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A few basic suspension questions


pugwash

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1. Is it beneficial to have equal droop and bump? how important is it?

2. Would you trade front and rear suspension balance for ultimate and agressive articulation

3. Is there a way of calculating how a change in spring rates will affect side slope stability.I would rather hvae better side slop stability that a huge amount of articulation

4. Is their a calculation (pretty complex i imagine) that would show the necessity for articulation when using lockers both front and rear? ie is there some way of working out the optimum articulation/ stability balance when using lockers?

5. What really effects how springs alter ride? is it the free length, the rate, the number of coils, the variability, or all of the above- what i am asking is if you have a standard height but want more bump what do you do? make springs longer but softer? does this mean you have more coils neccessarily?

6. If you want to run standard height suspension but maximise articulation, and your limiting factor is your shock, then the thing to change is the droop yes? to mazimise this am i right in thinking that you increase the shock length and increase the top mounting point by exactly the same amount? this would give the same bump but more droop yes?

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1. Is it beneficial to have equal droop and bump? how important is it?

I think so, dropp and rise are equally importnat, this allows the axle to flex having 1 side high and one side low, the more you have the greater the flex. Flex can be "Stopped" by a number of things - Bodywork - such as wheel boxes, bump stops (why mine are SMALLER than normal ones) and spring [pundage being to high - too low and the coil compresses fully and you have bind - not good

2. Would you trade front and rear suspension balance for ultimate and agressive articulation

There is in my opinion, little point in having massive travel one end and virtually none at the other. BALANCED is the ultimate aim, but without changing the front end significantly you will find the friont harder and more expensive to get near the back, 3 link is a huge step towards this goal, more articulation = more stress and wear U'Js Shocks mounts etc

3. Is there a way of calculating how a change in spring rates will affect side slope stability.I would rather hvae better side slop stability that a huge amount of articulation

Length poundage and lift all affect side slopes, +4 inch raise can feel hard with high poundage springs, and like jelly with soft - shove soft on a side slope and Ooooer !...Its more about getting it right than a simple yes / No.

4. Is their a calculation (pretty complex i imagine) that would show the necessity for articulation when using lockers both front and rear? ie is there some way of working out the optimum articulation/ stability balance when using lockers?

Trev LR90S spring calc is a godsend - use it and learn

5. What really effects how springs alter ride? is it the free length, the rate, the number of coils, the variability, or all of the above- what i am asking is if you have a standard height but want more bump what do you do? make springs longer but softer? does this mean you have more coils neccessarily?

To alter ride height again its complex, either use the same spring but have it lobger, or a sofdter sring and much longer or a hard spring and it could even be shorter. ride height and ride poundage are interlinked - and a nightmare to get right, without having at least front and rear weights of your truck you'll be stabbin in the dark....

6. If you want to run standard height suspension but maximise articulation, and your limiting factor is your shock, then the thing to change is the droop yes? to mazimise this am i right in thinking that you increase the shock length and increase the top mounting point by exactly the same amount? this would give the same bump but more droop yes?

See my posts on suspension mods, I have stad ride height but long long soft springs, disc cones, homemade top mounts, +5 shockls, modded polybushes bent rad arms etc etc, oh and chopped wheel boxes +3 to allow whell up and in, oh and modded arches too

Much more work than a simple +2 kit :(

HTH

Nige

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1. Is it beneficial to have equal droop and bump? how important is it?

They don't have to be equal IMHO, but obviously more of both is best. Bump becomes more important the faster you intend to travel.

2. Would you trade front and rear suspension balance for ultimate and agressive articulation

No - I tried both on my Ibex, balance is much nicer and predictable to drive with

3. Is there a way of calculating how a change in spring rates will affect side slope stability.I would rather hvae better side slop stability that a huge amount of articulation

Not as far as I know, the closest I've seen is the COG and roll-over calcs that I'm gonna mess about with at the weekend. Jeepaholics

Maybe if your maths was good you could build in factors caused by change in heights caused by softer/harder springs

4. Is their a calculation (pretty complex i imagine) that would show the necessity for articulation when using lockers both front and rear? ie is there some way of working out the optimum articulation/ stability balance when using lockers?

I have no clue what that would be, or why you would want it

5. What really effects how springs alter ride? is it the free length, the rate, the number of coils, the variability, or all of the above- what i am asking is if you have a standard height but want more bump what do you do? make springs longer but softer? does this mean you have more coils neccessarily?

On my Ibex - I ran known spec springs. Then got it weighed front and rear, and was able to calculate the increase in rate and ride height I wanted. This was before Trev's spring rate calculator ;)

Tell coilsprings.co.uk what you want and they'll make it for you

6. If you want to run standard height suspension but maximise articulation, and your limiting factor is your shock, then the thing to change is the droop yes? to mazimise this am i right in thinking that you increase the shock length and increase the top mounting point by exactly the same amount? this would give the same bump but more droop yes?

Thats the easiest way, which is why it "seems" the best, as Nige will testament, getting bump is much more difficult, but if you want a suspension to work at speed, then its better to do that.

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I'd concur with much of the above but suggest bump really is as important as droop if the truck is to remain balanced and to reduce the amount the trucks cog rises when it is articulating, esp if it is already on a side slope!

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These are anything but basic!

1. Is it beneficial to have equal droop and bump? how important is it?

The greater the proportion of rise to droop, the lower your average center of gravity. However, on a Land Rover, you are never going to achieve as mich rise as droop. You would have to seriously limit the droop and loose most of your bodywork, never mind the engine to give something with decent travel and equal droop & rise.

Go for as much of each as you can.

2. Would you trade front and rear suspension balance for ultimate and agressive articulation

Again, in an ideal world they would be equal and for similar reasons. It helps keep the COG inside the footprint of the tyres, which helps stop it roll. In practice however, if you have a bias towards the rear, it just requires you to have a bit more nerve because it just increases the amount of lean. I suspect ones bottom would let go before the angle was steep enough to make much difference.

I think the above to being spot on is only the preserve of suspension geometry fundamentalists - the same ones who have pure de-ocygenated unobtainium speaker wires on their Amstrad HiFi ;)

3. Is there a way of calculating how a change in spring rates will affect side slope stability.I would rather hvae better side slop stability that a huge amount of articulation

Yes. However, you will need to know the position of the COG of your vehicle and it's weight.

You need to pick a slope angle. You need to use trig to resolve the forces.....anyway, it gets complicated.

You are better off using a relative method. If for a given poundage of spring, you get a certain amount of body roll. If you half the poundage, you will roughly double the roll. This is improved a bit by dual rate springs. As you compress the spring, it's rate increases.

4. Is their a calculation (pretty complex i imagine) that would show the necessity for articulation when using lockers both front and rear? ie is there some way of working out the optimum articulation/ stability balance when using lockers?

If you were driving on solid rock with no deformation slipping of the surface, lockers front & rear on a vehicle with no articulation would give you the same amount of traction as one with infinite articulation and open diffs.

The problem comes when the ground moves under foot. A single tyre with twice the ground pressure does not give you the same resistance from moving as two tyres with half the pressure.

Thus, when driving on earth, sand, mud - articulation wins over lockers. Better to have both though!

5. What really effects how springs alter ride? is it the free length, the rate, the number of coils, the variability, or all of the above- what i am asking is if you have a standard height but want more bump what do you do? make springs longer but softer? does this mean you have more coils neccessarily?

If you make the springs softer, wou get a smoother ride - we all understand that. However, when you go over a bump, the spring will compress and rebound more. If the springs are too soft, you will hit the bumb stops & it will not be so comfortable!

If you reduce the spring rate, you need to increase the free length pro-rata to give you the same resistance to bumps. This in turn raises your COG which may not be what you want. Again, variable rate springs help this.

6. If you want to run standard height suspension but maximise articulation, and your limiting factor is your shock, then the thing to change is the droop yes? to mazimise this am i right in thinking that you increase the shock length and increase the top mounting point by exactly the same amount? this would give the same bump but more droop yes?

Ignore the quoted travel lengths for shocks. they are all measured from different places. Some +2 shocks have the same travel,

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These are anything but basic!

1. Is it beneficial to have equal droop and bump? how important is it?

The greater the proportion of rise to droop, the lower your average center of gravity. However, on a Land Rover, you are never going to achieve as mich rise as droop. You would have to seriously limit the droop and loose most of your bodywork, never mind the engine to give something with decent travel and equal droop & rise.

Go for as much of each as you can.

2. Would you trade front and rear suspension balance for ultimate and agressive articulation

Again, in an ideal world they would be equal and for similar reasons. It helps keep the COG inside the footprint of the tyres, which helps stop it roll. In practice however, if you have a bias towards the rear, it just requires you to have a bit more nerve because it just increases the amount of lean. I suspect ones bottom would let go before the angle was steep enough to make much difference.

I think the above to being spot on is only the preserve of suspension geometry fundamentalists - the same ones who have pure de-ocygenated unobtainium speaker wires on their Amstrad HiFi ;)

3. Is there a way of calculating how a change in spring rates will affect side slope stability.I would rather hvae better side slop stability that a huge amount of articulation

Yes. However, you will need to know the position of the COG of your vehicle and it's weight.

You need to pick a slope angle. You need to use trig to resolve the forces.....anyway, it gets complicated.

You are better off using a relative method. If for a given poundage of spring, you get a certain amount of body roll. If you half the poundage, you will roughly double the roll. This is improved a bit by dual rate springs. As you compress the spring, it's rate increases.

4. Is their a calculation (pretty complex i imagine) that would show the necessity for articulation when using lockers both front and rear? ie is there some way of working out the optimum articulation/ stability balance when using lockers?

If you were driving on solid rock with no deformation slipping of the surface, lockers front & rear on a vehicle with no articulation would give you the same amount of traction as one with infinite articulation and open diffs.

The problem comes when the ground moves under foot. A single tyre with twice the ground pressure does not give you the same resistance from moving as two tyres with half the pressure.

Thus, when driving on earth, sand, mud - articulation wins over lockers. Better to have both though!

5. What really effects how springs alter ride? is it the free length, the rate, the number of coils, the variability, or all of the above- what i am asking is if you have a standard height but want more bump what do you do? make springs longer but softer? does this mean you have more coils neccessarily?

If you make the springs softer, wou get a smoother ride - we all understand that. However, when you go over a bump, the spring will compress and rebound more. If the springs are too soft, you will hit the bumb stops & it will not be so comfortable!

If you reduce the spring rate, you need to increase the free length pro-rata to give you the same resistance to bumps. This in turn raises your COG which may not be what you want. Again, variable rate springs help this.

6. If you want to run standard height suspension but maximise articulation, and your limiting factor is your shock, then the thing to change is the droop yes? to mazimise this am i right in thinking that you increase the shock length and increase the top mounting point by exactly the same amount? this would give the same bump but more droop yes?

Ignore the quoted travel lengths for shocks. they are all measured from different places. Some +2 shocks have the same travel, but the body is 2" longer! Stupid huh?

Either find shocks which quote compressed & extended lengths or measure this when your new shocks arrive.

Measure the distance between the top & bottom shock mounts on your truck. Subtract the distance between the axle and bump stop. You have to allow a little more for articulation as when the axle articulates, the bottom shock mount can be higher than the bump stop because the axle is rotating round the bump stop.

Each 15 deg of articulation, gives an additional 1" compression of the shock. Subtract that from the total.

20 deg is about the limit for most LR's = 1.33". Call it 1.5"

Max compressed length of shock = shock mount separation - bump stop separation - 1.5

Having measured the compressed length of your shock, you know how much you need to raise or lower the top mount such that it will never hit it's end stop.

Si

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I tend to be pessimistic and work on a worse case max compression featuring no bump stop - that way in the event of one "departing" its not a big drama

Jez you mad scientist

can you say that again a bit slower and a bit simpler please chap- i've missed that you're saying.

ta

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1. Is it beneficial to have equal droop and bump? how important is it?

2. Would you trade front and rear suspension balance for ultimate and agressive articulation

3. Is there a way of calculating how a change in spring rates will affect side slope stability.I would rather hvae better side slop stability that a huge amount of articulation

4. Is their a calculation (pretty complex i imagine) that would show the necessity for articulation when using lockers both front and rear? ie is there some way of working out the optimum articulation/ stability balance when using lockers?

5. What really effects how springs alter ride? is it the free length, the rate, the number of coils, the variability, or all of the above- what i am asking is if you have a standard height but want more bump what do you do? make springs longer but softer? does this mean you have more coils neccessarily?

6. If you want to run standard height suspension but maximise articulation, and your limiting factor is your shock, then the thing to change is the droop yes? to mazimise this am i right in thinking that you increase the shock length and increase the top mounting point by exactly the same amount? this would give the same bump but more droop yes?

An interesting set of questions on an interesting and important subject. I have my own veiws on what makes a competent cross country suspension,but I won't go into detail here, as much of it is covered on the thread on my truck in the members forum.

It would appear that many members of this forum know each other personally, and with a bit of effort the answers to these questions could be arrived at in a more definative manner than just reading various possibly biased opinions. Andy ,AKA Moglite wants to conduct a series of experiments with scales, ramps etc, to determin how his latest creation stacks up against a variety of designs. My suggestion is that a few of the keen truck builder/modifyers among you get together to devise a series of controlled experiments and tests to determin what situations some design principals excel at and where they fail. One experiment I would like to see included is stability when climbing a steep slope or bank at an oblique angle with drivers side down to see how each design copes with propshaft torque contributing to instability.

Bill.

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One experiment I would like to see included is stability when climbing a steep slope or bank at an oblique angle with drivers side down to see how each design copes with propshaft torque contributing to instability.

Bill.

I'd like to see that too - from a safe distance with a video camera :lol:

Kinda off topic - but we've also got a winch test pencilled in too. With a load-cell and clamp meters for the electric boys.

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When the pencilled date asnd where ?

Jez and I want to bring along our silly oiley winches and break have a go with your load cell ?

Nige :)

I'll run it past the Shires committee tonight, if I get the go-ahead. 19th November at Romsey Hampshire. I'll start up a thread tomorrow if its a go-er

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:i-m_so_happy: Michelle, still waiting for the rest of crew but I likes it B)

Jim - I dont rely on a bump stop to actually stop an axle.. if you do, and fate decides to take that bump stop from you in the middle of nowhere then you are left with a damper that cannot compress enough and bottoms out with "entertaining results" (lots of breakage), my preferred method is remove bumpstops, cycle suspension to max articulation and jack the "high side" until its in contact with the chassis THEN set the upper suspension mounting height,

Load cell dyno - yay, I need to find weekspots so I can sort them this winter B)

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I'd like to see that too - from a safe distance with a video camera :lol:

It doesn't have to be a dangerous experiment. An articulation ramp would probably do the trick. But instead of stopping when a wheel lifts off the ground, you keep going until the truck loses stability. A safety strap attached to the chassis about mid wheelbase and sliding up a rail attached to the ramp should prevent any damaging mishaps.

Bill.

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Bill I think more useful feeback could be gained from leaving the car unsecured - Andys voice rises in proportion to vehicle instability - a Db meter would give a wire free data link as well as providing us bystanders with limitless entertainment

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Bill I think more useful feeback could be gained from leaving the car unsecured - Andys voice rises in proportion to vehicle instability - a Db meter would give a wire free data link as well as providing us bystanders with limitless entertainment

I am all for a spot of entertainment Jez,so long as the performance was recorded for us that couldn't witness it first hand, but I doubt Andy would get many vehicle owners prepared to put their beloved trucks forward as guinee pigs without a safety strap.

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Bill I think more useful feeback could be gained from leaving the car unsecured - Andys voice rises in proportion to vehicle instability - a Db meter would give a wire free data link as well as providing us bystanders with limitless entertainment

I propose jez to go first!

Daan

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