g32ecs wrote: ↑
Fri Sep 06, 2019 6:59 pm
I dont have the same understanding with geometry as you, but can you explain in more simple terms what you just said about 47 and 49?
Only asking because this tends to be my size with manufacturers. Currently using a Felt AR size 48 and I think it suits me well
https://feltbicycles.com/collections/ar ... 1180517494
I'm in search for an all rounder this time with emphasis on lesser weight, not much so on a more relaxed position
TLDR version: the Orbea size 49 will handle similar to your FELT. But different to most bike of larger sizes.
==== below are extra info about trail ====
the most dominant factor on how fast the bike handle (how easy it is to change direction) is trail value. It is a more dominant factor than wheel base etc. So we want to make sure a bike has trail value in range that make sense. Too low value (fast) and it is twitchy, too high trail value (slow handling) and it is sluggish.
Trail value is a product of head tube angle, fork offset, and wheel height (+ tire height/width).
There are multiple combination that create the same trail value:
for example 73deg head tube angle +44mm fork offset.
71.2deg head tube angle + 55mm fork offset.
Both handle (nearly) equally fast because of same trail value=58mm despite the 71.2deg head tube angle +55mm fork offset put front wheel much further away from you (longer wheelbase)
Normal range of trail value for racing road bike is 56-60mm. But small bikes generally got compromised here, because manufacturers slacken head tube angle to push front wheel away but don't create a dedicated fork with more offset to compensate for it (or not enough compensation).
FELT AR3 size 48 use HTA=71deg + fork offset 52mm -> trail=62mm (for tire size 25mm)
this Orbea size 49 trail=63, larger sizes are around 59mm
Specialized Tarmac size 49 trail=63mm , larger sizes are around 58mm
new Cervelo S3 and S5, trail=57mm on all sizes
New Cannondale Supersix Evo trail=58mm on all sizes (except size 44)
In any case mentioned above, those are above standard. They use multiple fork offset to minimize or completely neutralize handling difference across sizes.
Some common notably bad example i can think off are
Giant TCR size XS HTA=71deg+ fork offset=45mm (share fork with all larger sizes) -> trail=70mm while just going up one size to size S and you'll have trail=60mm
BMC Teammachine size 47 trail=76mm
BMC Teammachine size 51 trail=66mm