Camber Question

[sjensensr]

Great site!

I've got a question. I'm building a panel walled Grumman on a 5x8 frame. I've got a 3500# Dexter with 2000# springs, (I've got 35' Ford wire 16 inch wheels w/5 on 5 1/2 or I would have went lighter).

This is the first teardrop I've built, first trailer as well. I know the bend in the axle has to go up, but I was getting ready to weld the seats on when I noticed the camber angle seemed to be at least a couple degrees. I put the tires and wheels on and it looked kind of funny. I put the axle on jackstands and stood on it while my son held the square and he didn't see it move.

I have the frame just about built, basically 2x2x.120 rails with 2x2x.083 going across and a 3x2x.120 tongue. I have part of another 2x to throw on for a A frame as well, but even then I'm only looking at about 180 pounds with fenders. I don't plan on having too much added weight and can't see, (as of yet), having the total ever be more than 1200#.

I called the place I bought it from and they said to rotate the axle until the camber was right. I went out and turned it, and sure enough..

Does this sound right to you guys? If it is, how much angle do you thing I need, (if any), and which way is best to rotate the hump, front or back? I'm thinking front, so if anything it gives me more toe in under load, but I doubt I'll ever see the kind of load that would do that. Is there any rule of thumb when going light on a heavy axle?

Scott

[asianflava]

The peak does go up, it is supposed to help the trailer track better.

[brian_bp]

I think that the trailer tracks better with the bend up, mostly because the weight of the trailer essentially flattens it out, and you don't want negative camber. Nearly two degrees certainly sounds like excessive positive camber.

Trailer axles are usually spec'd with nearly zero margin - a typical commercial trailer builder would save money (and weight) with a lighter axle for this application, and it would flatten out. (It would also have 13" or smaller wheels, tiny tires, no brakes, etc).

Rotating the axle beam so that the final loaded camber is more reasonable makes sense to me... but now it will have toe-in (if the top is rotated back) or toe-out (if the top is rotated forward). I vote for rotating back for some compromise between excessive positive camber and excessive toe-in... my guess is that anywhere in between could be acceptable.

[sjensensr]

Thanks for the catch! Tilt back would increase the toe in. I'm going to take a real good look in the morning and then give Dexter a call. I really don't want to have to grind those seats off, after I get it wrong.

[Alphacarina]

Camber doesn't have a thing to do with 'tracking' - It's added to the axle to compensate for the anticipated bend in the axle when loaded to it's design weight rating. This ensures the tires will wear evenly across the tread face . . . . . but if you never use the axle with the recommended load on it, you will still have a problem

If you call Dexter and tell them you're worried about camber and are using one of their 3500 pound axles on a smallish, lightweight trailer, they are going to recommend you buy an axle rated for the load you expect to carry

From the FAQ on Dexter's website:

AXLES - Why are some axles bent in the middle?
The upward bend in the axle is called "camber". Camber is the angular relationship of the wheel to the road suface in the vertical plane. Axles are typically built with a pre-determined bend in the tube that compensates for the expected deflection under load.

The Harbor Freight axle for their 1740 pound trailers come with zero camber in them BTW - Many lightweight trailer axles come this way. Comes in handy if you want to lower the trailer by reversing the axle and mounting it above the springs as opposed to under them like it was designed

Don

[sjensensr]

I almost went the Harbor Freight route, but I want to use these wheels and I go offroad.

I called Dexter this morning and they said the camber should go neutral, once I load 1900# on.... They also said something about an axle with neutral camber that they build, (or maybe it was they could build an axle with neutral camber). They said to leave the hump up. This 1900# figure seemed a little arbitrary, so I emailed them a bit ago to get a little clarity about what 1000# or so is going to do to a 3500# axle.

I measured the axle w/wheels after work and my 3 deg. bubble camber scale maxed. I used a square and measured about 5/8 camber from the top outside to the bottom outside, (almost top and bottom - outside of the tire bulge). I rolled the axle back until I showed a half inch camber and the toe in was about a half inch. These tall tires really amplify the look.

Maybe I'm just being overly sensitive, I just hate seeing wheels lean out and don't want to weld the seats on as a learning experience.

I'm hoping Dexter emails back with some happy options; like, it should be just fine.

[G-force]

I would mount it straight up as intened and not worry about it. Heck, the roads we travel usualy have a pretty good crown in them, probaly a greater wear factor for tires than a little bit more camber. The front tires of the majority of rear wheel drive cars are consistantly changing camber as the suspension moves up and down. Worst case scenerio, the outter edges of your tires wear a little quicker. In the grand scheme of life, who cares? How many sets of trailer tires have most people actualy wore out from milage? 99% of the time the need replacing from age and rot.

[doug hodder]

I'm with Mike...I've built 4 all using a 3500# axle with a 4" drop and leaf springs. Heaviest is 1120#. I've got nearly 8K miles on one of them and no noticeable wear on the tires and it tows just fine. You do have a tall/narrow wheel tire combo that may be really showing the tilt off. If you use the axle you have now, I'd plan on setting it up with the crown straight up, or it is entirely possible that you might get some excessive tire wear, ie from toe in/out etc...Others opinions may vary. I'd just do it. Doug

[Trackstriper]

In the past I've looked on the internet for specific information about toe-in or toe-out for trailer axles and couldn't come up with much. I think that the axle manufacturers design with O degrees toe. For our old rear drive cars we would have a certain amount of toe-in to correct for the minute slop in the various front end links and tie rod ends. The basic dynamic drag from the tires would tend to pull the tires in the directiopn of toe-out and a little initial (unloaded) toe-in would allow the tires to seek a neutral toe alignment once the slop was taken out by the drag. A simple trailer axle does not have any linkages to be concerned about, the only slop being the bearing tightness...which should be inconsequential. At least this is my rationalization of what is going on regarding toe.

I think Don is right on the money regarding camber. The axle is prebent to compensate for the fact that the axle beam will bend under load 'cause you can't practically load the beam at the centerline of the wheels... it's always loaded inboard of the wheel centerline, whether it's a torsion axle or spring axle.

For your axle alignment I would be careful to align the axle tube with the camber bend directly up so as not to induce any toe effect. Then, if you don't like the camber when the trailer is finished and fulll of stuff, pull the axle and take it to a shop with a press and have them remove some of the camber. The camber was put in there by bending the tube tube in a press and can be modified the same way, just reverse some of bend.

[sjensensr]

Well, I've been emailing with a design engineer at Dexter, (that place has great customer service).

Basically, the default camber for the 3500# axle is 1.2 degrees. a 5 foot wide teardrop would have to weigh 2000# to to even cut that in half - not adding what the tongue subtracts. that's a little heavy for what I had in mind. I doubt 500# per side will even move it.

I've set this axle up in the driveway a few times now and tried to convince myself it'll be fine, but with tall tires that angle really sticks out and the straight edge of the open fenders is going to amplify this. Stuff a 1/4" off bugs me - this wouldn't be good, camping and looking at those wheels all the time. They are powdercoat red, wire spoke with shiney hubcaps - big focal point. 28" diameter sticking out an inch either side would make the fenders wider as well at 34". On to plan B, which I'll figure out today

[sjensensr]

Well, I better finish this off since I hate threads without closure. I took the axle back to the folks that said just turn it/weld the seats on/we've never had a problem.

On order is a 0 degree D35 (3500#) with 5 on 5.5 hubs, and should be here in a couple weeks. If you go this route and call around for pricing, be ready to explain yourself to everyone you call. They really like to sell from stock and I had responses like, "it can't be done", "it'll take months" and "it'll cost a bunch". I ended up ordering from an outfit about an hour away. He was $10 bucks less than the closest competitor and had a can-do attitude, which I'll need on this project. $125 for axle and hubs is only a few bucks more than the normal price.

Dexter was great to work with. The time difference and work hours I put in make it tough sometimes, but I did the whole thing through email and Christine always seemed to respond within an hour or so, (she even linked to this site).

Going normal sized wheels with a torflex is an easier option for sure, I like my wheels though:

[angib]

Dexter was great to work with......Christine always seemed to respond within an hour or so, (she even linked to this site).

I hope Christine uses the forum as evidence of exemplary service when it comes round to her pay negotiation time - she has lots of happy customers here!

I like my wheels though

Absolutely beautiful - tall narrow wheels just go with the teardrop shape.

I love the wires too, though you must have to get the axle mount looking pretty as presumably you can see it through the wheel.

Andrew