Shock pressures

mobil1syn · Post by **mobil1syn** » Fri Mar 11, 2016 7:00 pm

give me the following information
- amount of shock shaft showing
- length and rate of upper spring (which ever is on there now)
- length of upper spring at ride height
- repeat for lower
- how much uptravel before you hit the bump stop
- pressure in the bump

steve-oh · Post by **steve-oh** » Sat Mar 12, 2016 7:56 am

5 1/4 shaft showing, 14 in coilovers
7 inch on the upper springs, 14 inch free weight(175)
13 inch on lower spring, 16 inch free weight(350),

Bump stops at an inch which I know is to close, going to shorten them by two inches, but have them off at present time

mobil1syn · Post by **mobil1syn** » Sat Mar 12, 2016 2:02 pm

you need 200/250 with an 1.25" of preload. with the crossover 1.75" above the dual rate slide at ride height.

steve-oh · Post by **steve-oh** » Mon Mar 14, 2016 9:25 am

How did you come to that conclusion, I'm trying to learn something that's why I ask

mobil1syn · Post by **mobil1syn** » Mon Mar 14, 2016 9:10 pm

http://www.pirate4x4.com/forum/general- ... hread.html - the long winded version

the short version

(free length - compressed length) * rate = weight the spring is supporting

(travel of shock - desire shock shaft showing (generally you can use ride height but if there is motion ratio that doesnt work)) + preload (1" is rule of thunn for the front and 2" for the rear) = shock sag

sprung weight/shock sag = desire combined spring rate

spring rate formula
(rate 1 * rate 2) / (rate 1 + rate 2)

solve for spring rates that are around ~100lbs of each other

In your case i went with a touch more preload to keep the rates in 50 increments.

mobil1syn · Post by **mobil1syn** » Mon Mar 14, 2016 9:11 pm

CRAP - shock sag is actually spring sag

stupid sites that dont allow editing

BDKW1 · Post by **BDKW1** » Tue Mar 15, 2016 12:16 am

2" of preload is a lot, makes for a sloppy vehicle. Rock crawler territory. I prefer to have them just about rattle when fully drooped or even tender springed to take up the slack.

steve-oh · Post by **steve-oh** » Tue Mar 15, 2016 9:15 am

Been reading the pirate thread, lots of good info there, thank you. I'm guessing the guy Wayne works at fox, and makes sense with the spring weight you recommend for what he has been talking about.

steve-oh · Post by **steve-oh** » Tue Mar 15, 2016 9:17 am

mobil1syn wrote:that spring split is a little large. Generally I try to keep them within 100lbs on a solid axle.

dump the bump pressure to 50psi, destroke them, go with extra light on rebound and light/med on compression.

Would you still recommend revavling the shock or try the springs first and then revalve?

mobil1syn · Post by **mobil1syn** » Tue Mar 15, 2016 9:34 am

steve-oh wrote:Been reading the pirate thread, lots of good info there, thank you. I'm guessing the guy Wayne works at fox, and makes sense with the spring weight you recommend for what he has been talking about.

correct, about 6 months ago he left his own company alltech, to be the director of race and service at fox. i am now running alltech.

yes, springs and revalve.

steve-oh · Post by **steve-oh** » Tue Mar 15, 2016 11:26 am

All tech Motorsports?

mobil1syn · Post by **mobil1syn** » Tue Mar 15, 2016 6:13 pm

steve-oh · Post by **steve-oh** » Wed Mar 16, 2016 3:17 am

Thank you for taking your time to give me some help with this. Waiting on springs and shim kits now, I'll post when they get in and get started in it.

steve-oh · Post by **steve-oh** » Wed Mar 16, 2016 9:46 am

Was thinking, with what you have recommended, how do you think it will handle on the street?

steve-oh · Post by **steve-oh** » Wed Mar 16, 2016 10:02 am

I don't mind a little " loser " of a ride.

steve-oh · Post by **steve-oh** » Wed Mar 16, 2016 10:48 am

Guessing the stop ring will help with the sway?

steve-oh · Post by **steve-oh** » Wed Mar 16, 2016 10:52 am

But with the radius arm set up I don't think I will have problems with sway.

steve-oh · Post by **steve-oh** » Mon Apr 25, 2016 5:35 pm

Ok, springs swapped over 200/250, sent me the wrong valve kits but opened them up to see exact valving, was set to extra firm compression (Foa) and light med rebound, I opened up 5 of the compression holes on the pistons to 3/16, 10 holes,valved the compression to light and left the rebound alone(lack of shims) but was a stack of .10 shims, truck is definitely better but I feel it could be softer still, low speed,speed bumbs still seem to stiff, should I open all the holes to3/16 and valve rebound to extra light?

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steve-oh · Post by **steve-oh** » Mon Apr 25, 2016 5:37 pm

Was also thinking about removing the lowest leaf on the leaf pack to lower my spring rate in the rear as well

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shockseals.com · Post by **shockseals.com** » Thu May 05, 2016 2:26 pm

It felt softer because the shock wasn't working. On top of cavitating the shock you most likely sucked ambient air in through the seal head since they aren't rated for vacuum and now have an emulsified shock.

Shock pressure is relative to compression damping if the resi port is out the top, rebound damping if the port is out the bottom.

Pull apart, revlave and charge to at least 150psi but if the valving is high...go 200-250. Tuning with nitrogen pressure is not tuning.

Shock pressures

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Shock pressures

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Shock pressures

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