FUSO Suspension Help

[GR8ADV]

Hey folks. Just did the SRW conversion with the ATW 19.5's on my 2004. An unintended result is dangerously messed up handling. At highway speeds, uneven pavement causes the front end to swerve and dart in a very scary manner. It has been aligned to FUSO spec and does not pull either way. It drives like it has zero caster and then becomes quite unstable in a scary way. No issues prior to the wheel swap. The front does dip dramatically offroad/offcamber (seems to go along with crappy front springs, see below). I would love your thoughts. I will also be chatting with EC and ATW today further about their offerings on suspension.
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Dropping in at EarthCruiser on the way home from our last trip yesterday, Lance (who is amazingly intelligent about all things FUSO) noted the flatness of my front springs. We did chat about suspension, however one question I did not ask is why would this be an issue now, and not before. This got me to thinking about the increase in wheel size. I am wondering if the increase in wheel size has caused the issue with what could have been an already compromised problem. He seemed to think (via a quick inspection) that the flatness was caused by a previous owner lengthening the springs causing the shackle to be almost horizontal.
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The EarthCruiser FUSO set up at EC with the relocated shackle point drove remarkably well on the road. Quite amazing actually. So they seem to have it figured out. I did notice that they seem more concerned with wheel extension and not compression, and thus there did not appear to be an increase in the bump stop distance, one thing I would like to improve on. I will be talking with the ATW folks today as well to get as smart as I can get.
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I would love your thoughts on what may be my issue, and your thoughts on the EC suspension and the ATW suspension. But let us not get too dogmatic here. I really do want to hear what you have to say, but I don't want this to turn into a bashing thread, but one of sharing opinions and knowledge for me and other to use.
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Thanks, Ken

 

[pugslyyy]

Hmm, I'm at a loss to explain how larger tires would make a difference like what you are experiencing.

What pressure are you running the fronts at? Those new Toyos are going to be much much stiffer sidewalled than what you had before - that could be a more likely cause.

 

[GR8ADV]

Hmm, I'm at a loss to explain how larger tires would make a difference like what you are experiencing.

What pressure are you running the fronts at? Those new Toyos are going to be much much stiffer sidewalled than what you had before - that could be a more likely cause.

Yes I agree. We began the trip at 60/80 and it was bad. Inflating to 80/95 cold was much improved. I will check later today on what we had on the last stretch, it was ugly. Don't know for sure given the pressure changes made, some done hot some cold, and some done at altitude and at much different ambient temps.

But you point is well taken and noticeable at speed. At 35-40 mph there is no noticeable issue likely due to the much slower dynamic transitions.

 

[pugslyyy]

Do you have the inflation table for the Toyos?

View attachment Toyo tire RV inflation table.pdf

 

[gait]

something very much not right with springs, bushes (spring ends and shackles), steering links, etc. Particularly look at bushes. Worn king pin bearings. At a pinch wheel bearings. Even check u-bolts. If the springs are bottoming out frequently that will effect steering stability.

Silly question. Are the rear wheels aligned? What are the rear springs like? What are the bushes at the rear like?

Also silly question(s). Does swapping wheels front to back change anything? Are the wheels all reasonably balanced? Do they run "true" (struggling to describe that but line eye up on outer edge of rim while wheel rotating and there should be no left/right movement). Are they well seated? Plus of course, check the wheel nuts if you didn't tighten them yourself.

And another. Is it the same in 4wd? (but be careful about winding up the transmission on sealed surfaces).

And of course. What weight on front and rear axles?

Plus a comment. I read somewhere (don't we all) that the original Canter springs are different left to right to accommodate road camber. John will hopefully tell us that so are the ATW springs with ++s and --s marked on them.

My experience was adding bigger wheels changed the ride a bit. And it took about 10,000km on the first set of tyres to "run them in" - guessing the sidewalls became a bit more flexible. Second set no noticeable change over time. Tyre pressures don't seem to make any difference to my handling, just lower pressure softer ride. Changing to parabolics gave a floatier, less responsive, feel to steering that took a couple of days to get used to. The caster always felt very "strong" to me. The vehicle always seems to go where I point it. At highway speeds its relatively stable. "Rides over" potholes and uneven roads without undue deviation. I'm more likely to wince at the harsh thump than have to grab the wheel.

Just for reference. I have a bit of a medical problem which means I'm very sensitive to the constant pull on the steering wheel to keep the vehicle straight on a cambered road. Hardly noticeable in the Canter (regardless of left or right hand drive countries) in marked contrast to a new Holden hire car I drove recently which required more constant steering wheel pressure.

I'm never too sure what the wheel alignment guys actually adjust when aligning wheels. I understand the theory but when I look at a standard Canter I can't see either caster or camber adjustment. The only alignment I see is toe in/out. Then again, there's not much to go wrong with a solid axle (not independent suspension).

I had an alignment done after fitting SRW. There were a couple of things I hadn't noticed until the alignment guys picked them up. One was a bent steering link. They had the equipment to bend it straight. My first thought was "flim flam" but I looked and saw and watched their hydraulics from a distance. Second was camber. A noticeable slight pull to one side which was sorted with a camber kit (eccentric king pin bearing outer shell). Camber and caster are both king pin angle related. I'm lucky and have a very good truck alignment place near, used to squeezing reduced fuel consumption out of trucks. I came away wondering about perfectionists. Before anyone asks - I was cautious about "up selling" but the 9 hours of work over two sessions was at the original agreed fixed price.

 

[GR8ADV]

Likely pressure as the trip home had 70 front. Quite surprised in ATW who could not tell me anythng about their suspension with respect to increased distance to the bump stop or increased articulation in extension.

 

[whatcharterboat]

Likely pressure as the trip home had 70 front. Quite surprised in ATW who could not tell me anythng about their suspension with respect to increased distance to the bump stop or increased articulation in extension.

Hi Ken,

What did you ask? And who did you ask?

Regards John.

 

[GR8ADV]

Hi Ken,

What did you ask? And who did you ask?

Regards John.

Hi john. I asked Allan. I asked how much increase in distance to the bump stops and what was the increase in extension of the parabolic suspension on my 2004 fg.

 

[whatcharterboat]

Hi Ken,

OK. I will come back to you ASAP with that info for a 2004 model.

Regards John.

 

[GR8ADV]

That would be most excellent. Thank you John

 

[whatcharterboat]

That would be most excellent. Thank you John

Hi Ken,

PM sent

Regards John

 

[Buckstopper]

GR8ADV - not sure where in the NW you are located but you are welcome to take a look at the ATW suspension on my '05. I'm in the Portland area.

Buckstopper

 

[dtruzinski]

Ken,

Have you resolved the drivability? I am getting ready to purchase ATW 19.5's for the same year Fuso and want to understand if I am in for a similar experience. Also do you know what the stock front track was prior to the super singles and what it is after? I am trying to figure out how much turning radius I will be giving up. Mind you the turning radius on these rigs is unbelievable and it probably won't be much of a problem.

tnx
dave

 

[ianc]

I had a similar experience when I switched to 19.5"s albeit on a Mercedes Vario. I eventually ended up back with 17.5" wheels and Duals on the back.
My wows are well documented over on the Mercedes section