Rear Hub Spoke Hole Flange/Shell Confusion...??

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9/10/2016 3:35 PM
Edited Date/Time: 9/10/2016 3:38 PM

I am shopping for rear hubs and I noticed something very unique about rear hubs and has me all confused.

Obviously...Rear hubs have a drive side and a non drive side and therefore have a big difference/discrepancy in the size of the spoke flange on either side. Versus say...a front hub, where there is no drive/non drive side discrepancy and therefore BOTH spoke flanges are 'equal / the same'.

BUT...I noticed that different brands/manufacturers have 'different / varying' discrepancies in circumference/size between the drive side spoke flange and the non drive side spoke flange on the hub shell.

So...First off...

1. What's the general theory/concept for this discrepancy...? Why is 1 side bigger than the other...? Is it because of bearings/internals...?

2. Why such big differences/discrepancies in these hub flanges of the shell between different manufacturers/brands...?

For example...Cinema FX freecoaster hub...VS...BSD Westcoaster freecoaster Hub.

If you look closely...the size discrepancy between the drive/non drive side flanges on the Cinema clearly larger and more 'distinct'...VS...the BSD westcoaster...where the discrepancy is much smaller/closer and therefore actually looks a lot closer to be more in line with a front hub.

3. If all rear hubs, regardless of brand/manufacturer...Have the 'same internals'....Than why the differences and discrepancies in spoke flange sizes/circumference on the shell...?

4. Is the concept/theory mostly have to do with trying to make a hub that when laced...achieves optimal/best wheel 'trueness/balance' with the rim...?

Obviously...I'm no engineer or physicist. But...I am curious about how and why things work the way they do in BMX gear/parts. But mostly...I'm curious as to why bmx brands/designers design or create their parts in the ways they do and what their trying to achieve by doing so.

I am hoping that there is someone in here with more knowledge and know how when it comes to the physical/engineering side of bmx.



9/10/2016 4:17 PM

Flange offset


9/10/2016 4:38 PM

youre trying to make it hard for yourself by making posts this long, i dont think many people would read this let alone reply


ride bikes, have fun


9/11/2016 1:46 AM

Allow me to elaborate. Your theory is correct with regards to why the drive side flange is higher, it simply allows more room for the driver, bearings etc. The drive side flange is usually a little closer to the centre of the hub too, again to allow room for the drivetrain. However, a smaller flange is stronger than a large flange, so they keep the non drive side a little smaller. Also, short spokes are stronger than long spokes, and due to the flange offset on the drive side, the spokes will be straighter (more in line with the rim. So essentially, brands are making the most out of the 2 strength factors. Shorter spokes on the drive side, smaller flange on the non drive side.

Rims have different erd too (effective rim diameter) as the depth of the rim plays a part in how strong it is. The variants in all these sizes purely depends on the design, and how to optimise and utilise the benefits of each component. In theory, a very deep section rim, small flanges, and short spokes would be the strongest. But everyone worries about weight too, so that has to be taken into consideration. Hold 36 spokes and you'll realise how much weight they actually have


9/11/2016 10:35 AM

Thanks for the help and info. I think I understand the concepts now.