Ultralight panniers and rack

This idea revolves around adapting MEC backpack extender bags , 170 grams each, for use as relatively slim and low-volume panniers. The design is intended to integrate with both commercially available, and DIY racks. In this image the handcrafted composite rack is mounted with a 20 degree forward tilt. This angle moves the panniers centre of gravity slightly forward and down, keeps the top of the rack well below the seat and dropper post, and reduces the open area forward of the rear wheel thus limiting spray from the tire. There is ample room for a full range of pedaling positions even when wearing large winter boots rated to -100 degrees Celsius.

Overview: Please consider this DIY proposal to be a recipe to help shape your own decisions about the “ideal” rack and pannier setup for your needs. The same materials, construction, and mounting techniques should be adaptable to saddle bag supports and front “pizza” racks.
This system has been developed to provide a narrow profile and lowered centre of gravity relative to traditional metal racks and individual panniers.  The suggested rack angles are intended to allow full utilization of dropper posts while bikepacking. The top of the rack is left entirely open for carrying other items such as packrafts, non-inflatable sleeping pads, winter sleeping systems, etc. The rack is designed to be adapted to most non-suspension frames and attach very securely without the need for bosses or bolts. While doing your planning always be mindful of interference by the installed rack and adjust the design to avoid issues. The design incorporates a partial fender and the capacity to extend the fender with a closed cell foam pad that can be used for many other bikepacking functions… sitting pad, fire fan, door mat, tent sweep, shower mat, etc. The integrated rack and pannier system should have a combined weight of under 1000 grams and be extremely resilient and durable for loads of less than 10 kg.  Prototypes have been tested over many kilometres of four season backcountry bikepacking, primarily in the Rocky Mountains. This project is intended to be completed in 6 – 10 hours with simple hand tools and without a sewing machine.  Total cost of all materials should be ~ C$100, plus $20 for a Speedy Stitcher. While many of links are to Mountain Equipment Co-op products you may have access to similar supplies where you live.
This system has not been engineered and is undertaken entirely at your own risk.

Materials list – Panniers

• 2 – MEC Universal Cargo Pockets $16.50 each
• 5 metres of 19mm nylon webbing $1.30/metre
• 2 –  National Molding Standard Tensionlock buckles $0.75 each (Selected because they perform well when covered in mud.
• 2 – pairs of Nexus 20 mm Airloc buckles $1.50 /pair
• 6 – Fastex 25mm tri-glide buckles $0.50 each (Note: These are for building straps to attach the rack to the bike and will not be required if you’re attaching the rack by other means such as heavy plastic or stainless steel zip ties. Two metres of the Omnitape listed below is for these straps. You’ll get 6 straps out of this while only 4 are required for attachment.)
• 4 metres of 25 mm (1″) Velcro Omnitape from a local sewing supply store ~$3/metre, also available from RipStopByTheRoll Note: if you prefer to not use Omnitape, straps and buckles can be substituted.
• Small sheet of coroplast from a building supply store ~$5, typically 24″ x 48″ We prefer white as it provides good contrast to the bags black fabric.
• Upcycled piece of heavy fabric to join the two panniers together approximate raw size 10″ x 20″
• Cardboard for templates

Pannier modifications and assembly: Note: the bag side with the MEC logo faces towards the spokes of the wheel.

1. Turn the bag inside out and make a cardboard template of the inside area of the logo side of the bag. Return bag to correct side in preparation for attaching the corroplast back plate.
2. Cut two pieces of corroplast in the outline of the cardboard template. Orient the corrugations to be aligned with the long edges of each bag.
3. Work the corroplast over the grosgrain edge seam inside the bag. You’ll be stitching through the outside material, the corroplast, and the grosgrain covered edge seam in step 4. It can be helpful to use foldback paper clips to maintain the orientation between the bag and the corroplast.
4. Working from the outside of the logo side, use the Speedy Stitcher to bar tack around the perimeter of the bag at 10 or 12 regular intervals. Repeat process for the other bag.
5. Determine the width of the rack you’ll be mounting the panniers to and cut the heavy materials with a finished width 8 cm (3″) wider than the rack width.
6. Cut four lengths of 19 mm webbing 1 cm longer than the width of the bag.
7. Determine where on the bag the heavy centre material will attach. The example shown is roughly parallel to the top edge of the bag. This results in panniers that hang perpendicular to the plane of the rack. Make sure that the bag position will not be too low or too far forward and interfering with the drive train, any other bike components, or pedaling.
8. Align the inside webbing, bag, heavy fabric, and outside webbing and bar tack in at least three locations. Markings and clipping everything together will help keep things aligned while sewing. This can be a tricky and time-consuming step to get “just so”. An extra pair of hands may be helpful. Tacking the outside webbing and heavy fabric together first can be helpful. If you’re not sure about the best positioning spend some time visualizing pannier positioning.
9. Drape the completed pannier over your rack and adjust front-back positioning to meet your needs and the bike’s geometry.
10. Determine where the four Omnitape straps will be placed. Two at the back stitched to the heavy fabric segment (~35 cm in length) at appropriate angles, and one on each pannier on the forward facing side (~50 cm in length). In the example the upper end of the straps are near the front zipper seam of each pannier, with the lowest bar tack near the bottom of the pannier. The lower pannier straps loop under the chain stays and then put the entire front face of the pannier into tension, while also preventing rearward and lateral movement.

Straps for securing and compressing the panniers: You now have several vertical and horizontal daisy chains on the outside face of the panniers, and a single daisy chain on the spoke side. Time to put them to work. The shorter straps with Tension Lock buckles compress the lower 1/3 of the pannier and when looped around the intersecting rack stay and the single back-side daisy chain reduce or eliminate noise and movement between the rack stay and bags. The girth straps have three components; two identical straps with a “large’ish” loop (a) in one end and a male adjustable buckle on the other end. (a) the loop needs to be large enough to pass the rest of the strap assemble through the loop. The centre strap can be short or long. In the example it long enough to wrap completely around and secure an OR 20 litre durable dry bag filled with an uncompressed -40 camp and sleeping system. The images do not show that the strap has been wrapped around the rack several times. You’ll need to determine the optimal length for your needs that allow each buckle pair to compress the load from the opposite side of the rack. Once both buckles are connected the entire rack and pannier loads are connected to the bike frame at the seat or chain stays.

Materials list – Composite rack

• 2 – 72″ fibreglass driveway markers $4.29 each – It is critical that this exact item, or equivalent, is used and the material is free of any defects or damage.  The underlying material is called pultruded fibre reinforced plastic.
• 6 – 1/2″ PEX black plastic plumbing elbows, ~$1.00 each
• 3 – 1/2″ PEX black plastic plumbing tees, ~$1.50 each
• 1 – 1/2″ PEX black plastic plumbing cap, ~$1.00 each
• 1 roll of filament packaging tape. ~$5/roll Buy an expensive version as it’s stronger. This tape and how it’s applied becomes a critical component of making the entire rack strong, stiff, resilient, and lightweight.
• Fabric to cover the rack.  Be creative! The rack shown is covered with TPU coated nylon . Lightweight ripstop nylon also works very well and is less expensive and lighter.
• Super Glue to fix fittings and rods together. Any high-strength glue with at least 30 minutes of working time is acceptable. Wear nitrile gloves for all glueing and initial taping operations.
• 1 roll of high-quality, low-temperature, UL / CSA rated electrical tape, Scotch-3M has several good options, $3-5/roll.  If you don’t plan on using the rack in low temperatures then less expensive tape can be used. This tape will be wrapped around the rack stays and is a way to add colour to your project. The tape also serves to protect the underlying composites from degradation and damage due to sunlight and impacts.
• Corroplast pieces from the sheet purchased for the panniers
• 1 roll of Scotch-3M heavy duty double-sided mounting tape ~$8.00
• a 2 inch by 1/8 inch by 1 foot length of aluminum flat bar to be cut into angle and tee brackets to stiffen and support some of the PEX fittings
  Tools required: scissors, hacksaw blade, sandpaper/smooth file, razor knife, measuring tape, Stewart Speedy Stitcher, cardboard for templates

Design and Assembly: 1. Decide what your priorities are. Light weight, durability, and simplicity of mounting and removal? Theft prevention?  2. Determine the size and angle of your rear-rack deck and distance above the rear tire.  Cutting a piece of cardboard to the length and width of the deck will help you visualize your final product.  Consider also cutting a piece of cardboard to represent the 90 degree angle of the stays that will be attached near the bottom of each seat stay. Play with angles and distances to inform your design.  We’ve had good results from adopting a rack width of 2″ wider than the maximum tire width planned. Note: When glued and taped at 90 degrees the rack stays have enough flexibility to deflect for wider rear mounting options. For example,  the rack stays bend comfortably to match a 6.5″ rack (160 mm) with a 197 mm rear axle width, all with room for 27.5″ by 4.5″ studded Gnarwhals.

Assembly: There are fifteen main steps in building your rack.

1. determine dimensions of rack stay assembly and rack deck assembly

2. a) put on your personal protective equipment b) cut the three pieces of driveway marker for the rack stays, c) cut the four pieces of driveway marker for the perimeter of the rack deck, d) cut the one piece of driveway marker to mount on the back of the seat tube.  Note: an option here is to cut two additional short lengths of driveway marker to slide inside the tee fittings that will be secured near the bottoms of the seat stays

3. Remove the protruding plumbing alignment nubs from all the PEX fittings (step not shown)

4. a) Cut and smooth the three aluminum tee shapes, b) cut and smooth the two 90 degree elbows.  Note: an option here is to make a single U shaped bracket that spans the width of the rack stays.  This will take some extra tools and skills.

5. Tape all the components together with short easily removable pieces and test fit to the bike.  You may want to make a template of the angle between the rack deck and the back of the seat tube for use during final assembly

6. While the rack is on the bike, cut the two triangular pieces of coroplast that will bind together the two assemblies.  Insert string trimmer line into the inner and outer corrugations.  Note: Ensure that the small triangular segment that is removed in the back corner of each side is large enough to easily pass buckles and straps through.

As noted previously, the filament tape is critical to bond together the entire structure.  Think carefully about where you’ll start and end the different taping steps.  The tape MUST be pulled tight and pressed firmly to all components and other layers of tape.  This is another place where extra hands can be helpful.

7. Assembly gluing and initial taping: a) put on your personal protective equipment b) rack deck assembly – place enough glue inside each elbow to cover the entire interface between the fitting and the five driveway marker segments.  Glue the Do not glue the seat tube tee unless you can hold it at the correct angle while the glue is curing. c) run a length of filament tape around the entire perimeter of the rack deck assembly d) place the rack on a flat surface and ensure it is true and square. e) complete similar steps for the rack stay assembly taking note to get the tees on the ends of the rack stays at the correct angles to match your bike seat stays. f) go for an overnighter to allow the glue to set. 😊

8. With the heavy duty mounting tape place the aluminum tees and elbows, or U in the appropriate locations.  Mount the seat stay tee on the non-seat tube side, facing the rack.

9. Carefully and systematically wrap both assemblies with the filament tape at about a 45 degree angle.  Try to get a 50% overlap on the tape and pull the tape as tight as you are able.

10. Cut and test fit the coroplast deck surface with corrugations at 90 degrees to the long edge of the deck. It should be a snug fit without deforming anything.  If you’re incorporating string trimmer line into some of the corrugations now is the time to insert them.  If for some reason the deck is not square this is a step where you can correct it with the shape of the coroplast.  Set the coroplast aside.

11. Joining the two assemblies and triangular coroplast together. a) cut a length of heavy-duty mounting tape and place it on the back edge of the rack. On a flat surface squeeze together the rack deck and rack stay assemblies at the appropriate angle.  Tightly wrap filament tape around the resulting joint. b) Tightly tape each triangle into place with multiple layers and angles of filament tape.

12. Fit the coroplast deck sheet in place and wrap tape at multiple locations, including diagonally corner to corner.  Take care to not distort the rack during taping.

13. Apply a layer or two of electrical tape to all areas that won’t be covered with fabric.

14. Cut and affix your fabric cover. We’ve had good results with ripstop nylon and thermoset glue.  The double sided TPU nylon shown also gives a decent result and sheds mud and ice extremely well.  Cut the fabric roughly to a size that will allow everything, including the triangles, to be wrapped without adding little pieces.  Cutting a hole near the centre of the fabric and then sliding the fabric over the seat tube connection seems to work well.  Avoid using Gorilla or duct tape it’s heavy and is not durable.

15. Cut and sew at least four Omnitape straps.  In this example the seat tube straps are each 50 cm (20 inches) and the rack stay straps are 40 cm (16 inches) The seat stay ones need to be long enough to wrap tightly in a figure eight around the seat stay and the tees at the bottom of the rack stays. The other two should be long enough to loop several times around the forward rack stay and the seat tube.  Our preference is to use Omnitape rather than other options as it’s very strong and durable while still being easy to remove. Sewn straps are stronger than the commercially available thermally bonded straps.

Installation:

1. Wrap some tape around the frame at the three connection points.

2. Starting on the drive side seat stay tightly wrap the rack tee in a figure eight. Complete the same on the brake side.  Depending your brake configuration it may be slightly more difficult to thread the tape through on this side.

3. Tightly wrap the upper and lower straps around the seat tube and rack stay.  You can get double compression by completing one wrap on one side of the buckle and then twist the tape over do the same thing again with the other side of the buckle.