One of the most memorable characters in our cycling scene of the early 1970’s was Phil Wood who, with his wife Vada and manager Bern Smith, pioneered the modern use of cartridge bearings in bike components. Here Bern recalls some of the special challenges:
Here’s an introduction to the complexities of specifying, testing, purchasing, re-testing, lubricating and assembling bearings. Some of this will be pretty pedestrian to folks with working knowledge of bearings, but there’s plenty other facets to it.
In the earliest days of Phil Wood & Co. circa 1972, once Spence Wolfe had convinced Phil to manufacture some maintenance-free hubs, and they agreed that 50 pairs would be the most they could ever sell, Phil started testing bearing and lubricant samples. He settled fairly quickly on a single domestic manufacturer of bearings, but the grease samples were…disappointing…
He found ‘waterproof’ grease that dissolved in water, grease that absorbed water, swelled up and forced itself out of the bearings past the seals, and other oddities. Eventually he found a product from a local (Bay Area) supplier that was something of an oddity itself – the manufacturer produced only very small batches of this particular grease, and only occasionally. It was somewhat inconsistent in texture and color. But after Phil consulted with them a little, they changed the mix, and after that it worked really well in full immersion salt bath tests.
And it was green…
So we were off and rolling…
We specified that grease to the bearing manufacturer for lubing at their factory. Then the fun began.
A tangent (and a quiz) are required here.
• What is the highest rpm a bicycle bearing is ever likely to spin?
• How many rpm’s is a regular radial-contact industrial ball bearing typically tested to maintain without burning out?
• How hot do you think bearings get at max rpm?
• What causes that heat?
• What exacerbates it?
…and what is the maximum percentage fill of grease in the bearing assembly cavities (those gaps between the bearings, their retainers, and the seals) that most any manufacturer will agree to?
Back to the early bearings. We found soon enough that our idea of how much grease a bearing should have in it was vastly different from what the bearing suppliers were willing to provide. Typical over-the-counter industrial bearings are filled ~25% full with grease. That’s because those bearings, in a normal installation (an electric motor, say) might run as high as 10,000 rpm – 10 times higher than a bicycle bearing will ever spin. A bearing running at 10,000 rpm gets hot – really hot – from friction, and hotter still if it has too much grease in it (retaining heat in the assembly). Too much grease meaning anything over about 25%.
We specified 95% fill because our tests showed that provided satisfactory water resistance in the extreme tests we put bearings through. But the suppliers refused, citing product liability, and other not-pertinent reasons. So we had to lift seals and add grease to each bearing. That probly doubled our bearing cost.
At least we were getting good bearings…until…batches started arriving from the factory with large grit, wood chips, crystals and other unknown stuff. We rejected lots of bearings. It got so bad that, in the final batch we rejected from the original supplier, most of the bearings would not rotate. Now, there’s a handful of things a bearing needs to do, but above all…
Eventually we found a (foreign) company that produced consistently good bearings for considerably lower cost than the others. Were they eventually prosecuted for dumping bearings in the U.S. to put domestic factories under? Another story for another time…
Then the grease started to get weird…
As you might have guessed, as we grew more comfortable with the grease we chose, we had an idea that maybe we could use that grease for other purposes, and maybe other folks might like it as well. In particular, we felt that the lovely deep green color itself could help sell the stuff, and we settled on a slogan – ‘It’s Green!’. Anyway, we asked the manufacturer about making larger batches, that we could repackage from 55 gallon drums into 3oz tubes. They asked how much we might ever sell…
Each time we got ready to order grease for repackaging, I went to the lab at the lubricant plant and inspected samples. They had a few minor problems and we rejected some batches – turns out that the grease mixing vat was used for several different products and occasionally did not get cleaned out completely between product switchovers. Eventually the plant assigned a mixer for this grease alone, and things smoothed out.
At one point, after about 3 years without a single problem, I asked Phil if maybe we didn’t need to go to the plant to check the samples first. We looked at each other for a moment and said simultaneously “Check the grease”…So I drove to the plant and met the project manager in the lab, where he pulled out the latest sample. It was a beautiful, deep black. Lesson learned the easy way for once.
Years later, after the project manager had retired, I related that story to his successor, who laughed, and said “Oh, yeah – he was colorblind!”
In Part 1 we saw rims deform from tire pressure causing spoke tension drop and discussed the role of tire dimensions, noticing road tubeless clinchers have the most potential to amplify tension drop.
In Part 2 we established that design, not manufacturing inconsistency, makes for odd matches and extreme tension drop situations.
Here in Part 3, let’s ask what builders can do to minimize negative influences of tension drop. After all, builders invest spoked structures with tension and answer for wheel performance. Read more →
Part 1 showed how clincher rims can alter spoke tension when tires are inflated:
(1) Outward splaying of brake tracks, changing the rim shape, dropping spoke tension.
(2) Inflation pressure down on the rim bed, a constricting force that shrinks the rim causing measurable tension loss.
Tension loss can be confusing to wheel builders following tension recommendations from rim makers. We need to know why this happens and when to worry.
Here in Part 2 we explore how tires, independent of inflation, affect this dynamic.
First let’s review tire and rim sizing for those less acquainted. Why are they made to the sizes we see?
There’s hardly a more multi-tasking structure in all of engineering than the bicycle wheel. All its components are mutually dependent and interactive. Then no surprise tire pressure affects spoke tension. Here’s first of a 2-part discussion of this phenomenon, that is reaching a worrying scale in today’s wheels. Inflate a clincher to 90psi (6 bar) and you may see tension drop 20-50%. Why? Is tension drop bad? Should wheels be over tightened to compensate?
If wheel building were introduced today, but as a game, would it be popular? No VR but plenty of action: thrill of pursuit, unforeseen obstacles, counter moves by invisible players, presence of a formidable adversary, satisfaction of success.
Plus, the outcome can be ridden. Ka-ching! Wheel building has always been a game and its unpredictable challenges attract agile problem solvers. For many, the challenge of wheel building is compelling. Dependent variables exponentially increase system complexity. Tensioned wire wheels are elusive, almost intelligent, always unique competitors.
Removing tubular tires should be easy. Getting the tire off the rim should not require gorilla strength.
Over the past few years a new issue has arisen. Pulling tubular tires from carbon fiber rims can cause delamination of the rim bed. Creepy, to say the least. Is this normal? What is going on? What to do?
Carbon delamination – please, no!
No carbon rim maker wants to hear about structural delamination during tire removal. Every design effort is made so it cannot happen, as it is impossible with aluminum rims. We all have the same objectives. Under normal circumstances, the inter-laminar carbon layup strength is greater than contact cement on the surface.
Is the delamination important?
Plies (layers) of carbon cloth are extremely thin. Departure of several plies is visually dramatic but may not be a structural problem. It all depends on the design. The rim maker is your only reference. Hopefully, the departed plies are sacrificial, intended to be rugged and expendable.
Gluing is improving
We are seeing a growing appreciation for tire gluing integrity. More than ever, mechanics are using best practice for achieving strong bonds. In the past, when glue integrity was mainly a concern for high level road racing, technique could be less rigorous. Cyclocross, in particular, sees weird rim-to-tire combinations (where bed and tire form do not closely match), suffers water contamination (weakening bonds), and uses very low tire pressure (lower pressure = less tire grip to assist the glue). CX gluers are doing really good bonding.
How to minimize risk when removing a tubular
First, deflate the tire. Air pressure makes the tire grip the rim. Not enough grip to ride without glue but enough to interfere with removal.
Next, try and pry a small section of tire free. Use all your thumb and grip strength. If the tire is properly glued, you will fail. Well glued tires cannot be removed by hands alone. Still, give it a try. After working a 10cm section on one side, flip the wheel over and try opposite. With luck, some of the tire base tape will begin releasing from the rim.
You’ll then need a narrow pry tool, such as a slotted end screwdriver, to push into the glue and separate the tire from the rim. Your goal is to push the screwdriver (or equivalent) all the way through between tire and rim, from one side to the other. A steel tool like this can damage the rim or the tire. Use it gently, pushing carefully, wriggling small amounts, separating the tire from the rim in tiny bites.
Once you achieve tool insertion, replace the slotted (sharp end) screwdriver with a round, Phillips type. My best luck is with a blade about 6mm (1/4″) in diameter. A larger diameter dowel works but the rim and tire prefer the small steel shape. While seated, place the wheel between your legs, with the screwdriver handle in your dominant hand. I am right handed, so here the screwdriver handle is on the right.
Orient the wheel so the screwdriver is at the top. Pull the driver towards you with both hands while you rotate it clockwise (viewed from the right side). Pulling while rotating advances the blade towards you, rolling against the sticky tire bed and skidding against the smoother rim.
This rolling requires a strong turning hand (right for right handers) and a firm pull on both sides. The tire bond is no equal for this rotation. The tire will begin to separate from the rim as you pull and rotate.
You can also use a dowel but the screwdriver blade offers less resistance and a better separation angle. The glue joint is more susceptible to the small radius of the metal driver.
You’re inducing a glue joint failure and the angle of separation is better for the small rotating blade than a larger rotating dowel. We’re inducing a cohesive failure with glue remnant on both rim and tire, handy for future gluing.
As soon as enough tire is separated, pull the tire from the rim. Pull in the plane of the wheel so the tire is doubled over as it leaves the rim. This minimizes base tape separation as you pull it from the rim.
Back to our carbon rim problem, Using the small diameter metal rod induces cohesive failure and minimizes the chance of rim delamination. The final tire removal (over 50% of the circumference) is done without the metal rod, just arm strength. Doubling back the tire as it peels reduces delamination forces.
More than a few mechanics note that heat aids tire removal. At 70C (160F) rim cement is liquified. At 40C (100F) cement is substantially weaker than on a cool day. Using a heat gun to warm is impractical. A wheel is large and sheds heat. At least appreciate this principle and let wheels come to the highest available temperature before pulling tires.
Throughout tire removal, proceed slowly and watch the tire carefully. Stop if anything does not proceed smoothly. Some tires will disintegrate upon removal but it’s rare except for limited use track tires.
There is much to tire mounting that you must know. Demounting is not the opposite of mounting. Great instructions are available in many places: mine (here and here), Calvin’s, and Chip Howat’s scholarly works, among others. Gluing tires is done thousands of times a day and each job carries immense responsibility for rider safety. Learn your stuff and be part of the reason cycling is known as a healthy sport.
As ever, practice is the best teacher. Try different techniques, pester experts with questions, listen to all opinions, and develop dependable techniques. There are too few tubular gluing guru’s. Please join this club!
One of the many reasons we changed indicators to Mitutoyo is their host of download options. A single cable will connect the digital tool to any laptop via USB. The system is complete and fast. Best, it’s compatible with the SpokeService tension utility.
Now go one step further and incorporate a foot pedal. The foot pedal system is three components connecting the tensiometer to a computer.
Recommended by Mitutoyo for this application, the component kit sells as a set.
Best used (but not only) with the SpokeService.ca utility where, once started (and until you close the tab), the software resides and runs inside your browser; no web connection required. However, any spreadsheet program will work. The advantage of SpokeService:
With your cursor in the SpokeService utility active cell, place the tensiometer on a spoke. If the tool does not read zero, tap the foot pedal. Now release the tool, creating a deflection, and tap again. The program automatically sends the correct output number. This double tap routine becomes a reflex and tensions can be sensed and entered with great ease and speed. The cursor knows when to advance. If the tool does not need zeroing (often the case), just tap once. The software knows what is a number to be deducted and what is an actual deflection reading. Foolproof and fast. Watch a demo here.
Prefer not to use the SpokeService utility? Begin by placing your cursor in any spreadsheet active cell. Apply the tensiometer to a spoke, zero with the “Origin” button on the indicator, release the tool to see the reading. Tap the foot pedal once to enter the reading and the cursor advances.
Such ease of use and accuracy has only been available in industrial building systems often costing in excess of €10,000. Wheel Fanatyk is proud to be associated with a wheel building data collection breakthrough. Once you’re accustomed it will be hard to imagine building without.
To buy, check here.
• Lighter than square drive
• Cannot strip (spoke breaks first)
• Aerospace aluminum (2024-T6)
• Nearly impossible to scratch color
• A wrench fit every 60° rather than 90°
• Sleek, distinctive, better, available now
Why Not Square?
Fastener interfaces have evolved since the dawn of mechanics. Square was the first shape for fastener heads and matching wrenches. Square steel nuts were common on machinery of the late 19th through mid 20th century but today hex drive shapes have displaced them. One reason is that a hex pattern offers wrenching access every 60°, while square offers only at every 90°.
Square headed nuts were also known as cut nuts, made by drilling/punching a sheet of steel with holes in rows and columns. Then the sheet was cut in a shear creating strips each with a single row of holes. These holes were threaded and then a second shear cut across the strip making square nuts. The cutting process was often inaccurate and cut nuts were often not square nor the hole centered.
1949 agreements to standardize threads into ISO inch and metric spelled the end of square headed bolts/nuts (except for cycling!) since new and better machinery to make them would have been required. As machine design advances, nuts and bolts must fit in smaller spaces, meaning less room to swing wrenches through a useful angle. The more faces on a nut, the better.
Why Spline Now?
For bicycle nipples, we have a work in process. Square drive has been unchallenged for 1-1/2 centuries. With steel and brass as dominant nipple materials, enough torque can be delivered to build and repair worst case wheels. However, aluminum is fast replacing brass on higher performance wheels, reducing rotating weight and offering a range of decorative colors. Square is wrong for aluminum which is softer than brass. At the very least, decorative anodizing is too easily scratched, even during careful builds.
Stripped and deformed aluminum nipples are common, driving a backlash back to brass. With a spline drive, an aluminum nipple can resist more twist force than ever needed. In fact, a spline nipple fails only after its spoke snaps from the torque. You will never see a spline nipple torque failure. No wonder both Mavic and DT regularly use splined nipples of their own design.
To be precise, the drive standard on our nipples is compatible with Spline Drive of the 1990’s. An attempt was made to commercialize splined nipples by entrepreneurs in Southern California. Perhaps their approach was flawed, certainly the industry was not yet ready. They closed up but not before thousands of builders used them with many considering it superior.
Our standard is described in US Patent 5673976. Technically speaking, it’s not a spline but, instead a ribe drive. There is no wavy curve to the contour (like Torx). It resembles a freehub body with all driving surfaces meeting squarely. Enormous amounts of metal need to move in order for the drive to strip.
This wrench delivers more torque, engages every 60°, and won’t slip off the nipple by tipping away (fewer wrench drops). We offer one model in the familiar chromed wire loop, Park-type shape. Other styles will become available during the year. Though we are currently the World’s only source of 12mm aluminum spline nipples, this won’t last for long!
Now is a great time to dive in and enjoy this building option. Sleek, light, smart, and faster to build!
The Golden Nipple
At NAHBS 2016, we made a huge gold nipple from poplar. Below, it takes shape in Jon’s MT shop. By now it has been seen Worldwide thanks to journalists and other fans of the unexpected!
If your tensiometer grabs a spoke but the spoke thickness is not what’s expected, what happens? No surprise, the tension reading is WRONG. The news is how huge these errors can be.
All commercial spoke tensiometers read spoke thickness as well as deflection. The ONLY exception is the Wheel Fanatyk (Jobst Brandt) design. For all others (DT, Sapim, Park, Wheelsmith, Pillar, CN, Icetoolz, Hozan, Union, Centrimaster, etc.) spoke thickness is a major part of the reading.
Drawn wire is not as precise as one might assume. 14 gauge, for example, varies commonly from 1.96 – 2.02mm. Swaging (for butting) and forging (for blades) is also imprecise for dimension. Sapim publishes the CX-Ray thickness as 0.9mm. Many would admit this is often 0.95mm. Such variation is within normal spec but wreaks havoc on tensiometer accuracy.
Painted spokes are popular. Paint thickness varies all over the map, even within small batches. The chart below shows some careful (but limited quantity) measurements and the reading errors they induce.
For white CX-Rays, batch 1 and 2 were far apart but similar within the batch. Perhaps batch 2 was double coated? This would make for an extra rugged finish, hardly a spoke company error. But attempts to read tension go haywire.
Do not over-analyze this chart
These specific predictions are not the point. It is the principle that needs addressing. Spoke thickness (at the location the tensiometer is working) can be all over the map these days. To avoid huge tension measurement errors you have limited options.
(1) Rely on your trained sense of appropriate tension (comes with practice) to avoid big mistakes. This is especially effective if you have years of experience, have made many learning mistakes, and are familiar with the components in hand.
(2) Measure the spokes in your wheel before you use your tensiometer. The best way to determine thickness is not a basic vernier caliper. You want 0.01mm accuracy which can be consistently delivered by a micrometer. You need to know average thickness and approximate range.
Inferring correct tension from a measured thickness discrepancy is not so simple. Common sense leads in the right direction but tension vs reading is not linear and knowing the shape of the underlying curve requires a fair bit of math. A simple engineer’s task but daunting for so many tools, spokes, paint, and for each wheel. Certainly limited insight is better than blindness!
(3) Switch to Jobst’s design where NONE of this has ANY effect. Thirty years ago he wanted tension reading free of spoke thickness. With this priority in mind, many possible tensiometer designs are useless. The position of a deflection load, points of contact, and indicator location make a design vulnerable or immune to spoke thickness variation.
It is not a stretch to assume tensiometers of the future, whatever their appearance, will take care to isolate the deflection from thickness. Errors like builders are now suffering are entirely avoidable. There is no associated cost to a correctly designed tension measuring tool.
During NAHBS (2016) I was fortunate to learn about wheel building at Edco in Switzerland from Randy Kilgerman and Rob van Hoek. They use Hozan tools and painted spokes in some wheels and I worried about the possible tension errors as Hozan is vulnerable (like nearly all others) to spoke micro thickness variation.
They assured me, good engineers that they are, this is well understood and they calibrate their tensiometers to the spokes used. Their own calibration “chart” accounts for the painted spokes additional thickness (assuming it is consistent).
How many of you make your own calibration charts for particular examples of painted (and bladed) spokes? Spoke tension is not the end-all in wheel building but it is beyond silly to spend time measuring or discussing spoke tension if accuracy is absent!