SRW Testing

Hi , There has been a lot of talk about SRW conversions not being supported as far as warranty claims go. Just to throw in my 50 cents >I can tell you that there is an enormous amount of testing, documentation and interaction between the dealers, our transport authority and us as a company who does this type of work so that factory warranty and road worthiness can be maintained.

Just as an example> one of the main considerations is how brake performance can be effected by the larger diameter single rear wheels and to be compliant the vehicle has to remain within a very close tolerance of the original braking performance (running with the standard size wheels). As manufacturers are often unable to provide this data it means testing the original before fitting the larger SRW’s. Sounds simple enough but it ends up costing megabucks and is not something that can be done safely on the road so it usually requires the hire of a long bitumen airstrip in a quiet country town for three days (and a guy to follow us and tell us if there is any planes coming in. Serious. No skid marks on the piano keys either).

The testing consists of completely stopping the vehicle from various speeds, simulating front or rear failure, brake fade, handbrake hold on a given grade, etc, etc. Everything has to be recorded at different weights such as full GVM or with simulated weight of the final body (see the bags in the pics and our attempt at keeping the weight central under inertia). It means rigging the vehicle with a whole array of sensors such as pedal pressure, a fifth wheel, inertia, system air pressure, event timers, etc. and of course certified vehicle weights. Then there is the mechanical engineer with his data logging laptop. Oh yeah, you can just about throw away a couple of sets of tyres with big flat spots. BTW does anyone else want to STAND on the brakes at 100 kph with no load and no front brakes and try and keep the thing straight?

Obviously the truck passed everything with flying colours, but it is all about having the supporting documentation, especially as this vehicle was destined to be a passenger bus.
The vehicle is an FS550 Isuzu, (tilt cab retained) which was then stretched and fitted with our custom suspension but maybe that’s another thread. www.allterrainwarriors.com.au

It's great that the Australian government agencies are willing to work with your company so you can improve the factory vehicle for use off-road.

Since litigation is the national pastime of the USA, upfitters here are taking big risk when they deviate from the tires, suspension and brakes provided by the manufacturers.

It would be great if Isuzu would import the FS550 4x4 to North America! I suppose the 25% tariff on trucks not assembled here, left over from the 1960s, is what keeps them out.

There's talk about a establishing a free-trade agreement with Thailand, where all the small pickups are manufactured. Maybe Isuzu will start building medium duty trucks in Thailand to take advantage. Importing boatloads of Toyota HiLux, Isuzu DMax and Mitsubishi Triton pickups won't help the United Auto Workers, however.

Chip Haven

Fs 550

Hi Chip, Sorry for the delayed response. Just got back. I help look after a lighthouse a 100 k's up the beach from here (Double Island Point). Took some pics on the way home of a Fuso Rosa 4wd at Red Canyon. Will put them up on the FG forum soon.

I agree with you about the boatloads of cheap utes from Thailand. But with fuel costs and your dollar at the moment, maybe its time your car industry had a major paradigm shift in the type of vehicles they produce. Why can't they produce small cabover trucks like the FG's and NPS's and tacoma/hilux style utes?

As for the Isuzu FS-550, I can tell you that they are probably the most commonly seen 4wd in the 10 ton bracket. Actually there isn't much else here of that size anyway. Wish someone did something halfway between an FG/NPS and the FS 550. An 8 tonner would be perfect for most of the vehicles we build.

We did a SRW conversion on a Isuzu FS-750 (13ton) trayback recently for a sand mining company. These two models are common choice for mining, power, telecomunication, etc. While they may not quite have the offroad ability of a MAN, they are comparatively good value, super reliable and importantly Isuzu have established a huge dealer/support network here.

Here is a couple of 550's that were working behind my house and 2 that we converted to buses. One does rainforest day tours and the other does outback extended tours.

550

FS 550 still with duals

Much Ado About Nothing

On July 22nd Stephen Stewart wrote:

"As for the question on double rear wheels".
"The reason for double rear wheels is weight distribution. If you want to use the same sized (interchangeable) wheels all round and you want to put the load at the back you end up needing to carry more weight on the rear axle. If you want the best off road performance you want equal weight distribution. Hence single rear wheels."

"It is this that leads (IMO) to much of the prejudice against double rear wheels rather than their inherent problems."

"They do have a couple of practical disadvantages but these are not that serious for most overland trips."

"1.) You can get rocks stuck between them."
"2.) Inflating and inspecting the inner wheel can be difficult."

"I have traveled for more than 100,000 km with one particular double rear wheel vehicle and during this time he has had rocks stuck between his wheels on say 10 occasions. He has never had to remove the wheels to get the rock out (just wrap a light tow rope round the rock and get another vehicle, usually me, to pull them out). You get into the routine of inspecting your wheels after driving over the (relatively rare) size of rocks that are a risk."

"Access to the valve stems of double rear wheels can be difficult, but a few dollars spent on the correct fittings, a decent pressure gauge and/or extensions is money well spent."

"If you really are intending to drive up mountains and climb sand dunes then you may need a genuine off-road vehicle (like a Unimog) but if you are "only" intending to do the sort of journeys I have been doing an under loaded reliable truck with decent departure angle is fine. If there is a 4x4 version then it may be worth considering."

Srw

Hi Daniel,

Can't find the thread you mentioned from the 22-07 to put things in context but I think I understand where you're coming from.

I really only put this post up as an example of the type of challenges we face to keep a vehicle legally roadworthy and not violate the manufactures specifications as far as warranty goes. The SRW/DRW debate is a little bit more involved than the 2 disadvantages mentioned and checking tyres and clearing rocks are not really a problem for someone adventurous enough to go offroad anyway.

When going to SRW on the FG's and Isuzu NPS's and FSS's, we of course go to a much higher rolling radius tyre which not only is smoother over the bumps(hence easier on the suspension) but alters the gearing considerably. IMO (and I stress My Opinion) these trucks are geared far too low with the original tyres. Having driven many before/after conversions the taller gearing is a quantum leap in the right direction. (ESPECIALLY if you have "an underloaded reliable truck"). I drove an FG with DRW for 4 years doing pipeline work before I started at Allterrainwarriors and the first time I drove a fully loaded FG tour bus with SRW up the beach I couldn't believe it was the same type of truck (DRW do not work in sand). Also drove a short trayback unloaded with SRW. It really went hard. Easily loose your licence in it anyway. And of course the fuel consumption is also improved proportionally.

As for going to a Mog or MAN, the price of them here isn't usually justified. The tour bus operators turn the vehicles over usually every 4 or 5 years and the expedition crew like the 6 ton size of the Jap trucks and also their dual personality. With fairly simple mods (springs, shocks, tyres, seats) they are extremely comfortable ON the highway (The Mogs i've been in certainly aren't) and they are far more capable OFF than most people give them credit for (and reliability and dealer network and and).

After saying all that, we still build a large number vehicles with DRW (and standard suspension) and they perform perfectly for their role. I included some pics of 2 similiar campers and 2 more similiar tour buses with SRW / DRW.

Srw/drw

The one above in the bulldust has the duals. The silver one above is on Michelin 100R16 XZL's and this one is on 19.5/265 Hankooks.

Srw Fg

Hi again David,

Thanks for the comments. The camera shy guy is Don. He’s checking the installation of the generator. It’s his first one actually in production. Very clever bloke. His website is www.watts2c.com.au . Look for the Powermaker. It’s got a little Yanmar diesel putting out 2.5KVA @ 24volts through some really smart controlling software. It’s worth a thread in itself.

Anyway regarding your question of wheel sizes for a dual purpose FG >>> surely its going to come down to what wheel/tyre combos you can get hold of in your location. One of the problems we have here is finding 16” wheels that are strong enough to handle a fully loaded FG, so we have just started using 19.5” x 8.25” rims with really thick plate centres. In Aus, there are a couple of good dual purpose tyres available to suit these. We normally get the offsets made so that the wheels are inline. For the Michelin XZL 100R16’s, we use custom 7.5” tubeless rims. However they will go on the standard 6.25”rims allright. The tyres are pretty close to 36” diameter. In an FG on the road with these you rarely use 1st gear to take off and 100k should be around 2800rpm from memory (I could check this if it was critical).

I just spoke to the mechanic who looks after a fleet of FG 4x4s that we built cause I wanted to get it right before I posted this. They recently took delivery of their 26th bus from us and they sell them at about 300,000k’s and usually operate with 7 buses. What he doesn’t know about fixing them isn’t worth knowing. The vehicles do about ¼ road, ¼ dirt road and ½ sand and they do about 80,000k’s on a set of Michelins. These FG’s are driven very hard too as they are always racing the tides on the beach. They don’t bother with the cost of custom offset wheels so they just use standard rims turned around on the back. There is a trick to this however and that is you have to use a spacer (in place of the inside DRW) and lock it down with the original DRW nuts. If you look at the rear hub you’ll see that it’s shape doesn’t provide a good seating surface and this allows flex in the original rim which will eventually cause it to crack. According to Sean the spacer supposedly takes care of this.

He tells me they have NEVER had a rear bearing failure through normal wear during the 300,000k’s and the only time he has ever replaced them is if they get damaged from the retaining nut coming loose. Twice as far as he can remember. Some of the outback FG mechanics now Araldite the nuts on as a failsafe. The outback vehicles cop a lot of badly corrugated roads at high speed like the one in the dusty pic above. BTW the fiberglass paneled bodies we build get swapped onto a new chassis twice and are usually sold on the third chassis. The others trucks get the back of the cab replaced and are sold as cab chassis or as a trayback.

We have gone to more serious offroad tyres using big Michelin XML’s which must be closer to 40” but they are very shortlived on the road and not cheap. I think we ran 9.5” rims with these. Very hard to get 16” XML’s here. Usually only brought in for military use on our 8wheel drive tanks (Sorry that’s the only way I can describe them. Maybe they’re called ASLAV’s).

Hope this helps, David. These pics from my phone so not so good.
Shouldn’t this be in the FG forum?

One important consideration is that a US spec FG has 4.875 gears and an Australian spec has 5.71 gears, I believe. The difference in gearing makes fitting oversized tires to a US version questionable as far as gearing if the intention is to load up to near GVW.
On the other hand, gears can be changed; and maybe even lockers installed...
My experience with military Michelins is that XZLs are very durable on rocks but XMLs quickly disintegrate on rock; they should only be used in pure mud.
Charlie

Gearing

Hi Charlie,

If that's the case, of course you are quite right. I never even considered that they would be a different spec and looking back I see that David mentioned it. Why would FUSO do this? Will have to check on this tomorrow and get back. It still might be a good thing given how well they perform with the even bigger XML's.

Thanks.

my 93 and 2004 have 5.71 gears. I don't think they changed the gears until the bigger (+ 100 lb ft torque) engine.

I think the standard tires and wheels give 32 kph / 1000 rpm

Spacer

Hi David

They are not something that we make or fit so I'm guessing that the ones I've seen are 8 or 10mm and have the holes countersunk the same as the original wheels so that the inner DRW nuts can lock them down centrally. Obviously they are at least the diameter of the flat section of the original wheel centre. And no they are not to increase the width of the track as they are already to wide (hence why we get our own rims built).

I'm really concerned now about the different specs between US and Aus. I thought as "FusoFg" did and that all the previous models ran the 5.71 rear ratio and didn't realize there was a difference. You see the 4.9L model you have in the US won't arrive here till October (fingers crossed) and I haven't seen much info on it yet. If it has 4.87 diffs, and as this is such a big difference, I wonder if the transfer case ratios and the gearbox ratios are lower to compensate. Could someone tell me or direct me to a site that has the full gear split ratio specs.

Ours have 5th gear > 0.722, high range > 1.090 and as stated final ratio 5.714

I know the diff housings changed a bit here recently but I checked with some of the guys and the SRW Michelins have always given the around same 2800rpm @ 100k's so I think the gearing has always been similar.

Thanks

I looked up the specs in both countries to get the axle designations. Unfortunately the US site doesn't give the axle designations but the Australian site does. The front axles have the same load spec; the rear has a greater load spec in the US. So I can't tell if the 5.71s are transplantable into the US models or not. The rear axle is called D033H; the front F020TW/D1H(SP) - in Australian models. Perhaps a US owners manual will tell?
I believe the transmission and transfer ratios are the same but I'm not 100% sure.
How much torque is the 4.9L motor supposed to produce?

Charlie

U.S. current model Fuso FG gear ratios are here: http://www.hackneys.com/mitsu/index-specs.htm

Scroll down for the gear ratios.

charlieaarons said:

How much torque is the 4.9L motor supposed to produce?

Charlie

Click to expand...

Here's the engine specs for the current model U.S.A. FE/FG series:



[edit to add the conversions]
347 lb ft = 47.974 kilogram force meter
391 lb ft = 54.058 kilogram force meter

147 HP = 108.118 kilowatts
175 HP = 128.712 kilowatts


The T8 is for the automatic transmission chassis. I did some preliminary research on the differences. My service manager and parts manager swore that the fuel pump, injectors, etc. were all identical part numbers between the two motors.

The Fuso factory service rep told my service manager they were different because the manual trans couldn't take the extra torque. My personal opinion was that it was more likely there were making up for the losses incurred by the torque converter of the auto trans.

At any rate, I did not procure the fuel injection computer or chip for the T8, so I don't know if it is a straight swap with the T7 or not.