rear trac bar

[Deano2002]

after a nearly 1500 mile road trip I would really like to get my coach handling up to snuf. I would like to hear if the rear trac bar makes a significant difference. I noticed that when a semi comes along side me, it pulls me to it then, when it gets to the front of my coach it wants to push me away which I assume is normal for an old coach like this. The front end was aligned not long ago along with new shocks and sway arm bushings

 

[Gary RV_Wizard]

It's normal for any coach.  You have huge sail, and a passing truck or bus is pushing a great wave of air out to either side.  That wave first hits the rear and pushes it away, thus causing the coach front to move in the opposite direction.  The driver reacts by counter-steering, which happens just about the time the bow wave moves further up the side of the coach. The driver is now over-steering, so he corrects again, usually just as the bow wave reaches the front of the coach and pushes it away. That requires a final correction.

A track bar will help somewhat because part of the movement is the leaf springs shifting sideways under that pressure. A larger (stiffer) antiroll (antisway) bar also  helps. Nothing is going to stop it, though. The heavier the coach is, the less it reacts to the pressure of the bow wave, but adding 10,000 lbs to your coach probably isn't practical.  Buying a 40,000 lb diesel pusher does a pretty fare job of solving the problem, though. 

 

[Harvard]

What was the front end caster setting on the alignment report. Too little +caster can be counter productive when external forces attempt to upset stability.

 

[Deano2002]

What was the front end caster setting on the alignment report. Too little +caster can be counter productive when external forces attempt to upset stability.

I don't know what they set the caster at, I never asked. I think I read about that but, that was after I had it aligned

 

[Deano2002]

It's normal for any coach.  You have huge sail, and a passing truck or bus is pushing a great wave of air out to either side.  That wave first hits the rear and pushes it away, thus causing the coach front to move in the opposite direction.  The driver reacts by counter-steering, which happens just about the time the bow wave moves further up the side of the coach. The driver is now over-steering, so he corrects again, usually just as the bow wave reaches the front of the coach and pushes it away. That requires a final correction.

A track bar will help somewhat because part of the movement is the leaf springs shifting sideways under that pressure. A larger (stiffer) antiroll (antisway) bar also  helps. Nothing is going to stop it, though. The heavier the coach is, the less it reacts to the pressure of the bow wave, but adding 10,000 lbs to your coach probably isn't practical.  Buying a 40,000 lb diesel pusher does a pretty fare job of solving the problem, though. 

I think I will make the trak bar as my work has all the equipment to fabricate one and, go from there. I had planned on this a while back but, other projects jumped in line first. I had thought of larger sway bars but I cannot make those and are costly I thought. I would like to have a 40,000 diesel pusher but my budget is not going to allow that especially when looking at retirement in the next few years.

 

[John From Detroit]

I made two additions to my RV back in 2006  A track bar and a steering stabilizer

IN jan 2006 and again in Nov 2006 I drove from Detroit to Las Vegas to spend time with my Darling Daughter who lived there at the time..
THe first trip was BEFORE modifidcation and I can tell you it was a relief to drive the car once I got there instead of the big RV.

The 2nd trip was AFTER modification and the very same towed car.. was way harder to drive once I got there.

Same trip, Same MH (But with mods) Same towed Same driver.. BIG Difference.

 

[Denver Transplant]

After a very scary trip through the Debec Canyon on I-70 (east of Grand Junction) we decided that our ACE needed some suspension help. On this trip, winds of 40 MPH+ were blowing up the canyon and I felt like we were going to end up in the Colorado River. We ended up taking that part of the road at about 40 MPH and even then there were some interesting moments. On the rest of the trip on the I-80 across Nevada and Utah we got pushed around a lot by passing trucks. At the time we had a Safe-T-Plus on the front steering, but no other suspension improvements.

After we got back I decided to add a SuperSteer Rear Track Bar and also changed out the OEM Bilstein shocks with Koni FSD's. The track bar made a world of improvement. 90% of the push and suck from passing trucks is gone and the coach is less sensitive to cross winds. Tail wag is gone. We had it really bad as all of our tanks are behind the rear axle and once that weight got moving, it wasn't going to stop by itself.

Its still a big sail, but with the track bar, wind steering corrections are pretty much stable and I don't feel like I'm getting pushed off the road by little variations. The Koni's have greatly improved ride over expansion joints and road bumps - the rig doesn't porpoise like it did with the Bilsteins. Next on the list is a set of Sumo Springs, at least on the front in order to improve sway on curves. I have the CHF done on both the front and rear, which helped things, but there is still a ways to go. DW says no to upgrading to a diesel rig as she thinks I have way too much money sunk into the coach already.

 

[Deano2002]

I made two additions to my RV back in 2006  A track bar and a steering stabilizer

IN jan 2006 and again in Nov 2006 I drove from Detroit to Las Vegas to spend time with my Darling Daughter who lived there at the time..
THe first trip was BEFORE modifidcation and I can tell you it was a relief to drive the car once I got there instead of the big RV.

The 2nd trip was AFTER modification and the very same towed car.. was way harder to drive once I got there.

Same trip, Same MH (But with mods) Same towed Same driver.. BIG Difference.

I'm going to get going with the trac bar then, don't know what I could do with my front end if nothings loose but, it sounds like it is to me when I hit the bumps. I did put a new stabilizer on a few thousand miles ago

 

[Deano2002]

ended buying one on ebay for 375.00 shipped, new but, out of original box which makes no difference to me.

 

[Deano2002]

What was the front end caster setting on the alignment report. Too little +caster can be counter productive when external forces attempt to upset stability.

without any caster info from you I cant tell the shop what to do.

 

[Harvard]

without any caster info from you I cant tell the shop what to do.

Ford ships the E350/E450 cutaways with the caster set at about +3.5 Degrees which is OK for city driving but too little for highway driving. On the highway you want to have about +5.5 degrees , the specified range is about +1.5 to +7.0 degrees. Caster adds stability at highway speeds.

http://www.rvforum.net/SMF_forum/index.php?topic=40337.0

 

[Deano2002]

Ford ships the E350/E450 cutaways with the caster set at about +3.5 Degrees which is OK for city driving but too little for highway driving. On the highway you want to have about +5.5 degrees , the specified range is about +1.5 to +7.0 degrees. Caster adds stability at highway speeds.

http://www.rvforum.net/SMF_forum/index.php?topic=40337.0

this would be the same on my old P30 chassis?

 

[Harvard]

Caster is caster, that is why I asked the question about your alignment report...

Here is an example of increasing caster on a solid front axel...
https://www.ford-trucks.com/forums/1423437-steering-wander-corrected-5-degrees-of-caster.html

 

[Harvard]

Here is another example on the topic of caster.

http://www.rvforum.net/SMF_forum/index.php/topic,112427.30.html

Reply Post by 2kGeorgieBoy

Re: Wandering at highway speeds
Reply #36 on: March 14, 2018, 09:07:02 PM


START QUOTE:
Jeff..Although we have a 2000 Georgie Boy 31' Maverick "C" on  a Ford E450 chassis, I can fully agree on the caster effects, at least for us.  When we got the unit in  Jan 2014, the dealer had us take into a  truck shop for an alignment. It turned out OK....A trip to Moab shortly there after brought out the problems. I then started reading the threads and comments here about the caster settings....esp., from Harvard. I checked the data from the first alignment and found that it was set at about 3 1/2 degrees positive...about in the middle of Ford's recommended range. Shortly before a cross country trip to Maryland in fall of 2016, I returned to the shop where the first alignment was done. I talked to the service manager and he knew of the problems with the E450's and was happy to increase the caster as I asked. The alignment tech was also familiar with it and ended up with settings close to 5.5 degrees positive. WHAT A DIFFERENCE! The unit tracked straight down the road, passing semis no longer caused a white knuckle hold on the wheel, and overall it was just a lot more enjoyable. It did however increase steering effort a little but not anything to worry about.  But, be sure that the shop you go to is willing to "think outside of the box". Our first alignment was "plain vanilla", right in the middle like it was always done. Second time out, they were very willing to increase settings beyond what normally would be done, and still stay with in Ford's guidelines (0-7 degrees, I believe). I realize that our E450 chassis is an entirely different animal than yours, but I was trying to add support to the caster increase thinking and how it helped us......if you go down that road.
END QUOTE: