A Journey by Bike. . . VECTr – Weighing the Difference

Posted: January 14, 2016 in Uncategorized

So a bike blog, The Retrogrouch, makes passing reference to VECTr while showcasing another device (the Wavetrans) to show that expanding chainring devices are nothing new in the history of bicycle transmissions.  After noting the coolness of its various features, the Retrogrouch asks, quoting the  Wavetrans website:

You know what else is cool about Wavetrans? It’s ‘something . . . that you have never seen before.’ . . . Unless you actually know something about bicycle history, that is. In which case you know that these things go back almost to the beginning of the safety bicycle.

If you’ve read prior posts of this blog, you’ll know that the insight that expanding chainrings are nothing new, is itself nothing new.  I pointed out in a post on August 30 (here) that this had been tried for over 100 years, but that most of these devices tried to expand the whole circumference of the chainring all at once, which seems to be impossible given that the links on a chain cannot stretch.  The realization that changes in the chainring’s radius would have to occur when the chain is not engaging led me along the path to VECTr.  The Wavetrans inventor seems to have made the same discovery.

If you look at the prior designs over the last century, you will notice how massive and complicated they look.  And with mass and complication comes weight and expense.  This seems to have been the demise of the previous admittedly ingenious designs.  Retrogrouch draws this moral from his history lesson:

Something tells me that people today are no more likely to adopt a transmission that’s heavier, more expensive, and more complicated than a derailleur system than they were 20, 30 or even 100 years ago. I just don’t see the Wavetrans (or the VECTr, or any other similar ideas that might be brewing out there today) having any more success than their Victorian-era counterparts, or any of the revivals from the ’70s and ’80s.

The claim that the idea of an expanding chainring has been tried and failed is the most common criticism I have received about VECTr. I am somewhat surprised and disappointed that this is often the first reaction of the more serious bike enthusiast.  I would not have thought this was so conservative and staid a group.  They seem to reject new ideas, or new attempts to make old ideas viable, because they are not the now current standard.  Never mind that what is now old, was once new.


VECTr is truly worth its weight . .  and worth the wait!

The only really relevant question is whether the new/old device works and is worth what it costs. And cost is measured, for bicycles, both monetarily and in weight.  Prior expanding chainrings failed because they were not reliable enough given their price and weight. Retrogrouch seems to assume that every one must be heavier, more expensive and more complicated than current double or triple crank sets.  That looks to be true of Wavetrans, but not of VECTr.


The weight of the current version of VECTr  (in steel) compares quite favorably (500 g) to the triple chainring (Shimano Alivio (in zinc?)) and derailleur it replaced (475 g).  When VECTr is commercially manufactured, I am sure its weight will be reduced.

When compared with other in-line transmissions with regard to weight versus cost, VECTr is clearly superior:

Product MSRP Weight
VECTr $150 – $200 525g (steel)
NuVinci 360 $399 2450g
Patterson Drive/FSA Metropolis $300 1734g
Rohloff Speed Hub $1100 – $2000 1700g – 1825g
Shimano Alfine 8sp $360 1600g
Shimano Nexus 8sp $280 1500g – 2000g
Schlumpf Mountain Drive $700 1080g
Sturmey Archer SRF5  5sp $181 2010g
Truvativ HammerSchmidt $700 1623g

As far as reliability and performance, the jury is still out on VECTr as I am still tweaking and testing the design.  Again, it is supposed to outperform triples in having more gear settings, and in maintaining a consistent chainline.  It is more complicated (six moving parts) than triples (one moving part (the derailleur) and three relatively stationary chainrings). But that should be offset by the greater reliability of preventing dropped chains.

So, no, an affordable, light expanding chainring has not been tried.  VECTr truly is something you have never seen before.


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