Trailer math

[LAB3]

I've been shopping around for a trailer or possibly just a frame/axle combo to build one from. A lot of the threads I've come across on various sites say it's a good idea to extend the tongue to make it longer and have the axle pushed back toward the rear. Does anyone have any good, solid info on motorcycle trailer design geometry? Haven't had much luck finding anything.

[Steve]

I will agree that a longer tongue is beneficial, but a "standard" trailer, like the frame you would find at Harbor Fright will work just fine. If you make any modifications to that trailer, it would be to narrow it down about 6 inches. A car-top carrier on that frame is about as basic and affordable a trailer that you will find.

As with any trailer, you will need to pay attention to tongue weight. Moving the axle toward the rear will pretty much guarantee having some, but you don't want too much, either.

I have pulled trailers behind bikes since 1978. I have had several different models, they have all had pretty much the same geometry, as far as axle location is concerned. All have had the axle a few inches behind the center of the cargo box. The only time I have had any problem, it was because of the load I was carrying. It was a heavy load on top of the top rack, on a rather narrow trailer. Above 40 mph, it started rocking due to the top-heavy load. Slowed down to get it to stop, then got up to no more than 35 for the rest of the 3 miles home. Heavy loads are no problem, as long as the balance is correct. I even carried a bare block for a Chevy 350 once. (The bare block is surprisingly small.)

Any other time, we would ride somewhat normally. Keeping in mind that you have an extra couple hundred pounds behind you that slows your acceleration and hampers your braking, it does not otherwise intrude on your "less-spirited" riding experience.

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[LAB3]

I will agree that a longer tongue is beneficial, but a "standard" trailer, like the frame you would find at Harbor Fright will work just fine. If you make any modifications to that trailer, it would be to narrow it down about 6 inches. A car-top carrier on that frame is about as basic and affordable a trailer that you will find.

As with any trailer, you will need to pay attention to tongue weight. Moving the axle toward the rear will pretty much guarantee having some, but you don't want too much, either.

I have pulled trailers behind bikes since 1978. I have had several different models, they have all had pretty much the same geometry, as far as axle location is concerned. All have had the axle a few inches behind the center of the cargo box. The only time I have had any problem, it was because of the load I was carrying. It was a heavy load on top of the top rack, on a rather narrow trailer. Above 40 mph, it started rocking due to the top-heavy load. Slowed down to get it to stop, then got up to no more than 35 for the rest of the 3 miles home. Heavy loads are no problem, as long as the balance is correct. I even carried a bare block for a Chevy 350 once. (The bare block is surprisingly small.)

Any other time, we would ride somewhat normally. Keeping in mind that you have an extra couple hundred pounds behind you that slows your acceleration and hampers your braking, it does not otherwise intrude on your "less-spirited" riding experience.

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I've been looking at the HF 40"X48" trailer, some say the hubs are not all that great and the bearings should be swapped out for higher quality ones, some have also mentioned taking one or two leafs out or they tend to be too stiff with a light load. For a little less money there's a similar sized one with a car topper already on it built from a front straight axle off an old pickup with drop spindles and airbags, it's going to be heavier but solves the bearing, hub and spring issue right off the bat. Haven't looked it over yet, it's about an hour away and I'm waiting for the weather to warm up a bit before heading out to see it. Here's an idea I REALLY like, it's the back half of a HF trailer, the front is open for storage.

[Steve]

That's quite impressive.

You DO need to be concerned a bit about weight. However, you need to be even more concerned about WIDTH. Anything using the front axle of a truck is going to be nearly 6 feet wide, which is WAY too much. Try to keep it to no more than 4 feet, if possible. My trailers have all been between 3 and 3 1/2 feet wide.

One reason to keep it narrow is to keep it in your lane. If you are accustomed to riding in the left track of the lane, you have to remember that your left hand is getting close to the edge of the lane. Your hand is less than 1 1/2 feet from the centerline of the bike, assuming the width of the handlebars is 3 feet. With a 6 foot trailer, the edge of the trailer is another 1 1/2 feet beyond that, possibly putting it into the next lane, unless you are riding on the oil stripe in the middle.

You have any other pictures of that trailer setup?

The bearings on the HF trailers aren't all that bad, but it is highly recommended that you open them up and re-pack them first thing. Some will go the extra step and install Bearing Buddies on them, but I have never done that.

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[LAB3]

That's quite impressive.

You DO need to be concerned a bit about weight. However, you need to be even more concerned about WIDTH. Anything using the front axle of a truck is going to be nearly 6 feet wide, which is WAY too much. Try to keep it to no more than 4 feet, if possible. My trailers have all been between 3 and 3 1/2 feet wide.

One reason to keep it narrow is to keep it in your lane. If you are accustomed to riding in the left track of the lane, you have to remember that your left hand is getting close to the edge of the lane. Your hand is less than 1 1/2 feet from the centerline of the bike, assuming the width of the handlebars is 3 feet. With a 6 foot trailer, the edge of the trailer is another 1 1/2 feet beyond that, possibly putting it into the next lane, unless you are riding on the oil stripe in the middle.

You have any other pictures of that trailer setup?

The bearings on the HF trailers aren't all that bad, but it is highly recommended that you open them up and re-pack them first thing. Some will go the extra step and install Bearing Buddies on them, but I have never done that.

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Excellent point on the width, I had not considered that! The second one I mentioned has quite a wide track compared to the size of the bed, either way it goes I'll probably do some modifying at some point. The Goldwing factory service manual says 300lb max towing capacity fully loaded with a passenger, which will probably happen for at least awhile this summer. Several years ago I came across the "Stitch and glue" method of boat building, basically making a hull from Luan and glassing it over for strength and water tightness. After seeing that it's stuck in my mind for a "someday" project, you certainly couldn't build a trailer shell much lighter with basic tools!

[Grimly]

I've been shopping around for a trailer or possibly just a frame/axle combo to build one from. A lot of the threads I've come across on various sites say it's a good idea to extend the tongue to make it longer and have the axle pushed back toward the rear. Does anyone have any good, solid info on motorcycle trailer design geometry? Haven't had much luck finding anything.

I built a 4ft long x 2ft wide bike trailer about 25 years ago and pulled it around for years, quite happily. The reason I went for that size was to retain some ability to filter in traffic, should I need to. If you think trailers can't filter, you should have seen some of the City Link couriers in London using them and theirs were a bit wider.

A few years ago I came across the delphi forum relating to bike trailers and found some excellent handy information.

http://forums.delphiforums.com/mctrailertowing

Basically, the rule of thumb is to measure your trailer wheelbase and make the distance between trailer axle and hitch at least 150% of that, and going longer if you feel like it.
Once I lengthened the trailer draw bar by about a foot, and moved the axle line back by two inches or so, the thing was transformed. It was never bad before but now it's far better.


The trailer axle is simply a pair of Indespension units (you can probably get a local equivalent) with totally independent rubber bushings in a square tube-type short axle that are then bolted or welded onto the frame. I used the standard bearings in them for ages, but noticed one of them had got a bit grumbly, so replaced them with SKF or similar a few years ago. I was able to find a pair of 12" Minilite wheels on the back-of-the-shed local market, they cleaned up nicely.
Since that pic, I've fitted better LED lighting, but will be doing some more upgrades, possibly doubling the rear lighting and adding some side lights.

These are the hub and axle assemblies I used, but iirc, they were lighter, around 250kg rating.

[LAB3]

Love those fenders! Thanks for the info on the width to length ratio, that helps a lot. Those torsion stub axles are $179 a pair over here with no hubs, wheels, nothing else with them, another item I've kept my eyes on for a long time. A 40"X48" complete trailer is $240 with the 20% discount until the end of the month. It's a bit too wide as Steve mentioned and would require adding to the tongue length. Without access to equipment or necessary skills to weld, whatever mods are needed would have to be minimal to keep the costs low.

[tas850g]

I've been shopping around for a trailer or possibly just a frame/axle combo to build one from. A lot of the threads I've come across on various sites say it's a good idea to extend the tongue to make it longer and have the axle pushed back toward the rear. Does anyone have any good, solid info on motorcycle trailer design geometry? Haven't had much luck finding anything.

Check this forum out....I joined to get ideas for my 6x12 build. Great stuff there: http://www.tnttt.com/

[Steve]

The Goldwing factory service manual says 300lb max towing capacity fully loaded with a passenger, ...

When you get a chance, I would like to see a picture of that statement. Every motorcycle manual I have ever seen said that it was NOT permitted to pull a trailer. Yes, many of us have done it and gotten away with it, but it is not a factory-sanctioned event. The first (and so far only) motorcycle that I have seen with a trailer towing capacity listed is the CanAm Spyder. Not only does it list a capacity, they sell a trailer for it, too. Not interested in using my wife's Spyder to tow, though, at least not until I can find a proper hitch. The ones that are available from CanAm and others all attach to the swingarm.

The reason I went for that size was to retain some ability to filter in traffic, should I need to. If you think trailers can't filter, you should have seen some of the City Link couriers in London using them and theirs were a bit wider.

Not too many of us on this side of the pond have the luxury of "filtering". There is only one place that I know of where it's not illegal. In fact, it's only been quite recently that it was specifically made legal. That is in California.

When I lived there, I did a lot of filtering with my bike, which many said couldn't be done. It was a fully-dressed KZ1300, I think it was 38" wide across the saddlebags. The trailer I had at the time was 36", so if the bike would fit, the trailer would, too. However, just for the peace of mind of not having to worry about the extra length, I didn't filter much with the trailer. Yeah, there were times when I would go through a smaller gap, but only when moving fast enough that I would not endanger myself or others.

Good luck with the boat build, I'm sure we'll see you out there somewhere.



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[Rob S.]

So we're going to be towing a trailer with our scooter? I first thought of 'trailer' as in, "We live in a trailer at the edge of town," and I thought, "Math" said "Meth." But "Trailer Math" works as a title also.

Just funning with you, Len. How are you? How's the Wing? I like that picture of your portable outdoor lab, I mean library. Nudge nudge, know what I mean, know what I mean?

[LAB3]

Check this forum out....I joined to get ideas for my 6x12 build. Great stuff there: http://www.tnttt.com/

Thanks! Lots of great info there.

When you get a chance, I would like to see a picture of that statement. Every motorcycle manual I have ever seen said that it was NOT permitted to pull a trailer. Yes, many of us have done it and gotten away with it, but it is not a factory-sanctioned event. The first (and so far only) motorcycle that I have seen with a trailer towing capacity listed is the CanAm Spyder. Not only does it list a capacity, they sell a trailer for it, too. Not interested in using my wife's Spyder to tow, though, at least not until I can find a proper hitch. The ones that are available from CanAm and others all attach to the swingarm.

.

OK, you got me looking and it appears I've fallen prey to FAKE NEWS! That quote came from a response to this question on a Goldwing forum, sure enough I couldn't find it in the pdf version of the factory service manual.

So we're going to be towing a trailer with our scooter? I first thought of 'trailer' as in, "We live in a trailer at the edge of town," and I thought, "Math" said "Meth." But "Trailer Math" works as a title also.

Just funning with you, Len. How are you? How's the Wing? I like that picture of your portable outdoor lab, I mean library. Nudge nudge, know what I mean, know what I mean?

The bike is in need of the starter clutch to be rebuilt, it seems to not "catch" sometimes at first start and if it's below 30 degrees (F) it won't engage at all. Probably one of those things I could let go for as much of a hassle it is to make it right (complete engine removal) but you know those sorts of things go, they tend to crap out for good at the least opportune times so it's best to just deal with it. As to the reason I'm doing the trailer project I met a HOT and I mean really HOT lady who is about to retire and doesn't look a day over 40. Her: "Oh my god, you're 58?" Me: "Oh my god, you're 61?"

[Rob S.]

Trailer meth rocks!

Why are women like motorcycles? No picture, it didn't happen.

[Steve]

OK, you got me looking and it appears I've fallen prey to FAKE NEWS! That quote came from a response to this question on a Goldwing forum, sure enough I couldn't find it in the pdf version of the factory service manual.

Talk to virtually ANY Goldwing owner, they will tell you "it's OK to pull a trailer up to 3-400 pounds". Yeah, most of them HAVE pulled a trailer and survived. So have I. The problem is that the owner's manual specifically recommends AGAINST towing a trailer or mounting a sidecar. Many, MANY owners have ignored those recommendations and survived.

The CanAm Spyder is definitely capable of towing. 1330cc engine, 6-speed transmission, three wheels on the ground, all with disk brakes and ABS. The manual says a trailer up to 400 pounds can be pulled. My objection to using it is the swingarm-mounted hitch. Not only does it add to unsprung weight, it tends to shake the frame of the trailer. Some on the Spyder forum have reported the tongue has actually been shaken to death. Yes, it cracked the tongue where it attached to the trailer. If you have the typical cooler rack on the tongue, don't put any glass bottles in there.

Your Wing will be capable, you just have to change your overall attitude when riding. Since you have recently ridden a 450, you will be accustomed to slower acceleration and longer braking distances. The Wing with a trailer will do better on both than the 450, but keep your 450 performance expectations in the back of your mind.

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[LAB3]

Talk to virtually ANY Goldwing owner, they will tell you "it's OK to pull a trailer up to 3-400 pounds". Yeah, most of them HAVE pulled a trailer and survived. So have I. The problem is that the owner's manual specifically recommends AGAINST towing a trailer or mounting a sidecar. Many, MANY owners have ignored those recommendations and survived.

The CanAm Spyder is definitely capable of towing. 1330cc engine, 6-speed transmission, three wheels on the ground, all with disk brakes and ABS. The manual says a trailer up to 400 pounds can be pulled. My objection to using it is the swingarm-mounted hitch. Not only does it add to unsprung weight, it tends to shake the frame of the trailer. Some on the Spyder forum have reported the tongue has actually been shaken to death. Yes, it cracked the tongue where it attached to the trailer. If you have the typical cooler rack on the tongue, don't put any glass bottles in there.

Your Wing will be capable, you just have to change your overall attitude when riding. Since you have recently ridden a 450, you will be accustomed to slower acceleration and longer braking distances. The Wing with a trailer will do better on both than the 450, but keep your 450 performance expectations in the back of your mind.

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The hitch I bought (frame mounted) is made to work without the saddlebags and associated hardware installed, this will allow me to run the bike "naked" if i so choose making it more sporty for running the twisties. One of the ideas I'm kicking around is mounting the bags on the trailer or possibly using them as fender wells. I'd also like to take off the engine case guards, they really limit the room to put size 14 boot down when coming to a stop, those might make a cool set of rear bumpers for the trailer. Either way the rear rack would stay on, it's nice to be able to put the trunk on when making a grocery run or carrying other stuff.

[Steve]

I would leave the engine guards on. If anything, trim your size 14s back to 11s or so.

IF you happen to go down while moving, the guards <might> bend back a bit, maybe even crack the valve cover. Replacing a valve cover is easy and not all that expensive. If you DON'T have the guards in place when you go down, the front of the valve cover will snag on something and will experience "catastrophic re-arrangement" of all the parts contained within it. That will include the cam, valves and likely the head itself. In the process, the pistons will have come up to kiss the valves that are being held open by the non-rotating cam. Bottom line: you WILL need a new engine.

A better option is to put highway pegs or at least a small "toe tab" (smaller than a full floorboard) on the guards to give you room to stretch out a bit.

Lack of foot room is one reason I passed on getting a '79 Wing when I needed a bigger bike. All of the 4-cylinder Wings have the same problem. I don't have any problems with foot room on my 1500. I would like to have floorboards, but they are at an uncomfortable angle for me (damaged ankles), so I still have the stock footpegs. The floorboards I have added to my GS850 are great.

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