machined vs non machined brake track

[eddief]

so i am dealing with my cracked Stans 340 rear rim. accidentally ordered a Hed Beligium "black" rim with non machined brake track. it is a great stealth looking rim with the coolest decals. but it won't match my front machined Stans. i might think about keeping it just for the stealth, but does anyone buy non machined brake track rims? do they work ok?

[ryker]

They work great. With disc brakes.

[eddief]

Machined sidewalls? Nope, and here's why:
A rim starts life as a straight extrusion; and then it is rolled into a circle. Before it's rolled, all's well with the braking surface (sidewalls). But in rolling it round, the sidewalls get wavy. That's because the inner and outer circumference travel a different distance, in the same way as the runner in the inside lane of a track runs a shorter distance than a runner in the outside lane (assuming they start and finish on the same line). If the rim material were stretchy, maybe the outer portion (the part nearest a mounted tire) would stretch and get thin. But it's not stretchy, so instead, the inner portion develops waves, so that despite being on the inside, it still travels the same distance. It's like the runner in the inside lane running a curvy line to make up for his advantage. Is this making sense?


In theory, wavy sidewalls are bad, but only in theory. In fact, the degree of waviness is so small that it hardly matters. However, it is undeniable that perfectly flat sidewalls are the ideal, and have less of a tendency to draw attention to themselves on an initial test-ride. That's the whole deal, right there.


Nobody's happy when a customer applies the brakes and hears a squeal. It doesn't often happen with any rim, machined or not, but statistically it is more likely to happen on a raw sidewall than on a machined one. Because of that, rim makers have "solved" the squeal issue by machining the sidewalls.


You might think, so what's not to like? Well, something.


The side wall thickness starts out even, even as it gets wavy in the rolling. But when you machine the waves flat, you lop off the high spots, and that takes material away from the sidewalls. So although your braking surface may be flat, you end up with sidewalls that are thin here and thick there. Some rims start out extra thick to compensate for the shaving. But in those cases, the low spots that barely get skimmed remain disproportionately thick.


Since the waviness is so small to begin with, we think it's best to leave well enough alone, keep the wall thicknesses even, and let braking itself take care of the high spots, over time. It always does.


Sometimes when rims are machined, the tool isn't super sharp, and the process leaves visible, feelable grooves in the braking surface. While we're splitting hair with waves, we might as well continue it here by saying grooves are bad. They reduced the contact area between your rim and pad, so they make braking worse that way. And they're more likely, than a smooth surface, to trap water.


Machining rims is a way for rim makers to justify a higher price, and the only thing it does is make a rim worse, while making it seem smoother. You can still have a grand old time on machined rims, and they're not likely to cut your tour short. But all in all, we'd rather the rims were normal, and all the rims we sell are. In some cases, we've specifically asked the maker to NOT machine the rims when machining them was the default.

[eddief]

Subject: Machined rims
From: Jobst Brandt
Date: January 26, 2003

Just wondering if it really makes any difference. Some manufacturers don't even advertise whether the sidewalls are machined; others do. Velocity for example, makes both, but I believe they're the same price. What gives? Just marketing hype?
What you hear and read is mostly marketing hyperbole, but machining rims has its reason, and it isn't for your benefit. If you inspect a machined rim closely, you'll find a surface that looks as though made by a thread cutting tool. The purpose is not to get a flat braking surface, but rather to produce a series of fine grooves to prevent brake squeal on new bicycle test rides.

The machined grooves, about the texture of LP vinyl record grooves, can be felt by running a fingernail across the rim. These fine grooves usually wear off on the first braking descent in wet weather, the condition that causes rim wear in the first place. Even anodizing, which is a hard ceramic, whether thick or thin, is more durable than the machined rim. However, anodizing is not the solution to wear, because it degrades braking. Anodizing being an insulator that overheats brake pads and causes brake fade.

The claim that machining is for purposes other than suppressing brake squeal is far fetched. For instance, rim joints have been made with no perceptible discontinuity almost as long as aluminum rims have been made. Unfortunately, some people in marketing believe that rims will separate if not riveted (or welded) and introduced riveting that usually distorts rim joints. Fortunately, that rims were made for many years without rivets and had flawless joints proves otherwise.

In practice, machining solves the new-rim squeal problem at the cost of a rim wall of unknown thickness. It also adds a bit of sparkle to the new product by giving rainbow reflections in showrooms. Mavic, for instance, has rims listed as having "CERAMIC2", "SUP, "CD", "UB", MAXTAL", all features that substantially increase cost over plain aluminum rims that were offered at about 1/4 the price not long ago.

The web site explains that "CERAMIC2" is an insulator that improves braking even though the rim is "UB" machined, ostensibly for the same purpose, before ceramic coating. This is a tipoff, because without special brake pads, this feature overheats pads causing them to wear rapidly while degrading performance. Not mentioned is that it's main purpose is to reduce rim wear in wet and gritty conditions.

[bicycletricycle]

Machined sidewalks are good, welded and Machined rims are better

Consistent and smooth braking surfaces feel so much better at the lever.

[oldpotatoe]

so i am dealing with my cracked Stans 340 rear rim. accidentally ordered a Hed Beligium "black" rim with non machined brake track. it is a great stealth looking rim with the coolest decals. but it won't match my front machined Stans. i might think about keeping it just for the stealth, but does anyone buy non machined brake track rims? do they work ok?

Only if it's a disc specific rim cuz the sidewalls may be too thin for a rim brake. Once upon a time, a long, long time ago, all rims were non machined and they worked fine.

[titans]

Just had a set of HED tubular Belgiums laced to Campy Record hubs. Brake track sure looks to be machined but what do I know. Have to take a closer look to see if there are grooves in the braking surface.

[eddief]

full black without mahined brake track. I have a feeling it was meant primarily for disk builds, but my bet is the brake track is the same or even thicker than those on the machined rims...since it is nicely smooth, but not yet machined.

[eddief]

yes, rim was meant primarily for disk builds. would work just fine for rim builds, but would not be as pretty after brakes rubbed off paint on tracks.

great customer service. even though i bought through Amzaon, Hed offered to exchange it for me. Tim there one of the good guys.

[fiamme red]

I asked my LBS to order a pair of Velocity Synergy machined rims for a wheelset they were building for my commuter, and by mistake they received non-machined ones. I told the wheelbuilder to go ahead and use them. At first, there was a loud screeching sound whenever I braked, which I started to enjoy when I saw that it made texting pedestrians jump. A few weeks later, they were as quiet as machined rims.

[mbrtool]

So, if the cause of brake squeal on a non machined rim is due to the waviness when a straight extrusion is formed into a round shape, and the squeal subsides after a few weeks; where does the material from the high spots on the rim go? Is the metal actually formed back to a flat surface thereby ensuring equal stock thickness of the rim, or is the material abraded off so the net result is identical to a machined rim?

[oldpotatoe]

So, if the cause of brake squeal on a non machined rim is due to the waviness when a straight extrusion is formed into a round shape, and the squeal subsides after a few weeks; where does the material from the high spots on the rim go? Is the metal actually formed back to a flat surface thereby ensuring equal stock thickness of the rim, or is the material abraded off so the net result is identical to a machined rim?

It's probably from the powdercoat applied to the rims..Not much 'waviness' now or on older rims.