Bilstein VS Koni Options

[naro914]

Our autocross/hillclimb/street/fun/ whatever car Huey has Koni adjustables around, 225 lb springs, 21mm torsion bars, and whatever Weltmeisters big front roll bar is, no rear roll bar. 3.2 engine, 245/16 tires around. Car handles PERFECT. Autocross, hillclimb, and through the mountains, it’s predictable and confidence inspiring. Around town it’s definitely stiff, but not harsh at all. I wouldn’t change a thing.

This is great to hear. What are you running for a- arm bushings? I hear that can make a difference too.

And are you running Koni reds or yellows?

Ah....good question!
Elephant Racing Polybronze bearings... and yes, supposedly they do make a difference.

https://www.elephantracing.com/porsche/914/...914/polybronze/

[sixnotfour]

big dif in valving

[Justinp71]

Some one told me the Koni's are better for a mostly street car because they absorb the small bumps better with the dual tube design. Has anyone had experience with this?

[AnthonyM]

The two brands offer 2 different technologies for stock bolt in configurations. Twin Tube (Koni) vs. Mono Tube (Bilstein). Mono tube dampers have a larger piston than twin tube and depending on valving, will begin to create force at slower shaft speeds. Koni's have a separate foot valve at the bottom of the inner cylinder that creates compression force and not at the piston. The Bilstein/Mono Tube damper creates compression and rebound force at the piston. When adjusting a Koni, you are only adjusting the rebound forces and not compression. So yes, some people may say that a stock Koni may be "softer" over small bumps than a Bilstein.

[Cracker]

On my track-oriented 914, I have had both and much prefer the Bilstein shocks. Unfortunately, I have the Koni's on the all four corners at the moment - that will change. The Koni's ARE noticeably softer...for a street car go with the Koni.

T

[Mblizzard]

To be clear I am not a suspension expert and most of what I have here came from reading various sources and certainly is more of opinion than fact.

First I think having an adjustable suspension is a must if you want to control how your car behaves. But if you want a solid and well proven solution it is hard to look past Bilstein. Adjustable components are very useful in dialing out over steer, or under steer, increasing handling characteristics, and getting a better balanced car. So that is the choice I made.

There is not a one specific setting on an adjustable shock that makes all 914s handle well and there is no non-adjustable shock that is perfect for all 914s.

If you have adjustable shocks you need to understand what you are adjusting.

Typical "street" applications use either 1-way adjustable or 2-way adjustable shocks.

1-way adjustable changes the rebound only. 2-Way adjustable can be adjusted for bump and rebound. During bump, the shocks and springs absorb the upward movement from cornering or the road. Rebound is when the shocks extends back to their original positions using up the energy from the compressed springs.

Most Konis are 1-way (8010, 8041, 8210, 8241, 8610, 8641, 8710, 8741 Series). 2-way Konis includes 8011, 8042, 8211, 8212, 8242, 8611,8711, 8742 Series.

So you have to understand with 1-way adjustable you are only controlling how quickly the shock returns to its original position. That means too stiff of a setting and it is possible shock movement wont keep up with changes in the road surface = tires lose contact with road. Too little rebound stiffness and you ride waves of oscillation after each bump.

I have the Koni 1-way 8641-1077 Sport shocks on front and rear so I will discuss those. If you are advanced enough have purchased the 2-way you likely know this already!

While this is simplistic and there are many more factors to consider, this is a generalization of what happens when you play with the rebound stiffness on the front and rear.

Front rebound increase = More Under steer
Front Rebound Decrease = More Over steer
Rear Rebound Increase. = More Over steer
Rear Rebound Decrease. = More Under steer

So while we all want to crank up the settings to 11 (Spinal Tap reference for the young ones) and drive like hell. However, depending on your car, that might not keep the handling of your car consistent.

You can see that either increasing/decreasing rebound at both the front and rear tends to have a canceling effect. But depending on your sway bar, springs, ride height, and many other factors I don't claim to understand, it is possible that for the best or most neutral handling car, taking the approach of simply dialing everything up to 11 may not be right for your car.

I had been keeping notes on the changes I made on my car and found a slightly softer setting on the rear than the front kept the over steer more in check. So if you have adjustables resist the temptation to immediately go to the max as you will likely find that is not the best setting.

Of course now that I have added adjustable front shocks, adjustable sway bar drop links and rear sway bar I get to start all over.

[Justinp71]

Thanks guys! All points noted. Great info Mblizzard.

I love how the 914 is like a street legal race car, that if I want I can even take it to the local race track! So much fun...

I was surprised I was recently on the track with many modern cars (focus rs, wrx, genesis, newer mustangs) and I got my butt kicked. Even though I got a good power to weight ratio I have a lot to make-up in suspension and braking (and seat time too). None of those cars really interested me, but I would like to get it a little more dialed in and go back to hang with them better. It was cool though, many people there were enamored with the nostalgia of my 914. Part of my problem was I was to worried to wreck the car, so didn't want to push it too hard.

[Mblizzard]

Thanks guys! All points noted. Great info Mblizzard.

I love how the 914 is like a street legal race car, that if I want I can even take it to the local race track! So much fun...

I was surprised I was recently on the track with many modern cars (focus rs, wrx, genesis, newer mustangs) and I got my butt kicked. Even though I got a good power to weight ratio I have a lot to make-up in suspension and braking (and seat time too). None of those cars really interested me, but I would like to get it a little more dialed in and go back to hang with them better. It was cool though, many people there were enamored with the nostalgia of my 914. Part of my problem was I was to worried to wreck the car, so didn't want to push it too hard.

Worrying about wrecking the car is a good thing..

I learned a lot about what I was doing wrong and greatly increased my understanding of how a car works by reading How To Drive by Ben Collins aka The Stig.

No magical secrets just sound fundamentals we all should review.