Outer Limits 4x4 Board

Well, I'm off to an engineer tomorrow morning, to see if my Paj can be legally registered in SA, as is.

One of the possible outcomes may be a requirement to fit the late model 3.5 front brakes and rear axle.

According to Repco, all Pajeros NJ to NL use the same front wheel bearing kits. No "strength" benefit from changing the front assemblies, it would only be for larger discs.

According to our Bible, rear brakes are the same between models, but the rear axle is physically larger (+ stronger?)

So:

Has anybody done these swaps?

Any idea how much needs to be swapped to fit the larger discs at the front? I imagine the complete knuckle/hub assembly (for want of a better term) which hangs off the control arm ball joints, Do they use the same ball joints?

Is the rear axle assembly essentially a straight (and simple) swap?

Does the 3.5 rear axle assembly have a higher load rating than the 3.0 version? I recall reading mine has 1600kg front axle and 1700kg rear, but I have NFI where that came from.

Frank?

Cheers,

Scott

Hmmm the front brake upgrade would involve the larger rotors and calipers I'd imagine (although the larger rotors may fit with your calipers).
The pistons are the same size though (2 x 42.8mm) so clamping pressure will remain the same the only improvement would be the extra heat rejection rate of the the larger rotor.
I did the same thing on my old Cordia turbo - standard rotor was vented 242mm and I upgraded to the later 266mm vented ones and they fitted with my original calipers.
The 3.5 V6 rear axle will still have the same load carrying capacity as yours because the wheel bearing and outer axle diameter is still the same as the 3.0. The 3.5 axles only neck down once to the spline whereas the 3.0 necks down twice to a thinner diameter at the spline. The axle housing is pretty much the same. Overall the diff centre is much stronger (ARB told me it's in between a 80 and a 100 Series Cruiser in terms of strength) but the axle housings are essentially the same and of course the axles are thicker at the spline. The 3.5 assembly would cope with shock loading much better but essentially wouldn't be an upgrade in load carrying capacity as such.

Thanks Frank.

It's too cold for me to go out and measure the clearance between rotors and calipers. But we've previously established that the larger brakes need larger rims (for clearance) so something must be different. I'm guessing my chances aren't good - but I'll check.

By this time tomorrow I should know if I need the bigger brakes.

Cheers,

Scott

Oh yeah I forgot about that, your going from 276mm to 314mm so a radius increase of 19mm will almost certainly need the matching calipers. They take the same pad and have the same size pistons so the caliper mounts must be a bit longer to space it away to make room for the larger rotor hence the 16" rims.
Unfortunately I don't know anyone who's done this so your the pioneer.

Well, it's official. I need brake test and lane change test. Current quote, approx. $1100 - on top of the $150 I paid today.

Rather than risk failing the brake test I will attempt the upgrade. But not before I cross the Simpson - leave in two weeks!

And I'll hunt for some more quotes, too.

Cheers,

Scott

scott is this just for the wheel & tyre combo

trevor (kersbrook)

No.

He tells me the brake test is for the larger tyres, the lane change test is for the combined lift (50mm body lift, 50mm suspension lift.) He tells me that I'll still have to do the lane change test, even if I go back to standard tyres.

The bugger of it all is that I'm at their mercy. There is no published guidelines for modifications - well, none that anybody will tell me about.

I'll worry about it next month.

Scott

Bump.

This has taken longer than I'd realised. I changed engineers, and this one looked at the Paj a few months back. I was waiting for him to prepare a preliminary report, and contact me for the track test; when I rang him for an update, he'd forgotten all about it.

My Paj has now passed the tests.

We went out to Adelaide International Raceway this morning, and the engineer performed the braking and lane change tests. My Paj passed with flying colours - the engineer is impressed.

He did all the driving, and I was passenger for some of it.

Speedo check was first, against his GPS. Within 1km/h at 40, 60, 80 and 100km/h.

Braking tests were done next - 15 0.5G+ stops from 60km/h. Pulled up straight every time, brakes never began to fade or even smell hot. He was concerned that pedal pressure was too low but when he did an emergency stop from 100km/h (with a special box monitoring pedal pressure) he measured 25kg - he likes to see about 30kg, so he's happy. Watching from outside, the nose dived a huge amount. He considered it additional feedback for the driver.

Never looked like locking up, even pulled up straight when he had two wheels on the dirt. He was very impressed by the grip of the tyres - I like my STTs too.

He deliberately ran over kerbs all around the track, and was impressed by the lack of kick-back through the steering. He believes the offset of the rims (zero offset - Patrol rims) is a good match for the tyre size and steering geometry.

The lane change test was performed in the exact same spot where Mitsubishi test vehicles. The spots for the cones were marked on the track, on a short straight between two bends - the first bend was the one at the end of the main straight, so entry speed is limited by how fast you can negotiate that bend - particularly in a shorty Paj with lift.

The engineer had doubts about the limited droop travel at the front, but it was never a problem. I was watching for signs of the inside front coming off the road, but never saw it. He commented that the vehicle has lots of body roll, but accepts that this is unavoidable - especially when the rear sway bar was sitting on the ground alongside the track. The tests were passed without it, so I officially no longer need it. I also noticed my exhaust is loud, and the tyres aren't.

His only other comment was a little bit of float/squirm in the front end, which he puts down to the large tyres. He thought testing at 50psi might help, but decided not to bother. The test started with 36psi all round (my choice) and that will be on my new tyre placard.

He looked at the angle on the Panhard rod, and it's not enough to worry about modifying the chassis bracket. He suggested I install an adjustable rod to re-centre the diff, but it's not an issue. I had also prepared some "alternative" droop stops (6mm rubber strips) and he's happy for me to install and use them - but the test passed without them, so they're not essential.

All in all, the testing went as well as I could have hoped, and the Paj handled much better than he expected. Now I've got to wait for his report (and invoice), and get SA Transport to accept it.

-Scott- wrote:. Now I've got to wait for his report (and invoice), and get SA Transport to accept it.

You mean you have to pay him to flog the gutz out of your Paj, what happened to the good old days of doin it for "a slab". Good to hear it passed Scott and don't forget to give a copy to your insurance co. Interesting that you say the STT aren't noisy....mine make a racket. Maybe I should put the windows up hey!
Dave

scott
did you end up upgrading your brakes, or was the test done on your std brakes?
good to hear all went well and that you can legally leave the rear sway bar off.
if its not too much to ask, could you post the $$ amount it has cost you to get it engineered and registered. i think a lot of people would be very interested.
cheers
cookie monster

I ended up leaving the standard brakes. I figured the shorty is lighter than the LWB, so that would help offset the larger tyres, and I heard the larger brakes use the same pads, so the only gain would be larger discs to help dissipate heat. I do have Bendix 4wd pads - I don't know how much difference that made.

Hiring the track cost $165. I haven't been invoiced by the engineer; when it arrives, I'll post up.

Cheers,

Scott

Invoice arrived: $1100. More than I'd hoped for, but less than I'd braced for. Speedometer, brakes and handling tests, and new tyre placard for larger tyres.

Excerpts from his report:

Tyres and pressures: 36 psi all round during testing.

Wheel and axle clearance: adequate.

Lane change manoeuvre test procedures at 85km/h.
Outcome: 85km/h exit speed from 18 cone standard ISO test lane.
Roll damping: optimised for gross movement but underdamped for small oscillations*
Roll stiffness: high roll angle perception.
Yaw stability: no perceptible oscillations, tendency to understeer.
Directional control: predictable tendency towards quickly developing understeer.
Rear traction steeering effects: undetectable
Overall balance: controlling cornering signal is body roll
Overall rating: high level of directional control and stability for a high four wheel drive.

<snip>

Conclusion: With respect to modifications described, the vehicle is capable of being driven safely on public roads.
Please note: Droop provision was 48mm with 14mm thick droop bump stops. In the Engineer's opinion, not requiring re-testing, the droop stops could be reduced to say 6 to 8mm and droop provision increased for added margin against sudden wheel lift. (Wheel lift does not appear to have occurred during the test, the recommendation is for safety margin restoration.)

* this matches what ARB told me is typical for OME shockabsorbers.

Scot
thanks for posting up the final tally, gives us all an idea of costs and proceedure for re-engineering vehicles.

-Scott- wrote: The engineer had doubts about the limited droop travel at the front, but it was never a problem. I was watching for signs of the inside front coming off the road, but never saw it.

I had also prepared some "alternative" droop stops (6mm rubber strips) and he's happy for me to install and use them - but the test passed without them, so they're not essential.

re the 6mm bump stop stips - what have you used and how were you going to attach to vehicle?
my bump stops are at 15mm thick and was thinking to trim them back a bit more for extra droop. i noticed the other day when i followed the wife out of the petrol station that the front wheel was just airborn!
cheers
neil

All done.

Since my last post, I had an adjustable panhard installed to re-centre the rear diff. Ended up costing a little more than I expected, but drive in - drive out is so easy.

Two problems came up at the vehicle inspection:

LHF indicator (in bull bar) not working.
The window tinting on the front doors is illegal in SA. Apparently other states allow down to 35% transmission, the SA limit is 70%. (He demonstrated on my windscreen - 69% .)

He "missed" the indicator and (with my approval) butchered the tinting with a razor blade - in his opinion, I won't leave it as it is now.

I have SA plates. Sooner or later, I might even put them on...

I thought larger discs not only help dissipate heat but increase stopping power, as the outside of a larger disc travels slower than a standard size, making it easier to stop. Assuming the brake pistons have been moved outward the relevant distance. ??? Someone do the maths.

simmo404 wrote:I thought larger discs not only help dissipate heat but increase stopping power, as the outside of a larger disc travels slower than a standard size, making it easier to stop. Assuming the brake pistons have been moved outward the relevant distance. ??? Someone do the maths.

Yes, the larger disc offers some leverage benefits, but for a given road speed/tyre combination the rotational speed of the disc will be the same, and the linear speed of the outer edge will be higher for the larger disc, not lower.

Ultimately, a disc brake is a friction device. Kinetic energy is taken from the vehicle and turned into heat. If both discs have the same calipers with the same size pads any given pedal pressure will produce the same clamping force/same pressure on the disc. The only benefit is a larger disc mass and surface area to help dissipate the heat. There may also be leverage benefits reducing strain on caliper mounts - I'm not concerned by that.

I have no doubt that larger (front) brakes would be better. But I concluded the minor benefits wouldn't justify the effort and expense - and I didn't need to do it anyway.

While on the subject of brakes: on the brake tester, testing the rear brakes, I had the pedal as far as it would travel, and the rollers were still turning the tyres. I'm hoping that's the brake proportioning valve at work...

Scott