hey all i’m trying to find a way to describe a certain characteristic of my bike and not sure what it would be.
here’s the scenario:
i’m pedalling at my ideal cadence on a flat road on a regular loop i do. with some bikes, i can let go completely of my handlebars and the bike stays under me without needing to hold the handlebars. it’s a great time for me to take that picture of my ride that i know i’ll forget later.
when i ride a specific bike of mine, i notice that even if i’m at the same cadence/power/speed as my other bike, this one won’t sit below me and i feel like i can only let go of the handlebar for a quick second. with my first bike there’s no issue and i can go for the rough mile with no wobble or impression that i’m losing control of the bike.
the fits on both bikes are roughly the same (one’s handlebar is higher as it’s my gravel bike) and they’re both on 700c wheels
how would you describe this characteristic? would it be balance? handling?
any tips would be great as i’ve been curious what this characteristic is, and how to look for and figure out what i should be comparing to not have the issue in the future.
As with anything in cycling, it’s a complex answer comprised of multiple factors.
The core term may be “Stability”, which I see as the tendency for the bike to maintain motion in a forward direction (not steer or wobble). It’s not a singular term or concept that is captured in a bike, but one that is a result of many variables.
Bike Design: (These are the most relevant ones that I consider, but others may factor in later)
Wheelbase = space between the front and rear wheels
Head Tube Angle = angle of the frame tube and bearings that hold the fork steer tube
Fork Offset (Rake) = distance the wheel mount is offset from the steer tube center
Trail = distance from the projected Head Tube Angle contact with the ground, and the actual tire contact patch to the ground (results from the Head Tube Angle and Fork Offset)
Bottom Bracket Height (or Drop) = distance of the center of the pedals from the ground (Height) or below the wheel axis level (Drop)
Not sure these are the best resources, but some I found on Google:
Added to all that, is your actual position on the bike. Weight distribution (mass on the front and rear wheels in particular) have a large impact on handling in general, and is likely related to your question too. That means the position of your saddle and handlebars, relative to the entire bike can alter the feel and stability.
I had a similar issue a couple months ago. On my road bike I was unable to really go no handed even though I had been able to for years on other bikes and was able to do it no problem on my MTB. I kinda wrote it off as me just not doing it enough and being out of practice but the geo of the MTB made it easier. But as I looked at my bike more I noticed there was a lot of friction in the steering. If I picked the front wheel off the ground and leaned the bike to one side or the other the wheel didn’t seem to fall to one side very freely. So I loosened my stem and top cap, slid the fork out just a bit to be sure it was totally loose, and then re-tightened them down to the correct torque specs. Since then the wheel will flow side to side and I am able to ride no handed without any problems.
A slacker bike with a longer wheelbase will almost always be easier to ride no-handed than a steeper, shorter one but it shouldn’t be the difference between doing it for minutes and not being able to do it for a second.
TL;DR Check if you either need to replace your headset bearings or if you have over tightened your top cap and put too much preload on the bearings.
Generally, this is Trail (AKA Caster) and is the self-centering force on the handlebars and the best predictor of whether you can 'let go of the bars or not.
Like others have said, this is just factor though. For example, tire size is a factor here as tire size (height) matters in getting the quoted trail#; if you put road tires on a gravel bike, it’ll be less stable.
Bottom bracket height matters too, but not that much.