An Examination and Comparison of Boost Hubs (and some rambling)
Enve Composites recently published a good article on the newly released Boost standard. As soon as I learned about the wider hub flange spacing I was excited. There are many elements to frame designs as well as the components to be used- frame angles, dropout spacing, chainstay length, etc. When the concept of a 29” wheel size came about there was a lot of skepticism in the industry. There have been a lot of developments in frame and fork design to get the larger sized wheel to handle more like a 26” wheel but they simply are not the same- and that’s not a bad thing.
While I am supportive of Boost I can’t help but feel it is a long overdue afterthought. Perhaps when the designers (engineers, Gary Fisher, what-have-you, etc.) were toying with the concept of a larger wheel size, the consideration of designing a better wheel platform went untouched. This is speculation on my part but I do find it strange. Yes, dropout spacing for mountain bikes went from 135 to 142 but that was axle/dropout width only with the advantage of a 12mm thru-axle. The rear hub geometries essentially stayed the same. [You can learn more about the 12 x 142 rear axle standard here.] It’s fairly normal for the bike industry to phase “standards” out due to an influx of incompatibilities and better designs - but my main question for the origins of the 29er wheel size is: Did any of the designers consult a wheel builder or hub manufacturer about the potential for durability, stiffness and maximizing the design’s performance?” I can’t say because I wasn’t there.
I made four spoke calculations to demonstrate the differences between a non-Boost hub and a Boost hub. The overall designs of each hub are indeed different in flange diameter and of course flange spacing. I created two non-existent hubsets to further understand the properties of each build. The hubs I used in the calculation are made by White Industries, the rims are from Boyd Cycling and the theoretical hubs are based off White Industries’ designs but I switched the specs around each hub model. Click on each image to view a larger version.
Standard CLD Calculation:
Boost CLD Calculation:
Theoretical High Flange Hub Spoke Calculation:
Theoretical High/Low Boost Hub Calculation:
The difference between the Boost and the standard CLD is pretty significant in not just the bracing angles but also the tension ratios. The theoretical high flange hub dimensions provided very marginal differences in spoke bracing angle but did create a loss of 1% in tension ratio compared to the standard CLD. The theoretical Boost model with high/low flanges on the rear did not have any major changes in spoke bracing angle but did gain 1% in spoke tension ratio. Notice the high tension ratio of the Boost design!
Damon Rinard’s calculator is a great tool to better understand why or how certain hubs are a specific design. It’s fun to create different hub specs to see the effect it can have on designing a wheel. Damon’s calculator has become a standard for many wheel builders.
After spending the time using the calculator I really gained an appreciation for the designers that created and pushed for Boost to become a reality. Boost not only benefits the 29” wheel but the 650b/27.5” platform as well. When the prospect of making actual gains in strength and stiffness are real I believe riders and customers truly do benefit from the R&D. I take marketing with a grain of salt but plugging the numbers gives me enough evidence that this is a step in the right direction.
Disc road wheels have benefitted from the 135mm spacing but I would still like to see rim caliper road bikes with 135mm spacing to make up for the hub geometries of 11 speed groups. While Shimano/SRAM 11 speed geometries are very similar to what Campagnolo has been for some time I still feel wheels would benefit from better rear hub geometries. White Industries T11 hub is definitely a favorite of mine for addressing the issue. The first generation did have an issue with low non-drive side spoke tension but was corrected and made for a big improvement.
Road bikes will be a completely different topic for another day.
Contact me to discuss any opinions or offer corrections for any mistakes I may have made.
Thanks for reading and if you’re in the Mid-Atlantic I encourage you to attend the Philly Bike Expo to meet me and talk wheels. I will be displaying with Bishop Bikes and the White Industries Boost CLD to Boyd Ridgeline will be there to check out!