That’s my understanding, just covered this with respect to bearings in school.
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Next time I help someone adjust their hub bearings instead of saying “there’s this preload thing I don’t really understand” I’ll say “well, in the human heart the amount of ventricular stretch…”
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the heart preloads what it preloads
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This is untrue
Assuming casing with zero stretch, the deformed toroid has equal surface area but not equal volume. Anything other than the toroid’s natural inflated shape will have a lower volume to surface area ratio.
A deformed toroid with zero resistance to stretch (infinite stretch?) could have equal volume when deformed, but would not have equal surface area.
Everything in real life is somewhere between these two extremes. Balloons are closer to the second. Tires do have some spring in them, but they’re still much closer to the first.
The question of magnitude of the change is a different one, and I agree with @crowding there that it ought to be a very small percentage change
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an uninstalled bearing (and thing assembled with bearings) have some amount of slop in them. one part can move a little relative to the other. if there was no space for jesus, it wouldn’t spin smoothly- would get hot and/or bind.
preload takes up this slop. if you do too much the bearing binds, not enough and it wiggles and makes it so the races can misalign and damaged the bearing. just right and you’re good to go
most bike things have bearings in pairs so that the thing is supported and/or so that one bearing helps take care of the other
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But where are the sarcomeres?
That’s actually a great explanation and now I’ll think about ventricles and leaving space for jesus when I adjust my bearings.
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I learned that this is actually a specification, you can get bearings with different amounts of internal clearance for different applications. This is the initial clearance.
Residual clearance is what you’re left with after installation because of interference in bores/on shafts.
Running clearance is what you get in use with the effects of heat and additional load.
Running clearance needs to be > 0 even if by an extremely small amount, otherwise it will bind and damage the bearing.
In the room for Jesus analogy, Jesus is lubricant.
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right. like screws have a required amount of slop. simply would not work without it.
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go adjust your headset.
make it too lose. without actually riding (putting actual load on it) it would spin really really easily. but if you tried to ride it it would knock around and feel like shit. and if it was a loose ball bearing the balls could theoretically fall right out if it was loose enough.
make it too tight. that shit don’t wanna spin.
make it just right and it’ll work as intended.
also keep in mind that along the lines of what rauce said, bearings have a load rating. preload gets them to the lower end of that load and selection of the correct type of bearing ensures that the forces they will see while riding fall short of hitting that load rating.
Okay now explain preload on a spring
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Adjuster compresses the spring a bit without compressing the shock.
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i think jeffro got it. i don’t know springs but i reckon that preload can be used to cancel the weight of the thing it supports and/or to remove some “normal” input. like brake dive vs an actual rapid bump?
Spring rate is measured as the amount of force per unit of compression, typically pounds per inch or some such. So, if you have a 100lb/in sprint and need to support 400lbs, then you better be able to dial in 4 inches of preload at your desired ride height.
Have I made a mistake? My plan for these is to run 28-30mm tires mostly on road and a little gravel backroads 30-60km at a time on a gravel oriented frame.
I weigh 63kg and my max avg. speed is just over 30kph.
Is there a better choice at Light Bicycle?
I’m like 73kg and ride slower than you.
I asked similar and was recommended LB AR46 (both here and by Light Bicycle) for all surface 28-32 tires.
I’m still nervous about the deeper rims being less comfortable, especially for long distance…
But…I have an invoice for 2 rims with black Friday Discount in hand that i have 1 more day to waffle over 
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AR46 are about twice the weight! I get hit with a lot of crosswinds too, so I’m not feeling some deep deals.
I have to stop and start a lot too, so the inertia argument isn’t as good either.
I feel pretty good about my choice, but it’s a lot of money and hookless and the low max pressure has me nervous. I’m coming from 23mm and 90psi, though, which is a silly comparison. By most accounts everything I’ve ever ridden has been weaker in the ways that matter, so I dunno.
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with tubeless you’re not going to pinch flat, obviously, and i’ve hit an AR36 hard enough on the edge of a pothole to launch a water bottle, the rim was fine.
i’m interested to see how these work for you. ultra lite is out for me, but i’d go down to like 25mm for a light weight build
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DQ: Why would anyone get hookless rims unless forced?
I don’t feel like there are any excuses for hookless other than they are cheaper to manufacture and increase profit margin
Or am I wrong? They’re trying to sell them as an innovation but really it’s just crappification for profit
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You have to be going up a pretty steep grade for a while before weight starts to trump aero.
I have some of the new falcon pro rims in 45 and side wind effect seems minimal. My commute starts/ends with a completely unprotected bridge crossing and it hasn’t been the slightest issue. No crazy gusts the past few days, but in the past when the wind is really kicking I feel it on my body as much as my wheels.
No complaints about ride quality either. I think that whole shallow rim rides softer thing is largely a red herring. Whatever difference in rim or spoke deflection there may be, seems to be lost in the noise of tire deflection.
Also, the wattage savings of an aero front wheel pretty much offsets the drag of a dynamo. So there’s that.
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there was an episode of a cycling tips podcast where they had a pretty good talk with a SRAM engineer about the current state of tubeless rims and tires - what I took from it is that hookless is entirely fine given the newly-agreed upon ETRTO standards for tubeless tires, and it means that rim builders can build possibly lighter rims for less while also getting more consistent product. So yeah, there’s a profit motive but I bet more wheels than less will be hookless in the future.
The other big take away is that SRAM/Zipp really thinks people should generally be on less tire pressure than they’re running:
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