shock mounting

[bad_religion_au]

is there any disadvantage of mounting the shock absorber to the top of the axle (it's mounted to the spring pad on the rear of the 40.)

edit: it's used onroad, and basically day trip type 4x4ing round toolangi and stuff, with some sand dunes thrown in for good measure

[toughnut]

It changes the stability of the axel. The shocks are mounted to the bottom of the axel because it will pull down on the axel when you hit a bump. This is more stable than sitting on top of the axel. Try this experiment. Hold a tennis ball with 2 fingers opposing each other horizontally, now push the tip of a pen down on top of the ball. The ball tries to roll all the time right?! Now Tape some string to the ball so it hangs from the bottom of the ball about 2cm long ( the shock mount ). Tape the other end of the string to the tip of the pen and holding the ball the same as before push down on the pen. Much more stable. The only trouble with this is the shockie is left hanging in the breeze to get caught on obstacles. The best compromise is to lift the shock mount up level with the centre of the diff housing. You can get shock mounts ready to weld on from most 4x4 custom places like Snake Racing etc. No more getting hung up and still fairly stable.

[Rainbow Warrior]

It changes the stability of the axel. The shocks are mounted to the bottom of the axel because it will pull down on the axel when you hit a bump. This is more stable than sitting on top of the axel. Try this experiment. Hold a tennis ball with 2 fingers opposing each other horizontally, now push the tip of a pen down on top of the ball. The ball tries to roll all the time right?! Now Tape some string to the ball so it hangs from the bottom of the ball about 2cm long ( the shock mount ). Tape the other end of the string to the tip of the pen and holding the ball the same as before push down on the pen. Much more stable. The only trouble with this is the shockie is left hanging in the breeze to get caught on obstacles. The best compromise is to lift the shock mount up level with the centre of the diff housing. You can get shock mounts ready to weld on from most 4x4 custom places like Snake Racing etc. No more getting hung up and still fairly stable.

Hmmm interesting theory, also remember if you move the bottom mounting point up by 2 inches your shocks are going to reach full compression 2 inches earlier, this is a bad thing, you may have to raise your top mounting point equally.

[toughnut]

Or space your bump stops like almost everyone does. My up travel is governed by the tyres hitting the chassis anyway.

[Rainbow Warrior]

Or space your bump stops like almost everyone does. My up travel is governed by the tyres hitting the chassis anyway.

And seing you effectively let the axle travel 2 inches further down, remember on a coil sprung vehicle the coil may fall out at full droop unless you also space the spring mounts down the same amount or get longer springs.

[toughnut]

This is how I overcame that problem. I welded some spring cones to the rear spring hats and I'm thinking of how to lock the base of the spring to the diff at the moment.


and this is a pic of the rear lower shock mounts. Ended up lifting them about 3 in.

[bad_religion_au]

thanks for the replies. the vehicle in question is a 40 series, no coils there to worry about. the fronts are attached to the top of the axle from factory.

up travel is not a problem, the tire indeed hits the guards before the bumpstop and well before the shock is fully compressed

[bazzle]

Also check droop of axle without shocks. It may not drop as far as the new mount due to leaves.

Bazzle

[zzzz]

It changes the stability of the axel. The shocks are mounted to the bottom of the axel because it will pull down on the axel when you hit a bump. This is more stable than sitting on top of the axel. Try this experiment. Hold a tennis ball with 2 fingers opposing each other horizontally, now push the tip of a pen down on top of the ball. The ball tries to roll all the time right?! Now Tape some string to the ball so it hangs from the bottom of the ball about 2cm long ( the shock mount ). Tape the other end of the string to the tip of the pen and holding the ball the same as before push down on the pen. Much more stable. The only trouble with this is the shockie is left hanging in the breeze to get caught on obstacles. The best compromise is to lift the shock mount up level with the centre of the diff housing. You can get shock mounts ready to weld on from most 4x4 custom places like Snake Racing etc. No more getting hung up and still fairly stable.

I call BS
If your axle is twisting and the only thing stopping it is the shock you have serious problems!

Your control arms or leafs/traction bar is holding the diff in place and should resist any twisting forces.

Now depening on your setup the axle does twist a little as the suspension droops. Especially with coils and control arms, but it is all dependant on length of arms etc. etc.

I think the reason the shocks are mounted below the level of the axle is your stock four wheel drive does not have any lift and this is the way the manufacturer manages to fit in a shock that has enough travel for the suspension to cycle.

The shock does not really care where it sits on the tube.
The angle the shock is at can make a difference.
there are many things to consider when modifying shock locations, bump stops, coil mounts etc.

[bad_religion_au]

thanks again.

one primary reason (on top of the 4 inches of lift) for me to change teh shock mount is that i put longer springs in it, which move the axle back yada yada, causing the shock to A be on an angle and B to come pretty close to fowling the lpg tank.

[Slayer]

It changes the stability of the axel. The shocks are mounted to the bottom of the axel because it will pull down on the axel when you hit a bump. This is more stable than sitting on top of the axel. Try this experiment. Hold a <a href="http://www.ntsearch.com/search.php?q=tennis&v=56">tennis</a> ball with 2 fingers opposing each other horizontally, now push the tip of a pen down on top of the ball. The ball tries to roll all the <a href="http://www.ntsearch.com/search.php?q=time&v=56">time</a> right?! Now Tape some string to the ball so it hangs from the bottom of the ball about 2cm long ( the shock mount ). Tape the other end of the string to the tip of the pen and holding the ball the same as before push down on the pen. Much more stable. The only trouble with this is the shockie is left hanging in the breeze to get caught on obstacles. The best compromise is to lift the shock mount up level with the centre of the diff housing. You can get shock mounts ready to weld on from most 4x4 custom places like Snake Racing etc. No more getting hung up and still fairly stable.

I call BS
If your axle is twisting and the only thing stopping it is the shock you have serious problems!

Your control arms or leafs/traction bar is holding the diff in place and should resist any twisting forces.

Now depening on your setup the axle does twist a little as the suspension droops. Especially with coils and control arms, but it is all dependant on length of arms etc. etc.

I think the reason the shocks are mounted below the level of the axle is your <a href="http://www.ntsearch.com/search.php?q=stock&v=56">stock</a> four wheel drive does not have any lift and this is the way the manufacturer manages to fit in a shock that has enough <a href="http://www.ntsearch.com/search.php?q=travel&v=56">travel</a> for the suspension to cycle.

The shock does not really care where it sits on the tube.
The angle the shock is at can make a difference.
there are many things to consider when modifying shock locations, bump stops, coil mounts etc.

Well then if shocks dont stop axle wrap then why are hilux rears made with one pointin forward n one backwards??

[toughnut]

It changes the stability of the axel. The shocks are mounted to the bottom of the axel because it will pull down on the axel when you hit a bump. This is more stable than sitting on top of the axel. Try this experiment. Hold a tennis ball with 2 fingers opposing each other horizontally, now push the tip of a pen down on top of the ball. The ball tries to roll all the time right?! Now Tape some string to the ball so it hangs from the bottom of the ball about 2cm long ( the shock mount ). Tape the other end of the string to the tip of the pen and holding the ball the same as before push down on the pen. Much more stable. The only trouble with this is the shockie is left hanging in the breeze to get caught on obstacles. The best compromise is to lift the shock mount up level with the centre of the diff housing. You can get shock mounts ready to weld on from most 4x4 custom places like Snake Racing etc. No more getting hung up and still fairly stable.

I call BS
If your axle is twisting and the only thing stopping it is the shock you have serious problems!

Your control arms or leafs/traction bar is holding the diff in place and should resist any twisting forces.

Now depening on your setup the axle does twist a little as the suspension droops. Especially with coils and control arms, but it is all dependant on length of arms etc. etc.

I think the reason the shocks are mounted below the level of the axle is your stock four wheel drive does not have any lift and this is the way the manufacturer manages to fit in a shock that has enough travel for the suspension to cycle.

The shock does not really care where it sits on the tube.
The angle the shock is at can make a difference.
there are many things to consider when modifying shock locations, bump stops, coil mounts etc.

Correct me if I'm wrong but don't vehicle manufacturers have access to different lenght shocks???

It's all about physics. Or didn't you do science at school. If your going to call BS then make sure you have a believable answer. Here, I'll explain it a different way for ya.

For starters shock absorbers are the springs themselves not the dampers. Dampers dampen the shock and keep the vehicle stable over uneven surfaces. To make it easier for the damper to work effectively they make the pivot piont lower than the axel. This in effect pulls down on the axel when a bump in the road makes the axel travel upwards. It's a simple rule of physics that pulling something is much more stable than pushing something. For example. What's easier? Towing a trailer or pushing it? Same thing with the axel just on a different scale. Hope this clears up any questions. By the way the original question was not about how the axel is attached to the vehicle but how a shockie is attached to the axel.

[zzzz]

Correct me if I'm wrong but don't vehicle manufacturers have access to different lenght shocks???

Yes they do, and I was just taking a guess there.
They make vehicles within all sorts of constraints.

It's all about physics. Or didn't you do science at school. If your going to call BS then make sure you have a believable answer. Here, I'll explain it a different way for ya.

Can't wait...

For starters shock absorbers are the springs themselves not the dampers. Dampers dampen the shock and keep the vehicle stable over uneven surfaces.

you have lost me already.
the shocks are the springs?
Damper? don't you eat that?

To make it easier for the damper to work effectively they make the pivot piont lower than the axel. This in effect pulls down on the axel when a bump in the road makes the axel travel upwards.

The shock can't really pull down on the axle.
It is reactive and trys to resist the force of the diff moving upwards when you hit the bump..

It's a simple rule of physics that pulling something is much more stable than pushing something. For example. What's easier? Towing a trailer or pushing it? Same thing with the axel just on a different scale. Hope this clears up any questions.

Agreed, but we have to make design compromises to gain clearance and I think the change is miniscule.
Otherwise you would never see a comp buggy with shocks mounted above the axle.

By the way the original question was not about how the axel is attached to the vehicle but how a shockie is attached to the axel.

I realise that but your tennis ball story implied the axle would be more stable if the shock was mounted underneath.
It may absorb bumps better, but it has very little to do with the stability of the axle in a twisting plane.

Of course there are also many different design aspects to take into account.
A desert tourer who does a lot of higher speed dirt and corrugations does not really care that the shock hangs down, so won't bother taking that into consideration when trying to find the ultimate location for their shocks.

The same occurs for people that love playing the rocks, as it requires very high clearance and slow speeds. So having the lower shock mount out of the way is virtually the most important aspect of their design.

So different things appeal to different people and the original poster has not made it clear what sort of four wheel driving they are into...

[zzzz]

Well then if shocks dont stop axle wrap then why are hilux rears made with one pointin forward n one backwards??

You can move a shock through its travel with your own two hands.
How much force does that take to move?

Now how much force do you think axle wrap could apply?
Is this enough to overcome the shocks?
Why do aftermarket manufacturers make traction bars?
etc

I don't know all that much about leaf suspension, but I think I can safely say that shocks no matter where they are mounted cannot control axle wrap

[DamTriton]

Shock absorbers (dampers) are there to absorb the resonant oscillations of the spring (the "BOING"). The bulk of the weight and "shock absorbtion" of the moving mass is taken by the springs, with only an instantaneous minor amount being seen by the damper. The deformation of the rubber bushings of the damper would also contribute to the overall shock absorbtion mechanism (low frequency) as distinct from the oscillation damping (high frequency).

By way of general reasoning, the Hilux is the only vehicle that has fore+aft damper placements, and therefore should be seen as an exception to the rule (if there is one). If one wheel went up and the other down then the rotation of the axle along the axis of the half shafts would in fact be amplified.

Most aftermarket spoa setups seem to be quite stable using the "standard" shock placements, whether that be fwd, backward, or towards the centre of the vehicle. The important thing is to try and have the dampers as close to and parallel with the spring as possible, and as close to the axle housing as possible, otherwise you will end up with axle-tramp from the axle housing having its own flexion and resonance from the damper mount to spring perch area, reflecting across the span of the axlehousing ("Xylophone" effect).




but what do I know , I'm only a Registered Nurse with a Kia Sportage

[Gwagensteve]

I am going to preface this by saying that I don't believe that where the shock (oops, damper) is mounted relative to the axle makes any difference to its effectiveness, and I vote with the convenience of getting the shock length required into the car without going though the floor or excessively angling the shocks (loosing wheel rate) as the reason that the manufacturers mount the shocks (oops dampers... damper, mmmm ) below the centre line of the axle. How close the mounting lower mounting point is to the wheel will make a substantial difference in shock performance though. Shock performance is far more critical for a coil sprung car than for a leaf car, as a coil has no internal friction, and where the upper shock mount can be high ( in the front) it is usually mounted at or above the centreline, whereas in the rear, where floor clearance and space in the inner guard is an issue, they are normally mounted low.

HOWEVER,

Shock placement on the rear of Hiluxes IS ABSOLUTLELY there to reduce axle wrap. The very early hiluxes had the rear shocks mounted across the car, then in 1985 they moved them fore aft to counter axle wrap.

How can a shock counter axle wrap when you can move it with your hand? Easy - Try and move it fast - the faster you try and compress the shock, the more it resists. Generally, axle wrap in low power, stock applications is a momentary event, often turning into wheel hop or axle tramp. The resistence to moving quickly is why they work to resist axle wrap, so long as the mounting plane is correct. however, the fore aft mounting plane tends to cause bushing bind in articualtion.

PS, curernt model Chevy pick ups ( I think???? - saw a photo in a recentish Petersens) use a bilstein (Gas pressure shock absorber, as Bilstien themseves describe them) shock horizontally mounted on the top of the rear diff pumpkin to counter axle wrap.

Just my $0.02 worth.

[toughnut]

For starters shock absorbers are the springs themselves not the dampers. Dampers dampen the shock and keep the vehicle stable over uneven surfaces.

you have lost me already.
the shocks are the springs?
Damper? don't you eat that?

Thats just arguing for the sake of arguing.

To make it easier for the damper to work effectively they make the pivot piont lower than the axel. This in effect pulls down on the axel when a bump in the road makes the axel travel upwards.

The shock can't really pull down on the axle.
It is reactive and trys to resist the force of the diff moving upwards when you hit the bump..

Talking about the mounting point of the shock damper in relation to the axel.

It's a simple rule of physics that pulling something is much more stable than pushing something. For example. What's easier? Towing a trailer or pushing it? Same thing with the axel just on a different scale. Hope this clears up any questions.

Agreed, but we have to make design compromises to gain clearance and I think the change is miniscule.
Otherwise you would never see a comp buggy with shocks mounted above the axle.

As was stated in the first question, is there any disadvantage of mounting the shock absorber to the top of the axle (it's mounted to the spring pad on the rear of the 40.) Just trying to give him some info to make up his own mind.

By the way the original question was not about how the axel is attached to the vehicle but how a shockie is attached to the axel.

I realise that but your tennis ball story implied the axle would be more stable if the shock was mounted underneath.

May have been a poor example but.........It is more stable!

It may absorb bumps better, but it has very little to do with the stability of the axle in a twisting plane.

It does aid stability on a "twisting plane". Remember that the damper acts on high resonance oscillation so, with the shock mount lower than the axel it effectively means that the axel is pulling up on the shock. If the mounting point is above the axel then the axel is effectively pushing on the base of the shock. Having the shock mount lower than the axel places less torsional stress on the shock which means that the manufacturer can use smaller shocks which in turn mean less money. Tight bastards.

Of course there are also many different design aspects to take into account.
A desert tourer who does a lot of higher speed dirt and corrugations does not really care that the shock hangs down, so won't bother taking that into consideration when trying to find the ultimate location for their shocks.

The same occurs for people that love playing the rocks, as it requires very high clearance and slow speeds. So having the lower shock mount out of the way is virtually the most important aspect of their design.

So different things appeal to different people and the original poster has not made it clear what sort of four wheel driving they are into...

Completely agree.

[J Top]

Early Bundy's run 2 different rear shocks which I think are also each side of the diff.
I agree with you Steve
J Top

[DamTriton]

Early Bundy's run 2 different rear shocks which I think are also each side of the diff.
I agree with you Steve
J Top

"Poor mans" solution to a torque rod, before the ppl expected more power from the drivetrain???

[Mytqik]

Shock Absorbers - dampers = Same thing, just different name from different people. You say potatao, I say patatao.

Axle wrap is is a direct result of suspension setup. In effect the front half of a leaf spring (between the solid mount & the diff housing) can be assumed to be a solid link which flexs slightly under compression. The first 2-3 leaves are actually bound together with metal clamps in the front half of the leaf spring.

It is "solid link" this which stops axle wrap.

If what toughnut said was true, the leaf spring would be bending at extreme angles directly in front of the spring perch.

The rear half of the leaf spring & shackle is what does the majority of the suspension work.

The location of the shock absorber/damper is important for reducing the oscillation of the spring, however if the shock/damper is removed axle wrap will not increase.

So to answer the original question, there is no real advantage to mounting on top in terms of reducing the oscillation of the spring (the original purpose of the shock adsorber/damper).

HOWEVER you may find that the shock absorber/damper may bind against the diff housing under full suspension droop. This would then bend/crease the housing of your shock adsorber/damper. If this was going to occur, then I would move the lower mount to ontop of your diff housing.

[Patroler]

My rear shocks are mounted on top of the axle, car has a u bolt flip so the plates that are normally below are on top of the axle, the shocks are angled in a fair bit.
Seems to work ok so far, haven't had severe axle wrap yet, pulled a couple of leaves out the other day, and its running a 383 chev and 35's or 36's so no shortage of power or leverage.
I'd guess they mainly mount them below the axle due to packaging/floorspace, have a look at the new transit van, the shocks mount about 6 inches below the axle!!

[toughnut]

If what toughnut said was true, the leaf spring would be bending at extreme angles directly in front of the spring perch.

It only takes a miniscule amount of flex to disrupt the dynamics of the suspension. For instance if you don't correct the castor of the rear diff in some high lift applications (namely coil sprung vehicles) it can effect how your power is transferred to the ground. ie if you don't adjust rear castor your vehicle may lift the rear end when excellerating hard. If you adjust the castor then it will squat better and transfer the power more effectively. Drag racers do a fair bit of this when they tune thier chassis to get power to the ground better. It also helps eliminate axel tramp to a certain degree.

HOWEVER you may find that the shock absorber/damper may bind against the diff housing under full suspension droop. This would then bend/crease the housing of your shock adsorber/damper. If this was going to occur, then I would move the lower mount to ontop of your diff housing.

You can get or make spacers for this problem. In a lot of cases people replace the shock mount completely and lift it up out of the way. It's not usually the diff housing that the shock hits. It occurs usually to coil sprung vehicles when you have a fairly high lift without correcting rear caster angles. This causes the spring to bow out rearwards and can sometimes contact the shock housing.

[Rainbow Warrior]

For starters shock absorbers are the springs themselves not the dampers. Dampers dampen the shock and keep the vehicle stable over uneven surfaces.

you have lost me already.
the shocks are the springs?
Damper? don't you eat that?

Thats just arguing for the sake of arguing.

You started this one.
When you mechanic tells you your shocks are stuffed you can go and order new springs but I wouldn't.

[J Top]

Steve
this time I am questioning, .Whenyou are powering on you want lift at the rear, not squat, as for every action there is an equal and opposite action so if you are dropping the rear then you are lifting the diff which will lower traction
J Top

[zzzz]

Steve
this time I am questioning, .Whenyou are powering on you want lift at the rear, not squat, as for every action there is an equal and opposite action so if you are dropping the rear then you are lifting the diff which will lower traction
J Top

Uh, oh, We are about to cross the point where everyones brain will hurt
Now we get to talk about fun stuff like antisquat, roll centre, roll axis, centre of gravity, instant centre...

The shoclks have little to no effect on squat, and suspension geometry.
I believe they are primarily there to control rebound and stop the car bouncing.

Where's Stangerover? He does a great job of explaining this stuff.

I believe the main reason you want to dial in the amount of antisquat you have is to avoid the rear axle hopping when you are trying to climb something really steep.

Some people prefer 0% antisquat and it seems a lot of the moon buggys are setup that way, and then others like figures getting up to 150% AS.
It seems to be generally accepted that an AS around 100 is good.

This is a really good read:
http://www.jeepaholics.com/tech/quarterellip/

and this...
http://www.pirate4x4.com/forum/showthre ... anti+squat

cheers

z

[Busiboy]

Geeeeeezzzzzzuuuuuuuuusussssssss

There are some really funky ideas about shocks and springs in this thread.

So far from what I have read the registered Nurse in the Kia has the best idea

If you want to know what your shockie do, take them off, drive off a gutter at about 15kph. I did this (I had the shocks off for something else) and all I could do was laugh.

Shockies stop your car bouncing like a pogo stick after you hit a bump. THAT IS IT, the whole anti wrap thing is a bit much for me.

You can mount your shockies where ever you want, as long as they are secure. Directly above the axle is great. The reason for this is that if you have it behind infront etc your mount has to be stronger to take the leverage effect. Like putting a pipe on a spanner.

The reason for angled shocks is so that you can get more up travel out of a shorter shock absorber (shock absorber means it absorbs shock). The one forward and one rearward is just a bit more balance. The reason they didn't do it to the centre was you could get more angle by going rearward and forward.

I'll put that up and see the responses.

[Guy]

I am going to preface this by saying that I don't believe that where the shock (oops, damper) is mounted relative to the axle makes any difference to its effectiveness, and I vote with the convenience of getting the shock length required into the car without going though the floor or excessively angling the shocks (loosing wheel rate) as the reason that the manufacturers mount the shocks (oops dampers... damper, mmmm ) below the centre line of the axle. How close the mounting lower mounting point is to the wheel will make a substantial difference in shock performance though. Shock performance is far more critical for a coil sprung car than for a leaf car, as a coil has no internal friction, and where the upper shock mount can be high ( in the front) it is usually mounted at or above the centreline, whereas in the rear, where floor clearance and space in the inner guard is an issue, they are normally mounted low.

HOWEVER,

Shock placement on the rear of Hiluxes IS ABSOLUTLELY there to reduce axle wrap. The very early hiluxes had the rear shocks mounted across the car, then in 1985 they moved them fore aft to counter axle wrap.

How can a shock counter axle wrap when you can move it with your hand? Easy - Try and move it fast - the faster you try and compress the shock, the more it resists. Generally, axle wrap in low power, stock applications is a momentary event, often turning into wheel hop or axle tramp. The resistence to moving quickly is why they work to resist axle wrap, so long as the mounting plane is correct. however, the fore aft mounting plane tends to cause bushing bind in articualtion.

PS, curernt model Chevy pick ups ( I think???? - saw a photo in a recentish Petersens) use a bilstein (Gas pressure shock absorber, as Bilstien themseves describe them) shock horizontally mounted on the top of the rear diff pumpkin to counter axle wrap.

Just my $0.02 worth.

This is some kind of record .. for the 2nd time in a single year .. I agree with steve

[toughnut]

It's painfully obvious that I'm not explaining this in a way that all can understand. I was just trying to pass on a bit of info to bad religion so he could make his own opinion about the info on this thread. None of you know what kind of experience I have with suspensions and ditto for myself about you guys. I haven't seen such a display of blatent ignorance since I joined this thread. If you believe that the shockies only stop the bounce of the suspension then each to thier own. Nothing I say will change your mind.

To bad religion, I'm sorry that your thread has been hijacked. I hope that you can sift through pissing contest and get some decent info out of it. Well I've had about 50c worth too much.