I thought 427435 had a better answer. The reason is, assuming that the brakes are adequate, the maximum braking force is a function of the coefficient of friction and the weight on the tires. If you take weight from an axle with brakes and put it on an axle without brakes then you will decrease the braking force and increase the stopping distance.
A tag also doesn't carry an equal weight. My chassis has a 18000 gvw, the drives are 9500 while the tag is only 3000. So in my case the tag was added to stretch the frame and increase the gvw.
1993 Winnebago Vectra 37'
P30 - JetCo Air Ride w/Tag
Our coach built on the F53 20,500gvwr chassis has tags and is rated at 22,000gvwr. The tags have electric brakes with a controller you can adjust for loads. When towing I have mine adjusted at a setting of one notch under the maximum load setting. I set the sensitivity by applying service brakes where I can feel the tag brakes grab first then I back them off slightly where they engage in unison with the brakes on the steering and drive wheels. They seem to work very well, however, so far, haven't needed to make any panic stops.
Tag axles on gas coaches were added to increase the carrying capacity of the coach. My old coach had a tag and was rated at 20,500 pounds. The tag added 2,500 pounds of carrying capacity to the 18,000 Ford chassis.
When I talked to a Ford engineer, he stated "Your coach does NOT have the braking capacity as the 20,500 chassis in fact the brakes are too small for that capacity!" The manufacturer put a 36 foot motorhome on a chassis NOT designed to stop that much weight.
According to the engineer, the brakes on an 18,000 pound chassis are smaller and do not have a booster for the rear axle as does the 22,000 chassis.
I was a voice for tag axles and found that I was wrong after talking to the engineer.
The above does not apply to larger diesel pusher chassis, my information concerns the Ford chassis only.
I will also add that Ford did NOT cause this, the coach manufacturer saved small change using a smaller chassis on a larger coach to make money and put my life in danger.
So much for quality control.
ALL WHO WANDER ARE NOT LOST,
Mike, Jill and neat dog, Booger
2003 Tiffin Phaeton 38GH, Demco Tow dolly, 2002 Chrysler Town & Country
Good Sam, SKP, FMCA F292654
My choice would be a tag axle if I bought a new coach. My current coach has just enough brakes when fully loaded but would be nice if I had more brakes. I recently drove a 42' American Tradition tag axle. I found the stability excellent and the brakes very good as well. When you pull out of a driveway the side to side motion is greatly reduced. The only disadvantage could be a little less storage space and two more tires to care for.
Jaseds wrote: Tim and RVRMike you are both correct.
Sorry, while RVMike is correct, Tim is not.
Look at it this way. If the tag axle (without brakes) had really long air bags and could be lowered until the drive wheels (with brakes) were off the ground---------how much braking would the drive wheels provide??
The answer: None!!!!
So every pound that the non-braked tag axle is carrying is one LESS pound on the drive axle that can help provide braking force.
Mark
2000 Itasca Suncruiser 35U on a Ford chassis
2003 Ford Explorer toad with US Gear brakes,
ReadyBrute tow bar, and Demco base plate.
Tntman wrote: Tag axles on gas coaches were added to increase the carrying capacity of the coach. My old coach had a tag and was rated at 20,500 pounds. The tag added 2,500 pounds of carrying capacity to the 18,000 Ford chassis.
When I talked to a Ford engineer, he stated "Your coach does NOT have the braking capacity as the 20,500 chassis in fact the brakes are too small for that capacity!" The manufacturer put a 36 foot motorhome on a chassis NOT designed to stop that much weight.
According to the engineer, the brakes on an 18,000 pound chassis are smaller and do not have a booster for the rear axle as does the 22,000 chassis.
I was a voice for tag axles and found that I was wrong after talking to the engineer.
The above does not apply to larger diesel pusher chassis, my information concerns the Ford chassis only.
I will also add that Ford did NOT cause this, the coach manufacturer saved small change using a smaller chassis on a larger coach to make money and put my life in danger.
So much for quality control.
The Ford engineer was correct only if you had a tag with no brakes or no tag at all. Nothing wrong with putting a braked tag on a 18,000 lb chassis and re-rating it to 20,500 lbs. (provided the frame itself can handle it)
1) the more rubber on the road, the more traction and better braking
mp
Not true. Traction (highway, at least) is not affected by the amount of rubber on the ground----just the "softness" of the rubber, the condition of the highway surface, and the weight on the tire.
While I didn't make my statement as a scientific theory, if you increase the width of any given tire, at the same relative softness of rubber, you will have the potential to create more friction on the road surface and, if your brakes are up to it (also friction dependent devices), you will have more stopping power. Were that not the case we could all be riding on very soft and very narrow bicycle tires. lol
I do understand your position regarding the weight on the tire, as the weight per square inch does decrease as the tire gets wider, but you are adding more contact with the road.
And, I would never add wider tires to my RV! jmho
That's all I know and it's not much!
mp
2006 Revolution LE 40E
2004 Jeep Rubicon Toad/Brake Buddy or
20' Toy Trailer/Quads 'n Dirt Bikes
RVRMIKE wrote: Unless I am wrong, Tags are usually added to increase the GVRW of the coach. So if you take the 16,000LB chassis above, add a tag and rerate the chassis for 19,000LB, you need more brake to stop the additional weight. So IMHO with a tag with brakes, the stopping distance would be about the same as the weight has increased.
I would agree that the braking would be equal if the tag equipped RV was loaded to 19K lbs. However, if it is loaded below that 19K lbs limit, then you would expect the tag equipped RV to provide better braking performance over the non-tag RV.
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