Koni or Bilstein ? Options

[Fazasport]

I am looking to replace the rear shocks and front strut inserts on my 1970 914. I will be using the car for tours, rallies, spirited driving and maybe an occasional Autocross not for track work. I am interested in a firmer ride than stock but not a harsh ride. The car does not have front or rear anti-roll bars currently.
If choosing between Koni or Bilstein which would provide the LEAST harsher ride quality?
I will also replacing the rear springs. With that in mind, should I stay with the stock 90lb springs or substitute that 100lb springs from the 914-6?

[mlindner]

Six years ago at the end of my 914-6 GT Tribute build I went with adjustable Koni shocks and springs from Ground Control. Just the perfect fit for heigh adjustment, order any spring rate you want (I did 150). I pushing 80, still an auto-x, hill climb and just a lot of high speed driving. Best, Mark

[Steve]

I tried both.. Koni's on the softest setting is a slightly better ride than Bilsteins. Also put the front sway bar on the softest setting for the street. I did learn the hard way that pot holes cause a harsher ride with a stiff front sway bar. I am running a 22mm Tarret bar on the softest setting.

[tygaboy]

I don't mean to get deep into suspension geek mode but as a point of potential interest: The Koni Sports are one-way adjustable for rebound only. So unless you re-valve them, you get the valving they come with. Meaning your ride quality is down to factory valving plus your chosen spring rate. That also implies that if you opt for spring rates "outside the normal range", you're headed into under- or over-damped territory. Not to scare you away from Konis as that's true for any one-way adjustable damper.
Just something to be aware of as you're setting your expectations.

And yes, I have those same shocks on my LS car. They work fine but where I typically drive, the roads have lots of chop and sharp-edged bumps. So on the Ferrari swapped car, I'm going all in on 3-way adjustable: high- and low-speed compression and low speed rebound. I'll be working with a suspension tuner, providing unsprung weights, corner weight and suspension motion ratio information so they can work out specific valving and spring rates for the car. Yes, complicated and more costly but I want as sophisticated a ride quality as I can get. I'll document all this on the Ferrari build thread and report back on "is the juice worth the squeeze?"

[Superhawk996]

I don't mean to get deep into suspension geek mode but as a point of potential interest: The Koni Sports are one-way adjustable for rebound only. So unless you re-valve them, you get the valving they come with. Meaning your ride quality is down to factory valving plus your chosen spring rate. That also implies that if you opt for spring rates "outside the normal range", you're headed into under- or over-damped territory. Not to scare you away from Konis as that's true for any one-way adjustable damper.
Just something to be aware of as you're setting your expectations.

And yes, I have those same shocks on my LS car. They work fine but where I typically drive, the roads have lots of chop and sharp-edged bumps. So on the Ferrari swapped car, I'm going all in on 3-way adjustable: high- and low-speed compression and low speed rebound. I'll be working with a suspension tuner, providing unsprung weights, corner weight and suspension motion ratio information so they can work out specific valving and spring rates for the car. Yes, complicated and more costly but I want as sophisticated a ride quality as I can get. I'll document all this on the Ferrari build thread and report back on "is the juice worth the squeeze?"

(IMG:style_emoticons/default/agree.gif)
Geek it brother

Nice to see someone talking sensibly.

[Cairo94507]

I am running Bilsteins all around, 140 pound rear springs, stock 914 (later) F&R sways bars, Elephant Racing rubber bushings, raised spindles by 19mm with turbo tie-rods and stock torsion bars. My car is about 1" lower than stock and I run 15x6 Fuchs with 195x65x15 tires, set at 28 pounds front and 30 pounds rear. Everyone who rides in it says it rides nice. We drive it exclusively on the street and I am not racing anyone. Importantly, when my wife rides with me, or on occasion drives, she says it rides nice.

Now, given all that, I still wish I had a bit softer ride; probably the old man in me. On my list is a set of Ground Control coil-overs for the rear as I would like to corner balance the car. Maybe I will go to a slightly softer rear spring when I switch to coil-overs. I could probably go to a 120 with no issues. Yeah, probably splitting hairs here. (IMG:style_emoticons/default/beerchug.gif)

[Jack Standz]

We too are running Bilsteins all around, 100 pound rear springs, stock 911 front and stock 914 rear sways bars, raised spindles by 19mm with turbo tie-rods and stock 911 torsion bars. Our car is lower than stock and we run 16 x7 front and 16x8 964 wheels (D90) with 185/50 front and 245/35 rear tires.

When first driving this combination (with new control arm and trailing arm bushings), it was awful. Very harsh. Did not like it. Now after around 3k miles, it’s much better. Street only, so maybe next time less rear spring and softer torsion bars.

However, the current plan is to restore our ‘72 to very close to stock, but with the addition of front and rear 914 sway bars, leave spindle height alone, stock 4 lug Mahle wheels, etc. Already have stock rear springs and shocks/struts all around, wheels, sway bars, etc.

[infraredcalvin]

https://www.elephantracing.com/914-suspension-builder/

I’ve always liked ER suspension builder as a starting point. Be honest with it as it’ll go sideways really fast on you. I’d say you’re probably looking at sport resto 1 or 2, it’ll recommend a setup and price it all out. Click customize and you can see exactly what it selected (spring rates, shock types, etc) add or subtract as you see fit.

[Fazasport]

We too are running Bilsteins all around, 100 pound rear springs, stock 911 front and stock 914 rear sways bars, raised spindles by 19mm with turbo tie-rods and stock 911 torsion bars. Our car is lower than stock and we run 16 x7 front and 16x8 964 wheels (D90) with 185/50 front and 245/35 rear tires.

When first driving this combination (with new control arm and trailing arm bushings), it was awful. Very harsh. Did not like it. Now after around 3k miles, it’s much better. Street only, so maybe next time less rear spring and softer torsion bars.

However, the current plan is to restore our ‘72 to very close to stock, but with the addition of front and rear 914 sway bars, leave spindle height alone, stock 4 lug Mahle wheels, etc. Already have stock rear springs and shocks/struts all around, wheels, sway bars, etc.

Jack Standz - My '70 has 4 bolt 5.5" wheels with 195-65-15 Michelin Defender tires, I will probably change them out for `85-70-15 Vedersteins at some point. Also down the road I may add factory 914 front and rear sway bars in order to reduce roll on the twisties.
You mentioned that you have stock rear springs and shocks on your '72. Does that mean Boge shocks and 90 lb springs?

[mepstein]

We too are running Bilsteins all around, 100 pound rear springs, stock 911 front and stock 914 rear sways bars, raised spindles by 19mm with turbo tie-rods and stock 911 torsion bars. Our car is lower than stock and we run 16 x7 front and 16x8 964 wheels (D90) with 185/50 front and 245/35 rear tires.

When first driving this combination (with new control arm and trailing arm bushings), it was awful. Very harsh. Did not like it. Now after around 3k miles, it’s much better. Street only, so maybe next time less rear spring and softer torsion bars.

However, the current plan is to restore our ‘72 to very close to stock, but with the addition of front and rear 914 sway bars, leave spindle height alone, stock 4 lug Mahle wheels, etc. Already have stock rear springs and shocks/struts all around, wheels, sway bars, etc.

OK. I'm certainly no suspension expert but in my opinion, it's not the springs that are making the car harsh. The 19mm and 100lbs were on a stock 914-6. That car didn't ride harsh. I have found that some Bilstein HD shocks are very stiff and hash riding but not all of them. Maybe they don't have good consistency or maybe there are different production facilities and they are assembled slightly differently. Maybe they just need to break in. I don't know. Your tire size is also extremely low profile. Cars form the 70's definitely used the higher profile tires for shock absorption.

I bet if you went to higher profile tires and got the existing shocks rebuilt with custom valving, you would transform the ride for the better.

[JamesM]

I tried both.. Koni's on the softest setting is a slightly better ride than Bilsteins. Also put the front sway bar on the softest setting for the street. I did learn the hard way that pot holes cause a harsher ride with a stiff front sway bar. I am running a 22mm Tarret bar on the softest setting.

(IMG:style_emoticons/default/agree.gif)

I have installed both in a good number of cars. Both are streetable but Konis on the softest seting are a bit more compliant.

Bilsteins are a bit easier to source these days but both are available. Without a full adjustable coil over kit the Bilstein rears are also more height adjustable.


22mm sway bar is to large for anything but track use, from a practical standpoint anyways. Had one on one of mine for 20 years paired with 180 lb rear springs, caused a lot of push in the front end during the tighter stuff while autocrossing.

[Jack Standz]

We too are running Bilsteins all around, 100 pound rear springs, stock 911 front and stock 914 rear sways bars, raised spindles by 19mm with turbo tie-rods and stock 911 torsion bars. Our car is lower than stock and we run 16 x7 front and 16x8 964 wheels (D90) with 185/50 front and 245/35 rear tires.

When first driving this combination (with new control arm and trailing arm bushings), it was awful. Very harsh. Did not like it. Now after around 3k miles, it’s much better. Street only, so maybe next time less rear spring and softer torsion bars.

However, the current plan is to restore our ‘72 to very close to stock, but with the addition of front and rear 914 sway bars, leave spindle height alone, stock 4 lug Mahle wheels, etc. Already have stock rear springs and shocks/struts all around, wheels, sway bars, etc.

Jack Standz - My '70 has 4 bolt 5.5" wheels with 195-65-15 Michelin Defender tires, I will probably change them out for `85-70-15 Vedersteins at some point. Also down the road I may add factory 914 front and rear sway bars in order to reduce roll on the twisties.
You mentioned that you have stock rear springs and shocks on your '72. Does that mean Boge shocks and 90 lb springs?

The '72 still has the shocks/struts/springs, etc. it was born with, but this car is a project and hasn't been driven for years, hence the restoration. Don't know the brand or rate, but won't be using them anyway. They will be replaced with new reproductions, but doubt they are Boge.

Edit to answer your original question about adding firmness without harshness:

That's a pretty subjective thing you're asking about. How can we know your perceptions to suggest how to proceed with our gratuitous suggestions? However, all the things we did to our '74 added firmness and, at first, too much harshness. Currently satisfied with its ride after breaking it in, so no changes other than new tires in the foreseeable future. Koni or Bilstein is your choice. Higher spring rates will add firmness, but you decide how much is too much. Higher rate torsion bars will increase stiffness, but at what point do they become too harsh?

[Jack Standz]

We too are running Bilsteins all around, 100 pound rear springs, stock 911 front and stock 914 rear sways bars, raised spindles by 19mm with turbo tie-rods and stock 911 torsion bars. Our car is lower than stock and we run 16 x7 front and 16x8 964 wheels (D90) with 185/50 front and 245/35 rear tires.

When first driving this combination (with new control arm and trailing arm bushings), it was awful. Very harsh. Did not like it. Now after around 3k miles, it’s much better. Street only, so maybe next time less rear spring and softer torsion bars.

However, the current plan is to restore our ‘72 to very close to stock, but with the addition of front and rear 914 sway bars, leave spindle height alone, stock 4 lug Mahle wheels, etc. Already have stock rear springs and shocks/struts all around, wheels, sway bars, etc.

OK. I'm certainly no suspension expert but in my opinion, it's not the springs that are making the car harsh. The 19mm and 100lbs were on a stock 914-6. That car didn't ride harsh. I have found that some Bilstein HD shocks are very stiff and hash riding but not all of them. Maybe they don't have good consistency or maybe there are different production facilities and they are assembled slightly differently. Maybe they just need to break in. I don't know. Your tire size is also extremely low profile. Cars form the 70's definitely used the higher profile tires for shock absorption.

I bet if you went to higher profile tires and got the existing shocks rebuilt with custom valving, you would transform the ride for the better.

Tend to agree with you. Stock 911 front control arms with 911 torsion bars added stiffness. The 100 pound rear springs probably not too much.

New struts, new shocks, and new CA/TA bushings added stiffness/harshness, but the car is quite a bit less harsh now after breaking in, but still definitely stiffer than stock. The front 911 anti-sway bar, probably not a big contributor to harshness.

Yes, the low profile tires probably increased harshness some, but the wide and somewhat sticky rubber with low side walls added to a new LSD in the restored 901 transmission, it was something that just needed to be explored (IMG:style_emoticons/default/biggrin.gif) . These tires are somewhat past their "sell by" date due to the length of time it took to get this car back on the road so are being replaced with 195/50 and 225/50.