2012 Olympic Mountain Bike course launched

Essex course given thumbs up by UCI

The London Organising Committee (LOCOG) revealed the partially completed mountain bike course for the 2012 London Olympic Games late last week. The 550-acre Hadleigh Farm, near Basildon, Essex, in the United Kingdom will host the race.

Construction began in July and is expected to be finished in the spring of 2011. The venue consists of open, grassy hillsides and has few natural technical features.

"It is fantastic to be able to see the course taking shape as our Olympic dream becomes a reality," said Essex County Councillor Stephen Castle, Cabinet Member for the 2012 Games. We are committed to delivering a first class London 2012 Olympic discipline and a course that will test the world's finest Mountain Bike riders. I look forward to seeing further developments as we get closer to the 2012 Games."

Hadleigh Farm was chosen to host the mountain bike racing after the originally proposed course in Weald Country Park was rejected in 2008 as not challenging enough.

The UCI's Technical Delegate Peter Van den Abeele said, "Following a recent visit to the ... venue, we are extremely happy with the work that is happening on site. Great progress has been made which reflects exactly where we want to take the sport over the coming years, making the course more accessible to spectators and improving television images. We are confident that the combination of technical climbs and steep rocky descents will provide a stunning, challenging course for mountain biking and that it will be a great event in London 2012."

Organizers have brought in 500,000 tonnes of rock and are building technical obstacles and drops to challenge racers.

The course will have 70m in elevation gain - more elevation change than that of the 2008 Olympic Games in Beijing, China, according to Bike Radar. In total, the course will cost 800,000 pounds to build.

The course, which is on land owned by the Salvation Army and Essex County, will be about 5km in length and is expected to accommodate 20,000 spectators. It is being delivered by Essex County Council in partnership with the London Organising Committee of the Olympic Games and Paralympic Games (LOCOG).

"Hadleigh Farm is a stunning venue, in line with our concept of a compact Games and it will have an excellent legacy. I am very grateful to Essex County Council and to the Salvation Army for their hard work in making this venue happen. The course is shaping up to be a challenging one with multiple climbs and descents. I believe that the mountain bike competition will be one of the most exciting events at the London 2012 Olympic Games," said Sebastian Coe, LOCOG Chair.

"The course is great - much hillier than I expected," said Maddie Horton, who won the silver medal at the 2010 British National Championships, to Breaking Travel News. "I've ridden World Cup courses before, and this is definitely up there with the toughest."

The Olympic distance cross country mountain bike race will take place on August 11-12, 2012. Approximately 50 men and 30 women will compete for Olympic medals in a two-hour race. A pre-Olympic test event is expected to be run on the course as early as the summer of 2011.

Basic tickets for the Olympic mountain bike race are expected to cost 20 pounds and will be available for purchase in March 2012.

A separate legacy plan is being developed for how the venue will be used following the 2012 Games.

Source: cyclingnews.com

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iligan city downhill race (09.27.09)

mixing/matching tires

Most bikes come with identical tires front and rear. This is all right for general use, but if you want to optimize your bike, you should consider using different tires front and rear. The front and rear tires have different loadings and different requirements.

Narrower Front, Wider Rear

If lightness is the primary goal, tire width/weight is limited by the risk of pinch cut flats, a.k.a. "snake bites." Since there is more weight carried on the rear tire, you can get away with a slightly narrower tire in front than you can in back.

Wider Front, Narrower Rear

A wider front tire makes sense in many applications, however, when handling and ride comfort are considered. A wider tire will generally provide better cornering traction than a narrower one, assuming appropriate inflation pressure. 

A wider tire also provides superior shock absorbency. I personally prefer a slightly wider tire in front, since I suffer from some wrist discomfort on occasion.

Off-Road Issues

Bikes that are used some of the time on loose surfaces often benefit from a wider front tire, with a fairly agressive tread, coupled with a somewhat narrower, smoother rear tire. 

The wide, knobby front tire will provide the all-important front wheel traction. If your front tire skids, it almost always leads to a crash. For riding in soft conditions, such as sand or mud, a wide front tire is essential. If the front tire sinks in and gets bogged down, you're stuck. If the front tire rolls through a soft patch OK, you can generally power the rear through to follow it.

The narrower, smoother rear tire will have lower rolling resistance. Since most of the weight is carried by the rear tire, rolling resistance is more important on the rear than the front. If the rear tire slips, in most cases the worst that will happen is that you'll have to get off and walk.

This is a great idea that developed out of BMX racing.

Some mountain bike tires come in matched sets, with diffrerent tread front/rear. The front tires tend to have the knobs set up more or less parallel to the direction of travel, for improved lateral grip and better steering control. The rears tend to have transverse knobs for driving/braking traction.

source: http://www.sheldonbrown.com/tires.html

bottom bracket: interface types

Square Taper
This is currently the most popular design by far. This interface consists of a spindle with square tapered ends which fit into square tapered holes in each crank. Tightening the two together creates a relatively efficient and simple interface.

Octalink

This system was designed by Shimano. The Octalink system provided a greater contact area between crank and spindle, so it had a stiffer interface. Octalink exists in the marketplace in two variants, Octalink v1 and Octalink v2. The difference between the two can be seen by the depth of mounting grooves on the bottom bracket spindle. XTR, 105, Ultegra 6500 and Dura Ace 7700 cranksets mate to version one bottom brackets, while more recent mountain bike designs use the deeper-grooved version two. The system is proprietary and protected by Shimano patents and licence fees, thus relatively few companies aside from Shimano produce Octalink cranksets. Many competitors have adopted the square taper and ISIS designs as an alternative. In use, Octalink has been shown to loosen because it is not a taper-fit but merely a tight spline fit. Reverse torque loads can cause the crank bolt to undo, and the crank can be irreparably damaged if this is not checked.

ISIS Drive

ISIS Drive, the International Splined Interface Standard, is an open standard splined specification for the interface between a bicycle crankset and the bottom bracket spindle. It was created by King Cycle Group, Truvativ, and Race Face in response to the proprietary Shimano Octalink splined bottom bracket standard. Because the Shimano splined interface is covered by patents, the ISIS Group created the standard and put it in the public domain so that other companies could make interoperable components. As the standards are separate, parts made for one are incompatible with those made from the other; an Octalink-standard bottom bracket (8 spline) cannot connect to an ISIS crankset (10 spline) and vice versa. One shortcoming in the design of the ISIS bottom bracket is the decreased bearing life compared to square taper bottom brackets. This is because it uses a larger diameter spindle in the same sized shell, so the bearings are smaller. Arguably, it was this shortcoming that lead to the development of external bearing designs.

Outboard / External Bearing

Many current designs are now using an integrated bottom bracket with outboard bearings. This is an attempt to address several issues associated with weight and stiffness. Because of the relatively small 1.37" (36 mm for shells threaded to the Italian standard) diameter shell, designs that place the bearings inside the shell can either have large bearings and a thinner spindle, which lacks stiffness, or smaller bearings and a thicker spindle (such as the original Shimano Octalink), which is stiff but less durable. External bearings allow for a large diameter (hence stiff) and hollow (hence light) bottom bracket spindle. They also offer more distance between the two bearing surfaces which contributes to stiffness while allowing lighter components.

source: http://en.wikipedia.org/wiki/Bottom_bracket