ilikebikes

I hear a lot of cyclist saying that machined wheels are more or less junk? Can anyone tell me why?

Velocità

are you referring to a machine built wheel or a machined sidewall? a machine built wheel is probably inferior to a hand built one. a machined sidewall is just a braking surface and wouldn't affect the wheel.

jgedwa

There is no way you will ever get into art school asking a question like that. Machine built, non-machined wheels are the only way to carve your way down the avenue.

Peedtm

The machine that builds wheels puts undue stress on the rim as it assembles the wheel. The machine is set up to true the wheel in a certain amount of revolutions. The more revolutions, the more accurate the true and the adjustments are made in smaller increments. Obviously the cost efficient route is by setting the machine to complete the wheel in a few passes. This warps the rim itself (permanently) as it goes through truing because of the dramatic corrections the machine is making. So in conclusion, they're not necessarily crap (since the machine could be set up to spend hours per wheel,) but your odds go up.

If you mean machined sidewalls, quit listening to those people.

ilikebikes

Yes, machined sidewalls, Ill take you advice and stop listening to them Now, what the heck does art school have to do with this!

muzzymuz

This explains a lot, thanks

LóFarkas

Cheap machine built wheels seem to have ridiculously low tension and they obviously do not go through any stress relieveing... so they go out of true if you look at them funny.

The "few passes, brutal truing" theory is interesting but I'm not convinced. Rims can take a lil' bending, although I woundn't put lotsa bending past mfgrs, either.

ThunderChunky

aerospokes aren't machined, anything else is total crap.

j0e_bik3

so since no one responded to the ACTUAL question (you guys are like ellen degeneres on a side track )

the machined sidewall on some rims is to make rim braking smoother and more effective.
this in no way would do ANYTHING to weaken the rim, in fact, you only see machined sidewalls on higher end tubular rims which aren't going to be appreciably weaker because they have 0.010 thou machined off the side wall.

if you look at the machined rim closely you'll see many tiny ridges (like a ruffles potato chip) these ridges will groove your brake pads after a while, and that gives you more surface area in contact with the rim, so you get a mechanical advantage.

it also helps dissipate water if you ride in wet weather, and with proper toe in adjustment, you get nearly silent braking.

it also has a nice sheen at certain angles and I think looks really sweet on an all black hub/wheel/spoke set up.

I don't see why people freak out over a machined sidewall, unless they are those "NJS on the street" nit pickers,.. (just threaten to drill a brake hole in their fork! )

you get what you get with the idle obsessives

operator

JObstd brandt says that machined sidewalls are a disservice to rims.

I_luv_hooters

About machine-made... I've bought 1 set of wheels from Bens and a couple other from the lowest cost guys on eBay. They all say "handmade". I wonder if thats BS. The cost is so little. I've had good luck with all these wheels staying true so maybe it doesn't matter. The one wheelset that was crap came from flybike on ebay. Stay away from them.

dmg

Some claim that machined rims are weaker for the machining, and that a machined rim is less efficient than a broken in non-machined one. See https://www.rivbike.com/article/components/rims
Of course, Rivendell also claims that pretty much every other innovation in cycling is garbage and that sandals are the best riding shoes, so take it as you will.

ilikebikes

OK, Heres what Im looking at https://cgi.ebay.com/RIM-BIKE-ROAD-70...QQcmdZViewItem Ill be using them for a SS project and the bike will see daily use but not crazy hard arse riding, honest opinions please.

bonechilling

My honest opinion is that those rims are fine. My other honest opinion is that unless you already own the hubs, or have a hook-up for super cheap spokes, you'll be better off buying a set of pre-made wheels online.

Building your own will almost always cost you more money than buying a manufactured pair of wheels.

operator

100% true. Especially those mavic rims on forumla hub nashbar dealies a while back - what were they $140?

Landgolier

Brandt is normally pretty air tight, but on this point he argues that the brakes work like a tracer lathe, taking the same amount of material off all the way around and thus wearing an unmachined rim evenly with respect to its thickness, whereas with a machined rim the high points have already been machined down so the thickness is uneven. This is wrong on several points. The brake can't work like a tracer lathe, it's not that precise and there's no way it responds perfectly and without lag to minute changes in the overall rim width. We're talking about two pieces of rubberoid material on a lightweight Al caliper connected to several feet of lightweight twisted strand cable enclosed in a coiled wire housing and then ultimately connected to a human hand, and this is going to work as an ultra-precise tracer lathe? No dice.

I do believe that rim width is distorted slightly by being deformed into a hoop (Grant Peterson of Rivendell espouses this theory as well), but these distortions pale in comparison to those that are introduced once the rim is built up. Grant argues that if you look at a nonmachined wheel that has been run for a while, you will see that the high points created by the bending process are worn down more by the brake; Jobst says basically the same thing. These guys think that you're better off buying nonmachined rims and letting your brakes machine them for you, though Grant thinks that you're flattening out the high places while Jobst says the wear is even. My experience is that the sections that get more wear always start a little before the spoke holes but don't extend as far behind them. These high points can't have been introduced in the bending process, as rims are bent before they're drilled and there's no way the peaks introduced by bending end up exactly coincident with the drilling. These distortions are therefore not present until the rim is built up (unless you believe they're introduced by drilling, which I think is unlikely), and so machining can't have any effect on them. There probably is some distortion introduced by bending, but we'd expect to see it just as we see the wear that takes the spoke pattern I describe above, and I've never encountered it. We'd also expect to be able to find it by calipering the inside of a machined rim, but I can't find any variation at .01mm on the rims I've measured. My argument is that we see the wear we do (slightly preceding the spokes) because there is a high spot around every spoke, but hitting it opens up the brake a bit so the wear doesn't end up being shaped like the actual bump but instead leads it a bit. Think of a car hitting a speed bump, the front of the bump is going to take more wear than the back of it.

The data I'd need to prove this would be a machined rim with a visible coating applied later, like the Mavic ceramic rigs or (I think) those black Alien rims. I'd expect to see spoke patterned wear on these. Less conclusive evidence could be provided by looking at a dished rear wheel that isn't machined, you'd expect slightly less visible wear around the L spokes since there's less tension and theoretically less distortion, though it's also possible that there is a fixed amount of distortion and it occurs below the spoke tension for either L or R side. I can see a case for this, I'm not a metallurgist but I've noticed with cheap aluminum chainrings that they often deform up to a certain point at the base of the teeth and then stop, which I've assumed was caused by work hardening.

Metricoclock

After reading through Rivendells description on the building process of a wheel, I am surprized, not by their "revelation" but actually on their complete lack of understanding of machining and metal forming processes. I seriously would of thought they knew something about metal working being frame builders and all. By their logic a black smith hammering on a piece of hot steel will only weaken the steel.

Peedtm

I've actually seen a couple videos of this. One was of a Chinese factory that showed the entire process of building a cheap bicycle. A machine loads the spokes in the hub and then spins the hub so the spokes extend out. Then little machine fingers weave the spokes together as a rim is lowered in to the spinning mass. From there another machine starts inserting nipples and tightening to a predetermined amount of turns. Once a full revolution is complete, sensors are used to detect true/roundness and a couple more passes finish the job.

It's likely the "handbuilt" wheels you see online are mostly handbuilt. There's slower paced machines out there that assist with loading the spokes and holding the wheel in position as a person hand trues the spokes as they go by.

edit:

I annoys me what they say about pinned not being a consideration.

Landgolier

Rivendell doesn't build frames.

operator

On pretty much all the low end bikes we get around here, KHS/Dahon - the stock wheelsets usually come with extremely varying spoke tension, or extremely high. These are all obviously machine built wheels - but I hardly ever come across any out of the box that have super _low_ tension.

blickblocks

The early 80's tubular Mavic rims on my girlfriend's dad's Pugeot has spoke-patterned wear on the sidewalls. The sidewalls are also rounded, not flat, which might have contributed.

It should be noted that some rims, like the Mavic CXP-22, have a greater wall thickness for the machined braking surface, so the idea that machining would make especially thin points on the wall flies out the door. This might have been true back then, but modern rim extrusions are quite sophisticated.

Metricoclock

my mistakes, thought they did, but now that i look at their site, they don't. Makes a little more sense now.