Child is just old enough and it's now warm enough to appreciate a bike ride, or at least getting to the playgrounds faster. I didn't have a compatible bike or bike seat yet, and found this on FB Marketplace for 75$!
Given that I was expecting to pay at least 100$ for a seat alone, I jumped on the deal. Riding it home was fine, I was not quite used to the comfort/cruiser style sitting upright, but everything worked, the parts are basic as heck, and I think I found the original product: https://www.specialized.com/au/en/daily-1-step-through/p/49686?color=154166-49686
In any case, once I loaded my 23lb grub onto the back, though, I was surprised by just how terrible the handling was. I was wibble wobbling back and forth on startup, and I've been biking for years in NYC. I was putting a lot of weight into the handle bar as a force of habit; I think I could feel the bike flexing back and forth with the weight split between the front and the back. But i'm not sure how much a standard bike frame would help; do I still have to adjust positioning of the rear rack or bike seat to scooch CoG closer to me?
by CyJackX
8 Comments
I wonder if your rack is sufficient. Can’t see it, but I wonder if a burlier rack would improve the handling. But you have moved a lot of the weight back on the bike with a move to a more upright position and then where that seat is mounted behind the axel on the bike. If you move the seat forward, you will get less waggle.
The way it’s positioned looks like it would put a significant amount of weight above and behind your rear axle, basically where a stability handle would be on a kids bike when you’re teaching them to ride. Any side to side motion is going to get accentuated. The step through frame could add to this due to more flex at bottom bracket. If it’s possible to get the seat closer to being directly over the axle, it may be worth trying (but I’m just guessing).
Child seats on most regular bikes just make the ride a bit more wobbly inherently. It’s putting extra weight at a high center of gravity. Cargo bikes are much better at carrying children in the back because their racks are lower to the ground, but they are more expensive.
High center of mass – you may be taller but your weight is on the pedals transferring some (or all of that if you stand up) of the weight lower.
All of that mass is transferring through the bottom bracket trying to twist it.
I have had more success with child in front seats, but yes this is a challenging bike to do this with. Not impossible, you can get used to it. Dutch bikes that do this are typically much beefier because they don’t have much in terms of hills.
Child seats are a universal fit. Meaning they don’t every bike well. You installed the rack on a bike that has a very slack and short seat tube and it’s leaning back. Yes it’s bad, no it’s not as safe as it should be, yes it’s the bikes fault, no you can’t fix it without a more “traditional” bike.
I used a step thru bike with a rear seat similar to yours for years. I loved it and my kids loved it. The ride was very comfortable and I could only notice a bit extra weight in the back.
Here’s how our setups are different tho, you’re child seat is on a rear rack that’s putting weight on the back wheel over the axle. The seat I used has a bracket on the seat stay with flexible arms that hold the seat and even give it some suspension. the seat is called a Thule ride along if you want to see what it looks like
The setup I used has the seat still in the back but the attachment is directly under the riders body. This may really help stability. also the flexible arms mean there are less bumps transferred to your child’s neck and head which is far more important imo
I actually had a specialized daily bike of some sort for a while, and I never got used to the handling, regardless of the baby seat. Try putting the seat on another bike.
That’s actually a pretty complex subject.
It comes to 3 factors:
1. Just different weight distributrion that changes “handling parameters” in your “bicycle steering model” somewhere deep in your unconscious brain. Google “backwards brain bicycle”, its quite a brainfuck heh. It would still feel weird for a while even if “mechanically neutral”.
2. This different weight distribution is not actually neutral.
Bicycle handling feels the most stable with mass “smeared” across roll (Y) axis and concentrated on yaw (X) axis. Stable does not mean effortlessly manueverable (just much more important for recreatrional riding), but smearing the mass along X axis, *when your wheelbase length remains the same* is just plain bad.
By placing the child quite high and behind you, you did the worst thing – concentrated the mass on roll axis and smeared it on the yaw axis (high polar moment of inertia).
https://www.cycleworld.com/story/blogs/ask-kevin/how-motorcycles-carry-their-weight/
This article is quite fashinating.
*Overall* CG height, everything being equial, is actually quite beneficial – “high bikes” and ordinaries are actually very to balance because high CG objects tip over slowly and the bicycle is stabilized by an inverted pendulum model – the famous “balancing a broom vs a pencil on the tip of one’s finger”.
The “low CG is more stable” is a massive oversimplification… easily disproved by hopping on a recumbent lowracer and experiencing it yourself (I did). It should read “placing the masses *below existing center of gravity* is more stable”… like DH rides slapping an actual ballast on the downtube of their bikes.
3. Any flex (spring) is the system is going to massively affect your handling by absorbing and then overshooting your balance corrections.
A cargo bike places the load low (hence smearing your mass distribution along both axii, that sort of cancel itself out), has a long wheelbase and the cargo platform is very stiff (duh).
Hence, even much heavier weight does not change the handing much on it, compared to installing a child seat.
Source: I’ve been reseaching singletrack dynamics and making prototype recumbent bikes for last 10 years.
So, if you can adjust your child seat accordingly to those principles, it will improve, but don’t expect much. Just riding with it more and getting used to the quirks of different handling will help a lot.