I looked at a new bike last summer (2019).
The literature of cycling and bicycle manufacturing is vast. The Guardian published a survey and list of printed works in 2016. Some books and resources address innovation and engineering:
- David Herlihy’s Bicycle: The History;
- Article – The History of the bicycle (2012) at https://engineeringsport.co.uk;
- The timeline page The History of Bicycles at Bicycle-and-bikes.com;
The single speed bike with coaster brakes was the common bike for much of the 20th century. Many books are about competitive events – or the special bikes used in competition. Racing on tracks and roads became the most visibible use of bicycles at the end of the 19th century.
Much of the innovation for riding on trails and rough roads came in the mountain bike sector in the last 4 decades of the 20th century: frame design, wheels, wide tires, cleated tires or knobby tires for traction in mud and on climbs and descent on bare ground, wider gear ranges, more efficient brakes. Mountain bikes have been discussed in books, but seem to have been discussed in on the internet – for instance in inteviews and discussions like The genesis of the mountain bike, according to Tom Ritchey, published at Handbuilt Bicycle News in September 2016. [Update – August 2021. The Cyclist Magazine’s Podcast Episode 34 interviewed Tom Ritchey in two parts on July 8, 2021 and July 16, 2021. ] Special gear was developed – e.g. frame bags for mixed terrain cycle touring (i.e. bike-camping or bikepacking). Mountain bike races on unpaved roads and trails, touring on back roads, bike-camping and adventure rides became popular. Mountain bikes permitted new kinds of competiton. Cross-country mountain bike (XC) races became organized, and competition became specialized into XC, downhill, endurance and other events. Endurance blossomed into multi day ultra distance events along difficult and challenging routes such as Tour Divide and Trans-America
Cyclo cross (CX) racing is a well established competitive version of cycling. In the 21st century, cyclo-cross bikes are racing bikes with wider, knobby tires for traction and other features for races off of paved roads. As road bikes tended to use narrow tires at high pressure, road bike frames often did not have clearance for the right tires. Some mountain bike innovations were adopted to design and manufacture cyclo-cross bikes, including tire clearance. Cyclo-cross bikes retained nearly horizontal top tubes, for reasons related to conditions of those races. For some applications, users and shops began to adapt and develop monster-cross bikes.
Road bike riders began to use unpaved roads more extensively for training and recreation, and to participate in Ultra cross and endurance events on rough roads. Randonneur rides became more common. Gravel grinders – races or endurance events on gravel roads. Some custom bikes and adaptations provided some advantages in such events. Gravel riders started blogs or published on sites like Gravel Cyclist.
Salsa (a subsidiary of the conglomerate QBP released the Fargo, a fat tired bike with drop bars, a “mountain touring bike” in 2009 (it has since become favoured as a touring bike), the Vaya gravel/touring bike in 2010, and the gravel racing Warbird in 2012. Other manufacturers moved into gravel bikes. Production gravel bikes incorporate many technical innovations from road, mountain and all-road: disc brakes, threadless headsets, internal frame routing for cables, indexed shifting integrated in the brake levers, tubeless ready wheels and tires. Gravel bikes with disc brakes will usually have thru-axles (as opposed to quick release skewers). Thru-axles fit to closed drop outs with threaded fittings for the axle at ends of the fork blades and the rear stays. Some have suspension forks in the front; some manufacturers have some types of rear suspension.
The features of gravel bikes:
- wider tires than road and cyclo-cross bikes. Most new gravel bikes are shipped with cleated/knobby tires – an imitation of the way mountain bikes a shipped;
- most gravel bikes have drop bars; the drop bars are often wider, flared, and shaped differently than the drop bars on road bikes (article at Bikepacking.com);
- the geometry is different;
- gear combinations for moderately fast riding and moderate climbing:
- a single chainring or a two ring set similiar to a road bike compact -a large ring with 46 teeth (instead of 50 or 52) and an inner ring with 30 teeth;
- 10 or 11 cog rear cassettes. a range from 11-32 teeth would be normal. Riders can customize for small increments or larger gears for climbing.
- eyelets for frame bags, and for racks to carry panniers
Bike Insights describes the typical attributes of all-road/gravel bikes:
- Wider, smooth or treaded tires, typically from 38-48 mm;
- Trail (a design geometry concept related to the head tube angle and the responsiveness of steering) around 57-71 mm for improved handling off-road;
- Short to mid-length chainstays of 421-443 (Touring bikes have longer chainstays to allow riders to carry panniers in rear racks).