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Old 04-05-2013, 04:56 PM   #1
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Tire Pressure and Handling

I'm new to rv'ing and have only a couple hundred miles behind the wheel of a 40 ft Monaco. I know how my car feels and reacts to changes in tire pressure but don't have a clue with this coach and would like to make some small, incremental changes to optimize handling. For instance, I feel like I have to constantly make small steering corrections to correct the coach from wandering from one side of my lane to the other. Would you add a little or take out a little? Say 5 lbs.

All within the tire manufacturers specs of course.
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Old 04-05-2013, 05:04 PM   #2
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I suspect tire pressure wil probably NOT correct a wandering problem.

Wheel alignment is what has the most dramatic effect on that type of problem. Many following me will recommend some type of "safe-t-steer" or other gizmo to correct problems like yours. In my opinion, these devices just mask the underlying cause, improper alignment. Take it to a reputable truck service center and have the alignment checked. Wandering is often caused by the steer wheels being towed out or 0 degrees tow. I was always taught that just a slight amount of tow in will help the vehicle (any vehicle) track better.

Good luck
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Old 04-05-2013, 05:10 PM   #3
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Tire Pressure will have a major effect on how your coach handles.

Step 1 is to have your coach weighed. 4 corners is best but axle weights are better than nothing. Best done with full fuel, propane, and fresh water. Now add your passenger weights + your contents estimated weight if not loaded for travel.

Step 2 is to inflate to the tire manufacturer's recommended pressure per their Tire Inflation Chart. Many add 5 pounds as a safety factor.

Many tire shops and RV dealers over-inflate the tires as they inflate to the DOT placard pressures that assume that the vehicle is loaded to its maximum.

Our coach was sold to us with the tire pressures at the maximum. Ride was rough over concrete slab Interstate highways. Seemed oversensitive to steering but that could have been due to the fact that I was an absolute newbie.

An alignment is also good advice. Not expensive and will eliminate or correct a factor depending upon the situation.

Once I weighed and adjusted the air pressure it drove and handled like a dream.

DaveS
1998 American Eagle 40EVS
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Old 04-05-2013, 05:28 PM   #4
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FormerBoater has it right. I set my tire pressure to max for storage ~20psi over the correct pressure. On a warm day last month I took it out for a spin to give it some exercise and it handled poorly, seemed to be unstable and blown about the highway. I was concerned about it, then I remembered the tire pressure was too high. Last weekend I took it for an exercise spin again but this time I reset the tire pressure and it's back to handling the way it should.
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Old 04-05-2013, 05:34 PM   #5
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Quote:
Originally Posted by stik
I suspect tire pressure wil probably NOT correct a wandering problem.

Wheel alignment is what has the most dramatic effect on that type of problem. Many following me will recommend some type of "safe-t-steer" or other gizmo to correct problems like yours. In my opinion, these devices just mask the underlying cause, improper alignment. Take it to a reputable truck service center and have the alignment checked. Wandering is often caused by the steer wheels being towed out or 0 degrees tow. I was always taught that just a slight amount of tow in will help the vehicle (any vehicle) track better.

Good luck
This post is right on the money. Having your coach weighed and the tire pressures adjusted for those weights is a good idea and should be done, but the combo of having your ride height and alignment adjusted will do more than any other single thing to improve steering/tracking. The best place in the country for coach alignment is Josams in Orlando. If you take it to them for ride height and alignment and tell them you would like the toe-in and positive caster set at the max value in the spec, that will be the best single thing you can do.
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Old 04-05-2013, 06:51 PM   #6
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Actually, the most likely cause of your constant correction problem is YOU - or rather, your lack of experience with a Class A. Your view of the road is decidedly different than the family car, plus you are very concerned about the size and staying in your lane, causing you to focus at too short a range and spend too much of your time looking down at the road near you or in the side view mirrors assessing lane position. You need to loosen up and look further down the highway, at least 150 feet, and you should make note reference points for yourself so that you can tell at a glance if you are straying out of your lane. By that I mean note where the center line or road edge line crosses the dashboard edge when in your normal driving position and within your lane. It might be "a bit left of the speedo" or something like that, something you can easily note without looking all around to reassure yourself you are ok.

You should not be in doubt about tire pressure. There is a placard right by the driver seat showing recommended default pressures. Use those unless and until you have scaled weights that will allow you to use the tire manufacturer load tables to establish a norm specifically for your rig.
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Old 04-05-2013, 07:13 PM   #7
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No doubt it could be me and this coach is normal. LOL. The previous owner says he did not experience this and has owned rv's for 30 years. Also, I just had new tires installed and they WERE inflated to the max which I lowered to the tire manufacturers specs. This was still higher than the previous owner ran. He ran them slightly under recommended pressure for six years without problems.

So, I think I may go lower in pressure by like 5 lbs at a time and see how it feels. That doesn't do it , I think a trip to the alignment shop is in order.

My buddies that drive big rigs just shrug their shoulders and say It isn't a Mercedes and you have to drive it and I'll get used to it .
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Old 04-06-2013, 05:34 AM   #8
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Originally Posted by Gary RVRoamer View Post
Actually, the most likely cause of your constant correction problem is YOU - or rather, your lack of experience with a Class A. Your view of the road is decidedly different than the family car, plus you are very concerned about the size and staying in your lane, causing you to focus at too short a range and spend too much of your time looking down at the road near you or in the side view mirrors assessing lane position. You need to loosen up and look further down the highway, at least 150 feet, and you should make note reference points for yourself so that you can tell at a glance if you are straying out of your lane. By that I mean note where the center line or road edge line crosses the dashboard edge when in your normal driving position and within your lane. It might be "a bit left of the speedo" or something like that, something you can easily note without looking all around to reassure yourself you are ok.

You should not be in doubt about tire pressure. There is a placard right by the driver seat showing recommended default pressures. Use those unless and until you have scaled weights that will allow you to use the tire manufacturer load tables to establish a norm specifically for your rig.
I wish someone could convince my DW to look 150 ft ahead when she drives rather than 3 feet in front.....she hugs the right fog line and every 100yds or so she drifts over the warning wake up strips. Thats why I drive the motorhome. I have to keep telling her "stay near the highway Dear,or the Gps help us"


Bart Anderson
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Old 04-06-2013, 06:20 AM   #9
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When I first brought my coach home I started playing with the tire pressure to find the sweet spot for comfort and control. Started at placard pressure and increased up 5 pounds over the course of several trips. At 15 psi over the coach was going where it wanted and not where I wanted. Plus the ride was pretty harsh. The end result was 5 pounds over recommended.

Each coach is going to be different due to how the house weight was distributed by the builder and how much each of us pack stuff in and where. Even different tires on identical rigs will ride and handle different at the same pressure.

Race teams take tire pressures to the extreme with different pressures in each tire but since they only go fast and make left turns its a bit easier to determine optimum.
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Old 04-06-2013, 12:22 PM   #10
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Originally Posted by speedpeddler View Post
I'm new to rv'ing and have only a couple hundred miles behind the wheel of a 40 ft Monaco. I know how my car feels and reacts to changes in tire pressure but don't have a clue with this coach and would like to make some small, incremental changes to optimize handling. For instance, I feel like I have to constantly make small steering corrections to correct the coach from wandering from one side of my lane to the other. Would you add a little or take out a little? Say 5 lbs.

All within the tire manufacturers specs of course.
Mine came with 110 lbs all the way around. I'm not anyways close to the max weight on the coach. Too me mine felt like it wanted to wander all over the road. Two previous coaches did not do this. I started to lower pressures a little at a time. Ended up with 90 lbs in the rear & 95 lbs in the fronts. I noticed an extreme difference in the handling all for the better. Still haven't weighed it but my guess is I'm way under the max.
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Old 04-07-2013, 06:44 AM   #11
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Mine came with 110 lbs all the way around. I'm not anyways close to the max weight on the coach. Too me mine felt like it wanted to wander all over the road. Two previous coaches did not do this. I started to lower pressures a little at a time. Ended up with 90 lbs in the rear & 95 lbs in the fronts. I noticed an extreme difference in the handling all for the better. Still haven't weighed it but my guess is I'm way under the max.
I like what your suggesting here. The coach felt like it had too much air in the tires to me just like my car feels with hard tires. Dropping 5 lbs at a time until I get to the bottom of the recommended range seems like a plan.
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Old 04-07-2013, 07:33 AM   #12
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Tire Pressure will have a major effect on how your coach handles.

Step 1 is to have your coach weighed. 4 corners is best but axle weights are better than nothing. Best done with full fuel, propane, and fresh water. Now add your passenger weights + your contents estimated weight if not loaded for travel.

Step 2 is to inflate to the tire manufacturer's recommended pressure per their Tire Inflation Chart. Many add 5 pounds as a safety factor.

Many tire shops and RV dealers over-inflate the tires as they inflate to the DOT placard pressures that assume that the vehicle is loaded to its maximum.

Our coach was sold to us with the tire pressures at the maximum. Ride was rough over concrete slab Interstate highways. Seemed oversensitive to steering but that could have been due to the fact that I was an absolute newbie.

An alignment is also good advice. Not expensive and will eliminate or correct a factor depending upon the situation.

Once I weighed and adjusted the air pressure it drove and handled like a dream.

DaveS
1998 American Eagle 40EVS
X2 on Dave's comments!

In addition;

I just had my 1st service done at Freightliner and I had them check the alignment and ride height, both were out of adjustment and it did improve the handling once adjusted.

If this is your first experience driving a large RV I would also suggest that you attend a driver course. They teach a few techniques that help with handling such as looking further down the road v/s directly in front of the coach. This technique helps with the wondering, I have tried it and it works.

Good luck and happy travels!
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Old 04-07-2013, 08:00 AM   #13
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X2 on Dave's comments!

In addition;

I just had my 1st service done at Freightliner and I had them check the alignment and ride height, both were out of adjustment and it did improve the handling once adjusted.

If this is your first experience driving a large RV I would also suggest that you attend a driver course. They teach a few techniques that help with handling such as looking further down the road v/s directly in front of the coach. This technique helps with the wondering, I have tried it and it works.

Good luck and happy travels!
I have a lot of time behind the wheel of various types of race cars so looking as far down the road as possible is 2nd nature to me. I also spent the last 35 years as a chassis and suspension engineer in the racing industry so I know my way around the hardware. But, I have no experience with motor homes .

Thanks so much for all the suggestions. I'm not far from Lazy Days and like the idea of a driving school too. I love driving schools for race cars and have done most of the good ones. Maybe add the Lazy Days class to my resume.
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Old 04-07-2013, 08:30 AM   #14
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Be careful on lowering your tire pressures. Low tire. pressure in your tires is the number one cause for blow outs.
I suggest, do it right. An axle weight scale cost $10 at a truck stop.
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