I know there are a few frame designers and engineers on here, so I thought this might be an interesting question:
taking the headtube as a prime example - how much of a safety margin is built into the strength of a frame?
With the new regulations and testing for the EU, perhaps this is even clearer.
An example:
A frame is built for a 130mm fork, but sold to the general public, let's say without an upper weight limit. This assumes that a rider could be anywhere between 50 and 140 kg. So if an average rider is 75kg, a rider of 140kg puts 87% more strain on the head tube.
Compare this to putting in a much bigger fork, say 180mm in the frame designed for 130mm. If the 130mm fork was 500mm axle to crown, and the 180mm fork is 550mm, then this is only a 10% increase.
So by this logic, even a 100kg rider could put a 180mm fork in their 130mm frame and 'only' put 43% more strain than the average 75kg/130mm fork option. So well within the safety margin of 87% for a very big rider.
Does this mean that it's almost always going to be ok to put bigger forks in frames that aren't specifically as light as possible? (assuming you don't mind any geometry changes.)
