Struts - Inserts or premade?

[dyoungre]

I'm planning on using Koni Yellows, of some varient, in a new build. A common option is a tubular strut housing that can take either Bilstein or Koni inserts (8610 or 8611). I could also go the route of a Koni 8742 (essentially an 82 series Koni with purpose built attachment flanges).

I see trade-offs to both approaches. With a tubular housing, you get a high quality, stiff housing made specifically for racing. With a factory built Koni strut, you get lower weight - No outer tube, no gland nut... and potentially, better heat transfer.

Now I would think that the insert approach might give more durability, as it protects strut tube from bending ... but does that just mean that the rod will get damaged instead of kinking a tube?

Am I missing any other pros/cons? With a clean sheet, which way would you go?

[Z3_GoCar]

Hey Dave,

With the standard internet warnings such as YMMV. I use a coil-over set designed specifically for my car from TC Kline. This setup is similar to your second option of with the custom brackets weled on the outside. One item to note is that you'll probably be running higher spring rates than street, so no matter which way you go you'll want the damping range re-valved to deal with your higher spring rates. Have you looked at the online catalog from Truechoice? I've not delt with them, only TC, Mark, and Pete who have all been fantastic. Lots of stuff to drool over there...

[924Guy]

I'd agree with the expectation of better heat transfer...

But with a clean sheet, I'd avoid the Konis unless there was no other way... just haven't heard anything good out of their durability in IT cars.

Of course, I have to admit that I'm building my DSR up with Konis, but that's a different story. ITB car is Bilsteins all around, and can go for years without a rebuild...

[tom91ita]

I'd agree with the expectation of better heat transfer...

But with a clean sheet, I'd avoid the Konis unless there was no other way... just haven't heard anything good out of their durability in IT cars.

Of course, I have to admit that I'm building my DSR up with Konis, but that's a different story. ITB car is Bilsteins all around, and can go for years without a rebuild...

wow! have not heard about any thing bad about konis bad on IT cars. i do know of some that failed because there was not enough travel but i consider that a user error and not a koni failure.

but my humble crx is not as fast as certain 924's..........

for heat transfer, i have always heard that you want to fill the void with an oil or ATF or something so you don't have an air gap.

i have never needed my koni's rebuilt but they were dynoed, serviced and revalved once for free when i was at the NASA Nationals. that was part of the Koni service while they were at the event.

[dyoungre]

Since it is a clean sheet, I would have the struts valved for 600 lb springs. I've been in communication with Truechoice, thanks. I've always used low weight oil (10w) to cool the cartridge, but not having the outer housing would be even cooler. I used Koni's on my last car, no problems, and just don't have experience with Bilsteins. I could probably flip a coin between the two brands, but it really depends which brand can provide more support / advice (and that includes peers at the track, and which brand they are more familiar with).

So my question isn't so much which shock model to use, but which mechanical design has more merit over the other - insert or 'stock' strut body.

[trhoppe]

I'd agree with the expectation of better heat transfer...

But with a clean sheet, I'd avoid the Konis unless there was no other way... just haven't heard anything good out of their durability in IT cars.

Of course, I have to admit that I'm building my DSR up with Konis, but that's a different story. ITB car is Bilsteins all around, and can go for years without a rebuild...

Really? Odd. I haven't heard a single problem. In fact, I don't know of anyone else other then SM guys using anything other then a Koni. By far the best double adjustable option out there ;)

-Tom

[924Guy]

Really? Odd. I haven't heard a single problem. In fact, I don't know of anyone else other then SM guys using anything other then a Koni. By far the best double adjustable option out there ;)

-Tom

OK, you keep on keepin' on... ;)

Coupla years ago, when the ARRC ITB field was FAST - I think one car out of the top 5 had Koni's... the rest of us were on Bilsteins... :D :eclipsee_steering:

(though I will be the first to admit the non-adjustability sucks balz. My car would be at least a half-second faster if I could get those stupid shocks dialed in. But consistency and durability comes even higher on the list - and they're not that far off.)

[betamotorsports]

Koni inserts (8610/11) depend on a tight clamping of the upper bearing/seal by the gland packing nut. If that nut gets loose the upper bearing /seal will fail quickly. If the gland nut gets loose enough that the insert pounds in the strut tube the insert is usually toast.

[trhoppe]

OK, you keep on keepin' on... ;)

Coupla years ago, when the ARRC ITB field was FAST - I think one car out of the top 5 had Koni's... the rest of us were on Bilsteins... :D :eclipsee_steering:

(though I will be the first to admit the non-adjustability sucks balz. My car would be at least a half-second faster if I could get those stupid shocks dialed in. But consistency and durability comes even higher on the list - and they're not that far off.)

Funny. Opposite in ITA. I don't think anyone in the Top 10 did NOT have Konis :)

[tom91ita]

OK, you keep on keepin' on... ;)

Coupla years ago, when the ARRC ITB field was FAST - I think one car out of the top 5 had Koni's... the rest of us were on Bilsteins... :D :eclipsee_steering:

(though I will be the first to admit the non-adjustability sucks balz. My car would be at least a half-second faster if I could get those stupid shocks dialed in. But consistency and durability comes even higher on the list - and they're not that far off.)

interesting since i think one of the top crxes in ITC was on Tokico Illumina.

[jimmyc]

wow! have not heard about any thing bad about konis bad on IT cars. i do know of some that failed because there was not enough travel but i consider that a user error and not a koni failure.

but my humble crx is not as fast as certain 924's..........

for heat transfer, i have always heard that you want to fill the void with an oil or ATF or something so you don't have an air gap.

i have never needed my koni's rebuilt but they were dynoed, serviced and revalved once for free when i was at the NASA Nationals. that was part of the Koni service while they were at the event.

Strut vs Damper

In some models of koni makes a pretty big difference in terms of reliability

[Greg Amy]

Don't get hung up on the "inserts versus integral" design issue; it's irrelevant. The performance difference simply due to that design factor is insignificant. What's important is 'are the dampers doing what you need them to do and at a price you can afford'.

I ran Koni 8611s in the ITA NX2000, simply because there was nothing comparable available pre-made at a price I could pay. And, since no one made 8611 housing using a geometry that worked for our race car, Matt designed and fabricated our own housings. IMO, Koni 8611s are the best value-to-price strut damper out there; I never found anything that worked as well at that price. I did, however, have to have them revalved to work with the springs rates I preferred (~500F, ~1000 rear, at a near-1:1 motion ratio).

If you've got the coin, I don't think you can do any better than the Koni 2817 struts, but at $1500 each they're pricey. I suspect that had I kept the NX they'd have a set on them now... :shrug:

So, again, scan the market for what's available for your car, and get some shock dyno charts to see if they'll do what you need them to. But don't get hung up on the design details.

GA

[dyoungre]

Thanks Greg. My take-away is cost and availability. I haven't gotten quotes yet, but I'm getting the feeling that I'll find that the 8611+external housing will still be the cost leader by a large margin. I appreciate the feedback!

[lateapex911]

Talk to Lee Grimes. It's like an inside line to the engineers brain.

[quadzjr]

Talk to Lee Grimes. It's like an inside line to the engineers brain.

Talked to him last friday, probably spent 30 minutes or so on the phone..

He will be at SEMA all this week, so he will not be at the "office"