Bumpers
As you will see from the pictures of my kart, I didn't bother with bumpers. Mostly because of my lack of time and of course a Pipe Bender etc. But for anybody else's Kart I'm sure it is a must, even if it was only to be for aesthetic purposes. There's not much I can say, that hasn't been said about bending in the "Chassis" section. My only advice is:
If you don't have or have access to a pipe bender Forget about it!.
But here are the measurements anyways for those who are fortunate to have access to a pipe bender. All the piping used should be at least 25mm thick, especially if your using thin walled pipe. For thick walled pipe around 2-3mm I'd suggest heating the pipe until it was RED before trying to bend it.
A nice option would be to use Chrome plated Bumpers as that's what they have on the fancy racing Karts. It would look a nice feature, especially if the Pedals were also Chrome plated.
