Surly Big Fat Dummy Wideloaders

“Wideloaders” are a load-supporting framework that sit level to the rear axle on a cargo bike. They are not made for the Surly Big Fat Dummy, but the frame has fittings to attach them. Here is how I made mine with no special tools or fabrication skills.

The Surly BFD Project Menu
Prologue
Episode 1: 138L (each) Panniers… Seriously?!
Episode 2: Big Fat Dumb Wideloaders (you are here)
Episode 3: Kickstand Kaos
Episode 4: Add a Flight Deck. And a Hangar
Episode 5: Odds and Ends

Do It Yourself (its not like you have a choice)

Wideloaders go hand in hand with the use of XL panniers like Great Big Bags 2.0. If you have Wideloaders that your bags sit on, it lets the frame support part of the load directly and increases carry capacity. So, for my Surly Big Fat Dummy, I definitely wanted these.

Big Fat Problem

The Big Fat Dummy is a unique frame design. It is similar to the Surly Big Dummy. There’s a family resemblance to XtraCycle-compatible frames. There are many factory-original and aftermarket options for those bikes, but similar is not ‘identical’ or even ‘compatible’. BFD owners figure this out pretty quick.

The image below shows a bright green Surly Big Dummy frame overlaid onto a Big Fat Dummy frame. The front wideloader mounting points are lined up (look for the frame hole/white circle on the bottom tube extension, aft of the bottom bracket). This overlay makes it clear the rear mount holes don’t match. You need Wideloaders designed specifically for the Big Fat Dummy frame.

Image credit: Surly Bikes (click image for original page)

Unfortunately that product doesn’t exist. If you want them, you make them. So I did.

Lets Get Started

Your wideloaders are going to mount in the front and rear hollow tubes that already exist in the frame. These cross-tubes are both 7/8″ Inside Diameter (ID), so you will need to buy 7/8″ Outside Diameter (OD) tubing. Luckily, this is widely available. However you will find a variety of thicknesses, heat treatments and alloys. I’ll pass along what I think is the best to use, and, well, what I used. I’ll let you decide whether or not to follow my lead or make some changes, as what I did turned out to be really REALLY heavy duty, but also heavy for what it is.

What about copper tubes?
You can go a different way and use copper tubing and soldered joints for a very, very cool look. But its no lighter than the alloy and screw-together approach I used, requires semi-permanent solder connections and a whole lot more effort (and money) to put together. It will look incredible when its done though. If you go this route yourself, note that copper tubing is designed to have a specific liquid flow rate, so it is measured via its Inside Diameter rather than Outside. So while I am using 7/8″ tubing, your typical copper tubing that fits is going to be known as 3/4″ tubing. The deciding factor to proper fit will be wall thickness so pay attention when doing your buying.

Parts List

27.49  6063-T5 7/8" OD x 7/16" ID (0.219" wall) x 8 ft
43.00  AL7005 22.2mm OD x 1.8mm wall x 1000mm len (qty 4)
43.96  Stainless boat hand rail 90-degree elbow (qty 4)
43.92  Stainless boat hand rail Tee (qty 4)
12.88  Stainless Mil Spec 0.89" ID Washer 10 pak
11.98  2:1 1" heat shrink - 25 ft
14.98  Reinforced 7/8" ID garbage disposal hose
       (10 ft) (qty 2 optional)
 3.00  Stainless steel M6 socket caps
       flat washers
       nylock nuts (2 ea)
29.74  2" x 30" hook/loop cinch straps 6 pak (qty 2)
31.90  Ratcheting tube cutter (optional)
29.99  Inner/Outer Pipe Reamer (optional)
10.99  12" Flat Bastard cut file (optional)
----------
In original build but replaceable with disposal hose
----------
12.74  Corrosion resistant sleeve bearing (2)
 6.24  Abrasion-resistant cushioning washer 10 pak

Total project cost (not counting shipping): About $230.00. $304 with the optional tools added in.

Notes on the Parts List

Tools

  • Your life will be a lot easier with the tube cutter and ratcheting attachment. It makes doing the job of making repeated cuts easy and gives a perfect cut every time.
  • Once you are done cutting a tube, even if done with the tube cutter it will still have sharp and somewhat bulged edges. Use the reamer to give a finished bevel to the outer and inner edges. You could use a straight file, or a tiny long round file, and eyeball it until done. But this specialized tool does a quick, clean job in just a couple seconds.
  • You need a few passes with a flat file on the flat of your cut pipe to smooth out the surface after the cut. Well actually you don’t need it, but between this Flat Bastard and the reamer you will never cut yourself on a sharp edge. And yes I picked this file to link in because they called it a Flat Bastard (any bastard cut will do, or even a fine cut).
  • If you choose the 6063-T5 tubing you likely also will need a hacksaw. I am not linking one or giving a price. If you don’t already have a hacksaw in your toolbox you may as well pull your toga up over your head and accept your fate.

6063-T5 Tubing

This is an extreme-duty choice. With a wall thickness of just under 1/4″, it is heavy stuff. But use two of these as thru-frame cross-pieces and your wideloaders will not bend even with well over 100 lbs of cargo loaded on them. My record is about 160 lbs (72.5 kg) and I was glad I over-did it, especially when hitting road bumps… an overloaded bike that weighs over 500 lbs with the rider onboard is a runaway freight train: you have to just hang on and bulldoze thru things you would otherwise avoid on the ride home.

This tubing is too thick for the tube cutter. You can use the cutter to get it started, then switch to a standard-issue hacksaw, or find some other method of cutting this very thick tubing. Me, I went cutter+hacksaw. It worked fine, but was something of a pain in the ass.

AL7005 Tubing

This stuff is sold in metric measurements since it is coming from a bicycle frame tube supplier, but the measurements translate to 7/8″ OD tubing with walls about 0.071″ thick, in individual lengths of 39″. That is roughly the thickness of bicycle handlebars. As aluminum tubing goes, its thicker than most reasonably-priced alternatives, which is good. Its also much lighter than the 6063 I used for the crossbars. You can sub in two tubes of this 7005 for crossbars less insanely thick than the 6063. They will still be strong.

The pipe cutter makes life a whole lot easier.

Stainless Boat Rail Fittings

Being thick stainless steel, these marine boat fittings are all about durability and strength. Also they are heavy as hell for bicycle components. Once again, this is a job where weight weenies need not apply. You put these suckers on and screw down their grub screws into the softer alloy tubing and they will hold fast, regardless of whether or not you forget how wide the bike is and walk it into the corner of a wall … in that contest, the wall loses.

hmmm… This piece is not on the parts list

Worth Noting: In many of the pics here, you will see I am using tee and quad-fittings that allow more connections than are necessary for the project in this post. Thats because I was building with an additional integrated center-mount kickstand in mind. We’ll save that for a separate article. Stick to the parts in the parts list to just build the wideloaders.

Garbage Disposal Hose

What in the hell is that doing on this list? Fact is, I didn’t build my wideloaders originally with this in mind. You will see many pics here with the older bushings, washers and heatshrink tubing for coating. I got the idea a few months afterwards. Covering the outer tubes in thick tubing permanently dingproofs them and helps protect whatever I lean the bike up against.

Once I found cheap PVC garbage disposal hose, I realized I could further use it to replace almost all of the washers and spacers in the build.

Originally I used 3 layers of cheap heatshrink to cover the tubes, plus bushings and washers. The garbage disposal tubing replaces all of it and saves about $30 on project cost.

Since I had already built mine, I personally only used the disposal hose on the outer facing tubes, leaving the two inner lengthwise tubes covered in heatshrink. However, you could buy two units of the disposal hose and sheathe all of your tubing with it. Simpler, looks kinda neat and about the same cost.

25 feet of Heat Shrink

The need for this stuff was largely eliminated with the use of the garbage disposal hose. However, you still need about 2 feet of it (20″, actually) to line the crossbars inside the frame. In a cruel lesson in Chinese capitalism, 10 feet of 2:1 heat shrink is one cent more expensive than 25 feet. So what the hell lets get some extra. Also, the 3:1 that is widely available in shorter lengths is the marine grade with adhesive glue inside and thats too thick for our crossbar liners. So… maybe its not a bad idea to check your local hardware store before buying this stuff. Its not going to be any cheaper but if you don’t want an extra 23 feet of 1″ heat shrink tubing sitting in a drawer for the next decade, a local buy might fix that.

The Sleeve Bearings and Washers

I used these in my original build and you can see them in all the pics. They were optional then and, later on when I discovered the garbage disposal tubing, were replaceable in the project. The one remnant I would still use regardless are the “mil spec” steel washers. Why mil spec? They are cut to closer tolerances than ordinary washers. If you want a really snug fit to your tubing, with a not-gigantic OD to go along with it, these washers are pretty much the best option.

If you use the disposal hose to replace the cushioning washers and bushings for spacing, I would still use the mil spec washers up against the frame to ensure the most solid contact possible.

Set the fastening screws facing UP on your tee fittings. If they come loose you stand a chance of seeing the problem before they become UFOs.

Construction / Assembly

NOTE: While I often go into painful levels of detail, I won’t be specifying measurements on cut dimensions. I don’t want you taking my word for what works on your bike and your fittings. I’ll make one exception to this: The width of the crossbars, since that requires some thought and is worth discussion. We’ll get into that below.

Step 1: Cut the Crossbars to Desired Width

This is maybe your most important project decision. How wide do you go? Your answer will help determine what you bump into while trying to move the bike around, or smash into as you try and negotiate a narrow passageway (like a shared use path entrance). At a glance, a good rule of thumb for maximum width would seem to be ‘no wider than your handlebars’. That will mean whatever you are riding thru, if your handlebars fit then most likely the wideloaders will not snag, either.

While you are figuring this width out, know the center section of the Surly Big Fat Dummy is exactly 10″ wide.

The BFD 26″ bike in Bliolet uses Answer ProTaper bars; 810mm wide. That works out to almost 32″ of width, give or take. So knock 10″ off of 32″ (the width of the center section) and divide by two. Following the no-wider-than-handlebars thinking, you would have wideloaders 11″ wide on each side. The 1-piece crossbar would be a total of 32″ in width.

Thats way too wide. Forget about the handlebar rule. It sounds like a good thing to have that nice big shelf, but it will be VERY ungainly to have that much hanging off the side. Don’t even think about it. Another issue is trying to get the bike thru a door. Think how much fun it will be to get a bike 32″ wide (and almost 8 feet long) thru a doorway that is commonly no more than 36″ wide. And some doors are 32″ wide.

I settled on a bar that is 26″ in length. Subtracting the 10″ center section and dividing the remainder means I have an 8″ crossbar extension. The elbow will extend my width a bit more. So figure in the end, I have about a 28″ wide rear platform. Here again the dictating factor is getting thru a doorway (I park in a garage every day and bring the bike in thru a door at a sharp angle).

If you are unsure, its better to guess on the too-wide side. It is a whole lot easier to file or cut metal off than it is to put it back on again (fun fact: this is also the First Rule of Gunsmithing).

Step 2: Drill And Fit the Crossbars

This part is easy. I took the 26″ cut crossbar and measured it to 13″. Then I used a red Sharpie to mark the center. In the pic below, a test-fit, you can see the red mark coming thru the centered frame hole. Once you have confirmed the spot is in the right place (measure!), pull the tube out and drill a centered hole straight thru at the spot of that marker dot. Drill large enough for an M6 bolt.

Finalize Crossbar Fitment

Once you have drilled that hole you can fit the tubing right inside the 7/8″ ID frame tubing and attach the crossbar, centered exactly to the frame and fixed in place with a stainless M6 socket cap bolt, nylock nut and a washer on each side. However, there will be a small amount of play between the crossbar and the frame, which means these things will rattle. We can’t have that.

  1. Add a length of heatshrink – cut to a 10″ length to the center section of the crossbar. Using your heat gun, shrink the tubing so it sits tight on the very center of the crossbar. The hole you drilled will be a clearly visible depression on the bar.
  2. Get a bit of dishwashing liquid or similar non-permanent lubricant and smear it over the now-snug heatshrink.
  3. Push the crossbar into the frame. It will now be very snug thanks to the added diameter of the heatshrink. The dishwashing liquid will let you push the bar into the hole while leaving the heatshrink attached and placed on the center. You may have to experiment with lesser lengths of heatshrink as it might want to be pushed back by the frame as you get further into the frame and closer to centering it (I had to spiral wrap sandpaper on a wooden dowel and run it thru a few times to debur the interior of the frame. If you already own a cylinder hone of the right size this is a place you might carefully use it).
  4. As you push thru, when you see the depression in the center frame hole where heatshrink sags in under your drilled bolt hole, stop. Now just shove the washer’d bolt into that hole. It will break the heatshrink on its own. Clamp in with the nut on the other side.
  5. Repeat the process with the other bar.

Your crossbars are now tightly, permanently fit. Bolted into the frame and lined with a thin rubbery material, they will not rattle.

Step 3: Fit the Tee’s and Inner Lengthwise Bars

Now that the crossbars are bolted in, its time to attach the inner bars. What you see in the pic below is a test fit where I hadn’t yet finished Step 1 above. The crossbars aren’t yet bolted in. But the procedure is well-illustrated. Loosen the grub screw on your front tee. Stuff the bar into it until it stops. Measure how far it went in. Position the bar atop the rear tee. Its going to go in the same distance, so measure accordingly. Thats your tube length. Cut to size and if it fits, do one more like it for the other tube on the other side.

To do the actual fitting once the tube is cut, loosen the grub screws in the tees so they are still in place, but do not intrude at all into their opening (or remove them completely and stash in a safe place). Place the cut tube into each of the tees. Make sure the grub screw holes are facing up for both tees. Now slide this assembly over the attached crossbars and slide them inward to their final position. If they do not slide smoothly to the interior – if they hang up halfway down the crossbar for instance – you may have cut your tube a bit too long and need to make a second cut, or do some filing if its a near thing.

This is a good time to mention that for placement on the drive side, you want the inner bar to clear the derailleur when it is on the smallest cog, with some extra room to spare that allows for frame flex (although these wideloaders can’t help but stiffen the frame). Keep this in mind when you are deciding final placement on the drive side inner bar.

When the tees and tube are sitting, unbolted, in place, move on to the next step.

Position the inner tube on the drive side so it doesn’t hit the derailleur in high gear.

Step 4: Fit the Elbows and Outer Lengthwise Bars.

Repeat the process from Step 3 for the outer bars. This time measure fitment with the 90-degree elbows. In the pic below note I had a tee in place in the rear – I was considering doing an extension out behind. In the end I thought an 8-foot-long bicycle was plenty and squared it up with an elbow.

After cutting the tubes, do the same procedure as in the previous step with regard to placing the bar and elbows onto the frame without permanently attaching anything.

When the tubes are all cut, everything is lined up and you know it all fits, its time for Step 5.

Step 5: Add The Bumpers / Final Assembly

Since you didn’t actually tighten anything down in Steps 3 and 4 above, its easy to take it all back apart. Do so now, leaving only the crossbars, which should already be firmly assembled. Your next moves, in order:

Straighten out Your lengthwise (long) pieces of Disposal Hose

OK this is out of order because you should do this a day or two in advance of your actual build party. You want to give the hose some time to uncurl itself.

Off the shelf the hose is kind of a pain in the ass to deal with, considering between two and four lengths of it need to be cut fairly precisely to a bit under a 3-foot length. I found two ways to deal with this (and used both of them). First, the easiest way:

If you have some long lengths of 1 1/2″ hard PVC pipe laying around, stuff this curved tubing inside of it. Let it sit like this. You can do it with 1 1/4″ PVC but its a tight fit and really tough to get it thru in lengths any longer than about 3 feet.

If you don’t have PVC, use your actual wideloader tubing. If you are following the parts list above you have four individual tubes that are longer than you will need. Work with those. This is going to be a snug fit and require some elbow grease to stuff it on there. I stuffed on a couple of feet, then dripped on some WD40 and let it penetrate (there’s a bit of slack to let it dribble in) and just worked it. Once I had used enough of it (used… not over-used), and let it spread, they slid on and off easily. But it takes a little time and patience. Afterwards, wipe off the tubes. I didn’t worry about the residual WD40 inside the hose itself. Just enough remained to make final assembly straightforward.

I let this sit overnight and added a length of PVC on the still curly side to help straighten the rest of it

Cut spacers for frame-to-inner-tee fitting

You will cut spacers to desired lengths from the disposal hose. On each corner, use one of the milspec washers up against the frame for a total of 4 washers needed. The milspec sizing will give the washer a nice even fit.

On the build you see pictured, I used 1.5″ corrosion resistant bushings in the rear for a nice look and exactly the spacing from the frame I wanted. In the front, I stacked three of the rubber cushioning washers, sandwiched by two milspec washers. This front scheme was a leftover from earlier plans that did not include bolting in the front crossbar. Thats what you get when you plan a build and buy parts before you get the bike in hand to work with directly. You will want to just cut a short length of hose and back it with a washer.

Line the inner lengthwise bars

You are going to do one of three things here:

  1. Line the inner bar with 2 or 3 layers of heatshrink. Do multiple layers in case you scuff or ding the bar. Just one layer is easily torn. This was my initial build because its all I had figured out how to do at the time.
  2. Line the inner bar with a length of garbage disposal hose. to match all the other bars. Using the disposal hose is cosmetic on the inner bar, but it is more durable and will give you a consistent, beefy look. Doing this is almost the same cost as using the comparatively fragile heatshrink. If starting over from scratch, I would go this route.
  3. Do nothing and leave the bar bare. If you like the bare look then great you are done.

Install the inner lengthwise bars

At this point you are ready to do the final install of the inner lengthwise bars. Having attached any desired covering to the bar, loosely reattach the tees to the bar and slide it on just as in Step 3, again making sure the grub screws for the tee fitting are facing up. When in place up against the spacers you cut and installed above, its time to tighten the screws.

This is one of the few times a thread locker is properly in order vs. being a misused crutch. I personally prefer Vibra Tite. The blue gel is easy to apply, never hardens and holds tight regardless of vibration and impacts over time. Goop up the threads of each grub screw and tighten them into the softer alloy tubing until they are roughly flush-fit to the fitting. Nothing is going anywhere once that is done.

Line the remainder of the crossbar

Now you need to line the next section of crossbar if you care to do so. At this point I will say that heatshrink should not be an option – go with the flexible PVC (or do nothing if thats your bag). Cut each length to size and slide onto the tube.

Line the outer bars (or don’t)

Almost the same procedure as the inners: Affix your elbows to the tube and attach the tube assembly to the crossbars. Now you know how much exposed crossbar there is. measure this and cut your outer bar liner/bumper. Tighten ONE of the elbows onto the outer bar and remove the elbow from the crossbars. Now you are holding the outer bar with one elbow attached. Take your cut liner and slide it down until it is snug against the installed elbow. If you cut the liner to the proper length, it is now installed perfectly centered.

Since I did my bumpers after the initial build, I lined the outer bars first – the crossbars are bare in this pic.

Install the outer bars

Loosely attach the second elbow to the outer bar. Slide the assembly over the crossbars. Tighten all the grub screws down so there are no gaps, using thread locker and again tightening so the grub screws are roughly flush with the outer wall of the fitting.

We’re almost done .

Step 6: Add the Floor (Straps)

Up to this point we’ve created an empty framework. It needs a floor to help hold up the Great Big Bags that will be sitting on top of it. I opted to use 2″ x 30″ hook-and-loop cinch straps, 4 on each side, which are movable, super lightweight, have some give to them but at the same time are very strong.

I had to buy two 6-packs of straps to get what I want, so I could add more straps, but 4 is enough and more importantly I can space the straps in such a way they work in complement to the four pannier straps I use to provide additional support on heavy loads.

Since the bag straps also have to wrap around the inner bars of the wideloaders, the floor straps have to be out of the way, and what you see is spaced out to let me interleave the bag straps between the floor straps.

A Final Note on the Floor

At around $30, the floor straps added a noticeable bump up in job cost. Is there a cheaper way to do this? Probably. I considered a bunch of ideas including diagonally weaving super thick bungee cord into a floor. I have a spool of the stuff in my garage.

What about more tees and crossbars with the leftover tubing bits? Without question that would look great and be supremely sturdy… but is it necessary? I don’t think so, and I didn’t feel like taking the time, adding the weight or going to the expense. But for sure, it would look great. In the end I felt the straps got me to the finish line immediately and were easiest to manage over time.

What about skateboards?

Well, that would work great. If you are a parent and your wideloaders need to serve as platforms for little feet, and maybe you want your kids to be able to stand on them, then a skateboard is a great option. If you use the really thick 6063-T5 tubing it will for sure be well-suited to a couple of M5 holes drilled thru each bar to attach that board, front and rear. From there, find a blank deck to your liking and bolt that sucker on.

The floor straps are spaced so I can interleave two more bag straps between the two center floor straps for extra support with heavy loads.

Job Done. They Work Great!

These pics are from the initial build, and reflect the parts I used for spacers at that time, along with some showing a different strap setup. Your results may vary so the bags you buy or build may dictate a still different approach.

Author: m@Robertson

I'm responsible for the day-to-day operations at my place of business: Leland-West Insurance Brokers, Inc. We do classic and exotic car insurance all across these United States. I'm also an avid auto enthusiast, a born again cyclist (i.e. an ebiker) and participate in medium and long range CMP and NRA sanctioned rifle competitions.

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