Tag axle pressure

[MRUSA14]

I run 125 psi in the steer tires. They are rated for 130, so where’s the problem? I am under the rating, ride and handling are great, and I have been doing this for 5 years with zero issues . I think the OP may be imagining a problem where none exists.

[96 Wideglide]

Originally Posted by MRUSA14

I think the OP may be imagining a problem where none exists.

I guess thats what you say when there is nothing you can do about it!

None of us that can adjust our axle weights, would leave that coach the way it is! Why would you want only 200 more pounds on a 4 tire axle, as you have on a 2 tire axle .

[Johnontheroad]

Originally Posted by MRUSA14

I run 125 psi in the steer tires. They are rated for 130, so where’s the problem? I am under the rating, ride and handling are great, and I have been doing this for 5 years with zero issues . I think the OP may be imagining a problem where none exists.

That certainly worked well for you, and I can understand that. But my prior coach had an easy adjustment for tag pressure, and with some experimentation I got a much better ride, more precise steering, and better load distribution. So I assumed I could do the same on my Entegra. But since there isn't, I can live with that and look at other ways to spend my time and money.

I'm old and retired, but in my working life I learned that the more safety margin I had the better off I was. So for me, I would sooner run a tire rated at max 130 at 110 than at 125. If the weights allowed. But that's just me.

[Gary.Jones]

John

There are also minimum inflation pressures that you should not go under. Under inflation makes the side walls flex more than needed which increases tire temperature and increases the chance for tire problems.

Now, on my 2015 Anthem, I had the coach four corner weighed with full fresh water, full diesel, and gray and black tanks at 50% and the load of personal stuff that we usually carry while on the road. That is what I was trying to determine in my first post in this thread... did you have your coach four corner weighed, or did you just get axle weights for each axle? From what you wrote, it sounds like you got axle weights and don't have the weights one each set of tires (left steer, versus right steer, versus left drive pair, versus right drive pair, versus left tag, versus right tag). That is what 4 corner weights will give you and it is very important.... equally important or more important than axle weights. You certainly want your axle weights to be within the load bearing capabilities of your axles. You can know those axle load bearing values. If you don't have them, call Entegra and get them. Emtegra axles are usually made by Rayco-Granning and their weight loads are published. Usually, they are within the design limits of the coach as no manufacturer can market a coach that is above axle weights by design, and when loaded as most owners would have it loaded. They would be sued out of business if they did. Now, that means that the axle weights are probably ok, but your individual weight on each tire position might be over-weight, just below weight, or well under weight. So, your axle weight total may be fine, but you may be greatly overloaded on the passenger side but fine on the driver side, and fine over the entire axle. That is why "4 corner" weights are so important.

The weight on each tire position then bears directly on the load rating of that specific tire and tire position, and it also determines the tire pressure that you need to be running in that tire position. I had lots of "headroom" on my passenger side steer tire (Michelin 315s) on my Anthem, but I was 160# over max design on my driver side steer. That was produced primarily by the 8 house batteries which sat right behind the driver side steer, and its share of a full tank of diesel (when weighed). So, I would have to run my steer tire near its maximum pressure to handle the load, unless I took some weight off the entire front axle by lowering the pressure on my tag tire, which were well under their design weight (as were my drive axle pairs well under both their axle weight maximums and the tire pressure (295s) maximums.

When you get your coach 4 corner weighed, they will run a computer analysis of your tire brand, size, tire manufacturer recommendations on maximum and minimum pressure and then recommend tire pressures for each of those 6 tire positions (both pairs on a side of the drive axle are to be set at the exact same pressure as each other). In my book, axle weights are not particularly important unless you are over the design loads.... from a coach safety perspective, what is important is the 4 corner weights, and the recommended tire pressures within the design parameters of the tire manufacturer.

You might know all of that, and if you do, I apologize for too much information, but it might be helpful for someone else reading this thread.

Gary

[cruzbill]

Gary, Have you rechecked your axle weights after adjusting your tag tire pressure? I can roll into an unused highway scale and check mine. Very helpful.

[jadatis]

If you cant change the tag , you can lower the pressure of tires of them . This lowers the tag a little by the little more deflection . Has the same effect. More weight on drive and less on tag and front. Ofcource within the savety- limits for the new weights.
What is your tagtires pressure now.
EDIT Saw reading back ,Garry Jones also suggested this in his long story

[757driver]

Originally Posted by MRUSA14

That was my thinking too when I asked Spartan to adjust my tag to lighten the load on the front. They flat out refused to do it, saying that the tag is adjusted to keep the drive line in alignment, and changing the tag adjustment would throw the drive line out of spec.

I don't think you should be alarmed at your weights. The axle rating is there for a reason and you can use all of it if you need to without harming a thing. My front axle is right at its maximum, and the coach rides and handles beautifully.

Seems that Spartan can not get their stories straight. I have also inquired about less weight on the tag axle and a very knowledgeable individual at Spartan said that adjusting the tag axle pressure lower (not the tire pressure) will not affect drive line angles. Drive line angles are for the most part only affected by improper rear ride height settings.

This individual at Spartan also mentioned that the pressure in the tag axle is adjusted and set by weight at the Spartan factory but how can an axle be adjusted when there is no house built on top of it yet? Makes no sense that they won’t adjust it after the fact especially when you have a drive axle with 4 tires carrying less weight overall than a front axle with 2 tires. Stupid engineering in my book.

[Johnontheroad]

Originally Posted by Gary.Jones

John

There are also minimum inflation pressures that you should not go under. Under inflation makes the side walls flex more than needed which increases tire temperature and increases the chance for tire problems.

Now, on my 2015 Anthem, I had the coach four corner weighed with full fresh water, full diesel, and gray and black tanks at 50% and the load of personal stuff that we usually carry while on the road. That is what I was trying to determine in my first post in this thread... did you have your coach four corner weighed, or did you just get axle weights for each axle? From what you wrote, it sounds like you got axle weights and don't have the weights one each set of tires (left steer, versus right steer, versus left drive pair, versus right drive pair, versus left tag, versus right tag). That is what 4 corner weights will give you and it is very important.... equally important or more important than axle weights. You certainly want your axle weights to be within the load bearing capabilities of your axles. You can know those axle load bearing values. If you don't have them, call Entegra and get them. Emtegra axles are usually made by Rayco-Granning and their weight loads are published. Usually, they are within the design limits of the coach as no manufacturer can market a coach that is above axle weights by design, and when loaded as most owners would have it loaded. They would be sued out of business if they did. Now, that means that the axle weights are probably ok, but your individual weight on each tire position might be over-weight, just below weight, or well under weight. So, your axle weight total may be fine, but you may be greatly overloaded on the passenger side but fine on the driver side, and fine over the entire axle. That is why "4 corner" weights are so important.

The weight on each tire position then bears directly on the load rating of that specific tire and tire position, and it also determines the tire pressure that you need to be running in that tire position. I had lots of "headroom" on my passenger side steer tire (Michelin 315s) on my Anthem, but I was 160# over max design on my driver side steer. That was produced primarily by the 8 house batteries which sat right behind the driver side steer, and its share of a full tank of diesel (when weighed). So, I would have to run my steer tire near its maximum pressure to handle the load, unless I took some weight off the entire front axle by lowering the pressure on my tag tire, which were well under their design weight (as were my drive axle pairs well under both their axle weight maximums and the tire pressure (295s) maximums.

When you get your coach 4 corner weighed, they will run a computer analysis of your tire brand, size, tire manufacturer recommendations on maximum and minimum pressure and then recommend tire pressures for each of those 6 tire positions (both pairs on a side of the drive axle are to be set at the exact same pressure as each other). In my book, axle weights are not particularly important unless you are over the design loads.... from a coach safety perspective, what is important is the 4 corner weights, and the recommended tire pressures within the design parameters of the tire manufacturer.

You might know all of that, and if you do, I apologize for too much information, but it might be helpful for someone else reading this thread.

Gary

I had each week with checked. Right and left steers, duals, and tags. So I know exactly how my weight is distributed. That is what I use to select the right tire.

[Rollin101]

In my other life when I owned a Tiffin they installed an adjustable regulator on the tag axle so it can be done. Only stipulation was to not go below 6000 lb on the tag axle due to tag axle tire skid when braking on wet surface.

[Gasman 2]

Originally Posted by 757driver

Seems that Spartan can not get their stories straight. I have also inquired about less weight on the tag axle and a very knowledgeable individual at Spartan said that adjusting the tag axle pressure lower (not the tire pressure) will not affect drive line angles. Drive line angles are for the most part only affected by improper rear ride height settings.



This individual at Spartan also mentioned that the pressure in the tag axle is adjusted and set by weight at the Spartan factory but how can an axle be adjusted when there is no house built on top of it yet? Makes no sense that they won’t adjust it after the fact especially when you have a drive axle with 4 tires carrying less weight overall than a front axle with 2 tires. Stupid engineering in my book.

Don,
You're right on what they tell you don't make sense. How can Spartan adjust it for the load when there is no load on it?

Now maybe the coach builder can adjust it but I doubt it. So how do they adjust it ? Must be by the seat of their britches.

Yes there is a adjustment valve but it's bury in the frame between the axles.

Not much chance anyone will get to it and that's the way they want it. Afraid we would jack it all around and screw something up and blame them.

I agree with the OP. Obviously he has checked everything he should and the front axle is carrying close to what his four drives tires are. From a safety stand point this makes absolutely no sense. How many front tire blow out have been posted on this forum? Is it a tire problem or an overloading problem.

Some of these coaches have a sufficient in balance across the front axle.

Enough said.

[757driver]

Richard,

Agreed, across the same model Anthem (44B) there can be a large difference with what the weight is on the front and tag axles because of what pressure the tag axle was set to by Spartan for very similar loaded coaches. A bit of a hit and miss indeed.

[MxChief66-1]

The HWH Active Air System I had installed on my 16 Anthem last year allows me the ability to adjust my tag pressures from the main display in the cockpit. However, having done significant research on the matter along with some trial and error I believe the factory settings are adequate based on the way my coach is loaded out and will continue at 100% on my tag. While I’m close to my max axle weights on steering and tag I couldn’t imagine this coach riding any better. I’m probably one of few on here that have no desire to upgrade shocks. I recently trecked across I10 from SC to AZ and couldn’t ask for a better ride.

Thanks Entegra and HWH!

Mark

[Johnontheroad]

Final answer from the Spartan Tech direct:

“In earlier chassis models, there was a ratio valve to adjust tag pressure, but on yours, unfortunately, there is not, so there is no way to adjust the tag axle.”

I will buy higher capacity steers and close the issue.

[MRUSA14]

Good decision, John. Many thousands of Spartan Chassis motorhomes are operating on the roads without problems resulting from tag axle pressure. This is just not something that one needs to worry about.