Towing hitch

[pdg]

So, I want to tow with my 75... I've had a bit of a search but nothing I can find is particularly relevant.

Just looking for opinions on the hitch really, like where to mount it...

I'm intending to make the hitch assembly myself - I can't bring myself to spend hundreds on what is essentially a couple of tens worth of metal. From standing around the bike saying "hmm" a lot, I've come up with a few options.

1. Pick up the frame/gearbox mounts above the front footpegs.
2. Use the footpeg plate mounts with longer bolts and spacers.
3. Put a plate in between the stand mount assembly and gearbox.

All of the above would be mounted on both sides and would also have struts up to the subframe under the seat. I've seen a single sided version commercially available but I'd prefer the security of triangulating the mounts. One of the other commercial ones appears to use the pillion peg mount holes - I don't like that idea as the peg mount plate is pretty thin and it also has to carry the weight/stress of the cases on the 'z' frames (I want to keep the cases on too).


A few random details...

Legally here I can tow up to 2/3rds the unladen (wet) weight of the bike, or 150kg, whichever is less. From the info I can find, the wet weight on the K75S (the model I have) is 235kg, so 2/3rds of that is 156kg - I can do the limit of 150.

I'm not really bothered about the braking performance of the bike with that attached but even so I'm considering having over-run braking on the trailer if I can find compatible hubs - might seem a bit overkill with not much weight, but...


So what you reckon?

[Grim]

There is a hitch made for k bikes. It mounts up off the frame at swing arm or foot peg area and has a support leg that looks like it goes up to the shock mount.

 Saw an interesting set up that didn't use a ball but a articulated joint looked like an extension off the mud flap and pretty UN obtrusive when the trailer was off.  Was on a different make.

[pdg]

I think you one you're referring to is the single sided one I've seen. It's a pretty neat job, but very expensive.

I've also seen the other type that look like a mudflap extension - they usually have (depending on base bike and the strength of the mudguard/flap) two arms that pick up the rails under the seat. The arms are hidden by the mudguard etc. Most of these have a 'quick release' socket type fitting so that you can choose which type of attachment you'd like.

Over here we have ONE size of ball to choose from (50mm, replaced the 2" ball), or a ring and pin setup. I think you can use whatever you like, but that's all that carries type approval and is generally commercially available.

Because of the price of the commercial kits I'm going to be fabbing my own - I was just after ideas or possibly experience of the security of the mount point options...

[johnny]

trailer + k75 brakes = 911

j o

[pdg]

trailer + k75 brakes = 911

j o

One reason I was considering the trailer having it's own brakes.

But even so - I have extreme quality (read very cheap) Chinese HH brake pads so alles gute  :2thumbup:

[johnny]

the best hitches ive seen are those that when the trailer rolls the trailer can still be drug on its side without rolling the moto...

j o

[Gio]

I have been searching (un-successfully) for a hitch for my K75s and come to some conclusions :

1. I'm not the only one looking for a hitch (yet another testimony to both the appeal and longevity of the K bikes!)

2. The only option I could find (here in north America at least) was beyond my budget ($425 US + taxes/shipping etc)

3. The Reynolds R-740 keeps coming up in searches and seems to have been a great hitch - I particularly like the "single-sided" design  as I have read this allows for removal of the rear-wheel without removing the hitch - something we all need to do regularly for spline lube etc

I'm not looking to tow huge weight (150 lb trailer + up to 100lb payload) = 250 lb max

So,

Unless my search comes up with a used option (please PM me if you have or know of one) I'm thinking I may have to fabricate one from available information and/or measurements taken from the bike. I found a link to a 1985 brochure which shows the hitch fitted to the RHS foot-peg plate and makes reference to the 3 other mounting points.

Does anyone have any drawings of the actual hitch (and associated mounting hardware) which might add to this info? I did find a link to installation instructions and parts measurements - but no actual drawings or pics.

pdg - did you manage to build a hitch and if so how did that work out? Like you I also have / wish to retain Z frames for cases.

Any other experience / information on the Reynolds hitch (or similar) would also be much appreciated!

Gio

[Motorhobo]

trailer + k75 brakes = 911

j o

So Johnny so you feel the same way about sidecars and k75 brakes? Can you be more specific about your concerns?

[Gio]

I was pondering johnny's comment also ... the brakes on my K75 are not the best (I'm a heavy front braker, occaisional rear) but think (hope) they will benefit from new pads / lines and fluid before the new season.

And with regard to pdg's consideration of trailer brakes - that would make sense for a larger trailer / heavier load (his thoughts were to 150kg = 336 lbs) ... I don't know - it's additional expense / complexity and am hoping that having functioning ABS will help in my case ... ie stomp on the rear brake (as well as the front) and see what happens !!

Gio

[johnny]

i aints gotts no concerns... just putting it out there... perhaps im the only motobricker that thinks about trailer roll and stopping... if i was the only one when i posted it... im not now... mission accomplished...

j o

[Motorhobo]

all right -- trailer roll doesn't apply to sidecar -- I had 40k mi on my k75 sidecar rig with no aux sidecar brake and it always stopped when I hit the brakes.

[Gio]

No Johnny - you are not the only one to give this some thought - like I said, I have never found the brakes on the K to be anything other than ok compared to other/previous bikes (although the ABS seems to work well) - compared to the Goose (comparable weight) I would say three fingers vs one ... and having never trailered a bike before figure that at least some improvement is in order. That's also why I'm trying to limit the trailer weight to 250 lbs. Solo riding I have never felt the brakes inadequate - but the physics of adding another 250lbs approx. 7 feet to the rear make me wonder ...

Second only perhaps to decent tires, adequate brakes should be at the top of our list methinks!

[Motorhobo]

and having never trailered a bike before figure that at least some improvement is in order. That's also why I'm trying to limit the trailer weight to 250 lbs.

Be advised that adding 250lbs to your GVW with ABS will affect your ability to stop. I know this because he sidecar added about that much to the GVW. When I braked hard without the hack, I'd hear 'clack clack clack' and the bike would stop. With the sidecar, I'd hear 'clack clack clack clack clack clack' and eventually the bike would stop, but clearly the extra weight was adding extra momentum that the ABS wasn't figuring in to the equation. Stopping distance was increased considerably, I'd say 25% or more. That's why I bought another K75 without ABS as to tug the sidecar. With three wheels I figure I'm not going to high side if I lock up a wheel, so I would rather  brake hard with no ABS and take my chances on a skid  than have the ABS kick in and push my stopping distance out 15 feet so all I can do is sit there and wait for impact. Been in that situation and it sucks. With a trailer, I'd rather have the ABS than risk a wheel lockup...but keep in mind with all that extra weight, if the ABS kicks in you'll be thinking -- WTF...why am I still moving forward when I expected to be full stopped 2 seconds ago?

I don't know if 2-up, fully loaded riders have noticed this difference in ABS responsiveness compared to 1-up, unloaded riding as well...maybe it has something to do with the third wheel of the sidecar taking weight off the two wheels of the bike...I don't claim to undrstAnd the physics of it, all I know is that with ABS and an extra 250 lbs on the side my stopping distance and time was extended more than I was comfortable with.

[pdg]

Ok, so - I haven't actually done much more than think about this and start gathering a few bits...

Gathering:

Hitches are somewhat limited here - pretty much all that is available in towball format is a 50mm ball. So, I either have to use one of those, think about using a pin hitch, or fabricate something else. For simplicity the 50mm ball is what I intend to go for. I have sourced a trailer hitch that has the sliding section for brake operation and is free to rotate (which accounts for possible trailer roll as well as cornering). I also have a set of hydraulically braked trailer suspension hubs and a single output brake master cylinder.

The thinking/calculating part:

Weight - I stated up to 150kg (336lbs) as that is the maximum legal gross laden motorcycle trailer weight here in the UK. It's my theoretical maximum that I am designing the 'system' to be able to cope with rather than a target to load to every time. Now, I weigh aroundabout 70kg (155lbs) and in the 2 years I've had the k I haven't ridden it 2-up.

The k75s specs say the kerb (wet) weight of the bike is 229kg (504lb) and the max gross weight is 450kg (992lbs). So, me with 9kg (20lbs) of clothes on, on the bike = 308kg (678lbs). That leaves me with 142kg (314lbs) to play with - but, that is extra weight I could perch on top of the bike before BMW thought I would be running into possible issues.

The maximum gross weight of the bike is based not only on brakes, but also on suspension and engine power. Because the trailer would be essentially separated from the bike suspension (apart from a few kg for nose load) that can be considered as out of the equation. Once I get the trailer braking system set up correctly that should also be a negligible additional load. The only thing that really needs to be considered is the power aspect - and as a legal max trailer would only take me say ~20lbs over the gross bike weight and towing would be a leisurely activity anyway I don't think it's a huge concern. Yes, I know the figures are a little off, it's only rough conversions ;)


As for the towbar itself, there seems to be very few options as I'm sure can be seen from the earlier discussions. I think I saw one that attaches to the footpeg plates, but even a light trailer is a lot of weight to trust to parts really not designed to take anywhere near that sort of load - I can deflect them by hand so a loaded trailer during cornering would concern me.

I did see one setup where the main load bearing bar extended forward to where the peg plates mount to the gearbox, which is a little better. Either way, there also has to be a strut or similar to the rear subframe for extra rigidity.

My current thoughts are to pick up the gearbox to frame mounts so that the main loads are borne at a specific load bearing point - then to follow the frame up under the seat and finish down at the base of the rear mudguard. I would really like the hitch assembly to be as non-intrusive as possible so a whacking great bar really does nothing for me...

Anyway, that's pretty much where I am with it - I'd really like to get it done before summer kicks in (as much as it does here) so now there's at least one other person looking at this it would be interesting to bounce ideas around a bit.

[Gio]

Motorhobo - interesting observation. So if we add a pillion @ 160 lbs + gear + load the tragkorbs on top of a solo load - that's got to be + 250lbs ..? I'm thinking that must be more the physics of 3 wheels rather than 2 ..? see pdg's #'s of 992 lbs max which is + 488lbs over kerb weight - I'd place a fair bet that the ABS was designed to cope with that ?

Having said that I've only ever ridden the K solo - so that's all theory.

pdg - I wouldn't get hung up on ball size (no further comments please) - you can fit whatever size works, or pin-hitch to the tailing plate - also the "Reynolds" bolts not just to the side-plate - but to 3 other points at least 2 of which are to the sub-frame ... still researching this.

My time-line is much like yours in that my long trip is not until July so there's plenty of time to sort this out.

[pdg]

There are two reasons I said about ball size in my last post -

1. I forgot I said about it in the first couple of posts...... (it was well over a year ago)

2. In other places I have seen much discussion based around US riders berating the choice of ball size made by UK riders.

Now, that's cleared up  :2thumbup:


Right then. For motorcycle use I've seen 2 types of trailer. The first type is the same basic outline as a 'normal' trailer - it has a box/tray with a wheel each side. There is also the option of a monowheel trailer which has an inline  layout more like hitch-box-wheel...

For a normal trailer on a bike, I would agree/specify that a rotating hitch is required for safety - if the trailer flips it needn't pull the bike over with it and it wouldn't restrict the lean angle for cornering. This is obviously the easiest option to think about (as it's the 'picture' of a trailer everyone is accustomed to) but it might not be the best in terms of ride quality.

To the monowheel. This needs a different type of hitch. It has to move up and down in relation to the back of the bike and it has to turn to go around corners - but it cannot rotate at all. If any rotation is present it'll flop about all over the place behind the bike. There are many discussions on advrider (and other places, but advr seems to have the most information) about this type of trailer. The consensus appears to be a coupling that operates as a universal joint, with the vertical pivot canted so when the bike leans the trailer naturally turns.

I can see the appeal - the trailer wheel pretty much follows the bike wheels so much less chance of hitting kerbs etc. and if you have to avoid any other obstacles you don't have to mentally calculate wheel positions as much. It leans with the bike so grip levels are going to be similar - with a normal trailer maybe there is more chance of the trailer sliding?

On the other hand, a monowheel puts more weight on the nose and hence onto the bike - the wheel is at the rear, so you can't balance the load over the axle.

Also this wheel position means the unit is much longer for the equivalent 'square box' - but with thought that is easier to overcome.

So, maybe for light loads or if width is a concern a monowheel would be a suitable proposition? Personally, I'm slowly gravitating toward the idea of having a receiver for the hitch and having both types of trailer so I can choose which would be best for the situation........

[Gio]

Hi pdg

Then as it sounds like you know, there are two main ball sizes - 2" for standard trailers and 1 and 7/8" for smaller trailers. I looked at the single wheel option (eg Unigo) and whilst I can see / agree with some of the advantages have decided that a small two-wheel option would be better for my purposes - load balance and reduced tongue weight (for a given load) primarily. Here's my short-list :

Bushtec Spartan (US) - 140 / 350 lbs cap - nice light-weight trailer with 16" wheels and swivel pin hitch - but expensive ~$3000+
Denray Custom (Canada) - 150 / 300 lbs cap - medium weight but only 8" wheels but more affordable (less than $2000) and local
Aluma MCT (US) - 200 / 400lbs cap - medium weight, all aluminium with 12" wheels and LED lighting (approx. $2000 tbc)

The second two both use 17/8 ball hitches - and I see no reason why a swivel could not be incorporated if desired. I'm leaning towards the Aluma as the level hitch height of 14" would also work behind the car for camping / canoeing trips. (Anyone have any experience with this trailer?)

I'm not planning on doing any corner scratching whilst towing the trailer and so think that the standard 17/8 ball hitch (with option to add a swivel) will work for my application.

But first need to get the hitch figured out ...

Gio

[pdg]

Those do look like nicely made trailers.

For me though, they wouldn't work out well - for a start the price is way over what I could even begin to justify...

Over here, there are rules for the dimensions of trailers behind bikes, 1m (39.3") maximum width and 2.5m (98.4") maximum from the centre of the bike rear wheel axle to the rear of the trailer.

Anyway, I should be starting to measure/scribble some ideas for my hitch within the next week or so, so when I get something I'll post a picture up. In the meantime, I will probably continue to post here if I have any other thoughts.

[Gio]

I agree - even the more "affordable" options are not cheap ... but I'm also planning to use the trailer for local delivery of product from my farm in addition to the bike trip (any excuse to get on 2 wheels!) so can justify the expense that way.

I'm hoping the chap on the moa forum (http://forums.bmwmoa.org/showthread.php?66507-K75-Reynolds-hitch) will post additional pics of what I believe to be the Reynolds hitch and unless I can source a used one, plan to fab something along those lines ... this is my preferred forum and so will likewise post progress here.

Cheers!

Gio

Edit - have sourced a used Reynolds hitch out of TX and will report back when installed