@Emilio-Megamo Reason Right, physics not vibes - let's do this properly.
The fork swap (BB height)
Your stock fork (Fox 36 Float AWL HD, 160mm) has a verified axle-to-crown of 571mm on the 29" version. A Fox 38 at 170mm travel sits at 583.7mm A2C. That's a Δ of
~12.7mm longer, not the 10mm you'd assume from travel alone - the 38's crown is physically taller than the 36's.
That extra length runs along the steerer axis, which sits at your head angle (63.5° from horizontal on the Reason). So the front end doesn't rise by the full 12.7mm - it rises by:
Δfront ≈ ΔA2C × sin(HA) = 12.7 × sin(63.5°) ≈
11.4mm Then, because the rear wheel stays planted, the whole frame rotates about the rear contact patch rather than the front rising in isolation. BB rise is that front rise scaled by where the BB sits along the wheelbase:
ΔBB ≈ Δfront × (chainstay / wheelbase) On the
M frame (chainstay 454mm), using the verified geometry, that ratio is roughly 0.35 - 0.37 depending on exact wheelbase for your size - so:
ΔBB ≈ 4mm rise (ballpark - tell me S/M/L and I'll tighten it up, since wheelbase is size-specific and I don't want to fudge it)
Head angle will also slacken, by roughly 0.4 - 0.5°, for the same geometric reason.
Climbing - what actually changes
The BB/HA shift from the fork is small enough on its own to be background noise. The bigger climbing effect is your
55mm rise bar - that doesn't touch BB height at all (it's a cockpit change, not a suspension one), but it moves your hands up and back, which shifts your weight rearward. Combined with the slacker head angle putting the front wheel further out, expect:
• Steep techy climbs: front wheel gets light/wanders more easily - you'll need to consciously weight it, more than you do now • Smooth fire-road climbing: negligible difference, arguably more comfortable seated
• Standing/technical low-speed balance: very slightly less precise front-end feel None of this is a reason not to do it - it's just what you're trading for a burlier, more travel-forward front end. If you're mostly riding techy enduro terrain rather than long fire-road grinds, that trade is usually worth it.
