Surly Bill trailer customizations
 

A few months ago I posted about building a custom trailer from 80/20. A variety of factors made me not want to take that plunge. And I still didn't have a welding setup to make something simple from square tubing.

I wound up ordering a Surly Bill Trailer. It just seemed so nice...and also I could get one delivered pretty quick. Bikes at Work trailers are something like a 6 month lead time.

The trailer showed up just in time for Cranksgiving. It was definitely overkill. I couldn't afford to fill all of those bins like I hoped. But it was fun to see everyone's reaction to how admittedly fun and ridiculous my setup was. I did try to throw down some $$$ but it just hauls way too much stuff!

https://cimg2.ibsrv.net/gimg/bikefor...eacf434d9b.jpg

Long story short, the trailer tows like a dream. Super silent, and because I'm on an eBike I really don't notice it back there unless it's a steep hill. It's heavy, yes, at around 35lbs but that means it also doesn't bounce around like small lightweight trailers when unladen or lightly loaded. I guess it's a reasonable tradeoff if the eBike is doing a lot of the work.

Prior to getting it on the road, I had to figure out how to attach it to my Tern GSD. The big hurdle is that Surly only made a few hitch styles, and their universal one was totally sold out. So I had to take a chance on the hitch for the Surly Big Dummy. I reckoned that by ditching the bike attachment bar and just using the articulating hitch point, I could adapt something to fit the Tern's frame.

I purchased some 10mm hardware with a fine thread in an attempt to create a pivoting fixing point for the articulating hitch that was similar to the original intent of the Big Dummy hitch. This is on the rear left of the frame, just above the foot boards. There's a 10mm thru-hole and it's quite thick at this point, so it would make for a strong connection point.
https://cimg3.ibsrv.net/gimg/bikefor...834e428d64.jpg
I used some thick copper washers (brass would be better...but it's what I could get quickly and it seems okay so far) to create bearing surfaces on either side of the joint, and a jam-nut setup to make sure I could set the compression on the bushing without making it too tight (like on a cup/cone hub bearing).
https://cimg9.ibsrv.net/gimg/bikefor...1469c63151.jpg

Fortunately my adaption worked pretty well. Surly clearly went to great lengths to make a super robust articulating joint. I didn't want to trash the brass bushings with some lame setup. It wasn't perfect initially because I didn't have a way to get a slip fit between the mounting bolt on the Tern and the thru-hole connection of the joint, but it was okay for the initial outing.

Later I would come back and press in a sacrificial brass bushing that I sourced from McMaster. If/when it wears out, I can just replace it. My biggest concern is if Surly doesn't make parts for this thing any longer, then I will have a hard time replacing its wear items. So I'd rather pass the wear onto a common component that I sourced myself.

https://cimg4.ibsrv.net/gimg/bikefor...e201469fa8.jpg

Speaking of wear and tear, because this trailer is chromoly steel I decided to do whatever I could to protect it from the PNW rain and snow. Surly recommends frame saver being sprayed inside. I didn't have that, but I did have some high-end automotive cavity wax which I hope does a similarly good job. Using the 6mm threaded thru holes around the sides of the trailer frame, I inserted the spray hose and tried to send in plenty of the cavity wax. No idea if I did a good job, of course.
https://cimg8.ibsrv.net/gimg/bikefor...7921489591.jpg
https://cimg7.ibsrv.net/gimg/bikefor...1561f338ea.jpg

The frame of the trailer is pretty bare bones. It doesn't even come with a floor! It does have wheel guards fortunately. I was able to cobble some combination of old innertubes and bungies to affix 4 bins for the Cranksgiving run. But it looked pretty lame. My first major upgrade would be a floor for the trailer. I started with (and currently still have) a sheet of 5.5mm Baltic veneer plywood. I didn't want to start adding tons of weight as the trailer already was quite heavy. In my head, I thought it would be easy to just seal the sheet of plywood with some polyurethane and have a water tight surface. I bought some pretty heavy duty marine grade spar urethane. It was super stinky and I didn't enjoy laying it on. I wanted to use eco-friendly materials but while wood might be renewable...this noxious urethane certainly isn't.

https://cimg6.ibsrv.net/gimg/bikefor...dc4d24c83a.jpg

Prior to attaching the plywood I tried to mitigate rattling from the plywood by laying some thin rubber strips along the ladder frame. I suppose it's helping? I also applied a lot of helicopter tape to prevent rubbing on the paint because once that happens the steel frame can start to rust.
https://cimg0.ibsrv.net/gimg/bikefor...92d7426579.jpg

The plywood was attached using the six 6mm threads around the perimeter of the trailer frame. I used some large fender washers with rubber washers underneath to spread the load out on the plywood a bit.
https://cimg9.ibsrv.net/gimg/bikefor...815be90da4.jpg

This was the first iteration of my modifications to the trailer! I've done some additional stuff to it but I'd rather break this up into a few posts.

Looks cool, but does this trailer have brakes? I would be worried just using the bikes brakes with such a heavy loaded trailer.

It does not have brakes. At around 200lbs of cargo I can tell that I'm having to ask a lot more of my Tern's brakes. They are Magura 4-pistons with 180mm rotors which are actually pretty fantastic. But I am looking into getting at least a bigger front rotor for it, like a 203mm.

Cool project! Though I'm surprised there aren't brakes on that large of a trailer. And I guess the only way to add brakes would be to change out the wheels and figure out some kind of caliper mount.

I would look at the Magura MDR-P rotors. I am not using my 203 for cargo but it is fantastic with MT5s on my Supercharger. Really excellent stopping power and very very stiff and seemingly decent thermal regulation. You still might want to rig up a brake on the trailer somehow but they are excellent rotors.