Installing a Steering Stabilizer and Trim Unit

[gordonsick]

Other posts on this Forum have discussed steering stabilizers and trim units. I used them and other information to make the decision to install a Safe-T-Plus steering stabilizer (Damper Unit) with a SuperSteer Trim unit. I think that some Forum participants would appreciate a bit more information about this, so I’m starting a new thread.

This post will discuss the benefits of such a system and my product choice. I will also discuss some of the installation problems, since they may affect your choice of an installer. My next posts will discuss how I installed this system on my 2015 Berkshire 34QS with Freightliner XCR 34 foot chassis. Many people will not be interested in the technicalities, but those who are interested will find some detail that I couldn’t find anywhere else.

A steering stabilizer consists of a two-way hydraulic shock absorber (Damper) and spring system that connects the steering tie rod to the front axle. The Damper absorbs shocks from tire blowouts, wind gusts and temporary shocks to the steering from potholes or going off a paved road onto a gravel shoulder. The Damper doesn’t prevent you from steering, but it dampens the sudden effects from these shocks. The spring system tends to bring the steering back to a pre-set centre. Combined with the Damper, it tends to return the steering to a normal direction after a shock.

The normal direction of the steering can be set in two ways. In a pure stabilizer system, such as the Safe-T-Plus, it is set by adjustments made upon installation, and is fixed thereafter. With the addition of a trim unit, the normal direction can be adjusted on the fly as one drives down the road. This is a valuable feature when driving on the road with a strong camber, or when there are strong crosswinds.

My primary interest was in using the unit to assist me in strong crosswinds, so I needed a steering stabilizer with a trim unit. I live on the eastern side of the Rocky mountains, and the north-south roads in Southern Alberta, Montana, Wyoming and Colorado are prone to very strong crosswinds that last for days. You can’t simply pull over for an hour and wait out the situation. I one case, I was on I-25 in Montana, Wyoming and Colorado when the electronic road signs warned of winds up to 60 mph. A lightly loaded semi was tipped over on the road and I blew out a slide topper, as discussed in another thread. Our centre of gravity is much lower than for a lightly loaded semi, so we were safe from tipping over. But, I wanted to make it to Austin for the Formula 1 race, so waiting until the wind stopped was not an appealing option. After that trip, my arms and shoulders were sore for months and I did seek out medical treatment for it.

So, you might say that I’m just an old wimp and point out that cars and truck continue in such situations (I saw them continue on the road in this windy situation). Well, the situation with a motorhome is very different in such crosswinds than it is for cars, fifth wheels, travel trailers and semi-trailer trucks. This is because the very large sail area of a motorhome works with the caster effect of the steering to push very hard on the steering. The problem isn’t so severe for a car because it doesn’t present so much of a sail to the wind. And, most of the sail area of a semi-trailer tractor and rig is on the trailer, where it doesn’t work with the caster of the steering on the tractor to pull the steering. To avoid hijacking my own thread with a discussion of the caster effect, I’ve started a separate thread on the caster effect. http://www.forestriverforums.com/for...ml#post1928384

Choosing a Steering Stabilizer and Trim Unit
As near as I can tell, there are only two ways to get a steering stabilizer with a trim unit, although there are more solutions with the trim unit alone.

One of the product choices is the BlueOx TruCenter TruCenter Steering Control Freightliner | Blue Ox | Blue Ox
It operates an electrical solenoid that must work against a heavy spring that causes the trim unit to normally grab whatever holds onto the tie rod. Enabling the trim switch must cause the solenoid to pull the spring open to allow the unit to grab a new central spot. I have not seen one of these units, so I am just making inferences from what I have read about their unit from discussions and one picture. One advantage of this unit is that it will work on a front-engine gas coach that doesn’t have an air system. But, there have been problems, which may or may not have been resolved, whereby the solenoid burns out if the trim switch is held for too long.

The other choice, which I used, is to combine the steering stabilizer made by Safe-T-Plus Safe T Plus Steering Control / RV & Truck Steering Stabilizer with a Trim Unit from Henderson’s SuperSteer https://supersteerparts.com/product/...ering-control/
Safe-T-Plus makes four different sizes of the stabilizer damper unit and they recommend the largest unit for Class A motorhomes. The SuperSteer Trim Unit works with air pressure, so it needs a chassis that has air suspension and/or air brakes. By my calculations, the air pressure allows for over 1000 pounds of gripping strength in the trim unit. The air pressure is controlled by a simple electrically operated pneumatic valve that needs only a small current to operate and appears to be unlikely to burn out. The valve is similar or identical to the electrically operated pneumatic valves that are used to dump air from our suspensions in preparation for levelling. The SuperSteer Trim unit needs a mounting bracket that varies by chassis. My initial mounting unit, which is for Freightliner, created problems with clearance to the fuel tank. An email discussion with John Henderson of SuperSteer got me a prompt replacement with a RoadMaster mounting bracket that gave more clearance and also gave me the option of drilling new mounting holes for the Trim Unit in order to clear the fuel tank and tie rod. If you are installing this system on a Freightliner chassis, I recommend calling or emailing John at their service desk for advice before ordering, since he might recommend the RoadMaster mounting bracket instead. His contact information is in their online documentation.

From photos and descriptions, the Safe-T-Plus Damper Unit combined with the SuperSteer Trim Unit gives a bigger and stronger system than the BlueOx.

What to Order to get the Safe-T-Plus and SuperSteer Trim Unit
Installing a Safe-T-Plus Damper system alone (without the Trim Unit) requires ordering two things. You need to select the stabilizing Damper, and also the mounting brackets to mount the Damper between the axle and the steering tie rod. If you are going to install the SuperSteer Trim Unit, you don’t need to order the Safe-T-Plus mounting brackets, since replacements come with SuperSteer Trim System. SuperSteer supplies 1 3/4” U-bolts to mount one end of the stabilizer to the tie-rod, which resolves a question you need to handle if you only order the Safe-T-Plus unit – they provide U-bolts for three different tie rod sizes and you need to order the right one. Since the SuperSteer Trim Unit is only going onto a big diesel rig, it needs the largest size of U-bolts (for a 1 3/4” tie rod).

The choice of SuperSteer Trim unit depends on your chassis. I initially ordered the one for Freightliner and had problems with it hitting the fuel tank. John Henderson sent me a more flexibly designed mounting unit for a RoadMaster chassis and helped guide me in the revised installation procedure. The Roadmaster Trim Unit is sold at https://supersteerparts.com/product/...ontrol-monaco/

The SuperSteer Trim units also come with air lines, connectors, a trim switch, connectors, wires and the electrically operated pneumatic valve that allows one to fill the air chamber (normal operation) or dump air from the chamber (when trimming). It also includes a Haldex air chamber, similar to, but smaller than, the one that is used on my front disc brakes.

Cost
You can check costs online, but basically, you are looking at a bit over US$1000 plus installation for either the BlueOx system or the Safe-T-Plus plus SuperSteer Trim Unit. If you are not sure that you really need the Trim Unit, you can just order the basic Safe-T-Plus system for about $600 plus installation. If you do that, you have the option to upgrade that by installing a SuperSteer Trim Unit for another $500 or so, plus installation. You would waste a little over $100 that way.

Choosing an Installer
I chose to install my Safe-T-Plus Steering Damper and SuperSteer Trim Unit myself. There are many people on this Forum who could do it, and I’d say the skill and tool set is comparable to what I needed to install the Roadmaster tow plate on my Toad.

However, I did encounter an installation problem and you either need to be ready to deal with it or to select an installer who can deal with it without charging you an arm and a leg to solve the problem.

The installation problem comes from the proximity of the fuel tank to the tie rod in the Freightliner XCR chassis. The steering damper and trim unit sits between these two items. According to John Henderson at Henderson’s SuperSteer, Freightliner has been moving the fuel tank farther forward over time and he was surprised with the extent to which they had moved the tank on my unit. He sent me a special Roadmaster mounting bracket and I had to move the mounting holes by 7/8” to clear everything. If I only moved them 3/4”, I’d be too close to the fuel tank, and if I moved them by 1”, the U-bolts mounting the Trim Unit would be too close to the tie rod.

I believe that this is a fundamental issue that can affect all brands and models of steering stabilizers, so you should make sure that you select an installer who can handle this problem. (Even though the BlueOx system is smaller, its overall diameter is about the same as the small end of the Safe-T-Plus Damper Unit, which is where my problems with the fuel tank occurred.) If you travel near Henderson’s facility in Southern Oregon, I’d recommend that you get them to do the installation. If you don’t have them available, I recommend that you get an installer who has installed these items on a Freightliner chassis and who knows how to handle the problems. My local Berkshire dealer is listed as a supplier of the Safe-T-Plus product, but I have so little confidence in their mechanical competence that I wouldn’t go to them for the installation. Perhaps they would farm the job out to a suitable chassis or alignment shop, but then I would have even less control of the quality of the work.

It is worth noting that the problem could be solved by moving the fuel tank rearwards. I’ve got a 100 gallon fuel tank and there is enough empty space behind the tank to install a 150 gallon tank. Why Freightliner has chosen to mount the tank so far forward is beyond me, and it may just be a variation from one installation to the next. The fuel tank is held in a saddle and the bolts can be loosened to lower it a bit and move it back without having to move the saddle. All the connections come into the top of the tank and I can’t see whether they would get into trouble after a move, but I couldn’t feel anything being in the way. And, there is a drain plug at the bottom of the tank that would allow an installer to lighten the tank before the move.

Fortunately, I didn’t have to move the tank. I think I would defer to a Freightliner shop to do that for a fee, if I had to do it.

Installation doesn’t remove or replace any existing steering components nor change alignment
The installation does not require removal of the tie rod or any other steering gear. It does not affect the steering alignment. This is comforting to anybody who is worried about messing with their steering system.

Road Test and Using the Unit
I did a brief road test with and without a crosswind. The crosswind was so light that my wife didn’t notice it while driving our SUV behind me, but I could see flags pointing solidly in a crosswind direction.

Pressing and releasing the Trim switch did allow me to get a new central tendency of the steering in the crosswind, which did make the steering job easier. Note that pressing the Trim switch just moves the central point of the stabilizer to the direction to which you have set your steering. The self-aligning springs don’t kick in until the steering is deflected against them by the wind. This means that you have to still steer into the wind, albeit with less force. A trick that come people use, and which I worked on, is to oversteer into the wind while you press and release the Trim switch. This will preload the springs to steer into the wind. Before you do this, make sure there is nobody in the lane that you are steering into. Also, you will still need to adjust the steering if there are wind gusts. This isn’t autopilot.

I didn’t get a chance to try the unit in the presence of wind shocks from passing a semi on an undivided road. But, I was able to go through an underpass with the crosswind. This normally induces a twitch towards the wind when you enter the underpass and a full force combined with your counter-steering when you leave the underpass. This creates an interesting wobble or fish-tail effect normally. I do think the steering stabilizer damped that effect somewhat.

Finally, I was happy to note that the Stabilizer did not reduce the range of motion of my steering wheel. That means I still have the full advertised 55° steering angle available to me (almost 4 turns of the steering wheel from lock to lock). The limitation could happen if the two-way damper didn’t allow enough motion of the tie rod.

The Safe-T-Plus damper is the only component that comes below the axle level, but it is mainly blocked by the axle. It is not lower than the rear differential.

Overall, I’m happy with the system and would recommend it to anybody who wants to dampen steering shocks or to help in steering into strong crosswinds. I installed the trim switch on my left console in easy reach, so that I could steer while pressing the trim switch. The trim switch is spring loaded to return to normal operation when released. The switch itself is an old-school toggle switch with a retro style. It can easily be replaced by something that is newer. But, I do like the tactile way I can reach for and operate the switch, while holding the steering wheel with my right hand and looking down the road to select my trim direction. In other words, I like that it feels different from my other cockpit controls.

–Gordon

[gordonsick]

I looked at a lot of installation instructions and videos for both the Safe-T-Plus alone and the SuperSteer Trim Unit, and I must say that the instructions were generally very sparse and sometimes incorrect.

While the lack of good documentation is disappointing and likely to negatively affect sales of these products, I can see how the problems can occur. The products are to be installed in a great variety of coaches of varying sizes and designs, so it is not possible to give a full set of instructions for all the possible installation configurations. But, given that I’m restricting my instructions to a Freightliner XCR Chassis, I can be more specific. This chassis is one of the most popular Class A diesel pusher choices for coach builders and many of my instructions may carry over to other models. I imagine that Google may lead owners of other coaches to this thread for information.

Jacks, Blocks and Safety
It is important to plan on how your are going to hold up the front end of the chassis, given that you have to get under it safely and that you need to perform checks on the suspension (when fully compressed) and steering (at extreme angles). I backed my front wheels onto a 4.5” platform consisting of two wide wide pads that I’ve built for putting under my jacks when on soft ground. The are wide enough to hold my dual rear wheels for service. I drive onto the pads one step at a time, and use reverse because it has lower gearing than first. Then, I built up a crib of 12” long 6” by 6” blocks (side by side to become 12” by 12”), and added some more blocks (at right angles) to get the crib up to the height of the retracted front jack pads. Then, I “dumped air” from the air bags to drop the jack pads the short distance down to the cribs. To dump air, I set the jack system to auto-level. This removes air from the bags. Then, I immediately turned off the auto-level system to prevent the jacks from extending.

Some people might be inclined to just use the hydraulic levelling jacks on the chassis, but it is dangerous. They could fail while extended in a lot of different ways while you are pushing around on various chassis components from below.

It is important to think carefully about safety, particularly if your ground isn’t completely level and compromises the levelling blocks.

Torque Specifications and Procedures for Fasteners
You will be dealing with a lot of 3/4” bolts and nuts with 1 1/8” heads. Some of these are chassis bolts and some of them are the bolts that go through the ends of Damper unit. All the instructions say that you should replace the chassis bolts with torque set to the specifications of the chassis manufacturer. For 3/4” bolts, the Freightliner spec is 240-250 foot pounds. I was unable to achieve this much torque, given my lack of leverage while lying on my back under the vehicle, despite the fact that I had a 2’ torque wrench. However, I’m not concerned about that for two reasons. First, I had no trouble undoing all these bolts with a 2’ breaker bar. They clearly had much less torque than 240 ft lbs. They basically felt just a bit tighter than the torque needed to undo wheel nuts on my car, after they have been incorrectly over-tightened by a lazy mechanic with an impact wrench. Second, all of the 3/4” bolts in the chassis have self-locking nuts, so they won’t back themselves out and come loose, as long as they are tight enough to hold the metal together that they are intended to fasten.

If you want a little more torque on these nuts, you might succeed by using an impact wrench. I don’t know how much torque you can get out of these wrenches – this is an experiment that I might do with mine some day. The Safe-T-Plus installation video shows the installer using an impact wrench, but he doesn’t have a socket that is strong enough for an impact wrench. Clearly, he either doesn’t do many installations, or he backs off the wrench before it gets to full tightness.

The U-bolts that hold the unit to the tie rod are also self-locking. The U-bolts that hold the SuperSteer Trim unit to its mounting bracket only have lock nuts, however.

What does the finished installation look like?
The first photo below shows the installed unit, without the air line attached. It is in the driver-side wheel well. The front of the vehicle is to the left. The front axle has a bottle jack below it to test clearances when the suspension is fully compressed. The flat blue Roadmaster mounting bracket is fastened with the two rear nuts that hold the air bag to the axle. The tie rod is behind the axle and below the Trim Unit and Roadmaster mounting bracket. The black air chamber is from the front air brake for a small truck, and it is attached to the blue trim unit below it. Under normal operation, the air cylinder has air pressure and pushes a piston with over 1000 lbs of force onto the trim rod, which has the large self-locking nut on the end. That rod has a flat milled into it. Also in that photo at the right, you can see the left-front shock absorber. It is attached to a plate that comes back from the axle, which sits above the blue mounting bracket. It is held in place by two bolts with 1 1/8” heads. Note that this installation is using the flat Roadmaster mounting bracket, rather than the angled Freightliner mounting bracket to solve clearance problems to the fuel tank. The Freightliner mounting bracket would attach to the two bolts on the shock absorber mount.

The second photo shows the installation from below, looking toward the passenger side of the vehicle. There is another bottle jack under the passenger end of the front axle for testing. The large end of the Safe-T-Plus Damper unit is towards the passenger side and clears the fuel tank on the right. The small end of the Safe-T-Plus Damper is attached to the Trim Unit on the driver’s side, behind the camera. Note how the Safe-T-Plus extends below the front axle slightly.

The third photo shows the setup before any parts are installed. Note that this photo is on the passenger side, since I was originally planning to install the Trim Unit on the passenger side before John Henderson advised otherwise. So, the front of the vehicle is to the right. On the left is the RF brake assembly. On the right is the air bag. In the background, between the two is the suspension shock absorber. The mount going between the bottom of the shock and the bottom of the air bag has two bolts on it, which would be used if installing the original Safe-T-Plus mounting kit or the original Freightliner SuperSteer Trim Unit.

The fourth picture is also from the passenger side. It shows the front axle on the right and the tie rod going diagonally to the left of it. The fuel tank is farther left and very close behind the tie rod.

–Gordon

[gordonsick]

The first picture in this post shows the Safe-T-Plus dual action Damper Unit that has an internal spring. There are two sets of U-bolts. The packaged set attaches the the black bracket below it to the tie rod. The other set attach the Trim Unit to the Trim Unit mounting bracket. The angled mounting bracket shown is designed for the Freightliner chassis, but the flat RoadMaster plate is more useful in the tight situation. The rest of the parts are from the SuperSteer Freightliner Trim Unit, which I believe are the same as for the Roadmaster unit.

The second picture shows the mounting brackets from the SuperSteer Freightliner kit in blue on the left and those from the Safe-T-Plus Freightliner mounting bracket on the right. Note the similarities in the dimensions of the angled mounting brackets. They only differ in that the SuperSteer bracket holds the Trim Unit with U-bolts and the Safe-T-Plus holds the end of the Safe-T-Plus Damper with a single bolt. The Safe-T-Plus kit also includes a longer bolt and a spacer that can be used to replace the single bolt that holds the Safe-T-Plus Damper Unit. The spacer is intended to be used to improve clearance from the fuel tank, but I can imagine that it may need to be lengthened or shortened in some situations. Safe-T-Plus also provides two longer bolts to replace the existing bolts holding the mounting bracket for the bottom of the chassis shock absorber. This is needed because the bolts have to hold an extra 1/4” of mounting bracket. Note that none of these parts are used when using the Roadmaster mounting bracket, except for the U-bolts and tie-rod bracket.

The third picture shows the Roadmaster mounting bracket for the Trim Unit. It is flat because it attaches to the axle in a different way than the Freightliner bracket. But, the flat bracket gives more opportunity for adjustments. It comes with 4 holes for the U-bolts that hold the Trim Unit. In order to clear the fuel tank, I had to move the Trim Unit mount to the left (which is toward the front of the coach) by 7/8”. I did this by drilling 4 new 1/2” holes. I had to measure the required amount of adjustment carefully. Moving the holes by 1” would get the Trim Unit U-bolts very close to the tie rod. Moving the holes by only 3/4” would get the Safe-T-Plus cylinder very close to to the fuel tank. If there is not enough space, the fuel tank would have to be moved back.

The fourth picture shows the package of small parts that comes with the Trim Unit. There is some 1/4” air hose, air hose connectors, electrical connectors and a MAC Pneumatic valve that is electrically controlled by a solenoid. The fifth picture shows the MAC valve in closer detail. It is the pneumatic analog of an SPDT switch. Port 2 (not visible on the side goes to the Trim Unit air chamber. Port 3 is connected to the air supply. It is normally connected to Port 2, when there is no voltage applied to the wiring, so the air chamber is pressurized in normal operation. Port 1 on the other side is connected to Port 2 when the wiring is connected to voltage. It is used to dump air from the Trim Unit air chamber when the operator wants to trim the steering.

To be continued in next post

–Gordon

[gordonsick]

This post continues the previous posts. I am limited to 5 pictures per post.

The sixth picture shows the SuperSteer Trim Unit. The black air chamber bolts to the angled flange on the blue pipe. The flange has a 1” hole for the brass piston, which fits on the push rod on the air chamber. The brass piston presses on one of the two flats that is milled into the Trim Unit adjusting rod. Choosing between the flats allows for different installation options for different chassis. The adjusting rod goes through the pipe and is prevented from falling out by the large self-locking nut shown. When the chamber has air pressure, the brass piston grips the flat on the adjusting rod. When air is dumped, the rod can move to a new position. The other blue end of the adjusting rod holds the (small) end of the Safe-T-Plus Damper Unit.

The seventh picture shows how all the parts come together if using the Freightliner mounting bracket. The brass piston is in the angled flange and the air chamber bolts to that flange. At the right end, the Safe-T-Plus Damper Unit is attached to the tie rod bracket. Note that this differs from my final installation in two respects: it uses the Freightliner bracket, rather than the Roadmaster bracket. And the small end of the Damper is attached to the tie rod, whereas in my installation it is the large end that goes to the tie rod. The eighth picture shows the same parts, with the air chamber attached to the Trim Unit.

The ninth picture shows the Trim Unit attached to the Roadmaster mounting bracket, just before final installation into my motorhome. Note that it is convenient to attach the U-bolts, at least loosely, before attaching the mounting bracket to the axle. Also, note that one of the U-bolts was cut short to provide clearance to a bolt on the axle.

As well, the air chamber clamp was loosened so that then bolts could be turned to get out of the way of the chassis. In doing this, the air chamber actually separated on me, but it was easy to re-assemble. It contains a rubber diaphragm and a spring that pushes a foot on the pushrod towards the diaphragm. If you have read warnings about disassembling air chambers, those are for dual-chamber park brake systems as on a rear axle. One of those chambers has the very strong park brake spring, which can cause serious injury. This single-chamber system has a much weaker spring – just don’t stand right in front of it if you are adjusting the spring clamp.

–Gordon

[gordonsick]

The first picture in this post shows my first attempt to install the unit with the angled Freightliner bracket. With this installation, the Damper Unit hit the fuel tank when air was dumped and the front axle jacked up to simulate a compressed suspension. A really close look at the photo shows blue paint on the fuel tank and chipped paint on the Damper Unit at the end where it connects to the Trim Unit. This was the result of the Damper hitting the fuel tank on the first try.

The second picture shows the final installation, using the Roadmaster bracket. Note how the Roadmaster bracket is attached with the two bolts at the rear of the mount for the air bag to the axle. This is on the right of the picture. The bracket extends backwards and crosses above the tie rod in the middle of the picture. Note how the U-bolts that hold the Trim Unit just clear the tie rod.

The third picture shows how on of the rear Trim Unit U-bolts comes close to a chassis nut, so it was trimmed. That nut is on the rearward bolt of the mounting plate for the shock absorber. This picture was taken before the new holes were drilled to move the U-bolt even closer to the nut.

The solution to this problem is shown in the fourth picture. That shock absorber mount bolt was flipped so that the cap was on the bottom, giving sufficient clearance. This picture also shows the shock absorber (top right) and the complete installation of the Trim Unit. The Trim Unit is in the driver side wheel well, and the air chamber clamp bolts point towards the wheel. This is the most out-of-the way location possible for the air chamber. It is not in direct line with wheel spray and debris, and it clears the wheel by a couple of inches in extreme steering situations. Any other location would have the air chamber below the level of the axle, which would leave it quite exposed.

The fifth picture shows the other (large) end of the Safe-T-Plus Damper, where it is attached to the tie rod. Above the tie rod is the Panhard rod, where it is attached to the chassis. The other end of the Panhard rod is attached to the axle and holds the axle in place laterally. This is the only source of left-right asymmetry that I can see that might motivate John Henderson’s recommendation of putting the large end of the Safe-T-Plus Damper on the passenger end. He recommended that the small end of the Damper Unit to be attached to the Trim Unit on the driver side. There is ample clearance to the Panhard rod.

At this point, the bottle jacks can be raised and lowered to simulate the full range of motion of the front axle, and the steering can be turned from side to side. This allows one to gradually check all clearances and make adjustments to U-bolts to improve the clearance. Extra clearance to the fuel tank can sometimes be gained by rotating the U-bolts and attachment plate around the tie rod.

The project was finished by installing the air lines, pneumatic valve and electrical trim switch.

–Gordon

[gordonsick]

The attached picture shows the adjustable steering stop beside one of the King Pin bushings. It can be screwed out and secured by the lock nut if the Trim Unit and air cylinder get too close to the tire in extreme steering situations. I didn’t need to adjust this with my 255R70 22.5” tires. If the tires are much larger, such as 355R70 tires, it might be necessary to adjust the steering stop.

–Gordon

[btritschler1437]

Gordon did you discuss the pros and cons of the Super Steer Bell Crank housing for the Freightliner with John? If so would you tell us what his thoughts are on the use of tapered bell crank.

[gordonsick]

I didn't ask about the bell crank. There is no play in my steering around the bell crank, so I'm not in that market yet.

[gordonsick]

In my discussion of installing the Trim Unit and Steering Stabilizer, I noted that I had to switch to a Roadmaster mounting bracket (rather than Freightliner) and move the U-bolt holes 7/8" closer to the tie rod, in order to clear the fuel tank.

What I didn't provide is information about how close my tie rod is to the fuel tank, so other people can judge whether they will have similar problems, worse problems or no problem at all.

Today, I measured the clearance between my tie rod and the fuel tank when the wheels were pointing straight ahead, which puts the tie rod at its closest point to the fuel tank. My space is 3.5".

Thus, if you have less than 3.5" of space, you might need to move the fuel tank back. If you have 3.5" to 4.375" of space, you can use my technique after modifying a Roadmaster bracket. If you have over 4.375" of space, you can use the Roadmaster bracket without modification.

I don't know what space is required to be able to use the Freightliner bracket, but I prefer the Roadmaster bracket, because it lets me get the air chamber out of the way and more protected, inside the wheel well, rather than hanging below the front axle.

Gordon

[gordonsick]

Since installing the Steering Stabilizer and Trim Unit, I've driven 5000 miles. Overall, the system has provided the benefits that I expected.

The system removes the steering shocks from potholes and the passing of oncoming trucks on undivided roads. The coach moves a bit, but the steering wheel is steadier. It also helps to reduce the effect of crosswind gusts.

I've had some strong crosswinds that held flags straight out, but I think that can happen with a mere 20 mph crosswind. When I reset the trim in such a cross wind, I can hear the air dumping and presumably quickly refilling when I release the switch. This does reduce the effort of steering into the crosswind. To get the trim to take out the whole effect of the crosswind, I have to steer into the crosswind, moving the coach towards it when I press the trim switch. This is easier to do if I'm turning a corner into the wind. I had anticipated that this kind of adjustment would be necessary, so it is not a concern.

In other words, setting the trim does not put a bias into the trim to fight the crosswind. It merely removes some of the caster effect that pushes the steering wheel. To fully remove the caster effect, you need to oversteer into the wind, which you can do on a corner, or by changing lanes.

Overall, I find I can drive longer days without tiring as before, so I'm really happy to have it installed.

–Gordon

[dave-g]

The time and energy you put into your post is amazing. Always great info. Thanks

[gordonsick]

I was at a Camping World recently and looked at their description of the SafeTSteer stabilizer. It claimed that this unit was useful in crosswinds.

That is, at best, a misleading statement, and, at worst, just plain wrong. The stabilizer without a trim unit is only useful in crosswind gusts. Otherwise, it actually increases the effort needed to steer into a steady crosswind.

In this post, I'll only discuss the situation with steady crosswinds. It is an important issue with really strong crosswinds, but only a bother with minor crosswinds, of course.

First, consider the situation with no stabilizer. As I've discussed in earlier posts in this thread, the side pressure of the crosswind works with the steering caster to convert this pressure to a steering pressure towards the downstream direction of the wind. The driver needs to counteract this with steering effort and actually has to steer into the crosswind to steer straight. Suppose the wind is such that this requires a steering angle of 2 degrees, for the sake of argument.

Now, consider the situation with a stabilizer, but no trim unit. The stabilizer is set to have a neutral steering effect if there is no cross-wind, and the springs in the unit push the steering towards this neutral straight-ahead position. But, with the crosswind that requires a 2 degree steering angle, the stabilizer unit is actually adding steering pressure (toward centre) in the same direction as the crosswind. Thus, the stabilizer unit in a steady crosswind actually increases the steering effort to keep the vehicle driving straight ahead. With a stronger crosswind, this compound effect becomes stronger because a larger steering angle is needed to compensate for the caster effect.

Finally, add a trim unit to the stabilizer. If the driver follows a simple strategy of resetting the trim unit while steering into the crosswind, this removes the compound effect of the stabilizer adding to the steering effort required in the crosswind. This returns the situation of the first case with no stabilizer or trim unit. The driver is no better, but not worse, off than without any extra equipment. But, the situation is better than with a stabilizer and no trim unit.

Now, a skilled driver with a trim unit and stabilizer can reduce the steering effort required, relative to the situation without any extra equipment. The strategy required is to oversteer into the crosswind. I've been working on this strategy, and am getting more skill, but am still not perfect. Here are the techniques that I've used to reduce the steering effort:

• Follow the wind to one side of the lane and then steer into the wind while resetting the trim. This doesn't work perfectly if I stay in the lane. Going so far as to switch lanes does help.

• When the road has a curve towards the wind, reset the trim in the curve. It helps, but isn't perfect.

• In extreme crosswinds, slow down and pull over to the shoulder or a rest area. With the vehicle stopped, turn the steering wheel towards the crosswind and reset the trim. I haven't had a situation where I needed this, but I will do it the next time I hit a really strong crosswind.

–Gordon