Re GB metal guards, I would like to prevent stress fractures, but also would like to hear of others' experiences of how they have used the provided attachment bracket to attach the guard to the seat stay.
What type of seat stay does it fit? It is like an approx inch diameter disc, with a small cylinder protruding out of it, with a longitudinal bolt hole. But the cylinder isn't tall enough that the inch-diameter disc bit doesn't foul the seat stay, if that makes sense?
So, when I got some about 6 months or so ago I used a custom L-bracket - made out of some 2mm x 15mm steel that I just bent to the right angle.
Thought that would be fine, but it's resulted in a crack / stress fracture. Initially it went a bit rusty like this and cracked its way off the bolt:
So I basically hammerited it, replaced the bottom washer with a larger 'plate' and put it back together. This was fine for a bit, but has now resulted in a crack all the way across:
I thought I'd already done the most important thing to prevent stress fractures which is to make sure the guard isn't under stress i.e. being held in position against its natural tendency - i.e. if I remove the seat stay bracket, it stays in the same position, instead of springing into a different position
Other measures I can think of:
don't mount a light on (it's one of those very small dynamo ones intended to be mounted on mudguards)
don't mount mudflap on (it's a GB one)
put an extra stay on (I will have one spare - although this could put stress on the dropout due to the need for a longer bolt to go through both)
use a double bolt attachment like I have on the front one:
But not sure which of the above are most effective/necessary. Thought one of the main benefits of metal mudguards was that they were stronger but if they still crack what's the sodding point! I'm going to try one more pair cos these do have the advantage of being good looking, very well shaped, and actually pretty quiet and rattle free apart from the 'clonking' due to this issue, but if they crack again I might have to just go back to plastic with one of those 'bridge' affairs and just make do with a seat post mounted light.