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Rims

Know this about rims

Rim photoWe like silver rims for their looks and performance. Anodizing is mostly show, not go. In fact, once it starts to wear off, it's not even show no mo' and that's assuming you like the looks in the first place, and we don't. So silver it is, for us.


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.


Rim width All rims are strong radially (top to bottom, straight on), which is why you can ride smack into a brick wall, buckle your frame, break your helmet, and still have a perfectly true rim. It's lateral strength that matters more, and rims get that largely by width. Wide rims also hold tires better. There's less of a tendency for a large, soft tire to roll on the rim as you lean the bike around a corner. Any tire is just more stable on a wider rim.


Yet another benefit to wider rims is harder to explain without having a bike right here. It has to do with removing and installing wheels on bikes with sidepull brakes.


When you adjust your sidepull brakes for clearance between the pads and rim, you're also unwittingly determining how far apart the brake pads will get when you open the brake to let a wheel in or out. When your rim is skinny and your tire is fat, it's unlikely you'll be able to open the brake pads enough to slide the wheel in and out. You may have to deflate it.


That's a drag if you have a roof rack that requires you to take off the front wheel. It's a drag if you get a flat, fix it, and inflate the wheel before putting it back on your bike. It's never convenient to have brake pads that don't open enough to clear the rim, and it's more likely to happen the skinnier your rim is. So that's another reason we like wider rims.


Historically
Rims were wider than they are now, because only racers rode the skinny tires that go on skinny rims, and non-racers didn't feel so compelled to copy racers. But now that everybody wants to be Lance, rim and tire makers have responded by making skinnier rims and tires for normal guys.


What we now consider to be wide used to be medium, and what we now think of as medium used to be narrow. So when we say, as we're saying, that we like "wide" rims, we're really talking about rims that are medium. They're just wider than most modern too-skinny rims.


Rim Joints: Welded, pinned, or sleeved?
It doesn't matter. They all work, and we don't draw a hard line one way or another. There are more important rim issues.


Eyelets: Single, double, or none?
Our sentimental favorite is double eyelets, but almost nobody makes rims that way any more, and again, if the other more important things (like width) aren't in place, having a double-eyeletted (sometimes called "ferruled") rim isn't going to mean beans. A double-eyelet rim is one in which the rim's inner and outer walls are connected by a tube (ferrule) that distributes the load from the spoke between both walls. In the old days, most good rims were made this way. Single-eyeletted rims often drove you nuts when the eyelet (visible at the spoke hole) came loose and slid down the spoke. Today's single-eyelet rims must be made better, because that doesn't happen anymore. At least, we've not seen it in 11 years.


Single-eyelet rims are the norm, and that's how all of our rims are because the other stuff about them is the best, and it's good enough, so we go on.


Plain rims, with no eyelets, can be good, but the thing is, the reason for doing that is cheapness, and it seems not so good to tighten the spoke nipple against raw aluminum, with no eyelet to protect it. True, they beef up the aluminum at the spoke hole, but still it's a cost cutting measure, and it's too cheap for us.


Asymmetrical rear rims?
Yes. Whenever it's an option. On a normal rear wheel, the rim is not equidistant between the hub flanges (where the spokes go). Because of that, the spoke tension isn't even, and because of that, the wheel isn't as strong as it could be.


About ten years ago rim makers started to compensate for the uncenteredness by shifting drive-side spoke holes farther away. They had to redesign the cross sections in the process, but the result was a rear wheel with the rim nearly right between the flanges, as it is on the front wheel. This is nothing but good, so we prefer asymmetrical.


How many spokes?
More is always stronger, but at some point weight and marketability enter the picture, and rather than take a stand on 48-spoke rear wheels (which for the most part are strong but nutty), we settle on this:


Rear wheels
For loaded touring: 32 minimum, and then only if the rim is assymetrical. 36 is better. If you're heavy or have reason to believe that the stress is going to be continual and great, go with 40. For unloaded riding, general riding: 32 or 36.


Front wheels
For loaded touring: 32 minimum, 36 is better. If you're heavy or have reason to believe that the stress is going to be continual and great, go with 40.


For unloaded riding, general riding: 32 or 36. If you weigh less than 150 pounds and the road is smooth and even though you don't race you're still afflicted with the go fast bug, get 28.


The Effect of Tire size and pressure on wheel strength
A high volume tire run at low pressure takes tremendous stress OFF of wheels. So you can safely ride fewer spokes, if you must. It's hard for a 180lb rider to damage a wheel if the tire is 37mm wide and carries 50 psifor instance.