The last part of this series covered these wheel building optional topics:
– Rim washers
– Pre-stressing
– Tying
– Aging
Let’s close out with three options that are as much paperwork as mechanical and one important point that is mostly strategic.
This week’s list:
9. Stickers
10. Presentation
11. Tension, trueness mapping
12. Criteria for adopting new techniques Read more →
Nothing beats riding in newly arrived Fall weather. In the north hemisphere, those start now! Zipping through scenery colored with seasonal change, feeling the lingering warmth of Summer, such a magical experience—an invigorating and restorative tonic that reaches the core of our human experience. Frankly, despite my attempt, it’s well beyond words.
© New Yorker—cover 9/23/19, by JJ Sempe
Much of cycling is this way and doesn’t get better with analysis. Still, I find it irresistible to consider all the variables from physics to aesthetics, after the ride. Maybe I’m just trying to keep the endorphins coming!
On my list of leisure pursuits are podcasts and essays by well informed bicycle experts who do their best to demystify as well as entertain. We benefit from a fine selection of such voices these days. Near the top of anyone’s list… Read more →
There are no templates for success with a craft like wheel building, each of us creates a personal system unique to our situation. Since we never finish honing the craft, it pays to study other builders who are willing to share.
Rich Lesnik, master builder at Rivendell.
Wire spokes for bicycles come in three main types—straight gauge, single-butted, and double-butted.
Straight gauge (DT Champion)
Single-butted (Sapim Strong)
Double-butted (DT Competition)
Of these three, single-butted have been sleepers, hanging around in the fringes, not much used or discussed. However, their role is growing and they will inevitably become the workhorses of the wheel world. Why? Read more →
Among excellent makers of allen wrenches (think: Bondus, Allen, PBSwiss, Pedro’s, Park, Wihus, and others) only one has addressed engagement geometry like external socket wrenches have.
Hex screw on left. Allen screw on right.
Historically, allen screws arose for embedded fasteners. The wrench inserts into a fastener rather than surrounding it. But the hexagonal interfaces have similar limits. In order to transmit maximum torque to a fastener without deformation drive shape was devised for external sockets, often known as “flank drive.” That name belongs to Snap-On, a socket drive pioneer but you’ll find such drive geometry everywhere today. Read more →
Torque—the rotational equivalent of linear force—enhances the integrity of mechanical assemblies when applied correctly. Torque values are integral to engineering design as they apply to fasteners at joints which can be a structure’s weak points. Knowing the intended torque makes us smarter, safer mechancis.
Much talk of rim washers these days. When to use them? Which are best? While seasoned builders have questions beyond this post, for the rest of us, here are some considerations about washers to keep in mind.
Washers are often invoked to prevent galvanic corrosion between nipples and carbon fiber. The materials of nipples (brass and aluminum) wants to exchange electrons with carbon fiber. Direct contact makes it easy for corrosion to occur.
Simply for the purpose of discouraging corrosion, are washers sometimes overkill? Some points on this topic: Read more →
Here is a definitive anti-friction, anti-vibration treatment for spoke threads. Apply to clean threads like paint. Allow to dry, then build and ride, reaping benefits beyond the reach of other products.
Why FIX?
Available in 15, 30, and 60ml bottles with instructions. For OE quantities, please inquire. 15ml fixes about 75 wheels, 30ml~150 wheels, and 60ml~300. Each bottle comes with a handy York tip that, if clogged, can be easily cleared with a spoke. We use LPDE extra soft bottles for easy dispensing.
Each experienced builder prefers a particular spoke thread treatment. For many, FIX is the hands-down best and yields the most luxurious and effective building experience. Imagine nipple adjustment at high tension with a smooth, almost hydraulic feeling.
High performance and heavily used bicycle wheels need nipple thread treatments. Here are some popular thread solutions and considerations.
For many experienced users. pro’s outweigh the con’s for each of these methods, There is certainly no best way to address the challenges of corrosion resist, building friction, and vibration loosening. If you, like me, prefer FIX, then you are willing to master its application so it does not add excess time. It offers the pleasure of super low thread friction, compatibility with any lubrication before or during the build. Once you have been spoiled, it’s hard to go back to any other thread treatment.
The chart below shows the relationship between nipple friction and spoke tension. For the sake of discussion, only 3 curves are showed— a FIX coated thread, an oiled thread, and an oiled and Loctite treated thread. Granted, this chart is not literal but it’s meant to convey a relationship.
A wheel needs some (hopefully small) friction at zero tension to resist vibration induced loosening. However friction should be as low as possible in the rest of the tension range, especially the tensions encountered in building.
You can see how a FIX treated wheel would be a delight to build and easy to adjust even at finished tensions. I trust your choice for wheelbuilding thread treatment, but maybe it’s time you tried another idea!
Click here to download a users guide.
A severe side (lateral) load on a bicycle wheel is bad news. Wheels are strong for radial (vertical) and torsional (twisting) loads but vulnerable for lateral. Fortunately, high lateral forces are uncommon with single track vehicles that lean through turns. Still, they account for most wheel failures and the actual dynamics remain poorly understood by many.
Let’s examine an extreme lateral load and discover how a wheel responds. How can a tensioned structure with balanced, triangulated bracing warp instantly into an unrideable potato chip shape?
Familiar shape with a bit of frost.
A lateral force usually arrives from the tire-ground contact, perhaps from skidding. The load moves the tire to one side which, in turn, pushes the rim to the side. The rim resists the force with both bending and torsional stiffness. The force is felt by spokes in the immediate region.
A spoke on the the force side tends to maintain its tension. A spoke opposite the force loses tension. The rim does not budge until the opposite side spoke reaches zero tension. At zero tension (all within milliseconds) all forces still balance out, and the rim is undeformed.
lateral load sequence
Once the opposite side spoke buckles, the rim begins moving. Would be helpful if the force side spoke, tight from the beginning, could increase its tension to resist the force. However, due to the low relative strength of bicycle rims, the rim begins moving away from the load in an arc whose radius is the force side spoke. The rim section swings at the end of the force side spoke as a yo-yo swings on its string going “around the world.”
Bent!
In practice, the force side spoke cannot increase tension to keep the rim stationary. The rim is too elastic and swings rather than remaining the same distance from the wheel’s theoretical center. In this example, the lateral force is extreme and our wheel now has a pronounced side bend at the site of impact. Neighboring off side spokes are unloaded as the rim moves their way. Their reduction in tension makes for a positive push that creates two bends that are reverse of the side load. Such “wings” also occur next to broken spokes.
Depending on the magnitude of lateral force, the flexibility of the rim and the amount of spoke tension; a sine wave can propagate around the wheel, driven by the reduction of spoke tension in half, or more, of the spokes. All energetic states seek a lower potential. The loss of spoke tension drives the sine wave, bending the rim into a potato chip shape. This has been triggered by the initial extreme lateral force, but the eventual collapse is an implosion of the tensioned structure.
© The Bicycle Wheel, J. Brandt
This potato chip shape, also known as a pretzel or taco, is technically a hyperbolic paraboloid. You can trace the edges of one on the Dumbo ride at Disneyland. When Dumbo swings low, its radial arm acts like a spoke that is maintaining tension. Swinging high is the same, but like an opposite side spoke.
Dumbo rises and falls as the ride rotates.
Hyperbolic paraboloid—Wikipedia
In wheels with extremely springy rims that do not easily take a permanent set, a potato chip wheel can sometimes be fixed by banging sideways on the ground. A reverse extreme lateral force can cause a sine wave that neutralizes the deformation. It’s a chancy strategy but if you witness one, you’ll know it was special. Steel and wood rims are better for this than aluminum or carbon.
If you travel around the rim like a bug (or Dumbo) it will be obvious the rim is deformed left and right but also twisted. It’s a torsional deformation, not simply left-right. Rims with great torsional rigidity resist taco shapes much better. Torsional rigidity increases as the 4th power of the radius of the largest inscribed circle that fits in the rim section.
The rim above (from 15yrs ago) can fit a large circle in its cross section, giving it extraordinary torsional rigidity. It is nearly impossible to twist into a taco shape. It’s not just the little dude inside making this rim strong. Many deep carbon fiber rims have high torsional rigidity. Pushed by an extreme lateral load they either bounce or break. Notice how many of today’s more enlightened rims feature large open space in their profiles? Good design!
A taco wheel often displays four lobes, two in one direction, two in the other; and one is usually larger than the others. Safe to assume the extreme side load was delivered at this spot and the other three lobes formed as a consequence. Trying to true this wheel is wasted time if the rim has taken a permanent set.
Loosening spokes will reveal how extreme the bend is. Once de-tensioned, the true rim shape appears. If you must use the rim again (think: remote location expedition) try and make it as straight as possible without spoke tension. Be very careful to not introduce kinks or dents as you lever the rim to flat. Once the rim is flat, it will support spoke tension again and have no residual tendency to return to a taco. Truing without first bending the rim makes an unbalanced structure prone to deform again.
Before we leave the world of tacos, pretzels, and potato chips, let’s notice one further way a wheel can assume a multi-lobed deformation—excess tension. A rim can only support so much total tension, in proportion to its mass and shape. We used to build a favorite rim to 100kgf per spoke, with 36 spokes. The same rim with 48 spokes could not support 100kgf on each spoke.
An over tensioned wheel can “pop” suddenly into a wavy pattern. It’s the same principal as extreme side loads. Such a deformation will have many (not just 4) lobes, each small deflections. If you lower the tension total, with luck, the rim may behave as if nothing happened. It was just trying to reach a lower energy level. In its wavy state some spokes lost tension, others maintained. The total was lower.
Whether you ever undertake such truing, it is important to understand the forces involved. A wheel can suddenly become a taco shape with an extreme side force. In slow motion, this begins at one spot and a sine wave of deformation travels around the wheel often leaving a 4-lobed taco shape.
When it comes to metal bending and tension, most everything is reversible so, even if impractical, such wheels can be repaired. With these principles in mind, try your hand at it. You may not succeed but the exercise is always informative. Experience at the fringe of possibilities is what makes developing world bike mechanics so resourceful. Hone your own skills, don’t let them have all the fun!
As gravel beckons, where are we with disk road wheels?
Disk brakes have come late to road bikes and, until recently, have met a cool reception. Two questions arise:
1/ Will the feel and response match the best rim brakes?
2/ How well will road wheels support disk brake loads so fundamentally different than rim braking?
