Spring Rate to Damper Ratios???

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Mats
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Re: Spring Rate to Damper Ratios???

Post by Mats » Sun Mar 27, 2011 7:03 am

Sounds like a plan... :)
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Re: Spring Rate to Damper Ratios???

Post by PietereQ » Mon Mar 28, 2011 3:13 am

Since you guys are talking about dampers and ratios, I have a question for you.
I have installed new adjustable (rebound) GAZ shocks in the rear in my GTV6.
The rear of the car was standing on the jackstands, and the wheels weren't touching the ground.
I wanted to check, how the adjustment really works, so i set them for max stiffnes (5 revs on the knob)
Jacked the left side of de Dion, and released, to check how fast will it drop. Did the same on the right side.
Even though both were set equally, the actuall drop speed varied ALOT between sides. With some trail and error
one is set to 5 revs and the other to 3,5 - that gives more or les the same suspension drop rate.
Question is, should i return the shocks, and have it warranty checked? Or this is normal, that no shock, works the same?
I know this experiment had to do little with real road conditions but, hey the difference is huge
it just seemed a bit abnormal to me.
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Re: Spring Rate to Damper Ratios???

Post by GTV27 » Mon Mar 28, 2011 11:04 pm

I doubt that test would be sufficiently accurate to use for setting the rebound damping. I would suggest setting them evenly (same number of turns) and then, if there is any doubt from roadtesting, find somebody with a shock dyno to test accurately and rebuild as a matched pair.
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MD
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Re: Spring Rate to Damper Ratios???

Post by MD » Tue Mar 29, 2011 1:13 pm

Hey Pete, you know you can always count on me for helpful, high tech, and logical suggestions right?

Well here's another one for ya.

Get Bilsteins. :wall:
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Re: Spring Rate to Damper Ratios???

Post by killaz » Thu Mar 31, 2011 2:09 am

PietereQ: Try following; take them off and while in vertical position and stiffness set to minimum, compress them and stretch out 3 times each (full length). Mount them back, it should help..?

Another point; while measuring drop speed try to set equal weight that pulls each damper. -Maybe the best test would be while they are out..
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Re: Spring Rate to Damper Ratios???

Post by PietereQ » Sat Apr 02, 2011 3:13 am

Thanks guys, I guess I'll leave it for the time being it's not like I'm gonna drive the car anytime soon anyway. Mike Bilsteins? You mean custom solutions (I hate those two words)
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Re: Spring Rate to Damper Ratios???

Post by Mats » Sat Apr 02, 2011 5:42 am

Don't worry about it, at close to zero piston speed the shocks will look quite even unless they are gas pressure type. It will even out at driving piston speeds, or they are broken. But it's not like you can judge that by looking at jack-lowering-speed.
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PietereQ
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Re: Spring Rate to Damper Ratios???

Post by PietereQ » Sat Apr 02, 2011 11:36 am

Mats wrote: But it's not like you can judge that by looking at jack-lowering-speed.
I was actually hoping someone would say that :mrgreen:
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Re: Spring Rate to Damper Ratios???

Post by Zagato » Tue Apr 05, 2011 2:43 pm

But on the other hand, if you buy shocks like that, that type of problems is very likely, almost standard also in a testing machine!
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Re: Spring Rate to Damper Ratios???

Post by killaz » Sun May 22, 2011 1:23 pm

What's the conclusion here?

Does anybody knows what is max spring rate supported w/o revalving for Bilstein B6?
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Re: Spring Rate to Damper Ratios???

Post by WhizzMan » Mon May 23, 2011 11:21 pm

PietereQ wrote:Since you guys are talking about dampers and ratios, I have a question for you.
I have installed new adjustable (rebound) GAZ shocks in the rear in my GTV6.
The rear of the car was standing on the jackstands, and the wheels weren't touching the ground.
I wanted to check, how the adjustment really works, so i set them for max stiffnes (5 revs on the knob)
Jacked the left side of de Dion, and released, to check how fast will it drop. Did the same on the right side.
Even though both were set equally, the actuall drop speed varied ALOT between sides. With some trail and error
one is set to 5 revs and the other to 3,5 - that gives more or les the same suspension drop rate.
Question is, should i return the shocks, and have it warranty checked? Or this is normal, that no shock, works the same?
I know this experiment had to do little with real road conditions but, hey the difference is huge
it just seemed a bit abnormal to me.
Most adjuster knobs are seriously non precise. Especially on the extremes of the curve, they tend to be unusable. Try again with setting them in the middle and maybe put some extra weight on the wheels.

Read this guy's guides to setting up a car. It's biased towards US RWD cars, but it tells a lot of universal things that apply to most cars regardless. http://farnorthracing.com/autocross_secrets18.html
He has a lot to tell about why you want the 65% critical damping and all the other things already discussed in this topic.
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Re: Spring Rate to Damper Ratios???

Post by Carter Hendricks » Wed May 25, 2011 4:14 pm

I don't know if I should sneak this question in here [where we're talking about shocks] or start a new thread...

I found a pair of Koni 80-2241 Sport [yellow] and 2242 Sport [yellow], early discontinued fitment for 116 [Alfetta GT]. Does anyone have shock damping data on the 2241 Sport's???

Thanks!!

--Carter
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Re: Spring Rate to Damper Ratios???

Post by Duk » Wed Aug 31, 2011 1:40 am

The 'Bilstein Digressive Valved Damper' project has taken a pretty far back, back seat lately. What with all those silly things like other projects (lets all start sticking a Vortech supercharger on our V6 and finish that other model of car (Toyota) project :P ) and working that J.O.B. (just over broke :P ).
But some time has been spent playing with the spread sheet that La_strega_nera was absolutely champion in getting and posting 8) .
However, I have come to the conclusion that without damper dyno printouts from various damper valve combinations, I'm still pretty stuck :oops: .
Either that, or I have absolutely no idea about what's going on :shock: .

But anyways:

A few things I have had a bit of a guess at like:

Unsprung weight: 35kg.

Corner mass: Just working the front at this stage, so I said 350kg for a road going car.

The motion ratio is a strange 1. To get the known(ish) wheel rate to the known(is) spring rate, Ben had steered me in the direction of a Motion Ratio of about 0.39. To get the spring rate and wheel rate to be close on the spread sheet, I needed to have a Motion Ratio of 1.61 or 2 - the calculated MR (0.39) :| .

Tyre stiffness: I didn't have a clue, so I left it at 400kg/cm.

With my/our calculated standard TB rate plus my intended additional coil spring rate of 225lb/in that gives a calculated wheel rate of 32.8kg/cm and a natural body frequency of 1.54Hz. So far from being overly harsh for a road car that is intended to actually have some side wall in the tyres (225/45/16).
* This TB/spring combination isn't as stiff as I want, but we'll work with it for the time being.

Where I am a little stuck is actually getting my head around the the damper rebound force :? .
Bilstein quote their damper force numbers at a shaft speed of 0.52m/sec. To get that shaft speed on the spreea sheet, I need a body movement number of 139mm :o .
With the above information, 139mm body movement and 65% rebound damping, I need 5924N of rebound damping force.
Now, as I have read in the past, bump valving should be about half of the rebound valving. For the smaller Bilstein's 36mm (piston) dampers, a 70/35 is the highest rate (1/0.5) rebound/bump valving that I have seen, but this only equals 3800/1850N.
For the 46mm dampers, 80/40 is available, but that is still only 4200/2100N.

Has anyone else had a play with the spread sheet, 'cause my head hurts?
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Re: Spring Rate to Damper Ratios???

Post by killaz » Tue Oct 09, 2012 11:45 am

I have plots of my revalved Bilsteins from authorized shop, explained to owner that I want occasional track day car, medium stiff with additional springs in front 80kg/cm. You need them Duk?
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Re: Spring Rate to Damper Ratios???

Post by Duk » Wed Oct 10, 2012 12:04 am

killaz wrote:I have plots of my revalved Bilsteins from authorized shop, explained to owner that I want occasional track day car, medium stiff with additional springs in front 80kg/cm. You need them Duk?

I'll take any relevant information on the subject :D
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