110mm lift - Caster Correction

[toolsplus]

standard bushes Clive
but I had about 20mm cut out of the panhard rods

what do the drop boxes achieve,in layman's terms?

cheers

 

[Pumpy]

Think the drop boxes are only for 4"-6" lift, delivering a perfect 3.0 degree castor angle at 4"/100mm lift. They drop the mounting point on the body for the radius arms by about 4", which puts the castor angle back on the axle keeping all the geometry in the right place, so the drag link doesn't foul on the radius arms as it can do with the castor plate kit.
Here's the thread from FNB on them
https://www.landcruiserclub.net/community/threads/landcruiser-80series-dropboxes-released.143552/

 

[Lorin]

Drop boxes can be had for 2 and 3 inch lifts as well. I have a set of the Man e Fre 3" drop boxes that I am going to put on once I've removed the correction bushes. They also make them for 2" and 4" lifts. IIRC for lifts over 4" the drop boxs need to be paired with correction bushes.

My last 80 had a standard OME 50mm lift and benefitted hugely from having castor correction. I'm not entirely convinced on the idea that a 2" lift doesn't need castor correction. A good idea is to get a full alignment check that gives your current castor and see if it is within spec.

 

[clivehorridge]

Drop boxes can be had for 2 and 3 inch lifts as well. I have a set of the Man e Fre 3" drop boxes that I am going to put on once I've removed the correction bushes. They also make them for 2" and 4" lifts. IIRC for lifts over 4" the drop boxs need to be paired with correction bushes.

My last 80 had a standard OME 50mm lift and benefitted hugely from having castor correction. I'm not entirely convinced on the idea that a 2" lift doesn't need castor correction. A good idea is to get a full alignment check that gives your current castor and see if it is within spec.

I would tend to agree with you there Lorin, any lift is going to change the caster angle and that can't be good. The higher the lift the worse it gets.

 

[toolsplus]

Drop boxes can be had for 2 and 3 inch lifts as well. I have a set of the Man e Fre 3" drop boxes that I am going to put on once I've removed the correction bushes. They also make them for 2" and 4" lifts. IIRC for lifts over 4" the drop boxs need to be paired with correction bushes.

My last 80 had a standard OME 50mm lift and benefitted hugely from having castor correction. I'm not entirely convinced on the idea that a 2" lift doesn't need castor correction. A good idea is to get a full alignment check that gives your current castor and see if it is within spec.

thanks mate

i'll get the 80 on a lift and get an alignment check
i'll probably have to read and understand about castor angles and things
shame,i've managed to stay ignorant and avoid it til now

cheers

 

[clivehorridge]

thanks mate

i'll get the 80 on a lift and get an alignment check
i'll probably have to read and understand about castor angles and things
shame,i've managed to stay ignorant and avoid it til now

cheers

There's probably max/min angle tolerances quoted somewhere TP, but I get the impression that every truck behaves differently.

In theory, mine was in tolerance, the caster angle came up in green on my alignment report. But after fitting the drop boxes, the driving and handling difference (for the better) was amazing.

 

[toolsplus]

what's the effect of these drop boxes on the allignment of the car?

ie what do they drop,how much drop,why...?

i need a lecture in 4WD mechanics really
i'm at Trev's next week,i'll ask him

 

[Pumpy]

I'll have a go, please correct me if I'm wrong, every days a school day!

This is looking at yer front wheel side on, the red line is through the pivit points on the steering (swivel bearings) you can see that by adjusting the caster angle (x) it will effect how the car handles, brakes and steers, returns to centre etc. i.e. the geometry of the steering will change.

If the caster angle was changed by adding a 4" lift (say) you can also see why the propshaft will pull the caster angle up, additionally causing undue stresses on the propshaft U/Js - it's wierd to imagine but when the angle on each end of the propshaft isn't euqal, the propshaft actually speeds up and slows down to compensate, Caster correctiom reduces the angle again (x) found this vid explains the propshaft thing miles better...

Using caster correction plates effectively decreases x by twisting the axle within the radius arms, this corrects the angle but doesn't correct the whole geometry, the drag link can foul on the radius arm for example.

Using drop boxes the axle is effectively twisted back down by dropping the other end of the radius arm, which bring the geometry of the whole axle with them.

Castor correction bushes try to achieve the same thing, twisting the axle by changing the mounting points within the bushes on the radius arms to bring the castor angle back down, but word is, these things are the work of the devil

The more you lift from standard without castor correction, the higher x becomes, which will put undue pressure on U/Js, Diffs, and Transfer boxes, not to mention poor handling.

 

[Lorin]

Spot on I reckon Pumpy and that video is a brilliant explanation, especially of phasing.

 

[clivehorridge]

Yep, spot on.

With everything standard, as you raise the chassis relative to the wheels (as with a suspension lift) the front axle rotates as the drag links go up with the chassis. What the drop boxes do is lowers the chassis end of the drag link back to its original position (relative to the wheels).

Simples.

 

[fbnss]

That video is great, i finally kinda know wtf Chris was talking about now!

 

[frank rabbets]

Castor is steering only related nothing to do with the prop shaft. Altering the castor coincidentally alters the flange angle on the dif. This creates another problem as the prop speed and angle are then screwed up.

If your steering returns heavily you already have too much castor so adding the drop boxes would make it worse.

Think that's right.

 

[clivehorridge]

Castor is steering only related nothing to do with the prop shaft. Altering the castor coincidentally alters the flange angle on the dif. This creates another problem as the prop speed and angle are then screwed up.

If your steering returns heavily you already have too much castor so adding the drop boxes would make it worse. Think that's right.

It sounds right to me Frank, but quite how TP has too much caster angle is a bit of a mystery to me.

He has a 75mm lift which may be the maximum limit of correction with offset bushes. So it's more likely that the caster angle would be less than optimum.

The advantage of the drop boxes is that it takes out all the guesswork. You go back to standard OEM bushes (which are a much better bush IMO) and you fit the appropriate depth of drop box, in TP's case 75mm.

That way, the original factory angle must have been restored, without any guesswork of how much rotation you might have on the offset bushes if they're not fitted correctly, and the like.

Just worn bushes will throw the angle out. So by replacing them you know everything is ticketyboo. I can't think of any other reason for the angle to be too much or too little.

Excessive play in the top and/or bottom swivel bearings (kingpins) would screw up everything, caster and camber angles, so ideally, these should be checked first.

 

[SimonD]

Question for the folk who've fitted Chris's or Manafre's dropboxes. Since fitting the drop boxes my steering wheel is now off-centre - is this a usual outcome?

 

[clivehorridge]

Question for the folk who've fitted Chris's or Manafre's dropboxes. Since fitting the drop boxes my steering wheel is now off-centre - is this a usual outcome?

It shouldnt be, there's no reason whatsoever why it should now be off-centre. I'm guessing the mechanic removed the steering wheel or something, and put it back one spline out.

You can correct centering with the adjuster on the steering arm (the long one going from the steering box to one of the wheels).

 

[Lorin]

Question for the folk who've fitted Chris's or Manafre's dropboxes. Since fitting the drop boxes my steering wheel is now off-centre - is this a usual outcome?

Drop boxes had no effect on my steering. Two things can't really be related as far as I can tell. Something else has effected your steering.