What's new at sheldonbrown.com
We have added to our page about on-road repairs. There is now a quick list so you can check which particular tools you might need for your bicycle, and we have covered some additional tools.
The basic on-road repairs will get you home or to the next bike shop on your bike, almost every time. If you can’t find the time or inspiration to learn them yourself, you might ride with someone who did!
Introducing ShelBroCo QuadraTech Chainrings and sleeve nuts.
Throw away those obsolete chainrings! The unbearably vexing problem of sleeve-nut rotation has bedeviled generations of bicycle mechanics. Who else would you expect to come up with a solution but ShelBroCo?
We have added new sections on derailer maintenance to the derailer adjustment page, including how to cannibalize rear derailers, being careful about compatibility, and how to check cables, 
We publish another paper by Osman Isvan. He uses a simplified model with only 3 degrees of freedom and simulates system frequency response under steady-state and transient conditions. He investigates the effects on vibration isolation of several key parameters including tire pressure, frame compliance and riding position. The graph below from his paper, one of several, shows results when tire pressure is changed.
A few months ago, a reader prompted us to make some updates to our chainwheel bolt circle cribsheet. But now we have followed up on that effort, greatly expanding our coverage, and we have added a set of templates which allow you quickly to identify the bolt circle of alnost every model of chainring, and the tooth count, without the need to measure or count by hand. It’s all here: https://sheldonbrown.com/cribsheet-bcd.html. Example template is at the right.
If you can correct any inaccurate information or you can identify a chainring that we do not cover, please let us know. We are not too proud to take corrections, and we’ll even credit you on the site for your contribution!
New article about the GoPro Hero5 Session action camera, latest in our series of articles about shooting video from a bicycle. This is a very small and light camera which will not weigh down a helmet and is especially good for use on a drone. It has some advantages and disadvantages worth knowing about.Note: the photo may be larger than life size! The camera is about 1 1/4 inches on a side.
Older smartphone no longer maps bicycle routes well? Rides are recorded as 173,000 hours long? (Really!) New article by our friend Mark Sevier explains these problems and offers some solutions.
We have reviewed the bolt circle diameter cribsheet, checked bolt-hole spacings using trigonometry and made some corrections. Apparently, the spacings were measured rather than calculated based on angles — and measurement is never exact! We have also added entries for several new patterns. Some of the new ones with uneven spacings had to be reverse-engineered from photos and, though we think that we have them right, we welcome feedback.
Osman Isvan takes a deeper look into hills and winds.
Osman analyzes data from over 1000 of his own bicycle rides to see what they show, and describes what might be discovered by mining the huge troves of data held by Strava, RidewithGPS and other GPS-based mapping services. Osman makes a particularly trenchant suggestion for e-bike design based on his analysis, and discusses issues of data privacy. Find this along with Osman’s other articles at https://www.sheldonbrown.com/isvan.html
