650B, parabolas and the Greeks

I’m a person that reads both Dirt Rag and BRAIN. (Please note, these are not the only two publications I read)

This gives me a vantage point of reading the actual marketing and the reason behind the marketing. Or in other words, I read what industry insiders are thinking and how that translates into beta for the public.

I also like Math.

A while back, we discussed the wheel size dilemma. I felt at the time that I had done it justice and the I would have no need to return to the subject. Unfortunately, we are all about to be subject to a shit storm of 650B bikes. Why? Are they better? Well, let’s see.

Let’s consider, for a moment the equation Y=-X2. For the lack of the ability to do superscript on this website that is Y equals negative X squared. When graphed, this equation renders a negative parabola. The great thing about the negative parabola is that it reaches a maximum and then descends. This happens at zero.

It was the Greeks who surmised that something that grows and then degenerates has to pass through a point of perfection. For example, humans grow and then they die. This means that at some point humans must be perfect for they passed through a point of maximus. This could be boiled down to a millisecond when we stopped growing and began to age.

The parabola also is a great visual marker of a dichotomy with diminishing returns. Meaning, for our discussion, that a smaller wheel spins up faster, is strong and lighter is in direct opposition to the idea that a bigger wheel has better traction and a smoother ride quality. At some point, these opposing ideas must pass through the maximus meaning that there is a perfect wheel size.

It has always bothered me that no one has ever done any empirical research to find that perfect balance. To find that zero where, if you go smaller traction is lost, but if you go bigger it inversely effects wind up. It would seem, that an industry so hell bent on selling the next greatest iteration of technology, might have a little empirical data to back it up.

Unfortunately, no one has that data. And my guess is that no one ever will.

I learned from BRAIN that the 29″ wheel size represents the only area of growth for the cycling industry in the past few years. I also learned that forecasts show that this size has pretty much leveled off and will stay flat, much like every other bike category.

Specialized has stated that 26″ wheels are dead. And by dead I assume they mean that there will be no more growth in this wheel size. It is flat and therefore, not profitable.

And here comes 650B. Please refer to the above link of my past comments for reference of what this alphanumeric combination means.

The 29″ wheel was a thing of beauty for the cycling industry. It was a way to make people who already owned a bike think they needed a new one. Do already have a Stumpjumper? Well, now you need a 29er version. Have a hardtail? Well, if it isn’t 29er you’re an idiot and you better get to your local shop.

By the way, I must say I own both 26″ and 29″ bikes.

So now the industry is about to pop with an explosion of 650B bikes. Do they have any empirical data showing that this new “old” size is perfect? Have they measured wind up in comparison to traction and found a size that is the perfect dichotomy of both? As far as I know, they have not. Instead, they co-opted the next size emerging in hopes that riders will once again feel the need to by another bike simply because a new wheel size is available.

Do I think that 650B bikes have a place? Absolutely. But I am a hater of marketing. I don’t believe that any of us “need” 650B bikes. And I don’t feel that they offer any significant improvement over what is currently available. To me they are a jack-of-all trades size. Much in the same way that I am not attracted to the FSR Stumpjumper, the 650B is a tweener that doesn’t do anything awesome but does most things in a mediocre fashion.

Maybe it will prove to be that perfect size that puts both traction and wind up at zero. Or it may be just the next marketing scheme of an industry selling the most efficient vehicle known to man and that happens to be running out of reasons why you need a new one.

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One Response to 650B, parabolas and the Greeks

  1. andrej says:

    i like this idea of investigating the perfect wheel size. lets sketch it out a bit. and let that be correlated to the intended use, giving a space where you can compare the different parameters and how they interact. again, to avoid silly discussions about the perfect neutral base, lets include any physical fact only when it can be graphed together with it’s use spectrum. a wheel size profile, pun intended. i’ll get to an example in a minute.

    i am writing from switzerland, so please excuse my english. also, i happen to mostly ride a compact bike with 20″ wheels. i have been trying to understand why (and where not) i like it despite its obvious limits. also, i happen to be a certified bike mechanic and i do NOT have any preference but there must be “the best thing” for a specific requirement. So i can see why road bikes prefer big wheels for less rolling resistance. i used to take 26″ for granted due to their stability and our famous military bikes used just that (horrible tire format included). smaller wheels were for smaller size and offered even more sturdiness so you could build them cheaper and still get usable stuff like with kids bikes. nowadays, things ain’t so easy so you strike a nerve with that post.

    20″ compared to bigger sizes
    -better acceleration due to smaller radius of rotating mass
    -stronger wheel due to better levers
    -bad high speed due to high revs, all imperfections contribute to wobble and vibration
    -low rolling resistance with high pressured fat tires, since that depends only on the tire patch length, which in this case is short on a wide patch, like mtb tires when used in cities at high pressure
    -horrible rolling over obstacles due to a steep ramp when hitting that rock

    26″ compared to bigger sizes
    -better acceleration, usually lost due to the heavy tire on mtb
    -stronger wheel
    -acceptable high speed, though limited also
    -low rolling resistance at high pressure
    -good climbing

    28″ and more compared to smaller sizes
    -worse acceleration countered by light tires on racing bikes and getting worse with 29″
    -weak wheel asking for perfect wheelbuilding (i like, whatever the size!)
    -high speed rocks, revs stay low
    -rolling resistance varies with pressure, size and width and weight of tire
    -real nice climbing but real ugly high speed swerves (this should go with the rotating mass though)

    so, 20″ make good city bikes, 26″ good mtb’s and 28″ is for speed, simply put. really, i see no serious discussion without considering the intended use.

    parameters so far:
    -rotating mass (rims size, rim weight and tire size and weight all get to play)
    -resistance against deformation (sturdiness or why do 20″ wheels show up at polo)
    -high speed behavior (revs and how they multiply wheel imperfections, gyro fx)
    -tire patch form (long and narrow or short and wide, defined by tire diameter and pressure)
    -climbing ramp defined by size only, the bigger the better

    plus all those things not mentioned so far: tire tread count, tie & solder, tire pressure impact on vibrations (not to be underestimated due to the whole mass of the bike moving up and down, a suspension issue)

    i’d love to elaborate, care to join a loose wheel size muckers alliance?

    to get back to my experiences at the other side of the size spectrum:
    my bike is a full blown non-foldable compact with standard geometry, a custom i:SY with two gears. small custom wheels with fat low profile tires at hight pressure, they tolerate a lot of abuse. even go to the woods with ’em or down stairs (it hurts but works better than expected) and i really just ride them because i never thought it would work. they sverve so well and when i must eat a pothole, it leaves no mark. they accelerate like a dragster, i just love to make the racer cry for the next kilometer that has just looked at me sideways with contempt at the red light. they still suck when he takes me over and i try to keep up above 40km/h. though lately that nasty high rev was a cool thing riding over some bumps uphill without pedalling, there was a definite boost over each crest. higher revs wind down slower.

    but then again, high speed cruising is just not as good and mountain biking hurts. so i do not want to miss out and have different bikes for different stuff. that’s an avenue the market inc. does not persue, why say “better than…” if you could say “better here like this, better here like that, you just need more different bikes, woman!”

    thanks for your stuff and your patience with me.

    cheerio from switzerland and big up to diversity. but i’m serious about those profiles, where can we put them up and together?

    regards, andrej

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