924Board.org

[-nick]

I've been a fan of Koni's for a long time, just because you can adjust them. But, I know there are some Bilstein fans out there too. I've got a couple questions for you-

Do you know what spring rates the Bilstein's are rated for out of the box? There were a few options for the torsion bars (22m - 24.5mm for all the pre-'86 cars that use the same shock). Also, I haven't seen it confirmed but it appears the front spring rate varied a bit too (I think 140# is stock for the early 944's and I believe the 924 springs are a bit softer). So what matches with the Bilstein's?

My data point is an early light car with 200# front springs and 25.5mm rear torsion bars with yellow koni's all around. It feels great at events and on smooth roads, but it is stiff and light enough to skip over bumps on some of the weathered roads up here. Softening up the shocks makes it feel almost bouncy at highway speeds.

I'm thinking about using these springs rates on the much heavier 931. I think the extra weight of the 931 should match up to these spring rates pretty nicely.

My old koni's are just that- old. One of the rears and one of the fronts are weak (not bad considering the rears are ~15 years old and the fronts are 22!). So I'm thinking about what to replace them with.

I've heard bilsteins are valved a little stiffer than the stock shocks, but can someone give me some impressions of how they feel on stock/stiffer spring rates?

-nick

[Lizard]

never ridden with the Konis however the bilsteins are very nice, but I do like a harsh ride
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3 928s,

[-nick]

Harsh is fine, but when you skip over bumps you're also loosing traction = bad! You're running higher spring rates aren't you? Do the bilstein's control them well?

-nick

[Lizard]

actually the 931 that munk has now it has bilstein in it, and I would guess about 250# springs they are stiffer than the 220# that a 944 friend of mine has, and that car is an extremely well balanced car and is VERY flat through the corner, it has no problem with bumps at all and loosing traction
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3 928s,

[edh]

This may be a dumb question, but how do you stiffen up the rear when fitting stiffer front springs - otherwise you may get too much understeer

- is the best way to fit a thicker arb, or change the torsion bars?

- I'll be looking at this later in the year on my 924S (has no rear arb, so may have to swap torsion bars + arb anyway I guess)

Ed

[Lizard]

replace torsion bars to stiffen up back, or install a set of coil overs.
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3 928s,

[CBass]

Well, there are a couple ways to go about it. The general rule for production cars is running a stiffer spring on the front, and with a little stiffer front roll bar, so that the car won't spin out when average drivers push it hard.

My preferred method for a front engine card is running a significantly stiffer spring on teh front, about 15-25% stiffer after correcting for weight distribution and front/rear tire size differences. If you have a 100lb springrate at the rear wheels, 120 at the front, 200lb rear, 250 front, etc. To compensate for the understeer this will tend to cause, use a stiffer roll bar in the back, and stiffen the rear shocks. If you have two way adjustable shocks, set the front end rebound higher than the rear, with teh rear bound being stiffer.

The end result is a car that turns in very sharply, is prone to throttle off oversteer, but tends to understeer moderately under power. This setup is actually designed for inertia drifting at higher speeds, but it makes for an incredibly responsive car when using standard grip technique. This is definately not a good setup for a novice, as the tail will want to rotate under heavy braking. A good enough driver can manage the inertia properly when turning in, and be able to countersteer slightly and power out with very good exit speed.
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'81 931 in various states of assembly

[924RACR]

The Bilsteins currently available are the HD's - Heavy Duty. So they're a little on the stiff side, which should mean no problem handling a little bit extra spring/bar.

I have them on my 931, and do like them, although they might be a bit much for these lousy Detroit streets... might do better w/ stock or closer to stock stiffness, as that car is strictly a stock daily-driver and will not be getting modified. This car has never felt anything less than planted at speed (which are pretty high around here - speed limit is 70mph most places). Though I should add, if your alignment is off, that could contribute substantially to the car feeling bouncy at speed...
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Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype

[ljd 924SE]

konis are great for adjustability, but the effect wears off dramatically with age and the overally durability of the shocks is poor. also, the konis come from the factory slightly "miss-matched" with different actual damping rates varying as much as 15% for a set of 4 shocks. this is not so noticable on the street, but can ruin the balance of a track vehicle.

bilsteins on the other hand, do not have the adjustability, but are extremely durable and have extremely low variance from shock to shock.

i'm saving for a set of the HD's for my 924S sport edition. i'd go for the sports, but i think they'd be a bit much for the stock springs and torsion bars. i'm forced to keep the rest of the suspension stock to remain in SCCA E-stock for auto-x. if has a cheap source for the bilsteins, please share. the cheapest i've found is about $460 for the set of 4.
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'88 924S Sport Edition
http://www.cardomain.com/id/ljd924se

[-nick]

Is this from experience? Where do you get your numbers from? My current set of Koni's have been around for a _long_ time and the only problem I've had is that the rebound softens up as the seals wear out and leak. This is after decades of hard use on heavy springs. I have never heard of anyone complain about their durability (as long as the spring rates are reasonable). I haven't heard of anyone sending off a set after a few years use to get dynoed, do you have some data?

The impression that I've gotten so far is that Bilsteins probably have an edge over Koni's if you send them off to get valved for your particular spring rates. On the other hand, with Koni's you can experiment with springs and not have to have the shocks revalved each time to reap the most from the setup. For this reason, I decided to get a new set of Koni's over the Bilsteins.

The dyno comparison tests I've heard of (never seen) between the two have compared street Koni yellows with Bilstein race shocks. Big surprise, the Bilstein's came out on top! Otherwise, I haven't heard of any definitive tests one way or the other. I would love to know if there are some before I order a new set.

-nick

[CBass]

Koni's carry a lifetime warranty, if they have any problems, you send them back and they fix them.
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'81 931 in various states of assembly

[Lizard]

[CBass]

[-nick]

Too bad those warranties are only good to the original purchaser (he's probably died of old age by now!).

-nick

[Manning]

Yeah, I agree. Plus the fact that you have to yank the shock/strut out of the car and send it back to Koni to have them evaluate whether or not they deem it a warranty issue or not. What are you supposed to do in the meantime

Here are their guidelines:

1. Contact dealer from which shock absorbers were purchased, or to any authorized KONI distributor, or to KONI, 1961 International Way, Hebron, KY 41048, attention KONI Warranty, Phone: 859-586-4100, to obtain a Return Goods Authorization number.
2. Provide dated proof of purchase.
3. Provide copy of current vehicle registration form.
4. Provide your name, address, day phone number, make, model & year of vehicle and description of defect.
5. Return defective units) - (freight prepaid) - with all mounting parts and items 2, 3 and 4.
6. Upon determination of valid warranty KONI will repair or replace at its discretion.

I am on my second set of Koni Sports in 6 years, not including a set of old (though new in box) Koni Sport Hydraulics that blew out after less than a year. The current set is fried, but they were NOS as optional on our cars from the factory. Not much chance I can get those warrantied since Koni does not warranty their products if they came as OE on a vehicle. Here is their list of exclusions:

KONI makes no warranty for, shock absorbers that have been installed;
• Improperly;
• As original equipment on any vehicle except Ford Mustang SVO;
• On any vehicle that has been modified for a use other than or in addition to its originally intended use;
• For an application that is not specified in the KONI literature;
• On any vehicle that has been used off-road, for racing or for any other driving competition.

From now on Bilsteins. They are at least $30.00 less per strut insert too, so I'll wind up saving $60.00 buck over a pair of Koni inserts.
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Michael Manning
1988 924S Undergoing weight loss program