more - are they worth it?

BTW, I do not want a floaty cushion-soft ride. I know a lot of guys like that, but it's just not my thing. I like a refined, firm, connected feel that gives you great control over the car while allowing some forgiveness. I do not want a harsh grit-your-teeth full out race ride.

Thanks in advance!
-Dave

 

I haven't used Koni or Bilstein on a Jag, but have used them on several other German cars. My experience with Bilstein has always been that they are very stiff. Particularly in initial stroke, which tends to make the car fell all the little expansion joints in the road. Once you get past the initial stroke, then they just feel like a sporty shock. I'm speaking primarily about Bilstein HD and Sport shocks. The TC or Touring Bilstein's tend to ride smoother but don't handle as sharply.

Koni on the other hand, seems to provide a better ride quality while still delivering handling equal to the Bilstein's. The overall damping just feels firm but comfortable, not just hard and stiff. I recently put some Koni sports on a 1990 BMW 535i with the stock springs and the ride quality and handling were outstanding. I could roll over potholes with no fuss, but handling was greatly improved over stock.

Reliability goes to Bilstein, they are the most reliable shocks you can get. Koni are good, but nobody builds as reliable shock as Bilstein.

Having used both, I always go with Koni these days. However keep in mind that I have also noticed differences from car to car, with the same shock, so it's a bit of a black art to tune suspension well.

 

Thanks a lot for the info!

Also, it's worth mentioning that the shocks I am interested in (and the only ones available by each manufacturer for my car) are the Bilstein HD shocks and the Koni "Special D" shocks.

 

all the polyurethane bushes you installed will firm the suspension pretty good, if not harsh it, so you might start with cheap shocks and keep moving up to see which one you like.

my experience with Bilstein is also null & void, they are not exactly made for comfort. I had a Saab 900 Turbo which came with Bilstein from the factory and it was too hard on my back. Way too harsh. But so are Koni, not exactly a float-a-matic or marshmallow ride, and so are KYB, a cheap shock by any definition which they sell for a lot of money.

instead, I'm planning to order SPAX (UK) shocks, (google them), they are expensive but I drove a E-type with those shocks and I liked the ride very much. I'm not going to use the word "firm" or "harsh" but I'm going to use the word "refined". Not as firm as a Koni, not as soft as a Boge.

 

Shocks are a big purchase - I want to do my homework and get it right the first time! If poly bushings cause harshness, I'll replace them with rubber bushings.

I drove a 1986 Corvette with OEM Bilsteins. The ride was on the harsh side, though that could have had more to do with the stiff spring/light car setup. Then again, maybe the shocks were worn out, too.

What are some other details on the Koni car that you drove/rode in?

Yea, I checked out the Spax shocks. I think the ones offered for the Jag are "double adjustable." They seem to be in the same market as Koni - aftermarket, adjustable, high quality & price. However, I came across a few threads where people had failure problems. The failures were shortly out of the 2 year warranty period. Contrast that with Koni - it seems like Koni has a reputation for extreme reliability, and are also warrantied for as long as you own your car.

 

Koni, Bilstein, KYB = harsh. Firm shocks are always harsh. All shocks will fail at some point, the Bilsteins in my Saab leaked during and after the warranty (don't they always!). My XJ still has the original rear Girling shocks ("dampers" in UK), and they are fine, no leaks. I replaced the fronts with Boge and they were fine for a year, then they became marshmallows. Next time I'm going to try Gabriel or Monroe, cheep cheep, but that's what these cars came with.

I never have used Koni, (the adjustable type), but I know XJ owners who installed them and they complained that even in the "softer" setting, they were too hard for their XJ ride.

it's an issue of likes and dislikes, no shock/damper will give you everything you expect, it is always a compromise one way or another. it also depends on the use you are going to put the car through. Are you racing? are you cruising? or just city driving? If mostly city driving, where the shocks are not going to be put through their limits, any cheap shock will do, even Gabriels might be too harsh when you hit a pothole or a speed bump!

getting it right the first time? I doubt it, you'll find something you don't like no matter what you install, whether they are too soft or too hard.

and the reason Koni offers a lifetime warranty is that they don't sell them enough, so they have to entice buyers with something. but what good is a lifetime warranty if you don't like the shocks? will they refund your money if you don't like them? I doubt it.

if you install Konis, let us know what you think, I'm interested.

 

Hello:

The previous owner installed Bilstein HD shocks on all four corners of my car at great expense. The handling was great but it had a rather rough ride and every expansion joint sent a jolt through the car. After 5,000 miles I had them removed and replaced with factory units.
My car is dead stock and driven only about 4,000 miles per year. If I want a sporty ride I'll take my wife's AMG Mercedes.

Ryan

 

Interesting that I should find this thread. I have Bilsteins on my XJ40 and I like the handling. But there is a problem. I live in a State that constantly gets the #1 trophy for bad roads, add to that I live in an area of that State that gets little funding for roads. SO our roads stink. We have pot holes all over the place, we have waffling pavement at stop lights. Things are so bad that an attorney from on of those Brooks Brothers suited firms is advertising to start a class action for people who have been harmed by the bad roads.

This is anecdotal -- What I have found is that the Bilstein's may handle well but on my rough roads, you feel all the nastiness of the roads. I don't want to float but I don't want to feel every ripple in the roads.

I did some internet searches and apparently Bilstein's can have a reputation of being a bit firm. I like firm but man it sure jostles the teeth. I'm also wondering if the firm is the reason I eat through front shock bushings?

I really like a sport type shock but it is just getting to be too much jostling on my 1990 XJ40.

 

Thanks for the info! I am starting to lean away from the Bilsteins.

I can relate - I grew up in Western PA. The roads are terrible. In contrast, the roads down here in Virginia are amazing compared to the ones in PA. I smile every time I see a "bump in road" sign going through a VA construction zone - it's usually a just little bump. In PA, a "bump in road" sign means you're about to violently go over an 8" tall precipice.

 

Wait... are you guys sure you're not driving in Northern California???

 

But the roads look so nice in the "visit California" TV commercials!

Everyone in PA seems to think that roads are bad because of our (somewhat) cold winters and use of road salt, but I just don't buy it.

BTW, do you still have those Bilstein HD shocks, or did you throw them out?

I am cautiously considering KYB shocks, but I am afraid that they might be too soft. Don't forget, I'm setting my car up for 550+ hp with the torque of a root-style supercharger. You can get moving pretty fast in a short amount of time, and I want to make sure I can control it.

 

KYB makes a wide variety of shocks from mild to wild. Not sure what they presently offer for Jags but years ago it was merely their "base model" type shock.....which is an unremarkable shock and I found them to be a bit soft on my XJ6. I ended up going with Boge.

You might find that upgrading the front anti-roll bar and adding a rear anti-roll bar, while keeping OEM springs and Boge shocks , will give you all the extra controlability you want with minimal sacrifice of ride quality.

Add to that some good rack bushngs and 7" wide wheels that will support a decent tire and you might be surprised at the improvement....without increase spring rate or going to a stiff shock

Cheers
DD

 

Well, I already bought the springs, largely because my rear end was sagging and the springs were on sale. I just emailed the manufacturer to find out exactly how much stiffer the springs are.

Similar to what you're saying Doug - what I should do is perform all of my suspension, wheel and tire upgrades and then install the new springs with the old shocks and see how it feels. (The old rear springs just have to go!) This conflicts with my plan of doing the whole IRS at the same time, as I'll have to do the rear struts twice. Still, it's probably the best course of action.

 

How far north? I lived in Marin County and the roads did not even come close to being the piece of crap stuff in PA. Even up in Eureka they were fairly good.

 

Ya got that right! "violently go over an 8" tall precipice"

There is a bit of road I travel several times a day. Where the macadam meets the concrete roadway there is a big lip. I've measured it and the lip is almost 5 inches high. It is like flying off a sky jump.

Our problem is that most State funds go to Phila and Pitt. If you are in between, you must fight for the crumbs.