Gen III & Popup - OME springs + lifted popup

[Dr Gonzo]

Hi all,

This is probably a good example of the "If it's not broken, don't fix it" mantra, but it's now done and I thought I'd share the story plus a couple of pics.

I have a popup trailer I want to tow with the Montero, but I didn't feel comfortable with the trailer's standard 13" wheels and tires, so I upgraded to BFG AT's in 195/75/14 D-load (smallest size I could find). This enabled me to go from 1360lb max load tires to 1710lbs. Since the trailer is something around 2500lbs, I really wanted the extra breathing room. The main driver for this change was not lifting the trailer, but just having a bigger safety margin (and hopefully avoiding trailer blowouts) and using more commonly available tires (13" trailer tires are not common around here). The lift was a necessary side effect.

Given that the new tires are 25.5" OD (vs standard 24") I also added 3" spacer blocks between the torsion axle and the frame of the trailer. In the end, I lifted the popup just over 4" (tire+lift block). This gave me enough clearance for the tires (just) but also meant that the trailer was no longer level with the truck, as it was now sloping forward.

Enter OME. This situation provided the necessary impetus to upgrade my old springs (2003 NP with just under 110,000km / 70k mi) and replace the worn shocks. I went with OME "light" springs on the front and the +200kg ones on the rear (2914 /2917) and KYB gas-a-just dampers all around.

Success! (kind of). The trailer is now almost perfectly level (with a 2" drop hitch) with the truck. Side effect is that the larger tires mean much smoother towing. Since the trailer is now way higher, the rearview mirror is useless but the sideview mirrors are still good, and I'll add extensions if needed.

I have attached a couple of photos.



Now for the related issues:
* twitchy handling: When unladen, the truck now handles, in a word, horribly. It darts nervously into corners and follows with the threat of snap oversteer and an audible howl from the rear tires at the slightest curve at highway speed (80km/hr+ / above 50mph). It also howls in low speed maneuvers (think parking lot) but of course it's not as scary there. It was aligned after mounting the springs, but I'm hoping a realignment after the coils have "set" a bit will help. It's only done about 160km / 100mi of paved roads over the couple of weeks they have been mounted. I'm hoping some additional negative camber at the rear will help (maybe some camber and toe correction at the front as well). While towing it's just fine.

* Ride height: obviously it's taller, but it is noticeable in step over height. Would not recommend removing running boards until you try it if you have smaller children or adults with reduced aglity who use the car with any frequency. Of course this will not apply to many, just something to keep in mind.

* Ride comfort: actually better than OE springs + worn OE shocks, so no real issue there.

Hopefully I'll report back with some good news after I get it realigned. This seems to be an exceptional case as I have read nothing but good stories from others who have done similar modifications.

Thanks for reading!

 

[jeep-N-montero]

Have you considered a distribution hitch? Given the fact that the trailer is almost the size of the Montero and 50-60% of its weight, this is a bad situation just waiting to happen with such poor handling. Read up on the physics of towing, please.

 

[MonteroLTD]

Have you considered a distribution hitch? Given the fact that the trailer is almost the size of the Montero and 50-60% of its weight, this is a bad situation just waiting to happen with such poor handling. Read up on the physics of towing, please.

Generally, the curb weight of your tow vehicle must be at least 80% of the loaded weight of the trailer. I believe the issue here is the OP needs to get used to towing with the handling characteristics of the Montero. Also, all monocoque frames with be noisy after such a modification.

Edit: Nice truck :26_7_2:

 

[JamesW]

What way does the trailer sit when it isn't hitched to the monty? If say you just unhitched it and let go of it,would the trailer fall onto it's hitch or would it fall on it's rear? You need weight on the hitch part,otherwise it tries to lift up the rear of the truck,making it hella scary to tow with. Being single axle makes this effect even more noticeable,because it is like a see-saw.

Try add some nose weight to the trailer and see how it handles.

 

[magoh76]

* twitchy handling: When unladen, the truck now handles, in a word, horribly... While towing it's just fine.

It's not about the trailer...

Sent from my SM-N900R4 using Tapatalk

 

[Dr Gonzo]

Thanks for the comments everyone!

I was probably not as clear as I should have (as usual). But yeah, as magoh76 says, the handling issue is not when towing. When towing it is actually quite nice. Having said that, I will try what JamesW said: I'm pretty sure the trailer will fall on its nose, but I'll do the scale thing to measure the tongue weight and try to correct if needed.

The issue is actually when the truck's unladen and not towing. MonteroLTD makes a good point that the truck will be noisier, that's probably just something to get used to. I still think there's something "off" in the alignment and it's giving it odd handling characteristics. The feeling is sort of a disconnect between front and rear that wasn't there before. It dives into the corner and, like if you were loading a spring, the rear comes around a moment later but with a feeling of too much inertia. It feels like it wants to keep pivoting from some point in the middle of the truck. It may be too much rear roll stiffness (which would mean I'd have to get used to it or swap back to stock coils), but I think there's something else at play here. Before the changes it was actually quite a solid handler (for a tall SUV on narrow-ish AT tires).

I wish it was like "back in the day" with the sporty cars I used to drive, when just after a couple of km's the soft sticky tires would give you a fairly good idea of what the suspension was doing wrong via tell-tale wear or bits of rubber "balling" around in the tread. Right now, the tires show nothing odd and I'd rather not wait until they do.

Of course I did not think to ask for the alignment printout when I first went in, so I did a highly un-scientific bubble level test :sombrero: and I appear to have positive camber on the front and almost zero at the rear. So, rear *might* be correct but front could be causing the issue. I'll try to drive it on some trails this weekend to help the coils "settle" a bit and then go for a 4 wheel alignment again.

Cheers!

 

[Dr Gonzo]

So... given the recent increase in popularity of the Gen III in the forum, I thought I'd post an update:
I had the Montero aligned at the dealership and it is all good. At first sight it would seem as if all 4 wheels have a bit of positive camber, but they are at 0 (or within <1deg) and it drives perfect now. Mine has 245/75/16 tires (original OD + narrow-ish), so these probably exaggerate any alignment issue or appearance, but to me it looks a bit like the old square bodied LR Defenders, so I think it looks cool!

In the end, I would recommend the OME + KYB gas-a-just upgrade to anyone looking to reduce rear sag when loaded or a desiring a bit more ride height. Ride is slightly stiffer but perfectly acceptable. Sharp maneuvers or high speed (120+kph/70+mph) handling do show more of the effect of a tall truck with a relatively narrow track, but that's just physics at work, not many practical alternatives if one is raising a truck like this. On pavement it still drives and rides like the "old school" SUV that it is (i.e. not a CUV/raised sedan). It is even better than before on rough tracks where the ride is great even at speeds that would see serious head bobbing/head tossing on traditional live axle vehicles. Over more difficult terrain it does not seem to have lost articulation and still keeps the wheels on the ground most of the time, with the obvious invaluable advantage of greater ground clearance.

My daily drivers are low-ish cars, so I do notice the increased step over height but nothing dramatic and is similar to modern pick up trucks.

For good measure I also had them true the brake rotors since they need to be done while mounted to the hubs and not many independent shops do that (they dismount them and put them on a lathe or lathe type machine). This helps reduce pedal vibrations (vs the old school truing method) when slowing down on the highway for the extremely common toll booths around here. Drives great again. Cheers!

 

[Dr Gonzo]

Update

Hi all,

I finally had a (small) chance to take out the camper+truck combo this weekend. It was a very brief outing, about 400km of secondary roads (with large elevation changes) with a small (200m) dirt/mud trail to the campsite. I am pleased to report that the Montero handled it very nicely. I thought I'd post my experience in case anyone cares for some reference data on Gen III towing performance (at altitude, to boot).

* Camper: I tow the camper w/o water but with gas. With the roof AC unit and other assorted equipment plus minor stuff I load in the trailer, I guesstimate the weight of the trailer at around 2200lbs (dry weight is 1900lbs). Only modification is the tire change to 14" wheels (27" OD tires), which helps enormously on the rough roads around here. It has surge brakes.

* Montero: Mostly stock 2003, 110,000km 3.8V6. Only mods are OME springs + KYB gas-a-just dampers (and minor stuff such as CB, etc).

* Set up: We packed the truck with 4 full size adults (~310 kg) + luggage, including a full cooler (total guesstimated at 80kg). With a full tank of gas + ~90kg tongue weight, I was probably bumping right up to the 2715kg gross rating. Assumming the 1000kg (2200lb) trailer, I was well under the 5200kg gross combination mass at ~3700kg. I packed nothing heavy on the trailer, just minor stuff (bedsheets, a broom... that's about it, lol). For prep, I just checked tire pressures, fluids and put up the CB antenna and switched to the local trucker channel expecting to get shouted off the road, which fortunately didn't happen.

* The route: we left saturday morning, drove aprox 230km (the long way - slightly lost) and arrived at the campsite around 3.5hrs later. 70% secondary roads (~80km/hr - 50mph), 25% toll road (90-100kph / 55-60mph) and 5% urban/dirt. Reverse route on sunday was about 200km 85% secondary roads, 10% toll road and 5% urban, with rain this time. Some of the roads this time around were seriously wavy going through sugarcane fields, and lots of speed bumps all over. This is the altitude profile of the route:


I drove all the time in 4H (unlocked center) and in the "manual" trans mode, to enhance control and keep it out of 5th gear (reportedly lowers trans temps) - the manual mode is an invaluable asset in this vehicle IMO. As you can see, there are some serious hills to climb. Left to right was out on saturday, right to left was back on sunday. The climb on sunday was interesting, as we had to pass several dawdlers on the climb. I had to go to 2nd gear on a couple of occassions, such as when slower traffic forced me to drop below 70kph/40mph on the steeper climbs, I needed 2nd to start the pass when there was a chance. Otherwise the Monty handled it nicely. After just over 400km, I still have a bit under 1/4 tank left. While I admittedly drove conservatively and never exceeded 100kph, I'm still pleased with the consumption given the circumstances, which I expect will be roughly 6.3km/l or 15mpg over the whole tank (will know for sure once I refill). The truck never struggled to maintain my desired cruising speed of between 80-90kph/50-55mph, depending on the road conditions, and happily reached 100kph / 60mph in the toll roads.

Not sure how many forum members tow a lot with this vehicle, but it appears to be a popular choice in Australia for this use. I can report that it more than lived up to my expectations. While I'm sure that something larger (say, newer crew cab F150) would perform better (trailer? what trailer?) with similar or better fuel economy, the Montero is still way cheaper and very inconspicuous, which is an asset around here. Also, when not towing, it drives great and is extremely agile off road, still a "hidden gem" in the SUV world.

Potato phone pic of campsite:


Cheers!

 

[jeep-N-montero]

Over the weekend we towed our off-road camper about 200 miles and exceeded 10,000 feet in elevation including a 7 mile long trail that scraped the skid plate a few times, never put it in 4wd though, more than enough control in 2wd. So I'm trying to understand why you felt you needed to put it in 4wd on paved roads?