I have three forks I am considering using for a bike build project but I am a bit confused as it seems like the mouhting holes despite being 74mm apart use different bolts m5 vs the m6 bolts in my current gravel bike..also the mounts are not raised/angled like the mounts on my other bike fork
by AltAmericanCarnage
7 Comments
They are flat (not post) mount and require the front adapter for post mount calipers and forks.
They are all post mount. But post mount really just means the way the Calipers screw into the mount. The different mounts could be to accommodate different size rotors, which would make them look different and use different hardware.
I don’t know if that made sense. Also please correct me if I’m wrong. I’m trying to learn as well!
Cheers!
They would all appear to be flat-mount. Generally those would use M5 bolts, while the bolts for adapter itself and the brake would be M6. If I’m not mistaken.
Maybe you measured wrong?
M5 are usually for 70mm spaced holes for flat mount adapters. Road forks sometimes come with a flat mount or the 70mm spacing mount for flat mount adapters. There are also some brakes that directly fit on the 70mm spacing fork mount, they are weird.
M6 and 74mm spacing is post mount.
It’s a road style flat mount. Went down this rabbit hole myself.
https://www.twohoosierscyclery.com/trp-ff-5-fm-adapter-front-140mm-or-160mm-flat-moun.html?srsltid=AfmBOooZpcVTszTFTL9tooPqwzJUfBZ1yhZNu2uzUcFQphP6VY5KHQNR
Measure center to center. Edge to edge will give you about 74. There are exactly 0 post mounts that use m5
How sure are you that you’re measuring the bolt spacing to be 74mm? Because the fork on the left appears to be a Suntour GVX, which is a flat mount fork, but that means the bolt spacing should be 70mm – not 74mm.
You need to measure center to center, not outside edge to outside edge.
None of these forks look like post mount. Most post mount calipers extend a bit below the mounting surfaces, which is why (as their name implies) post mounts are usually on *posts*. I don’t see that here. The fact that they’re M5 also suggests that they’re not post-mount.