April 20, 2019 2 Comments
This is the motto of iGaging, one of the largest makers of measuring tools (who incidentally have no monopoly on accuracy). They're one of many top companies doing great work in this very important field. Bicycle mechanics are in the most technical era of our industry but accuracy has never been optional.
Going back to the 19th century, bicycles were among the first widely used machines with precision. Ball bearings and tensioned wheels depend on tolerances that were tighter than engineering of the past. Ever since that time, mechanics are accustomed to frequent measuring while building and repairing bikes.
A rule in measurement—whenever possible use tools that are more accurate than you strictly need. Granted, much bike work can be done without measurement, experienced eyes can judge, compare, and test without knowing the precise numbers. Today, however, mechanics want to understand quantified guidelines, follow (and sometimes bend) them, keep records, and perform useful testing.
Here is some advice and observation about measurements in today's bicycle world.
Get a micrometer
I was an overachieving bike mechanic for 30yrs without owning a micrometer. Today it's a necessity for me. We've all depended on vernier calipers but, frankly, we often called them "guess sticks." They are made to a variety of qualities, regularly nearly given away as promotions, and frequently barely work. They read to the third (0.001mm) or fourth place but are often not dependable to 0.01mm. At times we need better.
Spoke threads are a good example. Wire for 2.0mm spokes varies from 1.97 to 2.02. You need to detect and understand this. Builders report oval wire in blanks—can you find these? Thread outside diameter identifies how deep or shallow the thread form which affects building.
Especially for axles and pivot shafts, we need 0.001mm accuracy. When bearings are involved, such measurements are essential. Hydraulic pistons and bushings are likewise precise beyond verniers.
Would be nice to own a vast set of micrometers but just start with the one you'll use 90% of the time, 0-1" (0—20mm) is a typical size. We now carry one of iGaging's excellent digital micrometers. One belongs in your toolbox.
Rulers and tapes
Measure spokes to 0.5mm accuracy. Spoke length programs give such numbers so why are spoke rulers only marked in whole millimeters? Knowing a precise length is critical if you want to round up or down in your build. No spokes are particularly accurate (unless you cut them yourself) so know the length to 1/2mm. Here's a ruler with such marking.
Tape measures are essential in any workshop and get lots of use by mechanics and salespeople. They are also often not accurate! There are well developed standards for measures that professional mechanics need to appreciate. Find a measure that you trust and keep it near. Don't just scramble for any measure hanging around, the way we do for pens. For a professional mechanic a tape measure is a precision instrument.
We're in good shape here as smartphones host a variety of excellent and accurate angle apps—little need for separate tools.
In precision mechanisms, much that matters is difficult or impossible to see with the naked eye. Pitting in races, threads on small fasteners, cracks and chips in frames—all of these benefit from magnification. Get yourself a good 20-40X magnifier. Good news: iPhones iPads have a built in magnifier that is fabulous. Android may also. Check this Wheel Fanatyk product.
We use scales all the time as no sport is as weight conscious as cycling. Measuring to 1g accuracy is common but you deserve more! Get a scale good to 0.01g. No worry about limited capacity, you can't have such accuracy except in small scales. Small scales good to 0.01g are great for fast counting (nipples, washers) and precise mixing (epoxies). Such accuracy is cheap, often no more than $20.
Tightening force is the watchword of today's bicycle mechanisms. Make sure you have multiple excellent devices. There are many stars in the torque measurement world. Beware of single torque tools as some cheap ones are unreliable if dropped. Have unimpeachable tools to test these against. One particularly appealing kit is by Wera, the German turning tool powerhouse. They have a great attitude and just launched bicycle-specific products. We now carry this comprehensive torque kit. Get one or equivalent and don't be guessing anymore.
Spoke tension gauges are the favorite tools of many mechanics. Own several, get them recalibrated, treat them with respect. What a treat to know precisely what is going on with tension, an otherwise invisible force that directly affects wheel performance.
A plucked spoke's tone is a direct link to its tension. Many of us wear guitar/banjo finger picks while building to make comparisons. The harmonics of a complete wheel make it difficult to directly translate tone to tension but the principle is real. A Spoke Tension Gauge app for tone is available for iPhones and iPads. I have not found it accurate enough to replace tensiometers but you should buy and add it to your bag of tricks.
Hub and rim measurement
Don't use guess sticks and string! Have ERD and hub dimension measurement that gives you confidence. We have sold nearly 50 height gauge sets this year. Believe me, that is rather incredible considering what an obscure outpost of the industry we are.
Truing stand gauges
Stands need dial gauges even if you don't build with them. It's essential to know exactly what leaves your stand so when it returns in a different shape you will know. The biggest secret is using dial gauges from the start of a build. That takes non-linear readout that only P&K offer. Then you use the stand as your dishing tool, always adjusting the rim position towards theoretical center. When all adjustments are in the correct direction and never too much, build time can plummet.
If you want to know more about bicycles, reading road tests is not the quickest way. Do your own measurement and testing. Manufacturers talk about vibration, its absorption, its nature. Do you believe everything they say about frames, saddles, tire casings, tire pressures, seat posts, suspensions? Yet, how does one measure vibration?
iPhones and iPads can host "Vibration" a fantastic app that turns your smart device into a professional grade analysis tool. I've used it in wheel fatigue testing. You can strap or tape your device to a bicycle (or testing rig), for example, and record vibration frequencies, amplitudes, and changes with the accuracy of a $400 analyzer. Download results, alter your setup, and build a database. Be your own citizen researcher!
These are just a few measurement suggestions. Have you got some to share? What about tire pressure or moment of inertia?
November 02, 2021
Joshua at Silca makes reference to an Ashcroft digital pressure guage that’s good for a claimed + / – 1%. That’s a $400 guage ! Another thing that’s handy is a good units converter app and a table of decimal to fractional equivalents.
Great column, thanks Ric !
Comments will be approved before showing up.
November 02, 2021
so Ric what to do with this information?
‘Spoke threads are a good example. Wire for 2.0mm spokes varies from 1.97 to 2.02. You need to detect and understand this. Builders report oval wire in blanks—can you find these? Thread outside diameter identifies how deep or shallow the thread form which affects building."
how much variance is there in nipple threads ?
other then thread lubes , lockers , or products like Fix that can help some of the interface issues, what steps can be taken to head off issues like
a spoke that is a bit undersized and nipple thread accuracy since we can’t really measure, it is a bit of a random thing of chance that can create a possible issue if the spoke is undersized and nipple threads over sized .
I noticed awhile back a bit of variance in spoke diameter in some of our stock from the same manufacture.
any tips for working within these variances ? would thread depth on the morizumi affect this ?
just curious what you do with is information