Bigj66

I mentioned in this post that I’d read some information which stated the caster angle on a coil axle was different to that of a leaf axle, 12 degrees compared to 3 degrees. Reading up again on the subject, it seems that some people believe that the two are actually the same at 3 degrees. To avoid any further confusion for myself or anyone who may also be looking for this information, does anyone know for certain what that angle is, where I can find it documented or can recommend a way for me to measure it accurately from the axle I have? I think, in the interests of safety, it’s important that this sort of information is unambiguous and supported with some form of evidence if possible.

An optical illusion it was 🙈

I got impatient waiting so I popped a front wheel off the 110 to take a looksee. The wheels are set straight ahead and from what I can see, the TCA taper hole is definitely inboard of the top swivel pin and looks to be in line with the centre line of the axle as discussed earlier. In other words, slightly inboard of the kingpin line as it should be 👍 I placed a long bolt on the centre of the top swivel pin to try and give a visual reference point between the various positions. Again, it’s no big drama if the track rod has to remain at the rear.

Can’t the complete housing be swapped? I am a bit confused though because when I looked at the 110 yesterday, it looks like the TCAs are outboard of the kingpin pivot point and not inside it as the Ackermann principal suggests it should be for a rear track rod.🤷‍♂️ We’re going to have some fun when I get this axle delivered that’s for sure 🤣

For me personally, I will only go with a bolt on solution and if there isn’t one then so be it. The track rod at the front is a nice to have not a need to have but I’m finding the discussion very interesting and learning a lot so that’s win 👍. There’s been some good suggestions thrown up and lots of useful contributions but now I think the next step is to get an axle on the workshop floor and try to see what works and what doesn’t. On the subject of the calliper position, am I correct in thinking that the coil sprung caster angle is somewhere in the region of 12 degrees and that the leaf sprung caster is 3 degrees? My plan is to rotate the swivel ball to achieve a caster closer to that of the leaf sprung axle although if I end up with a few degrees of additional angle (5-6) then I don’t think that will have any major adverse effects on steering. If the swivel housings are swapped over to get the track rod to the front of the axle then I’m guesstimating that the callipers will be sitting in the 1-2 o’clock position and that rotating the swivel clockwise to correct the caster angle will move the calliper closer to the 3 o’clock position where conflict with the TCA is more likely? All this on the current assumption that there is no change in spring shackle length or wedging of the axle pad. This in itself may end up as a show stopper.

Interesting....🤔 So (theoretically 😉) swap them left to right and then use the coiler TCA ball joint mounts up front? Then use a kit like the Steve Parker one to connect the drag link to the track rod? Clearance wise, the coiler swivel ball will need to be rotated anyway to get it to the correct 3 degrees of caster that the series axle runs at so that may or may not help. What is it that makes a coiler swivel housing handed? Is it just the position of the arms or anything to do with the position the pins are located in the casting? On a coiler isn’t the arm cast into the housing? The calliper mounting points would also change wouldn’t they? Maybe not a bad thing though if it helped avoid the shock absorber. My two series ones seem identical except for the drain plug location. I think the only way to find out for sure with all of this would be to get an axle on the workshop floor and play about with different configurations taking measurements as you go. I have two coil axles on order so when they arrive I’ll do just that.

Interesting as to how that affects a 90 and 110. Presumably the Landrover engineers settled for a happy medium between the two?

Great illustration, thanks for taking the time to do it.👍 I knew there was a difference but this shows just how much it would likely be.

You see? Ackermann is the last thing I need to be worried about 🙈🤯

With that in mind then how critical would the 10mm difference in the position of the front drag link arm be on the coil axle compared to the rear track control arm? If the hole centre of the drag link arm is at the very worst, in line with the upper swivel pin and, if anything when looking at it from under the vehicle, probably slightly outboard, then as long as it isn’t inboard at any point then theoretically at least, it should still meet the general requirements of the Ackermann principle shouldn’t it? Not wishing to sound complacent or blasé about safety in any way, as I’m not, but when you take into account the manufacturing tolerances on vehicles of this age along with general wear and tear of related suspension and steering components, I do wonder whether differences like this would even be noticeable when the vehicle is driven? Maybe they would be very obvious 🤷‍♂️ I confess that I don’t know enough detail on the subject to say for certain myself and it would probably take an engineering boffin to work it all out but it’s an interesting discussion nevertheless. It does help to understand better the criticality of tracking settings on a vehicle though and their impact on the handling characteristics.

Just out of interest I clambered under the 110 and measured the centre of the TCA ball joint hole to the wheel rim and the centre of the drag link ball joint hole to the wheel rim. The difference is that the drag link hole is set inboard by 10 mm each side to the track rod hole. I wish my series axle was still assembled now so I could do the same exercise but comparing both assembled axles whilst sat on the workshop floor would be more interesting.

Just more marketing BS for us to contend with 😠

No, it won’t but it will allow the caster angle to be adjusted but that’s for later. 😉 The Ackermann principle refers to, and I quote from WiKi: “A simple approximation to perfect Ackermann steering geometry may be generated by moving the steering pivot points inward so as to lie on a line drawn between the steering kingpins and the centre of the rear axle.” If the kingpin inclination on a Landrover axle is formed by the angle between the top and bottom swivel pins and vertical, then as these upper and lower pins are not of equal distance apart, which one is used as the reference for the line between the steering kingpins and the centre of the rear axle as stated in the quote above? Is it the pin to which the TCA is connected to as opposed to the drag link or, is it a mid point between the two at a point in line with the centre axis of the axle? I know it’s a bit heavy for a Sunday morning but I’m a bit bored.😉

Interesting 🤔 Out of curiosity, where is the reference point for the measurement of the angle between the centre of the ball joint and the swivel? I’m looking (with some difficulty) at the axle on the 110 and I can see that the TCA ball joint is in line with the lower swivel pin but that the drag link ball joint is in line with the top swivel pin. With the swivel set at an angle inclining inwards this creates an obvious difference in lengths between the opposite sides front and rear of the axle casing that I might measure just for the sake of it. However, which swivel pin becomes the reference point for the angular measurement or is it the mid-point between the upper and lower pins? Either way the outcome is that the drag link mounting points are further inboard that would be required by the sounds of it so some you win and some you lose🤷‍♂️ One other question - what is the outcome with a ‘neutral’ Ackerman angle where the width of the TCA is the same as the distance between swivels?

Thanks for the discussion and good feedback gents 👍. I should have worded my previous query in a better way to make what I was pondering a bit clearer. For the time being forget my reference to the castor angle as that relates to a separate engineering challenge to overcome. I don’t have a coiler axle here or, my series axle assembled anymore to do a like for like comparison, but I noticed on photos of some of the coiler axles the swivel housings have both front and rear arms built in to them. In standard setup the track rod is attached to the rear arms and the front attachment points are for the drag link with one side remaining unused depending on whether the vehicle is LHD or RHD. I have no idea yet as to what the angle is of those front drag link arms, if I can call them that, in relation to the swivel pin but my question is whether it would be possible to utilise the unused drag link attachment point on the offside hub to connect the track control arm to and thus transfer the TCA to the front of the axle? Unlike a series axle, as there is only one attachment point on each side of the front of a coil axle, then in order to attach the drag link to the nearside hub, a modified linkage such as that used on the Suzuki in the other thread or, that used by Steve Parker, would need to be used. The big unknown for me is whether an arrangement like that would then provide the correct Ackerman angle that is required for the series vehicle that the axle is used on? I have no idea if it can or, even if it could, what other factors would need to be considered which is why I threw the question out there. If it can’t be done then the TCA can remain at the rear but then I would just need to address the clearance to diff and spring issues. I just wanted to discuss the possibilities. I hope I’ve explained my thought process a bit better and look forward to your comments 👍

But if the axle case is the series one and the hubs are coiler ones orientated to 3 degrees castor with an appropriate spacer between the two to restore the original series WF to WF length, then the Ackerman angle should be maintained as per original series spec shouldn’t it? As far as I’m aware from the Steve Parker website, that is a standard series axle they’ve fitted their power steering kit to.

Just referencing this post from Gazzar in another thread. There must be a smarter way around the steering track issue, too. I'd hate to lose the ground clearance the parabolics have gained. An alternative is to hang both the track rod and the drag link out of the front arm, suzuki style: http://bulletproofsteering.com/steeringsystems.html Not entirely convinced by this approach, the loss of the taper concerns me, but I don't know why. It should work, and the change to the hole and bolt style tie rod is probably an upgrade. Steve Parker has a drag link and track control arm adapter kit that allows the steering linkage to remain at the front of the axle in a similar way to the Suzuki kit. This looks like it could avoid the clearance issues at the rear of the axle for the TCA, diff and springs. I also updated Discomikeys thread with this in case anyone was searching for similar information.

Steve Parker has a drag link and track control arm adapter kit that allows the steering linkage to remain at the front of the axle in a similar way to the Suzuki kit. This looks like it could avoid the clearance issues at the rear of the axle for the TCA, diff and springs.

The law only sets minimum wattage limits for motor vehicles and prohibitions on use with respect to dazzling other drivers etc. This is why drivers get prosecuted for dazzling other drivers with poorly adjusted standard headlights. There are standards that cover the manufacture of the bulbs used in motor vehicles and these may contain maximum light output limits but I can’t find anything to specify exactly what that is for dipped and main beams.

I was just going by how my old 4 door was compared to my old mans Softdash and then later my own soft dash compared to my TD5 that has new brakes all round. There was a definite improvement in pedal firmness and brake response with the electric boost systems on the two RRCs compared to the vacuum ones that all seemed to have more travel. Ive never driven a vehicle with the hydroboost fitted so that would be quite interesting to try.

To fit the P38 system without ABS enabled, you’d need the wiring diagram for the electrical circuit and I’m assuming that’s all part of the ECU?

So the output valves to each corner are normally closed in a power off condition with the exception of half of the front circuit? When energised the solenoids open to allow fluid through until the ABS senses a locked wheel and shuts the supply to that wheel off? So as long as there is power to the system the solenoids will keep the valves open and in the event of a power failure, the front secondary circuit will still operate? Disabling the ABS input from the wheels should keep the entire system open circuit all the time then unless there is a power failure.

The hydro boost uses hydraulic power From the power steering system to provide the additional pressure whereas the Landrover ones use an electric pump. The firm pedal on the Softdash and later models is due to this improvement over a vacuum assisted version.

Yeah, it was just something I was mulling over. Do you mean a similar unit but without the ABS? What model used that?

The Ford systems just required power via a relay and the accumulator provided the reserve in case of power failure. I presume that’s how the system is designed on a P38. Found some diagrams of a similar system on Range Rovers.net