Fork Crown Width and height Dimensions (Fox Float 34 27.5+ and Rockshox Bluto)

I have to admit that I get a bit frustrated when component manufacturers have engineering drawings and/or specs for their components, but lack critical dimensions which they obviously have access to. If you are designing a frame while using one of these under-endowed drawings or spec sheets and you don't have the fork on hand yet, it makes the design process difficult. You are either left searching the internet for crown dimensions (i.e. wild goose chase with often suspect results posted by Gary from Kentucky [no offense, Gary, you're cool, I just don't trust you with a ruler]) or you're calling friends and bike shop contacts trying to find a fork to measure.

In an effort to remedy this, I'm going to post updated drawings of fork crowns whenever I get the chance. The first two on my list are the Fox Float 27.5+ and the Rockshox Bluto. I'll be sure to add more as they come across my work bench.

Fox Float 34 27.5+ Fork Crown Width Dimensions

Fox does a much better job than Rockshox in providing info. First, Fox has actual drawings of their forks. Second, all of Fox's drawing have axle-crown measurements along with some other stuff. That said, Fox still lacks fork crown dimensions. BTW, you can get access to Fox's fork specs and drawings on their All Specifications Sheets page (which is absolutely buried on their website). The Fox drawing of the Float 34 27.5+ is here. I'm kind of critical, what can I say?

As for the actual fork dimensions, take a look at the drawings in the Fox Gallery. The main clearance dimensions are the 105mm distance from the center line of the steerer to the edge of the knob on the top and the 18mm distance from the crown seat to the top of the protruding knob on the front. Because the fork stanchions are offset from the crown, the actual rotating radius (105mm) of the fork is greater than it's frontal radius (100mm).

If you want more to look at than the PNG of the drawing in the gallery, you can download a PDF or DWG of the drawing below:

Fox Float 34 27.5+ Gallery

Rockshox Bluto Fork Crown Width Dimensions

Rockshox is on the opposite end of the spectrum from Fox in terms of dimension provision. I just looked at their current Bluto fork specs and they recently removed the axle-crown dimensions (which are also rather important when designing a frame; axle-crown dimensions can be found here). There is no drawing. Maybe if I whine enough, they'll upload some drawings to their site.

Like the Fox Float, the drawing and some photos are in the Rockshox Gallery. The main clearance dimensions are the 125mm distance from the center line of the steerer to the edge of the knob (it sticks out past the crown when in the middle position) on the top and the 19mm distance from the crown seat to the top of the protruding knob on the front. Because the fork stanchions are offset from the crown, the actual rotating radius (125mm) of the fork is greater than it's frontal radius (110mm).

If you want more to look at than the PNG of the drawing in the gallery, you can download a PDF or DWG of the drawing below:

rockshox Bluto gallery