Dmax CV

Ziggy

Well-Known Member
Yes, I read through the thread.
The amount of sag will be a function of spring rate as well as load. If he's got 100kgs of bar and winch...
Then there's the extremes of travel; the spring may be poorly damped.
But my point is that if there's premature wear, wouldn't you hear knocking to begin with?
 

muc the truck

Well-Known Member
You only get knocking on a cv due to high km wear . Like 300,000kms camira clicking around corners because the balls have warn out in the cv.
You don't get the knock in cv joints as a warning in part time 4x4 because they get little wear due to most kms don't in 2wd , Normally the only knock you will here in a lifted irs is if you over range a cv constantly above standard running angle under load and you crack the housing first loosening the balls just before it falls apart . Sometimes the balls bind and shaft breaks.
 
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I am assuming your thinking unlifted the cv joints are not flexing as much and when lifted they are at increased angles thus placing side load while in 4x4 on the cv joints themselves which leads to them breaking . What has been explained much early above in the post is that the high rate of spring supplied left the vehicle at almost full down travel extent permanently unless a lot more load is placed on the vehicle as its a gmv upgrade in order to compress the stiffer spring . I suggested to fit the correct springs for the load but the OP had already bought a diff relocation bracket to try and fix it. I have stated above that I firmly believe the installation of the wrong springs to the vehicle constant load have been sold to the owner .
I agree with you muc the truck, that part of my problem was the high rated ironman spring. My Dmax only have a bullbar and a winch in front n have nothing on the roof. I'm changing to a medium spring.
 

muc the truck

Well-Known Member
Robert Pepper reckons that most bar/winch additions exceed the front axle load rating.
Anyone done the numbers?
I have xrox bar and winch , stock suspension with Bilsteins shocks . dropped 5mm with bar and winch. No way am I going for stiffer when its rough enough as it is . I cant understand why anyone would sacrifice suspension travel and comfort lifting an irs . They bought the wrong 4x4 to begin with. should have bought an 80 series , patrol or land rover with 4 coils . at least you can have your cake and eat it too . lift and flexy.
 

phs

Well-Known Member
Lift IFS and loose wheel travel
How does that work is it not just moving the travel to move upward and less droop. I would think the " travel " is much the same or am I missing something

Does a diff drop with a lift increase travel ?
 

muc the truck

Well-Known Member
Lift IFS and loose wheel travel
How does that work is it not just moving the travel to move upward and less droop. I would think the " travel " is much the same or am I missing something

Does a diff drop with a lift increase travel ?
Every mm you go up with a irs is a mm lost in down travel so when you going over a rut more likely to make a wheel in the air than standard . Going up also means increasing spring rate that means the vehicle has less chance of compressing down to the bump stop on one side when the other is dropping into the rut to make ground contact unless you add more weight to compensate the stiff springs. So the result is a harsher ride with more chance of a wheel in the air /spin/sudden wheel contact /sudden cv joint load / bust something . every 4x4 must have as much down travel as can be gained in order to provide as much traction so why anyone would take down travel out is beyond me . I have jacked some irs 4x4 up by one lower control arm and the spring rate so stiff at 2'' raised over stock that with the very first pump of the trolley jack after metal to metal contact of jack and control arm both front wheels come off the ground instead of the jacked side compressing up towards the bump stops with a few pumps of the jack first then lifting both wheels off the ground like what happens with standard . That's how travel is reduced

dif drops don't increase travel , they just correct a nasty cv angle . The upper and lower bump stops govern the range , the spring rate and vehicle weight govern how active the suspension is within the range .
 

phs

Well-Known Member
Yes but what you loose in downward travel you are gaining in upward ?

Travel is the same ( spring rates aside )
 

muc the truck

Well-Known Member
Yes but what you loose in downward travel you are gaining in upward ?

Travel is the same ( spring rates aside )
Did you even take into account my explanation . trolley jack . Your comment seems to tell me NO. If one increases the spring rate on a irs vehicle and doesn't increase the vehicle to compensate how does a vehicle compress the springs down the same as stock? Its the same old story . Springs too stiff to compress when you jack one control arm up. Your NOT gaining upward travel if the vehicle load cant overcome the spring rate . Your reducing travel because its no longer the bump stops restricting travel but lack of vehicle load . We may get full compression by being an ass to the car and flogging the life out of it on bad roads and tracks but when your negotiating slow tricky tracks you have less travel with raised suspension on irs to contour the 4 wheels on the ground.
 
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Ziggy

Well-Known Member
Stiff or soft springs are relative terms, not absolute. You select the spring rate to get the right sag with your normal load.
If your suspension travel is eg 150mm you want static sag to be about 30mm.
You need some headroom for rebound and also the shock works best around the middle of its range, not the ends.

The problem arises when folk run lightly loaded around town and heavily on a trip. You either seek a compromise or fit one of the adjustable preload struts that have come onto the market (eg. Terrain Tamer, Dobinson MRR).

muc the truck: you have ignored what the shock does. The purpose of the spring is to absorb road height changes. The purpose of the shock is to control the rate of wheel movement (in both directions). Both together provide some ride comfort plus maintain grip.
 

muc the truck

Well-Known Member
Stiff or soft springs are relative terms, not absolute. You select the spring rate to get the right sag with your normal load.
If your suspension travel is eg 150mm you want static sag to be about 30mm.
You need some headroom for rebound and also the shock works best around the middle of its range, not the ends.

The problem arises when folk run lightly loaded around town and heavily on a trip. You either seek a compromise or fit one of the adjustable preload struts that have come onto the market (eg. Terrain Tamer, Dobinson MRR).

muc the truck: you have ignored what the shock does. The purpose of the spring is to absorb road height changes. The purpose of the shock is to control the rate of wheel movement (in both directions). Both together provide some ride comfort plus maintain grip.
I have not ignored anything . My point all along has been that people are continually buying the wrong spring for there irs or over cranking torsion bars. I say again for example lifted and increased spring rate that exceeds suggested load of vehicle when its actually used off road (no good dreaming you have the load on the vehicle to suffice the gmv upgrade, you actually must have the load on the vehicle for the gravity be able to compress the springs down to bump stop and the easiest way to prove you got it right is to jack the vehicle up from one suspension arm and take note if it gets really close to hitting the bump stop before the other front wheel leaves the ground and no longer provides traction ) . I have lost count of how many tradie vehicles I have seen off road lifted to the hilt because they drop off there tools off home drive on tacks like toys , the tonka kind with buger all in suspension travel because vehicle load and our gravity is not good enough to compress the springs to contour the terrain . Yet people go home with occasional busted cv joints and commonly tell stories about how hard the track was , (wheels off the ground all the time ) I need lockers etc etc Yet I got there on stock suspension and Bilsteins Shocks. All most people need is active suspension , not over rated which is the most common mistake .
 
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phs

Well-Known Member
I did say spring rates aside

You said

"I cant understand why anyone would sacrifice suspension travel and comfort lifting an irs ."


I was simply stating that if done correctly the wheel travel is the same that is all
 
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Jackolux

Active Member
I have jacked some irs 4x4 up by one lower control arm and the spring rate so stiff at 2'' raised over stock that with the very first pump of the trolley jack after metal to metal contact of jack and control arm both front wheels come off the ground ]

muc are you serious with that claim , just out of interest I just jacked my Ute up with the trolley jack under one lower control arm .
Jack went to full hight wheel was at least 300mm off the deck the other wheel was still firmly planted .

I reckon the Ute would fall on its side before the other wheel lifted .
 

Jackolux

Active Member
Ziggy to answer your question , my Ute on the weigh bridge the other day went 1350kg on the front axle .
If my memory is correct that is right on Max front axle rating.
I only have a Single Hoop Bull Bar , Runva Winch with synthetic rope , no second battery under the bonnet, it's under the tray and a tiny 10" light bar .
 
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Tink

Well-Known Member
Ziggy to answer your question , my Ute on the weigh bridge the other day went 1350kg on the front axle .
I only have a Single Hoop Bull Bar , Runva Winch with synthetic rope , no second battery under the bonnet, it's under the tray and a tiny 10" light bar .
Which is the front axle rating for a Dmax.
Front 1350kg
Rear 1600kg
Tink
 

Jackolux

Active Member
Which is the front axle rating for a Dmax.
Front 1350kg
Rear 1600kg
Tink
That's right Tink , I just edited my post to include that .
All those that have heavier bars , steel cable , big lights and second battery under the bonnet would have to be over on the front .
When I drop the Tvan one the tow bar a few Kg comes off the front axle
 

muc the truck

Well-Known Member
I did say spring rates aside

You said

"I cant understand why anyone would sacrifice suspension travel and comfort lifting an irs ."


I was simply stating that if done correctly the wheel travel is the same that is all
same length . But its not all usable . The suspension droop you had is lost and the compression range is increased but unless the load is increased as well range is lost from the compression side too. So lost Droop/ Lost Compression. I have compared dozens of lifts on irs and this has been the same on all of them. If you go up 2 inches in height you need a lot more load to push it down to touch its bump stops. True. Try it
 

peterfermtech

Well-Known Member
Agree with muc. Simple maths. With linear springs if it takes x kg to compress the spring 25mm then it will take 2x kg to compress 50mm and 4x kg to compress 100mm and whatever to hit the bump stops. If you've used a heavier duty spring then you're even further against it. Less droop on one side and harder to compress (with heavier duty springs) on the other side means a lot more air time for one of the wheels. It also means more time running the CV in that highly flexed state.

regards
 

phs

Well-Known Member
Simple math on what spring rate ?

The travel is the same you just need the correct springs

It's not the lift, it's the spring that limits it.
 
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peterfermtech

Well-Known Member
Say the springs compressed 10mm for every 25mm of wheel travel and that there is 100mm of wheel travel up to hit bump stops when at std height. That means the spring would compress 40mm at std height or 60mm on 50mm lift before hitting bump stops. 60/40 = 1.5 or 50% more force (or weight) to hit bump stops with the same rate spring which of course would have to be longer to provide the lift. You would need a spring 1/3rd lighter to get the same amount of suspension travel. Probably very nice for rock hopping but not suitable for road travel.

regards
 
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