130Kg on a 2012 Brompton

[Brucey]

This may also be construed as a negative post but if the stresses exceed a threshold value often enough, you can be above the fatigue limit long enough to nucleate a crack, and once that crack is started, it will likely propagate even at lower stresses.

A few dozen high stress cycles can be enough to start a crack off, and once it is running the cycles pile up at a rate of knots. Pedalling stress cycles are of the order of one million per 4000 miles (for a one legged pedaller....) and wheel stress cycles pile up much faster than that; about five million cycles over the same distance, riding a Brompton.

Folding bikes almost invariably have higher local stresses than more conventional designs; the Brompton is a better bike that most folders but it is not an infallibly strong object; they can and do break, just less often than most other folders.

cheers

[horizon]

As discussed previously on this forum, aluminium has no fatigue limit, and will eventually fail. We don't know whether this will be in 5 years or 20, becuae it depends on very many things, but for a bike that is regularly heavily loaded, it will be sooner than for one that is lightly loaded.

There is no reason for a well-designed and correctly built steel frame to fail until it is significantly damaged by rust, even if the load it is theoretically designed for is somewhat exceeded.

The OP was talking about a Brompton (which is steel) so I've perhaps unfairly diverted the thread towards aluminium folders. Having said that, AFAIK nearly all folders are aluminium, even the renowned Airnimal. AIUI, this is a reflection of the design challenges inherent in a folding frame - you want lots of large, strangely shaped bits. But ironically it is the 16" wheel Brompton which I reckon is less suited to heavy duty travelling on rougher roads. I generally carry about 16 kg on my Tern (four panniers with overnight work stuff, no camping). It doesn't do a huge mileage (it was bought to enable me to go on trains) so I feel reasonably confident about it. But as you say, one day it will fail.

[s1965c]

One thing to consider is that a six year old Brompton still has a considerable cash value.

Rather than take a risk on it surviving, the OP could sell it and find something more suitable to restart his cycling career. I'm a big fan of roadifying steel 90s rigid MTBs for that kind of use. You can end up with a tough, strong bike for buttons especially if you go for a 7 speed freehub model.

[Gattonero]

One thing to consider is that a six year old Brompton still has a considerable cash value.

Rather than take a risk on it surviving, the OP could sell it and find something more suitable to restart his cycling career. I'm a big fan of roadifying steel 90s rigid MTBs for that kind of use. You can end up with a tough, strong bike for buttons especially if you go for a 7 speed freehub model.

I agree with that, but keep in mind there may be reasons why a folding bike was chosen in the first place. I like my Bromptons, but they are a different thing from my other bikes, i.e. I won't do my 20 miles commuting every day on a Brompton but a "rescued" single-speed bike works better for me.

[Cunobelin]

I have a 1994 Brompton T6 that is doing fine with regular use and a similar weight burden