My experience improving handling (long)

[mikebo]

There have been a few threads on this topic so rather than hijacking one of those I decided to go over my experiences over the last 3 + years with two different class c motorhomes.

The first motorhome was almost 29 ft long, with 181" wb, weighed about 12,600 lbs with about 9200 lbs on the rear axle. This motorhome had a very long rear overhang and light front end. It handled ok, not great but very drivable under 60mph with out a toad. With a toad it was horrible, the toad pushed the rear all over the place. It was blown all over by passing trucks.

I add a blue Ox track bar to the rear, hellwig sway bars front and rear and put Billstein shocks on it, I adjusted the hellwig rear helper springs as stiff as I could bear. I had the front end aligned with the caster at 5+ degrees.

The results of all these changes have the motorhome handling great without a toad and ok with the toad. The pushing from the toad is gone but the overall handling still feels sluggish compared to without the toad. Still get pushed by trucks passing but not uncomfortably so.

I traded this motorhome in on the one in my signature due to space issues but, the handling made the decision an easy one.

Current motorhome is just shy of 32 ft long, with a 220" wb, weighs about 14200 lbs with about 9300 on the rear axle. It has the same rear overhang as my older motorhome. When I drove this motorhome home from the dealer, empty, it handled better then my old one ever did. As I loaded gear in the motorhome and drove it, my feelings about the handling changed. The toad pushed the rear a little, but nowhere near what I felt on the old one and I felt some sway in corners.

I have added the Blue Ox track bar, hellwig sway bars and then took a 1300 mile trip. The handling is better that I ever had with the old motorhome with the toad. Only problem is the steering had a vague center feel. I have since had the front end aligned with the caster set to +5.8 left and + 6.6 right. This has made a very significant difference in the feel of the steering.

I am very happy with the handling now but have noticed the increased castor on both motorhomes seems to make the front axle ride a little harsher. I haven't noticed any shutter but on some road surfaces the harshness could be interpreted as shutter.

I don't profess to be an expert but I strongly recommend increasing the caster to 5+ degrees and adding a rear track bar on most any e450 class C. The sway bars work and have a side benefit of reducing the bounce from movement in the motorhome when parked.

Thanks to the knowledge I have picked up from this forum, I feel very comfortable with the handling of my motorhome, once I get out of my windy tree lined driveway, the white knuckles are gone.

And special thanks to Harvard.

[DaHose]

Thanks, adayjk. I figured it had to be some kind of camming mechanism, but an oversized hole with an insert is a very simple and effective solution.

Jose

[carringb]

Another way to make a toad tow better is to use a longer tow-bar. The effectively makes a longer lever so the motorhome has more control over the toad, and not the other way around. This is why many large trucks use long-tongue on their pup trailer even when they don't need it meet weights.

[Harvard]

Allen, do you have an opinion as to why the E350/E450 has such a wide specification for + caster? Typically it is a range from about +1.5 to +7.5 degrees of caster. I have postulated it may be a range to cover a cube van operated in the city (lesser +) and an RV operated on the highway (more +).

[adayjk]

DaHose wrote:
I also don't understand how they can adjust caster.

Jose

On the most common E series Ford chassis it is done with eccentric ball joint inserts. The upper ball joint stud fits into a hole that is far too big for the stud alone. The insert fills the remaining gap and had the small hole for the ball joint stud drilled off center. Other vehicles work differently.

As far as the toad: many vehicles now use SAI instead of caster to control straight line stability and steering wheel return to center. More caster many not be possible or adviseable. Some newer cars may only have a degree or two of positive caster, and that works fine. Any newer alignment machine can show SAI and verify that it is in specs after camber is set. In that respect a good alignment may still verify SAI problems, even though SAI is not typically "adjusted". SAI problems that still exist after a proper alignment (camber) typically indicate bent parts.

[Harvard]

DaHose wrote:
I also don't understand how they can adjust caster.

Jose

McPherson struts cannot be adjusted?

Quote:
"The good news is that most modern cars only have adjustments for toe. Caster and camber went the way of the dodo thanks to the McPherson strut."
End Quote:

Does the CRV have McPherson struts?

I am assuming the only reason a McPherson Strut vehicle has a Caster Tolerance in not for adjusting but for how bad it can be damaged in an accident and not necessary to be written off.

[Harvard]

mikebo wrote:
I don't know how he got the caster that high but the camber is in range. I have a CRV as my toad, it has been aligned to specs, I don't have the settings available right now. It weighs up to 3700 lbs, with kayak on roof and other gear.

I found a 2005 CRV spec on this SUV site:

Quote:
Caster: 1 degree 45' +/- 1 degree
Front Camber: 0 degree 00' +/- 45'
Rear Camber: -1 degree 00' +/- 45'
Front Toe-in: 0 +/- 2 mm (1/16")
Rear Toe-in: 2 +/- 2 mm (1/16")
End Quote:

If we were to theorize this one sample we might start off thinking a vehicle with this amount of caster might want to be a "wandering toad". It may be another detail to keep in mind when talking about toads. Time may tell.

[DaHose]

I also don't understand how they can adjust caster.

Jose

[mikebo]

I don't know how he got the caster that high but the camber is in range. I have a CRV as my toad, it has been aligned to specs, I don't have the settings available right now. It weighs up to 3700 lbs, with kayak on roof and other gear.

[Harvard]

j-d wrote:
That high caster number is impressive. How'd they get it that high? I'd heard that high caster tends to take camber out of the spec range.

Also, what do you have for a toad. I sometimes think the caster settings on a toad may explain why some toads do not adhere well to being a toad. They may have "a mind of their own" and want to go in a straight line more then others might. Just a thought. On the other hand, if a toad has little caster then they might also want to wander around causing discomfort to the towing vehicle.

For example we tow a 2007 Honda Civic with +7.0 Degrees of Caster but only a total of 3000 pounds of "authority". :B

On edit, the Honda caster is fixed at +7.0 and not the +6.0 in my original post.

[j-d]

That high caster number is impressive. How'd they get it that high? I'd heard that high caster tends to take camber out of the spec range.