Planned obsolescence and the relentless march of progress.

20 05 2016

You would be forgiven for thinking that the rate of new wheel/tyre dimensions available for mountain bikes would show some sign of slowing. Not so much!

For example, recently, Trek/Bontrager released the Barbegazi 27.5×4.5″ tyre. Wow.

This tyre is coming stock on numerous Trek Farley fat bikes in 2017 and is soon to be available aftermarket in the UK.

You wouldn’t expect me to be off the back, would you? Of course not!

En route as we speak is a Nextie Black Eagle Mk2 27.5x65mm rim and another Junglefox Mk2 27.5x52mm rim. I’m going to build the front up before the arival of the Barbegazi and the rear I will likely use with a Hodag.

This will, I believe, mount without fuss in to my Vertigo Cycles fat bike. While the HED’s are off, I will repair the rim that split and see if this new wheel size has any benefits/drawbacks. The initial number crunching suggests I’ll gain a few mm bb height as the front tyre has been reported as 766mm in diameter – very much in line with a 29×3″ tyre and a hodag on the rear I would expect to be around 745mm diameter. This is ~20mm more in the front and ~10mm more on the rear than I have currently. In terms of radius this means I might gain 5-7mm bb height or so? tyre squish might be more or less than the current 26×4.5/26×3.8 set up – we’ll see. It is going to be ball park.

I had an interesting chat at Bespoked with Keith Bontrager over a pint about wheel and tyre size. As you might expect his insights were carefully considered and relate much more to the ‘pros’ and ‘cons’ rather than being affected by any element of ‘fashion’ or a purely commercial interest. You cannot say that all these new tyre sizes are *not* designed to sell more stuff, but I firmly believe the people behind them feel they have numerous ‘pros’ over what is currently avaialble.

Time to find out for myself.




2 responses

20 05 2016
Steven Shand

I think we need to come up with a new way of defining what tyre/wheel size a particular bike is designed for. We seem to have 3 main wheel (rim) sizes 559, 584 and 622 with manufacturers on the whole labelling their bikes for the corresponding wheel size (26, 650B(+) and 29er(+) ) but this seems to correspond less and less to the wheels that can actually be used in the frame.

Not quite sure what it would look like but something based around tyre width and outer diameter rather than ertro rim sizes which are pretty irrelevant (for frame compatibility anyway) now that no one is using rim brakes.

20 05 2016
Cass Gilbert

Look forward to your musings!

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