What are these fork attachments?

[Mercianbloke]

In this article:

https://en.wikipedia.org/wiki/Bicycle_poverty_reduction

Almost every bicycle has a pair of rails from the fork dropout to the steerer, with a pair of springs at the top. What are these for?

 

[vcballbat]

I think they're brake drop compensating springs used to alter the angle of attack of the brake block in relation to the rim while riding on extremely bumpy terrain...or I may have got this complety wrong and I'm totally baffled.. :|

 

[Mercianbloke]

I was wondering if they're some kind of reinforcement, to reduce the amount of bend on the forks as the bike carries more than it was designed to.

 

[hamster]

They are meant as a kind of reinforcement and suspension. Do they work? No. It's just a fashion, like doubled top tubes which are also common. You see them on utility bikes in China too.

 

[adroitstif]

I agree it's principally fashion; as is debated often on this site, fashion dictates an awful lot of what we regard as normal. If XTR stuff is pearl-white in 2022, then the 2024 Carrera range will have white chainrings...

 

[danson67]

They are fork reinforcements/braces.

Generally not needed on forks made of decent chrome molybdenum or such, and are pretty much just fashion on modern girder forks such as Jones, Stooge or Black Sheep, but if you have some cheap forks made of mild steel, there is a considerable risk that the vertical loadings will overcome the yield strength of the material, and they will permanently deform (Bend), rather than just springing back.

This could be sorted by using a really thick wall in the fork blades, but that will ruin the ride quality and be harder to manufacture. So the braces are a compromise.
They are generally in straight compression & tension (rather than bending/bowing) as the fork blades flex, so can help the fork blades take higher loads by mechanically limiting the extremes of flex, thus preventing the fork material from going above its yield point and permanently bending.

All the best,