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Front wheel hubs for tadpole trike

March 12, 2025 — BarryK

Continuing the new "Meanderer" build-from-scratch recumbent full-suspension leaning tadpole trike project, here are recent posts:

Using bicycle parts where possible, is good; however, there is a problem with the front wheels. A bicycle front wheel has support on both sides of the axle, whereas only on one side on a trike. This is a problem; we need a certain type of bicycle wheel hub, known as a "thru hub". This has a shaft, or axle, that goes right through, usually of 12mm, 15mm or 20mm diameter.

We really want the 15mm or 20mm axles, which is another problem, as they are only used in premium mountain bikes. So, finding that type of wheel secondhand might be difficult. Suitable wheels could probably be purchased from a bike shop, or maybe a cheap secondhand tadpole trike could be located.

My first trike project, now mostly completed, was a cheap trike that I modified, with front suspension, etc. I'll refer to it as my "current trike". It has wheel hubs for a 20mm thru-axle:

img1

I got a bit confused, as this hub is only about 92mm wide, whereas looking online, available hubs are 100mm, 110mm, or 135mm wide. Nothing under 100mm. So I bought a couple, 15x100 and 20x110, to examine. After they arrived, I realised something; they are not "really" that wide.

To explain, here are photos of the hubs on my current trike:

img2

And the inside:

img3

...it looks very much like some extensions on both sides has been removed. The width of the inner alloy tube is only 82mm, and total width of the hub is 92mm.

Yes, the two hubs that I purchased have plastic extensions on both ends, extending the width to 100mm and 110mm. But, cut them off, and the with becomes 92mm and 84mm.

This is one that I purchased, 15x100, meaning 15mm diameter thru-axle and 100mm hub width, for AU$28.39 (plus 10% GST):

https://www.aliexpress.com/item/1005005254533680.html

The other, 20x110 32-hole, for AU$41.59 (plux GST):

https://www.aliexpress.com/item/1005008343824211.html

20mm axle hubs are somewhat rarer and much more expensive. Photo:

img4

I reckon those plastic width-extenders could be cut shorter. So, I plan to build the axle length on the Meanderer wheel knuckle for a 92mm wide hub. That will handle all three of the above hubs. Maybe make the knuckle axle a bit longer, and washers can be used if required.

A note about a tadpole trike; we need to be careful about overall width. For the Meanderer, I want total width to be no more than 730mm, so as to fit through my front door, and motel doors when touring. So taking 10 - 15mm off the hub is important.

If you want to read more about mountain bicycle front wheel hub types:

https://www.bikeradar.com/advice/buyers-guides/mtb-axle-standards

Should also mention, there are axle diameter reducers available. I bought this one to evaluate, 20x100 to 15x100:

https://www.aliexpress.com/item/1005006596535497.html

Plan to build the wheel knuckles soon, and there will be a blog post when that happens.    

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