UTTransplant said:
Mike, if we still lived in Utah, I would try to hire you to fine tune our coach. We are brand new to Class As, and we have driven it about 900 miles so far. We both commented on how much work it was to keep it on the road, but just thought we weren?t experienced enough. I now know the tire pressure is a lot of our issues! Pretty empty coach driving home, and the tires are at almost max pressure. Duh! We will finish loading it now we are close to home, then get it weighed. I bet it will handle better, but I will still be envious of Mike?s ?one finger driving?.
I'm not gonna lie Kevin, that one finger driving is pretty sweet.
When we first purchased the coach in 2007 I liked the ride but didn't care for the pull to the right and the bit of wandering that it had. I had it aligned and was told it was "within spec". Like a dummy at the time I accepted and thought that's just the way it is and is going to be. In the first several years a 400 mile day would wear my a$$ right out by the time we got to camp because of all of the sawing of the steering wheel and stress of keeping it on the road.
Finally about 4 years ago I said that's enough, I'm going to get to the bottom of this. I had heard of a wiggle test, which consisted of sticking a long 2" square tube in the receiver and going to town trying to move the coach around. I put my son on the end of the 10' tube while I crawled under the coach and began inspecting each and every suspension component. THAT is when I saw the play that took place in the OEM bushings and really noticed it at the end of the H-frame opposite where the panhard bar was placed.
Upon discussing with a couple of guys I met on another rv forum that were experiencing similar issues it was determined that something had to be done to make improvements. There were some differences as they each had the RR8R or RR8S chassis whereas I had the S-Series (tag axle) and was the only one of the group with a tag axle coach trying to fine tune his coach. First thing I did was replace all of my suspension components with ATRO bushings which have a higher durometer rating than the OEM rubber encapsulated bushings. This helped some but was marginal. Doing the wiggle test we still detected movement of the entire H-frame at the end opposite the panhard bar. While discussing with fellow RV'ers devising a plan I opted to perform a more detailed alignment of my own where I could see exactly where the wheels were pointed. In my opinion this is not as revealing as some think because on a solid front axle there is marginal results you can get due to the few adjustment options.
When I went around to the rear and checked the relationship of the rear axle with the front is when I was shocked. Basically the rear axle was moving over several inches by the time they got to where the front tires were. BINGO, there's my pulling issue, or pushing is more correctly stated. The rear axle had negative thrust angle which was basically pushing the coach, rear steering the coach, to the right. If I didn't have a firm grip on the steering wheel driving down the interstate the coach would try to go into the ditch within about two lengths of the coach, let go of the wheel and almost took a hard right. This was exhausting to drive due to constantly having to input force to the steering wheel and it was even worse on two-lane highways with road crown.
As you know there really aren't any adjustments on our RV's like there are on OTR trucks. I contemplated machining some adjustable sleeves in order to do a trial and error road test but didn't want the hassle of all of that work so I did some calculations to determine exactly how much the front axle needed to be moved forward to bring the rear axle (and ultimately the tag axle as well) into proper alignment with the front axle. I then added about .032" to apply a bit of "push" to the left so on two-lane highways it will push into the crown of the road. I cut, lengthened and sleeved the rear trailing arms on both the drive axle and tag axle on the left side of the coach and it handled beautifully after the first road test. On flat interstate if I completely let go of the steering wheel it will slowly "drift" to the left within several hundred yards but on normal two-lane highway (which we usually travel) I can let go of the steering wheel and it goes straight as an arrow.
With everything handling so well and being ecstatic with our coach at this point I still wanted to see if I could improve it any more. My wife says I can't leave anything along, but I don't know what she's talking about.
That is when I decided to built a Watts Link and apply it to the end of the front H-frame opposite the panhard bar. This is where I was still seeing some play doing the "wiggle test". This presented some obstacles as I discovered that on our coach the genset was positioned more rearward, closer to the front axle, than on any other Monaco coach I had crawled under. This would require some modification as well before I could even get started on the Watts Link. We call Monaco's snowflakes for a reason as I have yet to see two identical and each one has their own idiosyncrasies to deal with. My diagnosis was that on those long constant radius curves there was still enough give or play in the suspension bushings that the weight of the coach was causing the bushings to flex due to the placement of the panhard bar. This was requiring a bit more steering wheel input on my part to keep the coach going around the apex of the curve holding a particular line. After building and installing my Watts Link I was pleasantly surprised that on a long constant radius curve once I set the steering wheel angle going into the curve it will hold that line all the way through and not require me sawing the steering wheel to maintain the chosen line through the curve. I also saw an added benefit that by installing the Watts Link in the manner that I did, it lowered my roll center and in fact acts much like an added sway bar. I can handle canyon curves much, much better than previously with minimal body roll.
For example if anyone has traveled Weber Canyon on I-84 here in northern Utah when leaving the Ogden area heading east the very first curve has truck speed signs that say to slow to 55 MPH even though the car speed remains at 65 MPH. I could usually only hit that first curve at around 50-52 MPH if I wanted to stay in my lane and if there was a semi or even a car next to me going into that first curve it was a white knuckle drive, the remaining sections of Weber Canyon usually required me holding around 55-57 MPH until we exited the canyon around Mt. Green. My wife and I were doing a shake down run just after the completion of my Watts Link but before the long drive to Texas for an rvforum rally several years ago and I hit that first curve at about 57 MPH and it stuck to the road like glue. My wife was talking and I was concentrating and pushing it a bit, on each curve I pushed my speed up until I was cruising through the entire Weber Canyon @ 65 MPH. At one point at about 68 MPH one of my dinette chairs fell over and my wife asked why I was smiling and grinning like an idiot. When I explained the speed at which we just went through there and how well it handles she had no idea we were going through the canyon that fast, that's when she yelled at me to slow down. ;D
In the past 3 years now since I have had my Watts Link on and 4+ years since I really dove into my coach's suspension I can drive 650+ miles a day and not be tired or exhausted from the experience. Even coming back from the Black Hills last year we made the complete drive (630 miles) in one relaxing day and across I-80 from Rawlins to Rock Springs had consistent 40+ MPH winds and it handled like a dream. It was moving about slightly, enough to know the wind was blowing but NOTHING like years past and I didn't realize just how bad the wind was blowing until we stopped in Rock Springs to fuel up.
Long story short I would put our coach up against anything on the road as far as handling. I look forward to canyon driving and grin all the way through. We've had our coach routinely over/through Logan Canyon (Hwy 89), Teton Pass in WY, Burgess JCT./Pass (highway 14/14A) in WY and Highway 550 between Silverton and Ouray and feel like the coach is much more responsive, safer and actually fun to drive.
Just in case anyone is interested, I've posted a few videos of the mods to my YouTube channel but I will link them here in case someone may want to see exactly what was done and how it was done.
Here is the first video showing how I corrected the thrust angle on our coach.
https://www.youtube.com/watch?v=FrQR7ERBtOw
Here is Part 1 of the Watts Link build.
https://www.youtube.com/watch?v=Oj-AREsaI-s
Part 2 of the Watts Link.
https://www.youtube.com/watch?v=UGLW7KlqZpg
Part 3 and final video of the Watts Link.
https://www.youtube.com/watch?v=10H5eEB6ADo
Sorry to ramble, I just thought some may find it interesting to hear the thought process and sequence as well as the dedication and ambition it takes to really get the most out of their coach.
Mike