Xtends - Convert Your Bike Into a Long Cargo Bike




Here is how I added an extension to a bicycle so I could haul boxes of vegetables from a farmer's market. The Xtends unit uses a discarded bicycle frame and some electrical tubing. My cost was under $20 but the Xtends unit could be built for free if you have a good recycle pile.

The Xtends unit can be removed to return the bicycle to its normal configuration.

The Xtends unit involves welding. For a similar conversion that does not require welding see: https://www.instructables.com/id/Homemade-Sport-Utility-Bike-SUB/. Step 9 has some suggestions on how to make the Xtends unit without welding.

NOTE: I have added Step 11 to show you a way to make the Xtends unit that is simpler and stronger. Please check it out.

This project assumes you have some experience disassembling and reassembling bike parts. See this Instructable (https://www.instructables.com/id/How-to-Build-Up-a-Bike/) to get some idea how this works if you are not already familiar with it.

This project involves welding EMT conduit. Please see my Instructable for suggestions on ways to do this with a minimum of risk: https://www.instructables.com/id/Welding-EMT-Conduit/

Step 1: Select a Bicycle

Almost any bicycle can be fitted with an Xtends unit. Some bikes are probably better for this project however. I used a 26" bike with a heavy frame for strength. The stays in the rear fork are going to be carrying the load so it helps if they are sturdy.

I pulled this frame from my scrap pile after it had been stripped of handlebar, brakes, chain, front fork, etc. It looks weird because I just put parts back on it that I had lying around. It does support the idea that you can use whatever bike you have as a starting point.

I will call this the "main bike" from now on.

Step 2: Remove Rear Wheel and Related Parts

Once you have selected your main bike remove the rear wheel, chain, derailleur and rear brake. These parts will all be moved back to the Xtends unit in step 7.

Step 3: Select a Donor Frame

Now we need a bike frame to cut up. The frame should use the same size wheels as the main bike. That is, if you used a main bike with 26" wheels you will need a donor bike that uses 26" wheels. Only the rear fork of the donor frame will be used so don't worry about the condition of the front fork. You don't need wheels or pedals for the donor bike. In fact you need to remove them if they are present.

You might choose to keep the brakes and shifters if the donor bike has components as good as the main bike. Otherwise we will use the parts we removed in step 2.

The biggest requirement for the donor frame is that the angle between the chainstays and the down tube (shown with the red lines in figure 2) must be close to the same as the angle between the chainstays and the seatstays of the main bike (shown with the yellow lines in figure 3).

Figure 4 shows the final rig with the main bike highlighted in yellow and the Xtends unit highlighted in red.

Step 4: Prepare Donor Frame

Remove the seat,  wheels and pedals if your donor frame has them. Cut the head tube off the donor frame as shown here. These are rough cuts for now as we will give them a final trim later. Discard the head tube.

Step 5: Add Linking Axle

I made the linking axle from a scrap 1/2" diameter rear axle and 1/2" ID metal tubing.

Measure the distance between the rear dropouts of the donor frame (this was 5" in my bike) and subtract 1/2" for the two inside nuts. Cut the metal axle tube (at 4.5" in my case) and prepare it for welding (polish the surfaces that will be welded). See figure 2.

Polish the top of the inside of the bottom bracket shell in the donor bike and drill two 1/4" holes for the plug welds. Center the metal axle tube in the bottom bracket shell under the plug weld holes and clamp it in place. See figure 3. I used Vicegrip pliers for this.

When the welding is completed insert the threaded axle rod through the metal axle tube and tighten the two inner nuts to hold it in place. Add the two outer nuts so they are ready to tighten in the next step. See figure 1.

Step 6: Add Frame Clamp

The Xtends unit (donor frame with linking axle) is attached by inserting the linking axle into the rear dropouts of the main bike and tightening the two outer nuts "sorta tight" (tight enough to hold the linking axle in place but allow some rotation. See figure 1. (I have the rear tire is in place in the picture but it is not really needed yet.)

Rotate the Xtends unit so that the main tube of the Xtends unit swings forward toward the seat tube of the main bike (see figure 2). Mark the Xtends unit down tube where it overlaps the brake bridge between the two seatstays of the main bike. This location is not critical so locate it wherever you want the clamp to be.

I used 1" angle iron for the two clamp pieces (see figure 3). I cut my clamp pieces 4.5" long and drill 1/4" holes 1/2" in from each end. The upper end of the Xtends down tube (now cut to length) is welded to the middle of one of the angle iron pieces and the other angle iron piece forms the back side of the clamp. Two 1/4" bolts that are 1.5" long are used to hold the clamp in place. Either use nylon lock nuts or regular nuts with lock washers.

I used two 3" long pieces of bike inner tube to cushion the clamp and avoid scratching the main bike seatstays. Also do not over tighten the clamp as you could crush the main bike seatstays.

Step 7: Install Rear Wheel and Related Parts

Install the rear wheel in the Xtends dropouts. Add the derailleur and chain. You need to extend the chain to almost double what the main bike used. (I chose to set my bike up as a single speed rig so there is no derailleur.) You can reuse the parts you removed from the main bike in step 2.

Install the rear brake and replace the main bike rear brake cable with a new longer one. Keep the old cable in case you want to remove the Xtends unit.

Step 8: Add a Cargo Platform

There are lots of options for cargo carrying. I chose a simple platform as shown in figure 1. I attached some scrap seat stays to the clamp and to the top tube of the Xtends unit (see figure 2). I also added a piece of tubing into the seat tube of the Xtends unit (figure 3). I welded together a platform out of 1" electrical tubing and welded it to the Xtend seatstays and seat tube. This attachment is removable in case I ever want to reconfigure the cargo format.

Step 9: To Sum Up

This was a cheap and reasonably simple conversion. The main bike was not altered in any way that is not reversible. The new long wheelbase makes this bike a joy to ride. Now I just need to paint the Xtends unit!

You might be able to build the Xtends unit without welding anything. You could use bolts for joining tubes and U-bolts for attaching the metal axle tube to the bottom bracket shell of the Xtends unit. Welding makes it a LOT stronger, though.

I would welcome any suggestions or questions you might have.

Step 10: Parts List

You will need:

A bicycle to add the Xtends unit to. See step 1.
A donor bicycle to cut up. See step 3.
A piece of 1/2" ID metal tubing 4.5" long. I got this at Tractor Supply Company.
A 1/2" rear threaded axle with nuts.
Two pieces if 1" angle iron 4.5" long. I got this at Tractor Supply Company.
Rear brake and shifter cables.
A piece of bicycle chain to extend the main bike one.
A scrap pair of upper stays.
A piece of seat post tubing.
6" of bicycle inner tube.

You will also need these 1/4" bolts:

2 ea 1" hex head bolts.
2 ea 1.25" hex head bolts.
A 2.5" carriage bolt.

Welding supplies.

Step 11: An Even Better Way

This is an even better way to make the basic Xtends unit. I used a donor bike that had removable crank arms and a squaretaper crankarm spindle. The spindle was 4.5" end-to-end and just fit the rear dropouts of the main bike (Photo #1).

Photo #2 shows the bottom tube cut 15" long and the top tube rough-cut to match.

Photo #3 shows the spindle screws holding the Xtends unit in the main bike rear dropouts. The seatstay clamp is not yet on the bottom tube.

The clamp is 1" angle iron 4.5" long. Three 1/4" holes are drilled. Two are 3/8" from the ends and the third hole is at the midpoint. (See Photo #4)

A 1/4" hex bolt 1.5" long is used to attach the clamp to the cut end of the bottom tube (See Photo #5) and the basic Xtends unit is done. (Note the clamp can be welded on if you prefer.)

All the other previously described steps apply.



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    23 Discussions


    2 years ago

    Great idea, and nice looking! The only thing I would add are a couple of braces at the back of the cargo frame to the rear wheel stays. All in all very cool ! great job.


    7 years ago on Introduction

    Just thought you might like to know that your Xtend bicycle was the inspiration for my first bike build. I was looking for a cargo bike that I could build without too much hassle and came across yours. I will post my bike build instructable soon but just wanted you to know that I got my idea from this bike. Thanks and nice job.


    8 years ago on Introduction

    Was this the metal electrical conduit from Home Depot, or similar? Just curious because I'd love to use that stuff for welding, but from what I remember it's zinc-plated steel. Welding zinc releases toxic fumes, and enough of that causes some kind of metal poisoning.

    Might be fine if you do a very small amount in a well-ventilated area, just wanted to point it out. I wish they sold non-zinc coated steel conduit, because that stuff is a) cheap, and b) would be great for projects like this.

    4 replies

    Reply 8 years ago on Introduction

    Yes. The rack was made from EMT conduit. Electrical Metal Tubing conduit is cheap and readily available but requires careful preparation to weld.

    I prepare the area of conduit where the weld will be. I vaporizing the galvanized coating with a MAPP torch (done outside!). Then I use a flap-pad abrasive wheel to polish the welding area on the tubing.

    I do my welding outside my basement door with a 20" fan positioned so there is a constant flow of air away from my work area. Even when I am using old bike frame tubing I work outside and make sure the fan carries the fumes (eg. paint fumes) away from me.

    Thank you for the warning message. Welders come with DVDs these days and there are good safety tips shown there. Be extra careful of any fumes!


    Reply 8 years ago on Introduction

    Cool, that's great tips regarding the pipes. I almost bought some EMT a while back, since I have access to a welder and was going to play around. Just figured I'd point out the danger, for those like me with more equipment than knowledge.

    Good advice. Thanks!


    8 years ago on Step 10

    This looks like the base for a tandem with a bit of alteration. Nice.

    Great idea and design. I have a built a couple trailers and currently own a long tail bike. My long tail has the cargo hauling capacity mostly on the sides down near the center of the rear wheel (basically huge side bags). If you incorporate some way to carry part or all of you cargo lower you will like it even better. I have a trailer I built that was a big learning curve in this area.


    8 years ago on Step 5

    Had you considered using the existing bottom bracket cups and bolting the rear axle through it using some large washers?

    1 reply

    Reply 8 years ago on Introduction

    I will add some pics of a version I am building that uses a frame with the crank arms removed but the bottom bracket left intact. I can use the crank arm bolts to attach the Xtends unit in the main bike. Quick, easy and no welding required.


    8 years ago on Introduction

    from the back of the nice big rack that i really like, you should weld bars from the corners of the rack to a couple inches away from the back tires to add more support on the side,

    2 replies

    Reply 8 years ago on Introduction

    Thanks for the suggestion. The 1" tubing of the rack makes it pretty solid, but more support like you suggest never hurts. I want to be able to remove the rack and put a different one on the bike if needed. I will think about how to make a removable connection with the lower part of the seatstays.


    Reply 8 years ago on Introduction

    ya man make it like a tank man you should be able to pull a car from th e rack its so strong. uhmmm, i got an idea but i dont no if i can explain it with just words but here, it you the middle tube of the rack, were the seat post connects to it. you could have somthing like a seat post, just have it slide out, then those 2 little bars going from the cross bars to the front of the rack "the part that your backs to when your sitting on it" ya those bars you could make "lock in" to a little hole, notch what ever. so just have some bolts(a hinge) so when you want take it off you just slip the "lock" and slide it out. hope ya'll under stand


    8 years ago on Step 9

    This is a really good instructable! There is only one thing I've been wondering as I've been reading. It looks to me like the pedals come very close to the ground. Does that affect your riding at all?

    1 reply

    Reply 8 years ago on Introduction

    Thanks for your comment and question.

    I think my photos make the pedals look closer to the ground than they really are. I have to tip the extended bike to 40-45 degrees before the pedal hits. That is a lot more tip than I would care to do riding, especially loaded.

    The main reason for that angle-matching stuff in step 3 is to get the chainstays of the Xtend unit to line up with the chainstays of the main bike. You can see this in the first photo in the intro. The chainstays are parallel with the ground and so the pedal height of the extended bike should be the same as it was before the extension was added. (I think.)

    You could raise the pedals by adding some blocks between the Xtends unit clamp and the seatstays of the main bike. The angle that the Xtends unit makes with the main frame is easy to adjust.


    8 years ago on Introduction

    I just loaded 100# of cement blocks on the cargo platform and took the Xtends bike for a ride. It took a bit of balancing to get started. Once I was moving the bike was quite steady and easy to control. I really didn't feel the weight except when starting or stopping. I did figure eights in our cul de sac.

    The veggie boxes I want to haul are about 12" X 12" X 16" and weigh up to 40# each. If I build side platforms down around the level of the axle I could get wo on each side and one or two over the wheel. (I hope that big a load won't happen very often.)

    BTW the step-through frame choice was pure chance but it definitely makes it easier to get on and off the bike when it is loaded.