Toxophilite

2005 smart car cdi fortwo DIY trailer hitch info

100 posts in this topic

I'd like to get on making a DIY trailer hitch for my 2005 smart cdi fortwo.

I was going to  remove the rear crash bar and replace it with a 2' x 2' 1/8" thick square steel tube with a 1.25' receiver welded on bottom. Then cut a corresponding hole cut in the valance. A few people recommended this approach. My brother is a pro welder so that's not a problem.

It sounded straight forward but looking at the crash bar I see I need to weld a couple of plates to the back and drill some holes (which I can do no problem) to mount it properly

Is this what people are doing?

Does anyone know the bolt pattern or have a diagram? I'll likely pick up a T45 torx in the next couple of days and try to remove it and then I can trace it all out but I thought I'd ask.

 

Another one I saw the fellow seems to have mounted his tow bar outside the body using the two towing hook points and he was towing some big stuff. Anybody try that approach?

Edited by Toxophilite
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Version 1 was my approach and it is perfect..imho...far stronger than the crash bar, BUT, that crash bar is also designed to crumble when enough force is applied to reduce damages to framework of car. You must give and take.....It is by far the strongest hitch set up. There are two loose plates under bumper you can use to make the mounting plates for your bumper. I'd give those torx bolts a good rap with a soliid hammer before trying to loosen them, most will snap, or at least mine did! I also only made the smaller 1 inch sized reciever, or was that 1 1/4" reciever Class one I think it's called......no need to go larger as this one sticks out like a sore thumb as it is...many questions are answered it seems..lol.    What do you tow with that car,???? etc....etc....lol I usually say my cabin cruiser, or sail boat....but in reality it'll only get used for a very light single man camper.

 

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Weekest point is the rather poor original weld holding flange plate to rear of subframe. I TIG welded all around and fitted one additional bolt both sides. 

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sounds like the way i made mine...except i think i used 2 1/2 inch tubing across

 

for receiver i bought one from princess auto ..1.25 square...

 

for safety chain attachment i just bought a trailer spring shackle side plate and it was perfect to weld under the receiver and then i just hooked the chains in the holes 

 

 

i clamped everything to the original crash bar in order to mark the mounting holes before drilling

 

my end plates were 1/4 inch triangle shaped plate from the scrap pile

 

 

put small tack welds first then try on the bumper skin for fitment issues before doing a final weld...mine was awful close to the muffler but never did touch

Edited by LooseLugNuts

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I made my flange plates out of triple certified ship building steel ultrasonically tested for absence of laminations. 

 

You should fit the fourth bolt. Misterdotcom had to do that to get their tow bar through TÜF. 

 

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Cool, and thanks

I have a few further questions, Can I weld the attachment for the chains to the ball mount. It seems like if they're welded to teh receiver I'll have to have a pretty big hole in the bumper/valance.

Loose lug nuts did you buy a receiver and then have a separate ball mount with a securing pin?

I'll be going to princess auto too

 

Also can anyone tell me how much their 1 1/4' receiver sticks out past the cross member it's welded too.

I have a 2005 greenish yellow convertible diesel 450

thanks again

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In the UK a break away cable is only required if trailer weigh is above 750 kg. 

Cable can be looped around neck of ball. 

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20 hours ago, Toxophilite said:

Cool, and thanks

I have a few further questions, Can I weld the attachment for the chains to the ball mount. It seems like if they're welded to teh receiver I'll have to have a pretty big hole in the bumper/valance.

Loose lug nuts did you buy a receiver and then have a separate ball mount with a securing pin?

I'll be going to princess auto too

 

Also can anyone tell me how much their 1 1/4' receiver sticks out past the cross member it's welded too.

I have a 2005 greenish yellow convertible diesel 450

thanks again

 

the chains have to be attached securely to the car or receiver....not the ball mount

 

receiver i used

 

https://www.princessauto.com/en/detail/6-x-1-1-4-in-hitch-receiver-tube/A-p8205171e

 

similar ball mount i used but mine was just black steel

 

https://www.princessauto.com/en/detail/class-ii-1-1-4-x-3-4-in-zinc-ball-mount/A-p8717928e

 

 

used one of these welded under receiver to attach chains 

2 chains are required in canada and must be crossed under tongue

 

https://www.princessauto.com/en/detail/4-pc-3-125-in-shackle-straps/A-p8281560e

 

to remove bumper skin after hitch was installed i needed to remove the black filler panel...then peel the sides away and lift the skin up .....the shackle i used prevented the bumper from going straight back

 

also mine didnt stick out much...the receiver pin was almost touching the bumper skin...just do tack welds and then check fitment before commiting 

 

 

 

i wish i had pictures but i dont own that car any more

 

id also planned to modify a ball mount into a spare tire carrier for trips but never got around to building it

 

 

 

 

Edited by LooseLugNuts

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found 1 picture

 

the white mark on receiver is where the bumper skin would sit

 

it worked great for my use...my trailer was light 4' x 6' ...heaviest load ever on it was a riding mower

 

 

smart hitch1.jpg

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The above looks very much similar to mine as in how far it sticks out from the car. I refused to weld that chain attacment to it yet as I do not want a larger hole in the bumper skin.  So, if you attach it the opposite way, sticking out from the hitch and then bend it at a 45 degree bend downwards you can still attach a chain to it. When you take the skin off you can pull it back then allow it to drop downwards to get past the bent chain  attachment.....BUT..it will become a skin cutting machine and leave you liable i bet if someone were to walk into it In Ontario there is a new law out that makes it illegal to leave the draw bar or hook or ball in the hitch when not in use, just because of people walking into them and hurting themselves. So you would need to cover it lets say with a tenis ball so to speak or risk your wallet and licience etc....so the cop told me!   My RAV4 has a hitch on it that I had to drive the draw bar into as it had rusted so badly and filled up with dirt etc...yes i know should have looked after it better....oh well...anyway I jammed it in so hard there is zero chance of getting it out now and i was told about it at the grocery store by an off duty cop. Just him either being a nice guy or a dick .....I think the first case...maybe..lol.    So just something to keep in mind....most people do not remove their balls just because of this.

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1 hour ago, Willys said:

.most people do not remove their balls just because of this.

 

 

OUCH!

Thanks loose lug nuts, expecially for teh parts link, It takes some guess work out of it.

And Willy's I like your alternative chain attachment idea

Edited by Toxophilite

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Took off the back of the car, and the crash bar and has a good look. It seemed pretty straight forward, my crash bar is aluminum as are the backing plates. Picked up a 1 1/4" receiver, ball and ball mount and pin. Also bought a piece of 2x2 1/8' square tube...could've got some 2.5' not sure why I got the smaller stuff, that and a piece of 14" plate to male the mounts.

Heading over to my brother's place this weekend to do the welding.

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if i ever have to make another one im going to try and make it exit the body about an inch and a half to 2 inches lower 

 

so that the only body panel that needs trimming would be that black lower piece instead of the actual coloured main panel

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I thought of that also after I finished, but thought of the twisting torque that the set up would need to endure....so left it as is. Plus the muffler is very close as it is.....just more headaches than worth it.

The 2" square tubing is perfect, you'll see. Just do plenty of trial and test fitting if you can as you build it as per where the hitch sticks out from and how far.....too short and it won't have enough strength to work well..I over kill everything. Better too strong than too weak and have an accident. Better it bend the car than fall off and the trailer kills someone. I don't want to work my whole life to just hand it over to someone else.  Just saying.

Oh, if you do it similar to mine, by mistake..lol....seeing as you haven't seen any pics......you will find it comes out directly between the two tow hook locations. Then I will either use a drop draw bar to get the ball hieght correct or adjust the trailer I haven't built completely yet. Still have the draw bar to finish designing.

 

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Cool. It seems if you go too low you'll be sitting on the muffler, 

The crash bar is about 2.75" wide so there's a fair amount of up and down wiggle room for the two inch bar to sit on the 1/4" mounting plates

Trying to decide of I'm going to angle the ends ala the original crash bar, seems like it might be stronger/have more welding surface area.

Maybe not necessary though.

 

I like stronger too. I'm a paranoid tower. I've been towing little sailboats of various sizes for years all in the 14-16' range between 300-1200 lbs behind everything from a mercedes 240 D to a small toyota 22re. I double check everything, everything is lashed on several different ways and always two chains crossed under the hitch.

 

I was going to see how the smart would handle a 6-700 lbs tow  with a little wooden sailboat I'm restoring. I'll give it a mild test tow around the block on the level, maybe try a shallow hill. If it seems dodgy I'll buy a beater tow vehicle as I really like the little smart.  It's a fun experiment and mostly reversible. I wouldn't want to be on a steep wet boat ramp though.... I realize that weight is at the top end of what people say the 450 can handle. 

 

Edited by Toxophilite

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Box in the ends of the square tubing for added strength, so the welded area streads the strain to the whole box section compared to just the touching material against the flat plate. I also bought grade 10 bolts non torx to use as attachments again just to get  a better hold over the rond smaller headed torx heads. Not to mention the ease of wrenching IF they ever decided to sieze on again. They were also blue loctited into place.

6-700 lbs is asking a bit in regards to getting the boat out of the water , maybe? Does your trailer have brakes? Certainly would help the whole stopping power and not having to rely on the car's weight to do it.  I don't think if driven sensibly it'll be an issue.
My trailer is basically an alluminium coffin on wheels. It was designed to be pulled behind my 685cc bike.....but now I can add more structure to it......It'll have a metal covered wagon looking roof instead of a canvas pop up design....just getting lazy and it'll also help with the drafting effects.  I'm not sure it'll top out at 600lbs, but after loading it with minimal gear it may come close. I can still lift it off the ground but, no roof yet or draw bar, but has suspension and wheels and axle. Fingers crossed.

 

The look of it was a semi concern to me after thinking about it.....and also figuring out exactly where it would pop out of the bumper skin so as not to make the hole too big. Going for centre of the tow pins was easy.

 

Good luck.

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Trailer is very lightweight and non braked , basically a channel triangle with rollers and the smallest wheels (8"?)

Boat is a Sam Rabl Titmouse . It's a shallow draft boat with board up (6") .

I might see if I can take it somewhere to weigh it (transfer station/dump) to get a more exact idea of the entire weight.

 

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You could try putting it (stern or bow first) onto a bathroom scale and just balance it by hand to get an approximate weight.  No kidding .. we weighed my sister's canoe this way.

 

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hehehe I could see doing that with a canoe.

To give you an idea. It would take 3 or 4 peole to lift it off the trailer and I'd like to weigh the trailer too. I'm going to talk to the transfer station and the local weigh station tomorrow. It's an experiment , it might be like the tail wagging the dog.

with lid on.jpg

Edited by Toxophilite

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Hmmmm......I would worry about getting that out of the water as in does a Smart have the balls to pull this weight up hill?  I also would worry about as you say the tail wagging the dog....I made that mistake very early on in my towing life, I was towing the first Willys pick-up I bought with a CJ5 Jeep. Same sort of thing....very light weight front vehicle and a larger heavier towed  item.....OK until I started down a steep hill....at speed......lets say 50MPH.....It unloaded the rear wheels as it pushed me along and then the wagging started.....!!!  It was classic and I do not know to this day why I didn't wreck! The Jeep was going from side to side almost 90 degrees.....lifted and  large wide tires which I'm sure didn't help matters. But once it started I couldn't stop this action. The only thing that did stop it was I managed to get to the bottom of the hill and slowed the whole thing down to where it stopped  wagging!  I looked back up the hill and you could see tire marks where the jeep was nearly sideways ripping rubber from the tires! Other than a high speed roll over, the most scariest situation I've been in while driving.  Beware.    Then comes, tongue weight? The Smart can only stand so much......and that is what will keep the wagging at bay.  It may be a tall order to fill.....lol.

But......you MUST take pics of it all finished and hooked up just for the show stopping aspect of it....lol

Edited by Willys

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Sounds exciting!! This doesn't weigh more than the smart, maybe about half and the picture makes it look longer/bigger than it is. The boat is 15'.

As I said I'm a paranoid tower so I'll try it out on the level in some back streets and then if that seems tolerable I'll try a short moderate hill.

I will take pictures as I totally agree it will look hilarious.

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12 hours ago, Toxophilite said:

hehehe I could see doing that with a canoe.

To give you an idea. It would take 3 or 4 peole to lift it off the trailer and I'd like to weigh the trailer too. I'm going to talk to the transfer station and the local weigh station tomorrow. It's an experiment , it might be like the tail wagging the dog.

 

OK, I can now see why a bathroom scale would be totally inappropriate.  The way it was being described, I pictured something a little more physically maneuverable.  I towed a 800lb. boat on a 400lb. trailer behind an 850lb. motorcycle with no issues in over 596,000 miles of riding that bike (mostly with a trailer of some sort behind it)

 

Ron & Roni with Sailboat (1978).jpg

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21 minutes ago, Leadwing said:

 

OK, I can now see why a bathroom scale would be totally inappropriate.  The way it was being described, I pictured something a little more physically maneuverable.  I towed a 800lb. boat on a 400lb. trailer behind an 850lb. motorcycle with no issues in over 596,000 miles of riding that bike (mostly with a trailer of some sort behind it)

 

Ron & Roni with Sailboat (1978).jpg

Excellent!

I was in the midst of building a pop-up single man trailer to drag behind my KLR 685 to go out west with. Common sense is key when towing with anything......accidents happen standing int he tub, so......life's an adventure.
So that same trailer will be made into a hard top and pulled behind the smart....

The only thing I wonder about, can a smart pull up a ramp, as it seems to struggle just getting going sometimes...lol.

 

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Too true. I find it's the tiny bit of initial impetus and then it's off like a shot and feeling very strong. However I'm pretty paranoid about having a car in the salt chuck.. So I would test it out very much. For hauling out , little centerboard sailboats like this tend to have very little displacement and are sometimes still floating till the trailer itself gets a bit out of the water. They also , unlike power boats, move the water quite like a canoe, requiring very little effort...now if it was full of water.... let's hope never.

I'm going to weigh the tongue weight today

i took some pictures of hitch mockups

I mocked up on with the receiver sitting below the new bar and one with it sitting a further 1.5" lower allowing it to pass through the lower black panel but perhaps not clear the muffler. My brother the circus apparatus pro welder suggested coming straight out to reduce twist, probably insetting the receiver into the cross bar for extra strengthy Like Tolsen we were both wondering about the extremely lightweight nature of the flanges on the car that the whole deal would mount to.

The first is my parts laid out alongside the crashbar, the bar is uncut and the plates have since been shaped like the crash bar plates (tapers on inside ends)

 

hitch layout.jpg

 

a mockup, bar is still uncut

 

hitch mockup.jpg

 

mockup side view to see muffler distance

 

hitch mockup side view.jpg

 

lower mockup 1.5"

 

hitch mockup lower.jpg

 

lower mockup sideview showing touching muffler and what I could cutout of receiver and or step both parts out

 

hitch mockup lower side view.jpg

 

back panel top of green tape is where the receiver would sit in non-lowered mockup

 

rear panel.jpg

 

close up of same, lowering 1.5" puts me into the black lower panel but also cutting through the muffler shield.

 

rear panel close.jpg

Edited by Toxophilite

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