What is the Granny Wheels rack expander made of?
Unlike many rack expanders made from welded or bolted-together tubing—which can be fragile and prone to breaking—the Granny Wheels rack expander is crafted from a single solid 3 mm aluminum sheet. With no weak joints or connection points, it offers exceptional strength, stability, and long-term durability.
What is the size of the Granny Wheels rack expander?
18 by 13.5 Inches (46 by 34.5 cm)
Does it work with any bike?
Yes—as long as your bike has a standard rear rack installed.
How much weight can it hold?
The rack expander can safely support any load your existing rear bike rack is rated for—typically 25–55 lbs (11–25 kg). If the weight limit is ever exceeded, it’s the bike’s rear rack (with its small attachment points to the frame) that would fail long before the Granny Wheels rack expander itself.
Dive deeper in our blog post: Carrying Heavy Cargo on an Electric Bicycle Starts With the Right Rear Rack
Why does it install with zip ties instead of nuts and bolts?
There are two main reasons:
1. Universal compatibility.
Zip ties allow the rack expander to fit a wide range of rear rack shapes, tube diameters, and configurations. Bolts require exact hole alignment, which would severely limit compatibility across different bikes and e-bikes.
2. Faster, easier installation.
Tightening a zip tie is far simpler than maneuvering nuts and bolts—especially under the rack where access is limited. No tools, no alignment issues, no frustration.
Before choosing this system, we ran extensive test rides with different loads and terrains. The zip-tie mounting held up perfectly: no breaks, no loosening, no shifting. For maximum strength, we specifically sourced ultra-strong industrial-grade zip ties (12 mm wide, 2 mm thick) to ensure a secure and long-lasting attachment.
How much overhang can I have between the expander and the rack?
There’s no strict black-and-white rule because it depends on the weight of the cargo you plan to carry. In general, the more contact surface your rack has with the expander, the better.
However, for lighter loads—such as pizza bags or similar lightweight boxes—you can safely allow a noticeable amount of overhang. After installation, simply check the platform’s stability; you’ll quickly get a feel for how solidly it’s mounted and how much overhang is acceptable for your specific setup.
No matter what, there will always be some overhang because the rack expander is larger than a standard rear rack. That’s why centering the expander during installation is essential. A properly centered platform can handle more overhang because the weight is distributed evenly across both sides of the bike.
Also keep in mind whether the overhang occurs on one axis or two—in other words, whether the expander extends only toward the sides of the bike or also over the back. This can affect balance and should be considered when positioning the expander and planning your load.
What if my bike rack isn’t flat and has raised sides ?
You can still install the rack expander on racks with upward-tilting edges. There are simple fixes to ensure a stable, level platform. The most common solution is to rest the expander directly on the raised outer edges of the rack. This creates a small gap in the center, but you can easily fill that space with a flat support piece—such as a thin block of wood, a rubber pad, or any firm spacer (Now included in every kit).
Once supported, the expander mounts securely and performs just as well as it would on a fully flat rack.