Robert P

This Youtube bike vlogger shows a distorted wheel on a new Walbike but doesn't go into detail what we're looking at. From what I gather he was tweaking the spoke tension - what caused this?

AnkleWork

You ask anonymous internet strangers to guess what another anonymous internet stranger did. If you really want to know, why not just ask the source? What's this thread really about?

fietsbob

I was hoping for you to say something about your wheel & what you did to 'pringle' it , an adventure story.

Andrew R Stewart 

The wheel, as a system, will want to seek the state of less order/stress. very highly spoke tensioned wheels can and do tend to "spring' to the imaged "potato chip" form as it results in the least spoke tension. Newbie wheel builders experience this when using the technique of pre stressing the wheel with the wheel placed on the ground, axle vertical and touching the floor, then pushing on the rim at opposing points. A little of this will help bed in spokes and let wound up ones untwist. Too much and the rim goes past the point of stability and you have a potato chip. Andy.

Robert P

I'm curious what you imagine it might really be about...?

FBinNY 

Imagine a hill shaped sort of like an M, with a boulder nestled in the notch at the top. All things being equal, the boulder won't move because it has to roll uphill before rolling down either side.

In a way bicycle wheels are like that hill and boulder. When tensioned they remain in a delicate balance between collapsing to either side and forming the classic potato chip. However, the potato chip is a shape calling for much lower spoke tensions (for the same spokes at the same length), and if given the chance the wheel will act like my boulder and roll downhill if brought over the edge.

Bringing it to the edge isn't all that difficult, and I can do it to ANY wheel (100% of wheels) any time I choose to do so. Unfortunately, many people manage to do this on their own, even when they don't plan to.

So, back to the boulder, push it a ways in either direction, and it rolls back home, but push it too far, and it keeps going.

brianmcg123

The say to make a good straight wheel, you need to start with a straight rim. This rim was probably jacked up at the factory of wherever it came from and they tightened the crap out of multiple spokes to try to get it straight. Then they shipped it the wally world.

FBinNY 

There's no reason to assume there was anything wrong with the rim, nor does this explanation account for the fct that the wheel went through the bike assembly and packing, then stayed OK in transit, sitting around in a warehouse, then on the floor in the store, and finally chose to spring to the chip state without some other new provocation.

xenologer

*Point


also, that guy in the video annoys me
so my take on what happened is:

bike comes in for kid-seat install
videoguy starts tweaking other parts of the bike due to some overconfidence issues
he messes up the tension while trying to true a wheel and ends up making things worse
now he has to eat the cost of the wheel
then goes on youtube to rant about walmart bikes being bad

conclusion: if installing a kid seat ends with a taco-ed wheel, the 'mechanic' is doing something very wrong (like messing with stuff he shouldn't)

Doug64

Sounds like a jerk, and that did not look like a professional shop; at least not one I'd want to visit.

noglider 

bikemanforu makes several videos a week. He has a weird high energy to him, but I imagine he's a nice guy. His shop does seem to be his profession, but it seems like a low overhead shop in his home. Good for him if he's making a living out of it. He sells on ebay and locally, I gather. He's on Long Island somewhere.

Darth Lefty 

When it goes potato chip, all spoke holes get a little closer to the hub, until spoke tension and rim compression are relieved. A good comparison would seam of a baseball which is one baseball radius from the center but way more than one baseball circumference long.

But here's a question, why doesn't this happen all the time? What threshold must be crossed to allow it to collapse?

FBinNY 

It doesn't happen all the time because the wheel has to pass through a state of higher average tension on the way from normal to potato chips.

The point of no return is where the average tension is highest. However usually as we get there the tensions are very uneven. I MEAN this critical point is roughly when the rim is deflecked out to directly over either flange.

mtnbke

Increasing tension beyond what that rim/spoke spec could handle.

You want the max even tension for a given rim and spoke combo. You find that max tension by finding what is too much...then build again with less until it doesn't taco.

Too much tension is when making radial or lateral truing adjustments make the wheel worse in strange ways, not just tacoing.

Bike Gremlin

IMO, he should have pulled on parallel spokes on both sides (i.e. stress relieving) before trying to true the wheel. If a wheel fails that test, it's not his fault, he doesn't have to "eat the wheel". If it doesn't, fixing a minor lateral out of trueness would not cause the wheel to go "ping!".