how do you measure for shocks?

[jd4242]

Might be in the wrong place and didn really see a how too.I know you need to measure the compressed and extended.but how do you properly compress and extend them and where on the shock do you measure?I'm trying to order new shocks for the back.

 

[Maniak]

You measure from Eye to Eye (assuming it has eyes on both ends). IF it has a "post" on the other end you measure from the top of the "flat spot" that the bushing sits on down to the center of the eye.

You can measure the shock lengths off the truck by extending them (pull them until it stops) and compressing them. IF they are gas charged you will need a 2nd person to measure compressed since it will extend on its own once you let go.

If you asking about how to measure what length you need by measuring the truck, I haven't found any good way yet. I just put on a shock see how it does then disconnect 1 end to see if the shock was limiting the travel. If so, I then can figure how much shorter or longer I need the shock compared to what I already have

~Mark

 

[jd4242]

Yea I'm talking about on the truck.I think I'm going to just take the shocks and sway bar off and take a jack and jack up one tire as high as it will go till the other side starts to come off the ground and measure each side where the shock was.one should be max compressed and the other max extended.I think

 

[Maniak]

Unfortunately, Jacking the truck doesn't usually move the suspension enough. Normally you have to have the truck twisted up with the weight transfered to the corner you want to be stuffed to the max.

For the rear droop I tested it this way... I jacked up the truck and supported it by jack stands.. I took off the tires and held the axle up by a jack. I disconnected the shocks and let the axle down as far as the springs would let them go. In my case I found my shock was already about 1" too short to reach. I then added another couple inches to the length to "guestimate" the extra travel it would get using the levergage of the suspension to push it down a little more.

To see if I was bottoming out the shock I put a zip tie on the shock tube and I then flex the truck on something that will put all the weight of the vehicle on that corner. Then when on flat ground I can look at the zip tie. IF it is all the way up I am bottoming out. Then you need to take the shock off, do the same test again and then while sitting there in that precarious position measure how much distance you have between the upper and lower shock mount.


~Mark

 

[jd4242]

just found this
Suspension Travel Measurement

Do yourself a favor and remove your old shocks and articulate the suspension in a controlled environment to determine how much compression and extension your particular setup will allow BEFORE you order or buy your shocks.

This can be accomplished by parking on a level surface, removing the rear shocks and jacking up one side of your truck until the tire comes off the ground. (Make sure the truck is properly jacked and braced for safety.) Measure the distance from the center of the lower shock mount (on the raised side of the vehicle) to the center of the upper shock mount. This is your extension measurement.

Now measure the same distance on the opposite side of the vehicle. Even though you have one side jacked up, the other side is not necessarily fully compressed, so you have to compensate for this. Measure the distance between the lower and upper bump-stops and subtract this distance from the mount-to-mount measurement you just recorded. This will approximate your compression measurement. I say approximate because the distance between bump-stops is vertical, while your shocks will compress at the angle they are mounted. The bump-stop measurement will be slightly less than the actual additional compression of the shock, so subtract accordingly for your final compression measurement. For example, for a shock mounted at a 22.5 degree angle, the additional compression travel will be 1.0824 times as much as the bump-stop measurement. Be conservative with your compression measurement (better to error on the short side to avoid "bottoming out" the shocks). Also keep in mind that a hard hit (bottoming out) will compress the bump stop some.

If you find yourself in a quandary because the brand of shock that you want to use doesn't have a part number that matches up well with your extension and compression measurements, do not fear. You can always order a shock that has a little extra extension (so as not to limit axle droop) and then fit your truck with taller bumpstops to compensate for a compressed shock length that may be greater than your actual compression dimension. In my opinion, it's better to cheat yourself out of a little compression rather than sacrifice a little extension. (However, by reducing the available compression, you may inadvertently decrease your trucks potential to stay level when in a precarious situation where camber (tipping) is concerned.) On the upside, an aftermarket bumpstop can improve the available "cushion" over the usually thin, hard rubber factory stops. This can make bottoming out a little less harsh.

Let's use the following dimensions for an example:

23.25" - Extension (driver side)
14.75" - Compression (driver side)
8.50" - Shock Travel (drivers side)

23.00" - Extension (pass. side)
15.50" - Compression (pass. side)
7.50" - Shock Travel (pass. side)

 

[IZwack]

Unfortunately, Jacking the truck doesn't usually move the suspension enough. Normally you have to have the truck twisted up with the weight transfered to the corner you want to be stuffed to the max.

I think its good enough as long as you factor in some uncertainty/error. So say you flex it out and you measure 15" stuff and 19" extended eye-to-eye. Well you can probably go with a shock that compresses to 14" and extends to 20" eye-to-eye.

 

[Maniak]

That would work for non solid axles.. as there is "some" leverage action. If a tire is stuffed in theory it is pushing down somewhat on the other tire which will make it go farther down that it would just under its own weight. It isn't much but there is some force there.

Also, I like having all the stuff I can since there is still weight on the tire when stuffed which helps keep you flat. When a tire is drooped as much as possible there isn't much weight on the tire so your not gong to get near as much traction even if its on the ground.

At least thats my thinking on the subject.

edit: this was a reponse to what you found 2 messages above...

~Mark

 

[Maniak]

I think its good enough as long as you factor in some uncertainty/error. So say you flex it out and you measure 15" stuff and 19" extended eye-to-eye. Well you can probably go with a shock that compresses to 14" and extends to 20" eye-to-eye.

Exactly.

Thats how we did ours on the front. Once I had some rough measurments based on what I had before and what I was going to have for eye to eye measurments I got the shock with the shortest compressed and longest extended we could get without topping out or bottoming out the shock.

~Mark

 

[jd4242]

yea the shocks i have on the rear now max out really quick for compression.i think the gave me shocks for a 6"lift with lift springs.where the shocks mount under the axel.i have soa so the shock mount ontop of the axel. i can hear them hit when i hit dips in the road!!!

 

[jd4242]

That would work for non solid axles.. as there is "some" leverage action. If a tire is stuffed in theory it is pushing down somewhat on the other tire which will make it go farther down that it would just under its own weight. It isn't much but there is some force there.

Also, I like having all the stuff I can since there is still weight on the tire when stuffed which helps keep you flat. When a tire is drooped as much as possible there isn't much weight on the tire so your not gong to get near as much traction even if its on the ground.

At least thats my thinking on the subject.

edit: this was a reponse to what you found 2 messages above...

~Mark

yea im only doing the rear right now.im going to do jd dual set up front.i all ready know the compressed and extended up there.i just took the spring out and compressed it till i hit bump stop and then put weight on it and let it hang as low as it will go.guess i should have asked how to do the rear sorry.

 

[jd4242]

think ill throw some 50ld bags on cement on the tire that is hanging and measure it. then take and jack the rear bumper up with my farmjack and throw some bags on both tires and see what measurement i get that way too for droop

 

[jd4242]

so took everything off today and found out my shocks are way too short.they only have about an inch of compression before they max out.they max out at 18 and 31.the measurements i got with no shocks or sway bar on are, 17 compressed,24 extended,with 4" left till bump stop hits and the shocks are mounted at about a 70* angle. so to be safe i think i would need a shock that is 13 compress and 26 extended,im adding 2" to the extend because i want to put a add a leaf or shackles.that's 13" of travel,doesn't sound like muchnow time to try and find shocks that will work.also i didnt put in the brackets that move the bump stops closer so i might have to use them if i cant find a shock that will compress to that measurement.they are 2"o yea i have soa superlift brackets on the rear

 

[Maniak]

13" of travel for angled shocks inboard of the springs is going to translate to much more out by the tire.

I'm sure someone with much better math skills than I can figure out how much travel that is at the tire.

~Mark

 

[jd4242]

yea it sure looks like a lot jacked up in the drive way!!hey you still have that pdf link?

 

[Maniak]

The newest rancho catalog link I have is the 2008 one.

http://gorancho.com/assets/catalog/2008_Rancho_Catalog.pdf

~Mark

 

[jd4242]

my jack was maxed out and i ran out of blocks to get it any higher.the tire was about 15' off the ground,wasn't going to stick my hand under the tire!!could have gone way higher the other tire wasn't even close to coming off the ground yet.

 

[jd4242]

hum doesn't look like they have anything!!im going to call james duff tomorrow and see what they think

 

[Maniak]

Yea, I found the jack method just doesn't quite cut it. Run out of Jack, stability or just don't get enough weight on it.

The flex of the rear axle really increases when you get the weight on it. There is no way I can get our rear axle to move like this by just using the jack method.

~Mark

 

[Maniak]

hum doesn't look like they have anything!!im going to call james duff tomorrow and see what they think

What mount style do you need (what does Rancho call them)? They have quite a few shocks in there.. Just ignore the applications..

~Mark

 

[jd4242]

double eye.i just looked for one that was close to 13 and 26