JKOwners Forum banner

1 - 12 of 12 Posts

·
Registered
Joined
·
1,042 Posts
Discussion Starter #1
Ok I'm not sure I understand all the internals on shocks but I was talking to a vendor and they were explaining to me that you could use TJ shocks for the JK but they'd need to get re-valved. Why and what is the differences. I see some vendors have propietary valving and I have no clue what this means?
 

·
Openly Hostile
Joined
·
6,981 Posts
TEEJ - calling TEEJ :grinpimp:

I believe the valving is going to be different because the weight of the vehicles is different. In simple terms, haha.
 

·
Registered
Joined
·
1,042 Posts
Discussion Starter #3
TEEJ - calling TEEJ :grinpimp:

I believe the valving is going to be different because the weight of the vehicles is different. In simple terms, haha.
Got my answer from a few baja race articles and off road mag articles. I googled it and got lucky on the first set of selections. Weight, rollcenter, blah blah blah, basically I beleive it is 255/60 or 70 rating I would need to start unless someone has better dialin ratio's.

http://www.off-roadweb.com/tech/0501or_finding_perfect_truck_shocks/shock_technology.html

There are many other complicated versions of descriptions available by googling "What is Shock Valving"
 

·
Registered
Joined
·
275 Posts
sigh

Shock valving is a way of referring to the way the shock damps motion.

All a shock absorber does is slow down the motion gradually, instead of allowing the motion to jolt you.

Think of a catcher catching a 100 mph fast ball....

He does NOT just let the ball slam into his palm at 100 mph...it would break his hand (Jolt)....he pulls the glove back on impact, to allow the impact to be softened.


On a suspension....the perfect set up would mean your truck would stay dead level while your tires went up and down, following the terrain.

To allow the tires to go up and down, without the truck popping up or dipping down with the tires...the shocks have to be matched to both the SPEED and the WEIGHT of the motion.

If a tire is rising TOO FAST for the shock to compress with/or, the shock's RESISTANCE to compression is too much for the force involved...the truck is pushed UP on that corner.

If the tire is sinking too fast for the shock to extend with/or the FORCE of that motion is OVERWHELMING the shock's ability to resist it, the truck DIPS at that corner.

The AMOUNT of damping forces the shock can handle is represented by numbers that are referred to as the shock's VALVING.


Just like an RTI Ramp score, there are different scales used to rate that valving...but, generally, its in terms of Newtons (The FORCE) damped at a SPEED of 20" per second, or at 0.52 meters per second (metric version...).

To make it harder to understand, they THEN take THAT number, and DIVIDE it by TEN (10) to get the "Valving" number.

So, If I have a shock that is valved at 275/100...that means it damps 2,750 Newtons at 20"/sec on Rebound (Shaft Extending)/1,000 Newtons at 20"/sec on Compression (Shaft going back into the shock body...)

Generally, for control purposes....the REBOUND valving helps to control the SPRUNG weight (Frame, etc...), and COMPRESSION valving helps to control the UNSPRUNG weight (Axles, tires, etc...).

So - the shock has to deal with the Pitch (Brake Dive/Wheelie Pop type motions...) and Yaw (Roll in turns/Leaning over type motions...) of the TRUCK, as well as the motions of the tires and axles, etc, going up and down with the terrain.

For example, we said that Compression helps to control the UNsprung weight (Tires, etc...)....

...If the Compression valving is set to too high a number, the tire will skate over small bumps, etc....as it won't let the tire rise for each one fast enough, etc.

If the Compression is at too low a number, the tire will bounce up too quickly, and overshoot the next bump, or wheel hop, etc.


So there's NO universal answer, as different rigs have different forces to control.

My 2.5 ton Rockwells represent an ENORMOUS unsprung weight compared to your D30 for example, the stock 32's are very light compared to someone else's 37's, and so forth...so, if I am running larger tires, heavier axles, or a STIFFER SUSPENSION, like with LIFT COILS or stiffer leaf packs, etc...the spring's forces, AND the weights of the unsprung components, ALL change my ideal COMPRESSION valving ranges.


If I am running a CJ5, or a Sammi, etc...I have very little SPRUNG weight compared to a JK UL or a Ford F350, etc....so, the shocks will have different ideal ranges of REBOUND as well.


If I have a different lift HEIGHT, I am changing my Center of Gravity (COG)...and, therefore, both my Pitch and Yaw characteristics...as the higher COG leans more, etc.

and so forth.

If two rigs are at least similar in sprung and unsprung weight, and use similar suspension coil rates, etc...then the shock valving ranges will be similar as well....but, even THAT is subject to OTHER variables...

...For example, some shocks are mounted more straight up and down, and, some are set at an angle.

Well, that changes the LEVERAGE that the sprung, and unsprung, weights can exert upon the shock, and the speeds at which they will act.

If I am picking up a plank of wood, and your job is to hold it down, would you rather hold it down standing off to the side so your arm is at a 45 degree angle, or standing so you are over the board with your arm straight down?

Well, same for the shock...the more of an angle off of straight, the less leverage it has.

If it has 1,000 Newtons of resistance to offer at a perpendicular angle, it may only have an equivalent 500 at a 45 degree angle, etc...

Which means, if one rig has the shock straight down to the axle, and the other has the shock at a 45 degree angle, the one at the 45 degree angle may need a much stiffer shock to control the same weight.

and so forth.


So - that's what the valving numbers are trying to tell you.

:D




PS - Proprietary Valving simply means they don't list it, as, a lot of research went into figuring that out, and, they do NOT want to just GIVE all of that time and effort to a competitor/make it too easy for you to go to eshocks.com, etc...and order the same shock for less, etc...
 

·
Registered
Joined
·
1,042 Posts
Discussion Starter #6
Very good explaination TEEJ!!! Clairified valving allot more than I gathered through the web. Since I do not intend to relocate the stock locations I have a slight angle as you indicate. I guess one variable of Spring rate is not yet determined for my rig as I am looking for stiff springs for the rear to assist in Towing situations with around 3500lbs in the rear. SO likely the fronts are not going to be the same as the rears for overall valving as I would look for 600lbs springs in the rear and maybe 400lb for the front. I do it enough throughout the spring, summer, and fall that I need to take it into account.

My other variable is the lift as you mention and how this can change roll center of gravity (YAW). I need to plan for the final lift instead of what is on the rig now. 3.5" vs the 2.5" lift.

I will call to Poly to get their take. They have offered to discuss lifts, Roll center and Valving in the past. The other vendor is not someone I'm familar with so I have allot of thinking to do. Even though they are an offroad shop it doesn't mean they know the correct setup and valving.

By the way, you should get into writing. Maybe a Offroad Modification for Dummy's.
 

·
Registered
Joined
·
275 Posts
Very good explaination TEEJ!!! Clairified valving allot more than I gathered through the web. Since I do not intend to relocate the stock locations I have a slight angle as you indicate. I guess one variable of Spring rate is not yet determined for my rig as I am looking for stiff springs for the rear to assist in Towing situations with around 3500lbs in the rear. SO likely the fronts are not going to be the same as the rears for overall valving as I would look for 600lbs springs in the rear and maybe 400lb for the front. I do it enough throughout the spring, summer, and fall that I need to take it into account.

My other variable is the lift as you mention and how this can change roll center of gravity (YAW). I need to plan for the final lift instead of what is on the rig now. 3.5" vs the 2.5" lift.

I will call to Poly to get their take. They have offered to discuss lifts, Roll center and Valving in the past. The other vendor is not someone I'm familar with so I have allot of thinking to do. Even though they are an offroad shop it doesn't mean they know the correct setup and valving.

By the way, you should get into writing. Maybe a Offroad Modification for Dummy's.

Thanks, I get that a lot.

BTW - If you are going to change the front to rear balance...

Remember that when the nose dives, as during braking or heading down a steep ravine, etc...the front shock's are compressing, and the rear shocks are extending...with the opposite happening upon acceleration/going up a steep ledge, etc...

...and, when you change the shock front to rear balance you ALSO impact your over steer/under steer balance ...typically, with the stiffer rebound end taking longer to stick the tires...and a lower rebound taking a set faster.

Over steer is when the rig tends to react with the front end first, so, on a sharp emergency maneuver or hard turn, the rig has more of a tendency to spin...or to react to swing around autocross cones more sharply, etc. :D

Under steer is when the rig tends to ignore the steering at first, so the wheel is cut to make a turn, but the rig continues in a straight line, ignoring the steering wheel.

IE: TOO much stiffer Rebound valving in front can mean more under steer/plowing, and TOO much stiffer Rebound in the rear can mean more OVER STEER/Spin scenario.

Its a sliding scale of course, but, in a transition maneuver, the over steer/under steer balance is just that, a BALANCE between the two tendencies.

The JK has close to a 50/50 weight distribution, which often is associated with neutral handling (Balanced between over/under steer...)...

...BUT, corporate attorneys - in general, tend to prefer a bias towards UNDER STEER, as plowing straight ahead is typically cheaper than spinning out....

...and, Joe Consumer is generally not able to control a rig balanced at the hairy limits of adhesion...and tends to freak out, and over steer when in trouble...so a bit of built in UNDER steer helps to protect JOE C from himself, and the lawyers from Joe C, etc.

:D

If you ARE Joe C...well, a little under steer is a good balance.

:D
 

·
Registered
Joined
·
1,304 Posts
brevity is key.

valving shows the amount of force or lack thereof that a shock will exhibit on rebound and compression. there is no magic number. the weight of the vehicle, weight of the axles and the way you drive will effect how the different valvings will react on your particular application.

instead of trying to figure out exactly what valving you want and trying to find that shock, you can always get an adjustable, like the Rancho, Pro Comp, or Fox. these shocks will give you a range to work within. this is a range that the company has done some R&D on, and has decided that it is the range that will satisfy most people's needs for a particular application.

then dial in the front and rear independently of each other.
 

·
Registered
Joined
·
275 Posts
brevity is key.

valving shows the amount of force or lack thereof that a shock will exhibit on rebound and compression. there is no magic number. the weight of the vehicle, weight of the axles and the way you drive will effect how the different valvings will react on your particular application.

instead of trying to figure out exactly what valving you want and trying to find that shock, you can always get an adjustable, like the Rancho, Pro Comp, or Fox. these shocks will give you a range to work within. this is a range that the company has done some R&D on, and has decided that it is the range that will satisfy most people's needs for a particular application.

then dial in the front and rear independently of each other.

LOL, sure, if they know how one adjustment affects the other...and if they DON'T get the affordable versions of the shocks you mentioned, as they can NOT adjust both compression and rebound independently...even if they ARE "Adjustable".

:D



:D
 

·
Registered
Joined
·
1,304 Posts
LOL, sure, if they know how one adjustment affects the other...and if they DON'T get the affordable versions of the shocks you mentioned, as they can NOT adjust both compression and rebound independently...even if they ARE "Adjustable".

:D



:D

correct. didn't mean to imply that rebound and compression could be adjusted independently. meant that the valving in a shock (as set by the manufacturer or yourself if you can do that) has independent values for rebound and compression.;)

they can still adjust the front and rear independently of each other, through trial and error to find out what settings suit their rig and driving style the best.:bounce:
 

·
Registered
Joined
·
1,304 Posts
a good example of what TEEJ wrote in his novel is the TJ in his avatar. notice that the body is perfectly level, yet the axles are at extreme angles - and not just one axle, both are crossed up.

if you can do that, then you are a shock god!:eek:
 

·
Registered
Joined
·
275 Posts
a good example of what TEEJ wrote in his novel is the TJ in his avatar. notice that the body is perfectly level, yet the axles are at extreme angles - and not just one axle, both are crossed up.

if you can do that, then you are a shock god!:eek:
Thank you sir.

:D

PS - Bring'Em Home is Great.

:D
 
1 - 12 of 12 Posts
Top