Let's talk more about shocks and struts, John C?

[Guest JAMIE T]

I'm still on a mission to learn and understand shock and strut, compression and rebound etc...

 

On a Zcar, specifically a 240Z. Do all the inserts adjust in rebound or compression? Or is it a ratio of the two? For a minute, I'm going to talk in drag racing becuase that is what I know. A "90/10" allows the front end to rise quickly and settle down slowly. The 70/30 allows the front to rise not as quickly as the 90/10, but it settles down sooner. So "dampers" are all a ratio like that. Is that correct?

 

Does that mean that a Tokico Illumina adjusts in ratios? They are "Single adjustable"? What makes a double adjustable shock? Can one be adjusted without the other? What exactly does soft and firm mean in relation to shocks and struts? What goes into designing a shock for a specific car? Like Koni's for the Z I've seen you guys talking about. How is that shock valved to be Z specific? I really am interested in this information on a deep theoretical level and realistic driving conditions, etc...

[johnc]

What is "Bump" and "Rebound":

 

http://www.koniracing.com/roadsetup.html

 

Shock construction:

 

http://www.koni-na.com/construction.html

 

Do all the inserts adjust in rebound or compression?

 

No. Some are single adjustable and adjust both bump and rebound (Tokico Illumina), some are single adjustable and adjust only rebound (Koni 8610), some are non-adjustable, some a double adjustable where rebound and bump are separately adjustable, some are quadruple adjustable where low speed rebound, low speed bump, high speed rebound, and high speed bump are adjustable.

 

Or is it a ratio of the two?

 

On single adjustables where both rebound and bump are adjusted at the saem time then you are changing between set ratios.

 

For a minute, I'm going to talk in drag racing becuase that is what I know. A "90/10" allows the front end to rise quickly and settle down slowly. The 70/30 allows the front to rise not as quickly as the 90/10, but it settles down sooner. So "dampers" are all a ratio like that. Is that correct?

 

No, and the old 90/10 idea is no longer valid in most drag racing applications. Letting the front of the drag car rise trapped a bunch of air under the front of the car and hurt aero at mid track. There might be a few vintage guys still using fast rise front shocks but most competitive racers are using velocity sensitive shocks that control front lift.

 

Does that mean that a Tokico Illumina adjusts in ratios?

 

Yes, between 5 set ratios.

 

They are "Single adjustable"?

 

Yes.

 

What makes a double adjustable shock? Can one be adjusted without the other?

 

Separate adjustments for bump and rebound.

 

What exactly does soft and firm mean in relation to shocks and struts?

 

Defines the amount of control for that adjustment. Soft means less control (less damping) and firm means more control (more damping).

 

What goes into designing a shock for a specific car?

 

Engineering degrees, lots of money, lots of testing.

 

Like Koni's for the Z I've seen you guys talking about. How is that shock valved to be Z specific?

 

See above.

 

For theory see below:

 

http://www.amazon.com/exec/obidos/ASIN/1560915269/qid%3D1116435212/102-9279296-7051353

[Guest JAMIE T]

John, very informative. Thank you very much.

 

I am aware that the 90/10's are "old technology" That's why I used 70/30's on my Mustang. Not nearly as terrifying on the street either. I've used the old 90/10's in my Olds 442(1970). They were actually 3 way adjustable 90/10, 70/30, and 60/40.

 

Thanks for the links!

[Here comes trouble]

stock S30 1978-280 Z specs: rear sprlng : 127 pounds to inch, free length 15.43 inches..... Strut assembly:..0.98 ft/sec: damping force at piston speed........... Expansion :121 pounds .... Compression:66 pounds front spring: 115.4 pounds to inch, free length 15.71 inches strut assembly: 1.0 ft/sec: damping force at piston speed Expansion: 121 pounds Compression: 66 pounds

[Cal Poly Zmanaustin]

Great topic and great information guys. Thanks.

[Jsquared]

are those spring rate specs the same for the older S30s as well? Kind of funny that OEM S30 springs are the same rate or slightly stiffer than the 300-lb heavier S13...

 

P.S. thanks for the Koni link! very nice to have a set procedure for dialing-in shock damping settings.

[Drax240z]

ANother point, please realize there can be a difference between spring rate, and wheel rate. You can have a semi-trailing arm design with a 500lb/in spring rate that has a lower wheel rate than a 150lb/in chapman strut design. Generally struts wheel rate is equal to the spring rate at the corner, not so for many other suspension geometrys.

[johnc]

are those spring rate specs the same for the older S30s as well? Kind of funny that OEM S30 springs are the same rate or slightly stiffer than the 300-lb heavier S13...

 

There's a slight misperception regarding spring rates in the statment above. While sprung weight does play into the selection of spring rate, its by no means the most important factor. Ride and roll control are the final determinant in the selection of spring rate.

[rudypoochris]

ANy one know the 5 ratios of the illumina?

[Jsquared]

There's a slight misperception regarding spring rates in the statment above. While sprung weight does play into the selection of spring rate, its by no means the most important factor. Ride and roll control are the final determinant in the selection of spring rate.

understood, but the S13 with OEM springs is known for having quite a bit of bodyroll...