Top Cap Problem
 

Hey everyone,

For Christmas, I got an awesome top cap for my bike. The problem is the stem bolt on my 90's fast track trek is a quill stem that uses an m8 bolt. From the research I have done, all modern cap sizes use an m6 bolt. The only thing I can think of using is an m6 bolt and an adapter to use with the expansion wedge. I have looked online but can't seem to find a M6 bolt that is 160mm long let alone a m6-m8 adapter that will work. Has anyone had any success with navigating this problem?

Thank in advance!

Setting aside the fact that top caps for threadless stems are incompatible with quill stems, the top cap bolts for threadless stems use an M6 bolt because their only function is to adjust play out of the headset. That's why the first versions of Suntour's AheadSet system used plastic top caps: lightweight and appropriate strength for the application. (Later versions used aluminum top caps because end users---and plenty of bike mechanics---didn't fully understand how AheadSets differed from conventional headsets and objected to the plastic caps.)

The M8 bolts in quill stems require much higher torque loads to hold the stem in place in the fork's steerer tube. The use of M6 bolts in that application would result in loads dangerously close to the strength limit of the bolt.

Trakhak,

appreciate the information...exactly what I needed to know, especially regarding the torque limits! I'm bummed I won't be able to use the cap, but I would rather not risk the bolt failing for something aesthetic. Now the harder step will be convincing the wife I need a new bike so I can use the cap ;)