Compared with some of the other projects that we have become involved with, building a gravity bike is a real doddle.

We followed Dr. Neil Farrow through the process of building a Gravity Bike. The completed bike worked so well, Neil clinched a third place position in the Highland Extreme 2002!

	Neil started with a standard 20" BMX bike. He then stripped the bike so that he could invert the frame (i.e. simply flipping it 180 degrees). Inverting the frame CAN sometimes increase the rake of the front forks and make things less twitchy - but it depends on the type of frame you are using. Now that the bike is complete, Neil is considering flipping the frame back upright to see if it improves the handling... hmmm we will keep you posted on the findings.
	Seat: The seat post was removed and welded into the new postion. The new top mount is just behind where the crank used to sit. Neil left the seat post low in order to leave enough ground clearence just in case he wanted to flip the frame back upright. This seat is from a mountain bike which will do for now - a lengthened seat may be fabricated later.
	The base of seat post was welded into place as shown. Neil made new knee rests which slide into the old frame and are held in place with the old collar clamp. This pict also shows how the new rear brake was mounted.
	Knee rests: here is a photo of the knee rests which were easily fabricated. Ensure the tube section is the same diameter as the old seat post. Pads were made from pipe insulation and held in place by good old gaffa tape. We love gaffa tape.

	Wheels and tyres: Being a gravity bike there is no need for sprockets and a chain so they were removed. The rear rim was straigntened, and the bearings were in good condition so they were greased and refitted. New inner tubes were installed and Maxxis Ringworm rubber was fitted. The tred pattern looked like it could cope with some serious lean angles which is encouraging.
	Brakes: The old brakes were not up to the demands of this sport so new V-brakes were installed. This photo shows the 'adaptor mounting plate' and the new front V-brake in place. The pipe clamps which hold the equipment in place look a bit er... 'home-made' but they came with the kit and that's how they are supposed to look
	Rear brake: again an adaptor plate was used to mount the new V-brake. Disk brakes would perform better than V-brakes... but they were not an option since we were working on a limited budget.
	Handle bars: Neil used the handle bars from his Yamaha LC racing motorcycle. He is working on a new set of bars which will be positioned more forward, enabling him to be more speadout (i.e. less crouched up) and aerodynamic.

Before

After

Frame flip: Neil would like to try flipping the frame back to its origional position to see if it makes the bike more stable (its a bit twitchy at speed).

Steering dampener: Neil would also like to install one of the steering dampeners from his racing motorcycles to help make the front end more planted.

Consider buying a new BMX bike with good V-brakes, or disk brakes and possibly a suspension if the price is right. Remember a cheep suspension might not be up to the job so budget for rebuilding or replacing.

Disk brakes are recommended if you are going to be racing on courses where heavy breaking is required or in hotter climates. As with all bikes, something like 95% of your braking power is from your front brake, so if you can afford just one brake upgrade, make sure you invest it in the front.