I heard folders with small wheels like Brompton don't go straight or as straight as a normal bike but instead they wobble left to right. Is this true? If so is it that bad and noticeable?

False.

Small wheels---I have a couple of 20" folders but no 16"-- have a different feel than 26/700c wheels.

They have much less mass and do not resist turning as much as large wheels. When you first start riding a small wheel bike you will notice this. Also if the handlebars are narrower than your other bikes like the Swift bars and my Dahon bars are they will feel different.

The combination of different body position, bars, and wheel size may feel very "active" but not wobbly.

I could not ride without hands on either of my folders the first week of riding because they did not feel as stable. Now I ride without hands a lot. You will adapt to the feel of small wheels quickly. Now my big wheel bikes feel sluggish...

I have no wobble issues on my folders, none at all.

It certainly is different. I wouldn't call it wobbly, more like twitchy to me. Rick Imby's description of "active" is a good one. My work colleague's husband has a Brompton and she told me she just can't ride it even though she cycles a lot. She finds the bike twitchy and hard to control but her husband likes it and uses it daily. You get use to it.

Folders tend to be flexier than normal designs.
Smaller wheels also add their flavor the handling characteristics.
But it's not like they're unstable by definition.
To me, it's been something I've noticed rather than something that has troubled me.
Then again, it's not like I've ever tried for a personal best on a folder.

I would also use the term twitchy. Comes mostly because small wheels produce less centrifugal force which is what keeps most bikes going straight. It takes about 50 feet of riding to get used to it. Roger

Smaller wheels are are much more responsive than larger wheels, but definitely not wobbly.

Any twitchiness, at least for me, is offset by the low center of gravity and the low standover height. It is easy to hop off if the bike starts to slip and in some ways "feels" safer than my 700 c bikes.

Nope .. the bike goes straight , the company invests time and money in tooling to get the fits of all sections precise..

Though once there is the front bag with stuff in it , on the mounting block, it's low trail steering feel improves , IMO.


I have a Brompton & a Bike Friday (20" wheels + front pannier rack)




'/,

I just took the front rack off my Bike Friday (got right hooked and the only damage was my Nitto rack got bent). There is a noticeable difference riding with the front weighted versus unweighted. It's not wobbly, but I definitely was oversteering at first. Now that I am used to the unweighted front, I only notice it when I climb. If I'm pulling up on the handlebars to climb, I do need to shift my weight forward more than I was before. I would describe the handling as "more responsive" than a traditional bike - with a regular bike, you think about a move and then do it. With a smaller wheeled bike, the move is complete before your thought is complete =).

Now walking on Friday night may be a different story about Wobbling...

There the issue is the rider/pedestrian, Not the equipment..

You are both 100% correct. That's why I won't even attempt to walk farther than the bathroom when I've been drinking a few pints.

Strangely enough, this actually improves my dancing though. And contrary to forum opinion/speculation, I can dance quite well.

Only when ridden drunk.

Seriously, there are differences in steering response and steering axis inertia. So someone very dialed into a bike with larger wheels may find a folder a bit squirrely at first. But bike handling is a learned thing, and after riding a small wheel bike for a half hour or so, it'll feel completely normal.

I've been on a few folding bikes(20in. & 16in. wheels) over the years; Dahon(about 4), Schwinn(1), Bromtpon(2 my own, 4 test rides), Citizen(1), etc. I don't find that their wheels go off in random directions.

This sometimes crops up and sometimes the larger wheel have more gyroscopic stability compaired to smaller wheels myth also.
Its been dissproven in 70s.......

Small wheel responsiveness is just something to get used to. Been riding my Brompton mostly and now my full sized bikes now feel like trucks to me.

Twitchy is definitely the right word. My citizen rides straight...but starting off... any little pressure on the bars one way or another results in big movement in either direction.

Not sure what you are referring to that has been proven.

There are a lot of different terms for centripital, centrifugal, gyroscopic, momentum, rotational gyroscopic effect, etc that have specific scientific meaning that I am not certain of.

These facts are true. The small wheels have a different feel when riding than larger wheels, they are less stable at speeds under 5mph, and the smaller wheels take less energy to get up to 15 mph.

However in my opinion nearly all two wheelers are fun to ride...

This is all pretty much disproven. The effects of small wheels dont reduce stability afaik.
The theory was gyroscopic forces kept bicycles stable. Smaller wheels would have more, not less ,of this force as faster spin speeds but beside the point.
Bikes were made that had traditional wheels that were set at 90' to normal and tiny caster wheels they actually moved about one. Several of these bikes were made in the worst possible combinations for gyroscopic stability. They were all ridable. We balance a bike by altering the steering mainly is the theory currently in favour afaik.
Not sure their is data to support small wheels being less stable at lower speeds either. Their may be difficulties due to reduced counter weight leverage of the smaller wheel but this is due to a difference in weight that could be made the same'(with a heavier wheel), rather than the actual size of the wheel.I dont know if this is just my theory, but it may explain the differences in feel. I dont think one would notice a small wheel at the back having any effect on handling.

I ride a 12" wheeled PedalFlow, matching peoples walking speeds (SLOW!!!), and I experience no wobbles. I also don't really experience any issues with my 20" wheeled folders, while riding fast OR slow. I find twitchiness & wobbling to be something I don"t experience. Maybe I'm just used to riding folders? Even when I had a Dahon Curve for a short time, I had no problem riding it. It felt amazingly solid, and I was quite impressed at how the ride was more like a larger wheeled bike.

Like I said, I'm probably used to riding folders,...I really don't notice issues.

The steering stability strongly depends on trail, the distance between where front wheel touches the ground and the intersection of and the point where the steering axis intersects the ground. A longer trail makes steering more stable and may permit riding with hands off. A shorter trail makes the bike behave squirrelly. The need to fit a rider into the necessarily reduced dimensions of a folding bike typically forces designers to reduce the trail, resulting in a steering instability. Other factors affect stability as well but the general rule is that the more constraints you impose on a design, the less successful it is going to be in the areas unrelated to the constraints.

The steering stability of my Bike Friday New World Tourist is pretty awful. The Brompton is OK, but not where a full-size bike typically is.

Loading the front end of a Low trail Bike is Known to make it handle well

and the inverse The handling of a big load like the French Porteurs carried ,

(several Bundles of the latest Newspapers they carried From distribution centres , thru the city streets to news sellers Kiosks)

was Made better by reducing the front trail.

VBQ magazine has done a Big series of articles on this , spawning a Lot of low trail 650B replica Porteur bikes to Be Built.


'/,

One thing is 'twichiness' due to geometry, wheel size and contact patch. Another thing, quite different, is 'wobble'. A bike, any bike regardless of size, wobbles when its wheels are out of true or bent, its drop-outs are not precisely parallel, the wheel axle is not seated evenly on the drop-outs or the frame is bent. Wobble suggests poor quality, a need for maintanance or damage. The 'wobble' that people experience are the first attemtps at and unfamiliarity with the lively steering of small wheel bikes. They try them once, find them unfamiliar, never ride them long enough to master the steering, and therefore proclaim them 'wobbly'.