A customer came to me with a problem. He was a big boy (over 220 pounds) and he was complaining about a harsh topout in his Magura Thor fork. This was a common problem with this particular air spring system. Many people have sent their forks back Magura to get fixed, only to have the same problem return some months later. The system Magura employs is really similar to a Fox Talas cartridge. It’s a travel adjustable air cartridge and like the Fox, it really isn’t known to be reliable, especially under heavier riders that require high pressures. So what’s the solution? A regular non adjustable air cartridge? That was an option definitely on the table but I don’t like air cartridges at all for heavy riders. You have to either have a self equalizing air spring to get the right negative air pressure or a coil negative spring. It’s all doable but heavy riders always mean high pressures and it makes for some highly stressed o-ring seals. Coil is always the most reliable. Perfect, I had a good old Fox Vanilla coil assembly ready for modification. Here it is beside the original travel adjustable air spring below.
There are some details that had to get ironed out before the Vanilla coil internals could fit inside the Magura fork. It needed a custom top cap, which I made from raw aluminum roundbar and machined in all the exact dimensions needed to fit the original Fox Vanilla preload adjuster knob assembly.
I also opted to make an aluminum negative spring perch that snaps into the upper tube using the stock snap ring.
Lastly, I needed to make a 10mm hexagon at the bottom of the Vanilla shaft in order fit into the corresponding hexagonal profile inside the bottom of the Magura casting. I made this hexagon thread right into the shaft, just below a threaded shaft extender so the fork is able to get full travel. There’s one more extender on the other end of the shaft, which isn’t very visible as its behind the negative spring.
So there you have it. The only other modification needed was to turn some material away from the black plastic spring guide, as I wanted the fork to be able to fit Rockshox coil springs, which are readily available in many rates even for the big boys.