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Ask Dr. Koni
Last Updated: 11/16/2010
Author: Skip


Question: What's the difference between the red Koni and the Sport Yellow Koni?

Answer: The valving is different. Sport Yellow units have stiffer valving than their Standard Red cousins. Where both applications are available for your car, the Standard Red units would be best suited for primarily street driven cars where ride comfort is paramount. Sport Yellow units are best suited for applications where aggressive driving or track events will be undertaken. They are not, however, too stiff for street applications. Many of the factory Koni shock applications were Sport Yellow.

Question: I know my Koni's are adjustable for rebound, how much adjustment do I get and what's the best setting?

Answer: Generally you get 100% increase in the rebound forces from full soft to full stiff. There really isn't a "best" setting for your shock. Variables such as spring rate, sway bar size and track condition will all play a role in determining the proper rebound setting. Testing the different settings will produce the best rebound force for your car and your driving style.

Question: I've lowered my car, will my shocks still be ok?

Answer: Generally if you've not lowered the car more than 2 inches you'll be ok. If the car is lowered you may want to shorten the bump rubber a bit to regain some of the shock stroke you lost when you lowered the car. ALWAYS run a bump rubber, failure to do so will destroy your shock.

Question: Some friends told me I ought to put some type of coolant in my strut housing before I install the insert. What are they talking about?

Answer: It's a good idea, particularly if the car is tracked, to put a the strut tube prior to installing the insert. You can use a 50/50 mix of water and antifreeze or hydraulic oil. Many inserts that you remove prior to installing your Koni's, will leave hydraulic oil in the tube. You can use this oil or the antifreeze mix. You'll want the coolant level to be about 2/3 of the way up the insert. It won't take much fluid because the insert will displace most of it. Use the dipstick method to check the level of the fluid. A paper towel can be used to soak up excess if needed. Never run straight water in the tube as if may freeze and collapse your insert.

Question: I see all of this stuff about needing to know what kind of strut you have, yellow, red, black and such. What's up with that?

Answer: Many Porsche(TM) models feature rebuildable front McPherson struts. These models can include 911,912 and 930's up to '89: all 924's and 924S's, all 914's and many of the normally aspirated 944's. Porsche(TM) has used several different OE suppliers for these rebuildable struts. They include Koni, Bilstein and Boge. The color of the front strut (assuming it hasn't been repainted) will indicate which strut you have. Red will be Koni, Green will be Bilstein, and Black will be Boge. A further indication will be that the gland nut (the screw on cap that holds the insert in the strut housing) will be a fine thread on a Koni strut and a coarse thread on the Boge strut.

Question: Ok, how about this, my 911 has a black strut housing but the upper dust cover is green. What's this, a Bilstoge?

Answer: No, genetic engineering hasn't taken over! Bilstein supplies new dust covers in their characteristic green when you buy their inserts. What we have here is a Boge strut that has had a Bilstein insert installed.

Question: What a rip, my 911 has original Koni struts and many places are telling me the only thing I can install are hydraulic, standard adjustable Koni inserts. Seems strange that I have the wiz bang original Koni strut and I can't even use Koni's externally adjustable gas insert.

Answer: This used to be true. We were able to modify the gas insert to fit original Koni struts (at extra cost) but recently Koni made everyone's life much easier. A change in the design of the insert will now allow you to utilize the externally adjustable gas insert in your original Koni strut. You do have to use the correct production date insert though.

Question: Hey, you guys told me there wasn't an externally adjustable shock for the rear of my 911, I've heard there is.

Answer: What we probably said is there isn't an externally adjustable gas shock for the rear of a 911. There is the 8210-1159 Sport unit which is an externally adjustable hydraulic unit. We don't usually recommend it because it's valving is on the soft side. If you have a stock torsion bar early 911 it will work fine, but we don't recommend it on the later, heavier cars, especially if they've installed larger torsion bars.

Question: I've seen other advertisers listing a racing insert for the front of the 911 and 914. What are they talking about?

Answer: The 8610-1159 is an externally adjustable hydraulic Koni racing insert that can be used in many different types of cars. It features 50/50 valving and shorter length. In the 911/914, it will only have an advantage in a shorter strut tube. If your class rules allow you to shorten the length of the strut tube, this insert may be for you.

Question: Do I have to get an alignment after I install shocks on my 911?

Answer: Only if you've changed the ride height. High pressure gas shocks (like the rears on a 911) can tend to raise the ride height of a car a bit. Although we don't have too much problem with this, it does happen. Periodic alignment probably isn't a bad idea, but merely installing new inserts and shocks won't change alignment settings unless ride height is altered.

Question: Wow, I've noticed a big price decrease in the front strut for the C2/C4 and the 993. What happened?

Answer: Koni recently released the externally adjustable gas 8641-1365 Sport insert for these applications. This is a special insert that is bolted into your stock strut housing after cutting it open. It sounds intimidating, but it's really not difficult. Complete instructions are included in every language known to man.

Question: I bought a set of 911 struts to go on my 914, what insert should I use?

Answer: Dimensionally, the 911 and the 914 insert are the same. The difference is in the valving. Many shock companies use the insert for both the 911 and 914 (read lower cost to them) but Koni has designed different valving for each application. So if you're installing 911 struts on your 914, you'll still want to use the 914 Koni insert. If you're installing the 914 insert into a 911 Carrera strut, please ask us to include a special centering washer that these later struts utilized.

Question: Do I have to get an alignment after I install shocks on my 944?

Answer: Yes and no. When you remove the front strut on your car you have to reset the cars camber. The strut is held to the spindle with two bolts, one being an eccentric that controls camber adjustment. Replacing the rear shocks won't affect your alignment unless you've also changed ride height.

Question: There's all this talk about some of the 944's having rebuildable struts and some not, how do I know?

Answer: Generally it works like this, '83-'86 normally aspirated 944's will have rebuildable struts. Beginning in '87, many of the normally aspirated cars had sealed struts. All 944S, 944 Turbo and 944 S2's had sealed struts. You can verify the rebuildable/non rebuildable status by taking a look at your strut. On rebuildable struts there is a screw on cap that holds the strut insert into the strut housing. Take a look at your strut. We want to look at the point where the shiny piston rod goes into the lower strut housing. You may need to stick your fingers inside the spring and push up the plastic dust cover that protects the piston rod. Ok, like I mentioned earlier, if you have a rebuildable strut there will be a screw on cap on top of the strut housing. You will know it's screw on because you will see a few threads visible on the cap. Non rebuildable struts don't have a screw on cap, they will have a silver colored cap that will be "crimped" over the top of the strut housing. Rebuildable struts can utilize a replacement insert whereas non rebuildable struts must be replaced with another sealed strut unit.

Question: I've got a 944 Turbo (non S), can I install the ride height adjustable Turbo-S front strut on my car?

Answer: But of course! Although the original Koni application on these cars was single adjustable for rebound, the unit Koni is now building for us is double externally adjustable (bump and rebound) as well as maintaining the ride height adjustment. These units ran a conical shaped spring so you'll have to secure a set of the factory springs or Turbo Cup Units listed in this catalog, or you can convert to our 944 ride height adjustment kit which will give you unlimited spring rate choices. Koni assumes that you're installing this unit on a car that already has the ride height adjustable unit on it so you don't get the lower spring perch and jam nut. The additional parts you will need to source from Porsche are:

 944.343.531.01  Factory Spring (or other listed above)
 951.343.525.32  Lower Spring Perch
 951.343.524.00  Lower Jam Nut
 133.412.341  Upper Perch

Question: Changing torsion bars on a 944 is a real bear, does Koni have a coil over shock for the rear of my car?

Answer: But of course!  These shocks are Koni 3012's which are aluminum bodied, high pressure gas monotube units that run inverted for better unsprung weight. Each unit weighs only 3 lbs.! You can purchase these units on our main page.

Question: Can I get the new Koni 28 series racing dampers for my Porsche?

Answer: Yes, but so far only for the 924/944/968.  These dampers are the pinnacle of Koni racing development.  Koni 2812 racing dampers are in use by top Formula One and Indy Racing League teams.  Modified versions of the 2812 and the 2816/2817 struts are used by top European and Asian Series Touring Cars.  Koni 28 series dampers are monotube high-pressure gas shocks and feature a height-adjustable coil over body and damping adjustments for both bump and rebound (8 clicks each, individually adjustable).  These dampers are built to order... Please call for more information (361.289.8834)

Question: I hear that Koni discontinued the sealed strut application for 944's and 968's.  Is there another Koni Sport I can use on the front of my sealed strut car?

Answer: You heard right.  Koni discontinued the 8641-1136S in favor of a more affordable alternative.  The replacement 8641-1414S is a strut insert specifically designed to be installed inside the sealed strut housing.  This is the same action that was previously taken with 964's.  The advantage to the buyer is a reduction in price of approximately $100 per strut.  The modification to the strut is easily accomplished by a novice, and requires only basic tools (bench vise, hacksaw, drill, file, wrenches).

Question:  I'm having a problem with the Koni Struts that came with my car.  Does the lifetime warranty cover them?  Do you guys handle warranty work?

Answer:  It sounds like you may be referring to Original Equipment Konis (as came with the car from the factory as an option code or group).  Unfortunately, these are not covered under the lifetime warranty.  OE Koni shocks and struts are only covered for the period of the manufacturer warranty (3/36, 5/50, etc).

If not, and these are Konis that you purchased and have the receipt for, we would direct you to Koni North America headquarters in Hebron, KY.  You can find all of their contact information and warranty policies at their website,

Unfortunately, we do not deal with warranty service on Konis in the manner you suggest.  One reason is that Koni themselves test every returned shock to assess the cause and type of failure.  In some cases, the refund, rebuild or replacement will be prorated based on their findings.

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