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Shock Tuning Guides


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#1 John Woods

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Posted Feb 22 2015 - 11:20 AM

Here is a link to "The Grand Prix Legends Shock Force Chart" that Lee Bowden, (Lee200), posted awhile back.
Note that 50/50 shocks, (a baseline for tuning), in the setup menu corresponds to 4 in bump and 1 in rebound.
This is because the setup menu has a built-in 1967 F1 historically accurate 1:3 ratio of compression to release.
So, 1/1 is softer than 5/5, but for both the ratio of bump to rebound is 1:3.

http://srmz.net/inde...t=15#entry49280

Here is a link to an easy-to-read shock tuning guide:

http://www.bimmerhau...cktuningTN.html

Couple of quotes from the guide:

"And one last general guideline to keep in mind...

10. In general, stiffening one end of the car will reduce the mechanical grip on that end. In other words, when you raise the spring rate, increase sway bar size or stiffness, stiffen the bump or rebound of a shock, install firmer bushings, etc. you will reduce the grip on that end and decrease traction. To increase grip you must lower the spring rate, increase the sway bar size of stiffness, soften the shocks, use softer bushings, etc. (Tire pressure is another contributing factor, but that's a discussion for another day.)"


Then later on regarding tuning rebound on Koni shocks:

"It should be noted that too much rebound on either end of the vehicle will cause an initial loss of lateral acceleration (cornering grip) a that end which will cause the vehicle to oversteer or understeer excessively when entering a turn. Too much rebound control in relation to spring rate will cause a condition known as "jacking down." This is a condition where, after hitting a bump and compressing the spring, the damper does not allow the spring to return to a neutral position before the next bump is encountered."

Hopes this helps...maybe some more later.

Edited by John Woods, Feb 22 2015 - 11:54 AM.


#2 ginetto

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Posted Feb 23 2015 - 05:34 AM

Sorry for being ignorant on the matter but if the ratio is 1:3 shouldn't be the neutral value 3 bump and 1 rebound instead of 4 and 1 ?

#3 John Woods

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Posted Feb 23 2015 - 06:02 AM

View Postginetto, on Feb 23 2015 - 05:34 AM, said:

Sorry for being ignorant on the matter but if the ratio is 1:3 shouldn't be the neutral value 3 bump and 1 rebound instead of 4 and 1 ?

Check out the chart and see that line representing 4 in bump is mirror of line for 1 in rebound. So 4/1 is 50/50.
Then check lines for any combo of 1/1, 2/2, etc and see they are in ratio of...somewhere between 1/2 and 1/3?

Actually looks to me now like GPL shock chart shows force ratio is closer to 1/2 than 1/3, and/but as I understand authentic ratio is closer to 1/3?

Guessing...its the rate that is 1/3?

Notice that for 1B/1R, it takes three times longer to get to value of -50 (bump) than it does to +50 (rebound).
It also shows that stiffer shocks are faster to same force value than soft.

Curious about bump number being negative.
Guess that makes sense, but shock rate has always been referred to as "added"?
Or its that spring rate when in bump is negative?

Shock force is progressively added/subtracted from linear spring rate etc?

Here's another shock tuning guide, this one is for ovals but has some good info:

http://www.sardesonr...hock_tuning.htm

Edited by John Woods, Feb 23 2015 - 11:13 AM.


#4 Pete Gaimari

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Posted Feb 23 2015 - 08:07 AM

Seems to me in the 60's we used shocks that were 50/50. Why Papy has a built in 1/3 ratio is confusing.

Another point is the built in 1/3 ratio for bump and rebound is not reflected in the default setups.

Edited by Pete Gaimari, Feb 23 2015 - 03:13 PM.


#5 John Woods

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Posted Feb 23 2015 - 09:34 AM

Seems its 1:2 for shock force, (rebound is twice force for same time), and 1:3 for shock rate, (rebound rate is three times faster getting to same force?

Think Kaemmer and all thought they were doing us a favor by building the ratio in so we wouldn't have to wonder about it. The beta testers did what seemed right for them?

Here is a link to the shock tuning page on a very nice site, one of my favorites:http://www.ozebiz.co.../shocktune.html
Definitely worth a visit to check out entire site.

Edited by John Woods, Feb 24 2015 - 10:26 AM.


#6 Robert Fleurke

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Posted Feb 24 2015 - 01:22 PM

Thanks John, and Lee of course, interesting! :)

#7 John Woods

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Posted Feb 24 2015 - 01:44 PM

Thnx RF, really just trying to get enough all in one place to give others a good start if they are interested and me a good place to get back to because I forget everything.
Any ideas/contributions would be welcomed for sure.
BTW, if you search SRMZ for Lee's posts its like an encyclopedia of Grand Prix Legends good stuff to know.

Shock Tuning for the Mustang FR500S

Guess Ford Racing and Sachs is credible enough. Scroll down PDF to page 5 for nice chart showing what to do when.

Edited by John Woods, Feb 24 2015 - 03:18 PM.





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