Deep section VS shallow

johngti

Relative to what? The stiffest thing since Pritti Patel’s starched undies or a 4-week old banana left in the sun?

MattFalle

Pritti Patel in a lab coat toying gently but firmly with your deep rim spokes.

Now you're talking.

MattFalle

Question though, at what point is compliance to be punished? What is one person's compliance is another person's stiffness.

Still doesn't take away from TDV in a lab coat though.....

darkhairedlord

its not just the stiffness though, what about the resonant frequency?

MattFalle

TDV in a lab coat can twang it for resonant frequency any time....

me-109

So ....
Two rims, same box section could be different thicknesses and therefore potentially quite different lateral stiffness, but perhaps barely different radial stiffness due to the inherent nature in that cross-sectional shape.
Equally, the rim is part of a wheel 'system' and is not designed in isolation. There would be a design consideration of how many spokes were required/desirable by engineering/marketing/swooshnoiseselector. Those spoke could also have variable cross-section shapes and sizes. And lengths too, which would affect their springiness in coordination with the rim shape/size/material. And the tension necessary or desired to keep the structure stable, not destroy the hub or rim, or snap through fatigue, and provide the desired ride feel. In combination with any lacing pattern that affect the above and gets the marketing dept in a lather.
Essentially, you're an engineer, you should understand that the consumer market has no interest in the quantifiable elements, and that a manufacturer might destructively and non-destructively test wheels from another manufacturer, or just rely on their own people to come up with the goods.
Outside of the companies that make this stuff you're not going to find it.

Chaz.Harding

me-109 said:

So ....
Two rims, same box section could be different thicknesses and therefore potentially quite different lateral stiffness, but perhaps barely different radial stiffness due to the inherent nature in that cross-sectional shape.
Equally, the rim is part of a wheel 'system' and is not designed in isolation. There would be a design consideration of how many spokes were required/desirable by engineering/marketing/swooshnoiseselector. Those spoke could also have variable cross-section shapes and sizes. And lengths too, which would affect their springiness in coordination with the rim shape/size/material. And the tension necessary or desired to keep the structure stable, not destroy the hub or rim, or snap through fatigue, and provide the desired ride feel. In combination with any lacing pattern that affect the above and gets the marketing dept in a lather.
Essentially, you're an engineer, you should understand that the consumer market has no interest in the quantifiable elements, and that a manufacturer might destructively and non-destructively test wheels from another manufacturer, or just rely on their own people to come up with the goods.
Outside of the companies that make this stuff you're not going to find it.

Cheers. I kinda guessed, by inability to find the stuff I was interested in, that basically nobody cares enough to test the precise shit that I (probably quite alone) find interesting. Or the companies who do test it, found that the results would likely damage sales of their latest shiny thing.

I should have said to normalise for width, spoke tension, material, count and lacing pattern, but either way it doesn't help as it seems nobody has tested my question hahaha.

I asked, because I've bought a few sets of carbon rimz from China. All 32h. All will be built by a decent wheelbuilder. All with Sapim CX-RAY spokes, on same set 148 / 110 boost hubs.

29er MTB rim (30mm IW, 35mm deep), a 700c (25mm IW, 50mm deep) and a 650b (25mm IW, 35mm deep).

I wondered, before my obvious bias, if there was a way to see if indeed the supposed stiffer rims were actually noticeably stiffer. I can guess probably laterally, but vertically? I get that shorter spokes should in theory mean more rigid, but if the difference is tiny, I'm unlikely to actually tell the difference.

Reviews and stuff are difficult to get unbiased. I have never noticed any rim being uncomfortably stiff, but have had weedy rims flex significantly enough to rub on my chainstays to polish them up. Maybe I'm powerful. Probably I'm just too fat. We may never know.

Although I can't say, even with cheap poorly built wheels, I noticed any flex other than sideways. Maybe I'm just not that sensitive to it? Perhaps, with wider tyres at lower pressures, it's not even really measurable. I don't know.

david37

MattFalle said:

Pritti Patel in a lab coat toying gently but firmly with your deep rim spokes.

Now you're talking.

I only got as far as "toying gently"

david37

Chaz.Harding said:

me-109 said:

So ....
Two rims, same box section could be different thicknesses and therefore potentially quite different lateral stiffness, but perhaps barely different radial stiffness due to the inherent nature in that cross-sectional shape.
Equally, the rim is part of a wheel 'system' and is not designed in isolation. There would be a design consideration of how many spokes were required/desirable by engineering/marketing/swooshnoiseselector. Those spoke could also have variable cross-section shapes and sizes. And lengths too, which would affect their springiness in coordination with the rim shape/size/material. And the tension necessary or desired to keep the structure stable, not destroy the hub or rim, or snap through fatigue, and provide the desired ride feel. In combination with any lacing pattern that affect the above and gets the marketing dept in a lather.
Essentially, you're an engineer, you should understand that the consumer market has no interest in the quantifiable elements, and that a manufacturer might destructively and non-destructively test wheels from another manufacturer, or just rely on their own people to come up with the goods.
Outside of the companies that make this stuff you're not going to find it.

Cheers. I kinda guessed, by inability to find the stuff I was interested in, that basically nobody cares enough to test the precise censored that I (probably quite alone) find interesting. Or the companies who do test it, found that the results would likely damage sales of their latest shiny thing.

I should have said to normalise for width, spoke tension, material, count and lacing pattern, but either way it doesn't help as it seems nobody has tested my question hahaha.

I asked, because I've bought a few sets of carbon rimz from China. All 32h. All will be built by a decent wheelbuilder. All with Sapim CX-RAY spokes, on same set 148 / 110 boost hubs.

29er MTB rim (30mm IW, 35mm deep), a 700c (25mm IW, 50mm deep) and a 650b (25mm IW, 35mm deep).

I wondered, before my obvious bias, if there was a way to see if indeed the supposed stiffer rims were actually noticeably stiffer. I can guess probably laterally, but vertically? I get that shorter spokes should in theory mean more rigid, but if the difference is tiny, I'm unlikely to actually tell the difference.

Reviews and stuff are difficult to get unbiased. I have never noticed any rim being uncomfortably stiff, but have had weedy rims flex significantly enough to rub on my chainstays to polish them up. Maybe I'm powerful. Probably I'm just too fat. We may never know.

Although I can't say, even with cheap poorly built wheels, I noticed any flex other than sideways. Maybe I'm just not that sensitive to it? Perhaps, with wider tyres at lower pressures, it's not even really measurable. I don't know.

It isn't the stiffness of the wheel its the relationship of wheel to frame stiffness and the missing ingredient x where x is the deflection of of the tyre which of course changes according to pressure, angle of attack and force applied. Other variables will include the surface the tyre is on, air pressure. The wheel on its own is irrelevant because its part of a system that interacts with the environment. on its own it doesn't flex at all.

What I do know "anecdotally" and through repeatable observation is that ultra stiff wheels can cause brake rub at the rim more than less stiff. This is because the frame/ bottom bracket is also flexing.

I also know that the answer is how long is a bit of string and in the context of riding a bike makes cack all practical difference. perhaps as an engineer you can commit years of your life and fortune to identifying a comprehensive equation to describe it; peer reviewed of course. You could publish in the Who cares journal of geeky wankdom.

Failing that go on an empathy course. ride the spectrum

Chaz.Harding

david37 said:

You could publish in the Who cares journal of geeky wankdom.

Failing that go on an empathy course. ride the spectrum

So edgy.

Sic burn brosef