Tag axle and traction

Not sure if this is the right place for this, but since it's a Winnebago Tour, I'll start here. My new 2010 Tour has a tag axle and today was my first opportunity to drive it in the rain. When starting to roll from a stop, the drive wheel would spin, not something that I would have expected it to do.

This particular coach is right at or a little over the 14,000 front axle weight. I have plenty of total CCC on the rear axle. I have read that by adjusting the air pressure of the suspension on the tag axle, I can get more weight on the back axle and less on the front. If there is too much pressure on the tag, could this be the reason why the drive tires spun? Any idea how to adjust the pressure?

Get your coach weight by axle at any good truck stop. If your Main rear axle isn't at  or 18 or 19,0000 lbs adjust the tag pressure down to get more weight on the main rear axle - this will also take a little off the front axle.

In your engine compartment you should see a pressure gauge and pressure adjustment for the tag. The procedure should be explained in your owners manual.

ken

Here?s an update for what has transpired so far. While in Connecticut, I went into the Freightliner dealer to see why I had no traction. It turns out that one of the height sensing valves on the drive axle was faulty and the air bag wasn?t inflated. They fixed that and I went on my way. I had to go back to Florida and discovered during a rain storm that the traction problem hadn?t been solved.

In November, I was in Livingston, TX, I used the Escapees Smart Weigh. Here?s what they found for weights:

　        　Left - Right (GAWR)
Front  7500 - 7000         (14320)
Drive   5100 - 7880         (20000)
Tag   5100 - 4570         (10000)



'Wow' would be an understatement. I had more weight on the front axle than I did on the drive and it was over weight. The tag was almost maxed out and there was very little weight on the drive axle. I called FCCC and they said that these were ?screwy? weights. (I believe that?s a technical term) They suggested that the tag axle suspension proportioning valve is bad. I made an appointment at Dallas Freightliner to have it looked at.

The dealer replaced the valve and with a lot of conversation with FCCC, adjustment to the valve, and several trips to the CAT Scale across the street, FCCC decided they were happy. Here were the weights when we were done: I couldn?t do individual position weights due to the scale configuration.

Front - 13900
Drive - 16880
Tag - 6800

While on the way back to Mesa from Quartzsite last week, I stopped in Congress and went through Smart Weigh again. Here are the new weights.


　　 Left - Right (GAWR)
Front 7310 - 6660 (14320)
Drive 6650 - 9450 (20000)
Tag 3600 - 3250 (10000)

I see two issues. First, the left front wheel is still overweight. The max weight for the tire is 7160 lbs at 120 psi. Secondly, the weight distribution is strange. The worst is the drive axle, but the front and tags are heavy on one side and the drive is REALLY heavy on the other.

I spoke with FCCC and asked if I could continue to adjust the tag weight to bring the front wheel into spec. The guy there was concerned that if I unloaded the tag any more, the right drive wheel would go over its weight limit. I also asked about the disparity of weights and he seemed to shrug it off. I think he?d like to blame Winnebago for building it so out of balance. I am not so sure it?s a Winnie issue. If it was heavy on one side, wouldn?t at least the tag and drive axle imbalances be on the same side? I asked if it could be a ride height valve adjustment issue and he grudgingly agreed that it might.He offered 3 options.

Adjust the tag within limits (but he really didn?t like that option).
Check the ride heights and adjust is out of spec. He gave me the specs.
Get larger tires for the front. I currently have 275/80. I can go to 295/80. The next limiting factor are the spindles and hubs. Bigger tires would get the front axle to 14600 lbs (7300 per wheel). That would get me in spec., but the left/right imbalance would still be there.

When it comes to distributing our belongings, I don't think there's anything I can do. The full fresh water tank is directly behind the front axle. The fuel tank is under the water tank. I don't have enough in the front to move to the back to make any significant change. My kitchen is in the right front and the fridge is in the middle of the left slider, so I have no idea why the right rear is so much heavier than the left. Again, I don't have enough belongings to compensate for that.

We?ll see what happens when I measure the ride height.

The imbalance is bothersome but not unusual in motorhomes. 600 or more lbs difference is all too common. That's probably why the tech rep shrugged it off. And of course, the overloaded front tire needs to be corrected.

I don't see any reason not to increase the tag load a bit to try to relieve the front a bit. Just have to watch the effect on the rear as well, so you need a good scale at hand. A judicious tuning of the tag axle balance might also help get the rear balance somewhat closer.

The only way to lighten the front axle is to lighten the tag, too. The only place for that weight to go is the drive axle. At 9400 lbs, I am a little hesitant to add any more weight to it. 6-800 lbs difference is OK. I am more worried about the nearly 3000 lbs difference.

I am leaning towards bigger front tires. I am not excited about the expense, though. After I check the ride heights, maybe I'll figure out how to adjust the tag regulator. A trip to Congress and the Smart Weigh guy might be a good place to mess with the tag weight.

release the air on your tag axle and raise it just like a greyhound bus

Sometimes it's a bit hard to predict what a change to the tag axle load will do, since it tends to cause a teeter-totter (pivoting) action around the drive axle. If it lifts too much, it can transfer weight forward to the front axle and lift the drive right off the ground. Lighten it and maybe the front lifts up as weight shifts to the drive. But sometimes the drive just gets heavier and the front stays the same - it's a matter of balance and spacing between drive and tag.

Winne had a big problem with weight distribution on the Tour and Ellipse through 2012.  I have had fits with my 2012.  There is way to much stuff (gen, water tank, propane tank fuel tank and people.)  They corrected it somewhat in 2103 and it is about right in 2014.  The only way that I got it to be acceptable was to go to an Oasis dealer and have them work on the phone with Freightliner.  It says in my manual that you can't run with a full tank of water.  Very poor engineering.  I am surprised that freightliner is so willing to work with the owners since it is definitely a Winne issue.

Did you up your tire size on the front? How much are you now carrying?

The 2012's came with the larger tire up front because of this issue.  I think that it would be a wise thing for you to do.  How much am I carrying?  If it refers to water, about 3 inches from the bottom of the tank unless I plan to dry camp for a while in which case I fill it up close to the point at which I will be camping. 

Take it to Gaffney, SC  where the chassis was built. They had my weight and balance corrected In an hour...
I go every year for preventive maintenance.

What did they do to correct it? I am about to go into the Tollson Freightliner dealer tomorrow for ride height adjustment. I have already replaced the tag axle proportioning valve to get weight off the front and tag and onto the drive axle. There's no way I can make to Gaffney until some time next year. We're pretty much booked for the rest of this year.

Currently, my front weights are 7310 and 6660. My real problem is a couple of hundred pounds on the left. If I carry half a tank of water, I will be right at capacity. We're headed to Alaska this summer and really need a full tank to plan for any eventuality. Going from 275 to 295's will increase the axle capacity to 14600 (7300 per wheel). That should work.

If I could somehow balance the two front wheels, I wouldn't need to do anything. That would save me about $1500 for new front tires.

How much propane do you carry?  A little goes a long way in your coach.

Not enough to matter. They adjusted the ride height in the back. There wasn't enough done to affect the weight. I am trying to decide if I'm going to live with it or get new front tires. Most of the expert advice I have gotten is to live with it until it's time for new tires.

A little off topic, but relating to your weight issue. I just did Alaska last year, and no, you don't need to run with a full tank of water. There are lots of places to get water and to dump. Save yourself the worry. Run with about 30% fresh and you will be fine.

Going from 275 to 295's will increase the axle capacity to 14600 (7300 per wheel).

Click to expand...

You haven't actually increased the axle GAWR (unless the tires were the only limiting factor), but the bigger tires should help with the side-to-side imbalance issue, where one end is heavier than the tire can handle, even though the total weight is still within the GAWR.

It was real interesting to monitor the temperature of my tag axle tires before and after they reduced the weight on the tag.  Quite a difference.

Gary RV Roamer said:

You haven't actually increased the axle GAWR (unless the tires were the only limiting factor), but the bigger tires should help with the side-to-side imbalance issue, where one end is heavier than the tire can handle, even though the total weight is still within the GAWR.

Click to expand...

If tires were the limiting factor, then you might be able to get  Freightliner to issue a new weight sticker to legally increase the GAWR.

ken

The front axle rating on the 2004/5/maybe '06 Horizon/Vectra was 12,000 pounds which turned out to be marginal,  when we fulltimed, I was always right at or over the 12k limit.  Starting maybe in '06 (?), Freightliner increased the front axle to 14,400 and the only difference was a larger steering box and Load Range H tires instead of G.  This was a Zonderfunk (ZF) IFS axle.

Seems like Winnie engineers sometimes don't get it right for two or three model years  .

My Phaeton has a #14320 front axle.  Interestingly it is the same front axle that is on the 42' Phaeton as well. Freightliner XCR chassis.