View Full Version : trailer question-axle placement

10-13-2004, 07:19 AM
I know the rule of 40/60 % on axle placement. My plans call for a 15' long bed(not including the tongue). My figures show the axle should go 6' from the rear or 9' from the front. Seems correct? My concern is weight. Should I take in to consideration what I'll be hauling and adjust the axle center line so I'll have 10-12% tongue weight or just stick with the 40/60 rule? Thanks.

Terry Lingle
10-13-2004, 09:10 AM
The "Rules" and guide lines are really just to get you close. If you are building the trailer as a" one off" the best way is to complete it without the spring perches put a roller under it set it for the toungue weight that you want. now load it as you expect it to be loaded . Your loaded tounge weight must be positive and less than the hitch systems rating. Ideally it should be close to the unloaded weight. Adjust axle position to optimise the two conditions if nessesary and you have the correct position for your trailer. If it is a production trailer set the axle to give resonable unloaded toungue weight and you will be ok.
The reason that each trailer design needs customising has to do with the weight distridution along the frame and the ratio of tongue to deck. Add a set of strong ramp to the back for loading on an existing trailer or change the tongue length and you will understand the reason the formula is not an absolute . Terry

10-13-2004, 09:30 AM
As it was already pointed out, depends on what you will use it for. I would suggest you add one foot. 16 foot is better and doesn't waste expensive metal.

For utility trailers I use this rule of thumb : 60/40 with the 60 measured from the coupler, or center axles on the trailer frame. Makes a well balanced trailer.

Tongue weight is a loading exercise. Try to get the greater weight over the axles...

Hope this helps.


10-13-2004, 11:04 AM
Maybe I can help clear this up. Then again, maybe I will just confuse everyone, but here goes.

The placement of the Axle has nothing to do with aerodynamics. It has everything to do with center of gravity. If the center of gravity is not in front of the axle, the trailer will try to whip arround. Go to the grocery store and push the cart frontwards (don't hit the little kids) and you will see that it tracks fairly well. Turn it around and push it backwards, and you will see that it wants to whip around. The further forward you put the CG, the more stable it is, but you also don't want all the weight on the hitch. This is how we get the 10% rule for toungue weight.

Now, you have to look at what you are hauling. Most trailers simply put the axle at the 60/40% position and leave it up to the user to distribute the load correctly. In the case of boats or cars, you are limited in how you load the trailer. This is where the designer must consider what is being hauled. If you are hauling something that is very aft heavy, you may need to put the axles farther back than the 60/40%.

Did I help or hurt?

10-13-2004, 11:12 AM
What Frodo said explains it very well. You can design the trailer perfectly and someone can come along and ruin everything by loading it wrong. The 60/40% rule has more to do with weight than distance. Since the tongue usually doesn't carry significant weight, it doesn't come into play. If you put a heavy tool box on it, that assumption goes out the window.

10-13-2004, 11:19 AM
Getting the correct loading is why I like the heavy haulers with the adjustable axles. If it doesn't hit right, set the brakes, pull the pin, move the trailer foreward or back, reset the pin and away you go. In some respects, truckers have it good.

10-13-2004, 11:30 AM

That's cheating. Takes all the fun and frustration out of the equation!! :)


10-13-2004, 11:54 AM
That may be, but it sure saves your butt when the DOT starts checking axle weights. Those tickets are expensive. :eek: It is too bad that type system isn't available on small trailers. I could use it from time to time.

10-13-2004, 02:25 PM
There was another general rule for axle placement I came across the other day. The end calulations come out very close to the 60/40 rule.

Take the 15' bed divide in half = 7'-6". You add 1" for every foot = 15". Add to the 7'-6" you get 8'-9" for the center of the axle from the front of the bed. This was for the 10 - 15% tongue weight rule. However, loading and placement will always determine how a trailer actually handles.

10-13-2004, 04:37 PM
Snidley, that's how we've always built our trailers, and they've always worked excelent.

10-15-2004, 09:08 AM
I didn't know the 60/40 rule when I built my welding trailer. I set my single axle a little forward of dead center and the Hobart welder where the engine is over the axle. There is space in front for o/a tanks, compressor, stuff, etc. I've pulled that thing many a mile and no problems....except the time I forgot to slide the collar up on the bulldog hitch !!!!....Thank God for the safety chain and skid ring I mounted under the front of the tongue. I built a rack out of 1 1/4 14 g square tubing over the whole trailer to carry ladders, material, stuff. I did add a fold down adjustable wheel on the tongue. Oh, also, I made a sleeve type tongue. That is, a larger pipe was welded to the trailer and then a smaller pipe was put inside of the larger with a bolt and pin. Then the coupler was welded to the smaller pipe. This way, if I had to leave the welder anywhere, I could disconnect the front half of the tongue and take it with me.

10-18-2004, 01:10 PM
Take the 15' bed divide in half = 7'-6". You add 1" for every foot = 15". Add to the 7'-6" you get 8'-9" for the center of the axle from the front of the bed. This was for the 10 - 15% tongue weight rule. However, loading and placement will always determine how a trailer actually handles.

Thats how I always do it

10-18-2004, 06:09 PM

Ken M.
10-18-2004, 06:31 PM
I did some quick calculations that follow. I found the 60/40 rule to be very close to my own. Like mentioned, the big factor here is how the load is distributed and how much weight you want on the tounge. I assumed evenly distributed. Another type of loading could be worked out in the same manner.


10-20-2004, 03:28 PM
60/40, worked well on this 8'x5' utility trailer.

I based my design on this website.