any experience with atw parabolic springs on Fuso FG?

[westyss]

Ives

Just wondering what axle weights you are carrying at those pressures. I am sure that at my axle weights I would destroy tires in pretty short order due to sidewall flex and heat buildup. Not so for you?

Just out of curiosity, do you check the temps of your tires during a highway drive [> 55 mph]? I use both my hand as well as an IR thermometer. In fact, I use the latter to compare temps across the face of the tread [3 readings: inner edge, center, outer edge]. If the center is significantly hotter, I am overinflated; if significantly lower, I am under inflated. ["Significant" is something on the order of ±5°F, established intuitively, not determined empirically]. I have improved my wear and reduced pulling to one side or the other this way, possibly because this approach takes into account heat of the day/road surface and altitude. Doing the IR measurements is much quicker and easier than taking valve-stem pressures, so I find I do it more frequently.

John

Hi John,
Yeah I am sure you would shred your tires at those pressures seeing as my whole truck probably weighs less than your rear axle weight, but my tires just dont seem to heat up much, I do adjust the pressure if I am fully loaded and heavier than normal but the last time at the weigh station I was 5500lb front and 5000lb rear with limited water in the tank but loaded otherwise, I estimate a total weight of around 11,000lb as a general rule for my truck. When converting the registration to a Motorhome the front axle came in at 5390lb and rear 4048lb for a total of 9438lb's. My tires are rated at somewhere around 6000lb's each so I interpolated a pressure graph I found online to match my weight and that is what I came up with. Granted the graph did not go low enough for my use and may be problematic at lower pressures but I used what I had. Comfort of the ride takes precedance over tire wear for me due to my wifes back issues so my reasons are skewed a bit but so far nice even wear on the tires.

When I was trying to find a good pressure to operate with at the start I would just feel the temperatures by hand and never felt much difference except when they where very deflated and travelling faster, then the sidewalls felt a bit warmer but it just was not enough to be concerned or noticeable difference from low pressure to high. The lowest I have had them was 20 psi and at those pressures drove a forestry road at good speed, around 30mph and felt the most heat from the tire but it was still slightly above ambient temperature.

I do find the sidewalls are very stiff and take some use to become a bit more pliable so with age I can keep the pressure up a bit more.

What temps are you measuring with your IR guage?

Yves

 

[westyss]

I have a set of ATW parabolic springs going thru customs right now.
I will install them and post the install process as well as my impressions about the change in the ride.
It was a hard decision at that price, but with better wheel/spring articulation there is less stress on the truck frame.
If it rides down the highway better and gives me a little more peace of mind offroad it's worth it to me.

If I understand correctly that the price of the parabolics include the shocks, no? this to me is as important as the leafs and a good shock that is proven to work will be worth the money, once my shocks die I will be looking into the ATW shocks if they fit my set up.

 

[kerry]

I too am curious as to the answer to your specific questions. Concrete expansion joints are the worst in my FG. Things significantly improved when I went with Aeons and new OE shocks. Expansion joints became tolerable but they're still not pleasant. I think the basic issue is lack of travel in the suspension. I can't imagine why Fuso designed the front axle with so little travel. I'm running about 11,900 fully loaded.

 

[gait]

it depends on the concrete roads ....

The parabolics made a bit of difference, the joints a bit less jarring. German autobahns were tolerable but no "good" speed regardless of springs. It just seemed that the wheelbase and the joint frequency made it like riding a see-saw.

We labeled the concrete E65 near Brno in Czech Republic "the world's worst road". There's a photo and a bit of description halfway down this page. http://www.epicycles.com/Truck Blog/2013-05-02/2013-05-02.php We gave up and took minor roads ... only time in last 70,000 km we've had to do that. Not in the blog, some of the passing trucks looked like their back ends were bouncing along the road.

We also struggle with concrete roads that have seal over them. No jarring, just the see-saw.

I have two (heavy) spare wheels hung on the back end which may contribute to see saw (something about moments of inertia and square of distance from centre of rotation).

We replaced original springs after breaking a few leaves (accumulated wear from China/Mongolia/Russia). Choice was same again or parabolics. My limited understanding is that the number of leaves in the parabolics depends on the axle load.

So far 20,000 km in Europe and Morocco. Through Albania. Currently in Turkey. General good improvement in ride and reduction in jarring - I can change the radio volume without breaking my finger.

One thing I noticed, it seems easier to find better tyre pressure compromise for speed/load, wear, and comfort (with ATW singles). GVM 4500kg.

No serious long distances on deep corrugations yet. Stony tracks in Morocco tolerable where similar part formed roads in Mongolia on old springs was tedious and back breaking. Cobbles tolerable whereas previously were dreaded.

Sweden was hard going and tedious at times on the old springs. Every 100m on some roads subsided culverts. Parabolics probably would have made a bit of difference but we still would have slowed down.

Transition from flat to dune and back again is much easier. As are river entry/exit. And crawling through rocky creeks.

Short answer is that there is always an improvement due to the parabolics, just that there are so many variations in road surface its a long story. Sometimes lots, sometimes just a bit.

Would I have changed if the old springs hadn't died. Probably yes. I was thinking of it before we set out but ATW weren't ready. We also have suspension seats.

We keep reminding ourselves we made the change for comfort, not speed.

Minor hiccough with the shocks. First set (provided with springs) of adjustable leaked oil after a couple of thousand km. ATW replaced with a set of Monroes (a good recovery). All good now. Parabolics are known to be harder on shocks than conventional.

Minor downside. The increased suspension height and travel means prop shafts have sharper angle. Front now vibrates above about 50km/hr. Only an issue for 4wd and reminds me to unlock hubs. UJs look ok. No obvious movement in splined joint. I'll look more closely when I get home (in about a year).

Probably unrelated but may be due to different dynamics. A wheel nut loosened which led to sheared stud. Two more followed before I noticed. I now have wheel nut indicators (plastic arrows on nuts). Hopefully the changed dynamics don't effect anything else.

Fitting was easy once I knew which end and which side was which. Basically "side of the road" flat patch of solid ground. I bought a couple of tall heavy axle stands. Replaced both front then both rear. Trying to replace one side then the other makes it difficult to align. Old "pommie" term about "offering it up". Bought a large metric nut (22mm IIRC) and bolt to make "slide hammer" to remove front pin of rear springs. Not as young as I used to be and crook back so took leisurely 2 days. Shock absorber replacement about an hour. Trick with front spring front half bushes, fit one half to spring and other half passes through side of carrier before inserting pin. Add break pipe bracket before removing springs as it gives a bit of extra jacking movement for axle.

I'd also replaced a king pin bearing but wise anyway to have front and rear wheel alignment checked after replacement.

Its basically a truck. Possibly designed for uneven front/back weight distribution (duals at the back and overload springs may be a clue). Put a camper body on the back and distribution is no longer as designed for. Possibly even front heavy.

 

[Andelles]

Hi we got a set fitted to our 2003 FG649 dual cab about 2 weeks ago and have only done approximately 175kms on highways , the ride has greatly improved the jarring has seamed to be gone.
But the real test will be next week when we head off to Cape York for 4 weeks.
Our travel weight is approx 4400kg and will be towing a trailer(approx 550kg) with food,fuel,tyres,spares,swags etc for the motor bike guys we are going with.
We also have ATW srw set up too.

How many leaves do you have on each corner.do you find with no weight in the back it's sill a harsh ride?