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Old 05-11-2019, 04:00 PM   #11
CJPJ
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Default Re: KONI 87-2661 Adjustable Front Strut/Shock NCV3 4x4

A seat of the pants feeling for rebound setting for driving preformance ; would be ..while driving /.. after a G-out-compression of the suspension, the spring rebound should be dampened enough that your butt doesn't hover rise much from the seats foam.

Now - the rebound setting for slow-G-0uts; such as controlling rocking from enter a driveway would require a much higher slow speed dampening setting. A compromise, In that at road speed the suspension reaction is too slow and causes the ride to be deeper into the spring rate. Making a hard ride so that your butt rises and pounds the seat foam.

Last edited by CJPJ; 05-11-2019 at 04:40 PM.
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Old 05-11-2019, 08:00 PM   #12
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Default Re: KONI 87-2661 Adjustable Front Strut/Shock NCV3 4x4

A springs reaction to an impulse is an oscillation at the springs natural frequency. This is the same frequency as when the chassis is rocking. It doesn't matter if the spring deflection is caused by a G-out or just entering a driveway, the spring reaction is the same. The spring deflection amplitude may be different, but the oscillating frequency is the same.

The function of the shock absorber is to dampen the oscillation so that it doesn't go on indefinitely. The key unit of measure in a spring/damper system is the damping factor. It determines how many oscillations occur before they are not noticed anymore. The damping ratio also determines the springs reaction to the initial impulse. The goal is to achieve a damping factor of 0.2. My T1N with stock shocks had damping less than 0.1. That makes the suspension very volatile.



The initial bump gets amplified by more than 80 percent. In other words, if there's a 2" bump, the spring reacts by deflecting 3.6" and there's more than 6 oscillations that are noticeable. After installing Koni struts and Fox 2.0 shocks (damped to the max), the damping factor is now close to 0.2.

The damping ratios I mentioned are calculated from logged accelerometer measurements.
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Old 05-11-2019, 08:34 PM   #13
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Default Re: KONI 87-2661 Adjustable Front Strut/Shock NCV3 4x4

I didn't know there was going to be any math involved ��..... I just want to know how they "feel" when installed and if they are any better than the factory struts in a direct comparison....
already have remote reservoir Foxs in the back and Sumos in the front... may add the VC spring pack in back...
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Old 05-11-2019, 09:20 PM   #14
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Default Re: KONI 87-2661 Adjustable Front Strut/Shock NCV3 4x4

I spared you the math.

The damping factor IS what you'll feel.
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Old 05-15-2019, 06:07 PM   #15
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Default Re: KONI 87-2661 Adjustable Front Strut/Shock NCV3 4x4

Quote:
Originally Posted by calbiker View Post
A springs reaction to an impulse is an oscillation at the springs natural frequency. This is the same frequency as when the chassis is rocking. It doesn't matter if the spring deflection is caused by a G-out or just entering a driveway, the spring reaction is the same. The spring deflection amplitude may be different, but the oscillating frequency is the same.

The function of the shock absorber is to dampen the oscillation so that it doesn't go on indefinitely. The key unit of measure in a spring/damper system is the damping factor. It determines how many oscillations occur before they are not noticed anymore. The damping ratio also determines the springs reaction to the initial impulse. The goal is to achieve a damping factor of 0.2. My T1N with stock shocks had damping less than 0.1. That makes the suspension very volatile.



The initial bump gets amplified by more than 80 percent. In other words, if there's a 2" bump, the spring reacts by deflecting 3.6" and there's more than 6 oscillations that are noticeable. After installing Koni struts and Fox 2.0 shocks (damped to the max), the damping factor is now close to 0.2.

The damping ratios I mentioned are calculated from logged accelerometer measurements.
You are giving me flashbacks of mechanical vibes and control systems exams
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Old 05-16-2019, 09:48 PM   #16
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Default Re: KONI 87-2661 Adjustable Front Strut/Shock NCV3 4x4

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You are giving me flashbacks of mechanical vibes and control systems exams
Me too! Square root of k over m... ugh... Need a beer...
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Old 05-16-2019, 10:44 PM   #17
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Default Re: KONI 87-2661 Adjustable Front Strut/Shock NCV3 4x4

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Me too! Square root of k over m... ugh... Need a beer...
There you go...

Square root (k over m) is proportional to the oscillating frequency. Frequency should be around 1 Hz. If the mass increases then spring constant should increase (more springs). And of course damping has to increase as there's more mass to control.

In the case of my heavy Sprinter 3500 motor home, it came with the same shocks that come with the lightest Sprinter van. What a disaster. The front end would bottom out when there's a dip in the freeway.
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Old 05-20-2019, 06:26 PM   #18
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Default Re: KONI 87-2661 Adjustable Front Strut/Shock NCV3 4x4

Just bit the bullet, my new Koni Struts should arrive Weds and I plan to be feeling the difference in ride by Sat !!! Bought them from the Sprinter Store and they are setting them to the max dampening for me, Jared there said they normally set them to 75%, 7 pairs left in stock....

Last edited by aksotar; 05-20-2019 at 06:29 PM.
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Old 05-20-2019, 07:46 PM   #19
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Default Re: KONI 87-2661 Adjustable Front Strut/Shock NCV3 4x4

Be sure to test them before they get installed. Put one end in vice and pull them apart. It should be difficult to get extension. It may take a minute and a lot of exertion to get full extension.

Some 11 years ago I purchased Koni shocks & struts from the Sprinter Store. They were supposed to be adjusted to 80%, but they were not. I wasn't that happy with the performance. Still, it was a lot better than before. After 4 years I removed them and sure enough they were set to min. Not so bad changing shocks, but struts are a bigger deal.
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Old 05-21-2019, 05:38 PM   #20
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Default Re: KONI 87-2661 Adjustable Front Strut/Shock NCV3 4x4

Tested out the new knoi 4x4 struts on recent trip. Took about 3 hours to install both of them (forgot to put the boot on one so had to do one twice). You need a 21mm crescent wrench as there is not enough space between the lower bolt and the caliper to get a socket wrench in. I did not adjust the struts and used the factory setting. I was surprised on how much better the ride was as I was having buyer remorse on spending $500 on replacing what I thought where perfectly good struts. No longer feel like I was hit by a photon torpedo at every bump. Have the fox shocks on the back and feel the new struts improved the ride more then then the fox shocks. Sorry I don't have any graphs or equations to quantify the improvement but would recommend them.
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