PFTV3: What's Up with Wheels, Rims, Hubs, and All that Jazz...

Wheels. Every bike has two of them, but if you’ve ever had to look for a replacement you’ve probably been overwhelmed by the sheer variety of sizes, specs, and standards. In today’s episode of Pure Fix TV, Amanda will guide us through the web of wheels so you can make the right pick for your ride!

Rim Size

First things first, let’s make sure you’ve got the right size rim. When it comes to measurements, the bike industry is plagued by competing standards, confusing naming conventions, and lots of parallel engineering that leads to multiple solutions to a common problem, all called something separate. Rim sizes are no different. Your bike growing up probably had wheel sizes measured in inches, but "grown-up" bikes generally use one of the French standard sizes: 700C, 650C, 650B, etc…

700C

The most common rim size on the road today is the 700C. With a diameter of 622mm, these bad boys are big enough to roll over pot holes and uneven pavement with ease, and get up to some serious speed without spinning themselves (and your legs) to death first. All of our fixed gear bikes (Original Series, Premium Series, Keirin Track Completes) except the Micro Series run 700C, as do the larger Pure City Step-Throughs, and Classics. 

650C

With a diameter of 571mm, these smaller rims help lower the frame making them an ideal choice for shorter riders, or kids who’d have a hard time climbing all the way up on to a 700C frame. That’s what makes this the perfect rim size for our Micro Series!

26”

Ah yes, back to some imperial measurements. Contrary to common sense however, 26” wheels aren’t actually 26 inches in diameter, they measure up at a cool 559mm. That’s because rim sizes are named after their circumference with a tire mounted, and because tires come in so many shapes and sizes… well, they had good intentions. Still, that means 26” rims land right between the 650Cs and 700Cs, making them the ideal size for bikes where some ground clearance can be sacrificed for comfort and making mounting and dismounting a breeze. That’s why it’s the size we use on our smaller Pure City Step-Throughs as well as the new line of Cruisers.

Rim Depth

Rim depth refers to the measurement between the tire and the spokes. When building your own wheels, it’s an important piece of info to make sure you choose the right length-spokes, but what’s the point of all that extra rim, and how do you know which size is right for you?

The good news is, unlike rim sizes, you’ll never find a rim that’s too-deep or too-shallow to fit – rim depth really only affects ride, weight, and durability. Deeper rims are sturdier and stiffer than shallow rims because the extra depth reinforces the wheel, lets you use shorter spokes, and generally just keeps everything more rigid, ensuring your power gets transferred to the road and isn't lost in flex and stress on the wheel. That’s also why you’ll even see full carbon disc wheels on the rear in Olympic track cycling. Those things are so stiff that all the power is going to the track. Less flex in the wheel also means they’ll stay true longer, so that’s a vote for durability as well.

There’s also an aerodynamic advantage to a deep-v rim where you’ll see a deep rim that tapers into an aerodynamic “v” shape. That “v” cuts through the air much better than the whisk-like spinning of spokes, and that translates into less resistance when you’re really pushing the pedals. Olympic track cyclists will even do away with "wire" spokes completely and that’s when you see those full carbon tri-spokes (or the infamous Spinergy RevXs).

The downside to all that extra rim is weight and cross-breezes. Sure, you cut through a headwind like a hot knife through cream cheese, but when the wind hits you from the side those deep-dishes can turn into a sail and really drive you off course. That’s why you won’t see full disc wheels on street bikes (Often. I see you bike polo kids). When choosing your new rim depth, just imagine your typical ride and weigh the pros and cons of stiffness/durability/aero vs weight/cross-breezes and choose accordingly. Or if all you care about is looks, go deep. That way there’s more room for stickers, swag, and friendly graffiti.

Braking Surface

All of our rims have a raised braking surface just in case but, if you’re going to run brakes, a machined braking surface will make your life a bit easier (and a lot more quiet). With a machined braking surface, the paint is cleared away where the brake pads will contact the rim and small grooves are machined into it to increase the surface area, friction, and help clear water and debris from the pads. The result is some more responsive braking (and none of that brakes-on-paint squeal you’ll get as you wear in your brakes on painted rims). For a machined braking surface, check out our 30mm Pro Wheels.

Hub Width

Hub width is measured by the distance between the lock nuts, and this is one of those that you want to get right, or you’ll find yourself with a pair of wheels that won’t fit. Luckily, there’s been a good amount of standardization over the years and now you can ride confidently knowing that most front rims will have an OLD (over lock nut distance, or width) of 100mm. When it comes to rear wheels, there’s still some variety, but it mostly shakes out based on gearing. Singlespeeds and fixed gear bikes typically have a 120mm hub in the rear, while geared bikes will generally be wider so they can fit the cassette, derailleiur, etc… Here’s a reference chart of our bikes, so you can be sure to scoop the right sized hubs when you’re on the market.

Hub Bearings

Last but not least, let’s talk bearings. These are the magic little balls that keep everything spinning and the difference between a well-maintained set and a rutted, degreased, bump-fest is night and day. Loose ball bearing hubs use cones behind the locknut to hold the bearings in place and adjust the tension so you can get that buttery spin. They’re a bit touchy (tighten the cones too much and you’ll bind the bearings up and get no spin, too loose and you may lose some bearings and damage your hub as everything spins a little too freely/violently. But when they’re dialed in and just right… it’s perfect.

Sealed bearing hubs use pre-built cartridges that contain the bearings within the hubs. That means they’re less exposed to the elements (so you can go longer between services), replacement is a breeze (just pop in some new cartridges), and, with a seemingly endless variety of cartridges available from basic shop-replacements to high end Phil Woods/ceramic/etc… the possibilities are endless.

When it comes to choosing which set up is right for you, it really comes down to how much you like to tinker, and how regularly you like to do maintenance. Some purists swear by loose-balls for the level of control you have and the classic-cool points, but a lot of riders opt for cartridges for ease of use and replacement.

Check out this reference for the different bearing types used in our wheelsets, so you can choose accordingly.

And that’s it! Use the charts above to figure out what you’re rocking now and what you can consider come upgrade-time! And don't go too far, we've got even more Pure Fix TV coming up.