Shock Valving

[Bham_Mike]

Can someone explain the terminology used for compression/rebound valving. For example, a Bilstein 6100 8" comes with either 275/78 or 180/75. How can I relate that to a given application.
thanks
Mike

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[ntsqd]

According to the Bilstein catalog the numbers are Newtons (N) (of force) needed to move the shaft at a velocity of .52 m/s. Just so that you can get a feel for what a Newton is, one hundred Newtons roughly equals 22 lbs-force. Because of the valving design, if you use a different velocity you will get different numbers so appearently Bilstein has standardized on using .52 m/s as the test velocity for quoted damper values. 0.52 m/s is about 1.7 foot/sec or 1.16 mph.

TS

"It only seems kinky the first time"
-- Bumpersticker seen in Lost Wages

[Bham_Mike]

Good Info. How can I apply that to a spring rate, vehicle weight, etc. to get a good match?

[ntsqd]

Haven't a clue. Somebody ?

TS

"It only seems kinky the first time"
-- Bumpersticker seen in Lost Wages

[Kritter]

I posted an equation on the ideal spring rate with explanation of the variables on another page but it could be the ideal damping rate also with a change of variables...it is very common DE used in control systems and a suspension system is very much a control system. As for a quick and dsirty way...I dont know of one

Kris
"I was thinking the exact same thing about you..."

[Bham_Mike]

Sounds like I'm getting in over my head here. Just trying to gain a little knowledge for a future project.

Mike

[ntsqd]

I'm not convinced that a DE can be successfully applied because the input freq is too varied and too random. I think you could use it to get you close by using generalities for the input freq(s), but from there it's cut-and-try.

I would start by asking the manufacturer of the damper for a recomendation. that will, worst case, get you in the ball park.

TS

"It only seems kinky the first time"
-- Bumpersticker seen in Lost Wages

[Kritter]

I agree to the DE but its somewhere to start without tearing down a shock. If you are going to be jumping the truck you use one F(t), if you are going to be running hard in the whoops you use another F(t) and then you bridge them together and get a happy medium.

I actual did contact a company regarding valving and did not get any useful information from them besides the stock shim stack dimensions

Here is what I got from a shock manufacturer-sales engineer, verbatim from the email
"GENERAL RULE OF THUMB FOR VALVING IS IF THE SHOCK BOTTOMS OUT REAL EASILY THEN YOU NEED TO STIFFEN UP THE COMPRESSION. IF THE SHOCK GIVES A BRONCOING EFFECT OR MAKES THE TRUCK BOUNCE ONE MORE TIME AFTER A JUMP THEN YOU NEED TO STIFFEN UP THE REBOUND."









Kris
"I was thinking the exact same thing about you..."

[ntsqd]

"GENERAL RULE OF THUMB .."

Wow, what a revelation........

I suppose a 39th order DE (Differential Equation for those lost by the abreviation, commonly called a 'Difficult Equation') might put you really on top of things. I sure as heck don't want to develop it.

TS

"It only seems kinky the first time"
-- Bumpersticker seen in Lost Wages

[Kritter]

Only 2nd order so its not so bad...could be a lot worse. Here is an example using a math package could do same in excel with some effort..scroll down to example 8.3
<A target="_blank" HREF=http://www.awlonline.com/nagle/downloads/pdfpc/Lab08.pdf>http://www.awlonline.com/nagle/downloads/pdfpc/Lab08.pdf</A>

Not saying it is the way to go but it could be used to get a ball park number...experience also works too, but a lot of us dont have valving experience.

Kris
"I was thinking the exact same thing about you..."