I've started cycling (learned to cycle as a kid but never really did it more than once a week) to lose weight. I've been using a family friend's folding bike and a bike sharing app. I also just got a brand new bike today (yay!) but haven't taken it out for a spin yet. While using the folding bike and bike sharing app bikes, I find that I will suddenly feel off-balance and veer to one side. Of course, this can be very dangerous, and I'm putting my plans to join cycling groups on hold because I might crash into to other cyclists if I don't figure out how to stop doing this. Any tips or advice? Since this has happened on different bikes, it must be me, not the bikes.

You’re probably pulling to one side or the other when you’re looking that direction. Concentrate on holding the bars straight when you look to the side or back.

Need a bit more info. Are you taking a hand off the bar, looking down or to the side, turning your head, or doing something else when this happens, maybe day dreaming? Or maybe you are coming onto a section of road with more camber?

I got DW an Apple Watch for Christmas, and she has mainly been using it to track all her exercise activities. Out of everything she does: swim, elliptical, treadmill, free weight ... cycling burns the least calories, hands down. I mean, even after 30 minutes/5mi. with one wicked hill to climb, she has barely busted 250 calories! For this reason, and all the reasons the o.p. mentioned, I stick by my opinion that, for getting or staying in shape, diet should be the cornerstone, supplemented (or not) by a gym (or home gym) program of hard free weight or machine strength training.

Cycling is for fun, and/or transportation, and it absolutely helps to be fit so you can get maximum enjoyment/efficiency from it, but the people that are shedding 10lb/wk on their cycling program are forgetting that simultaneous with their purchase of a bike to kill the unwanted extra calories, they also started to cut way back on unnecessary calorie intake. Novice riders can and do get seriously injured (and worse) far more than experienced cyclists. It's a catch-22, I know. How do you get more cycling experience if it's so dangerous to cycle as a novice ... well, it helps if you started young when you were still made of rubber, and also before SUV's were invented and drivers got so damn mean. If you didn't beat those deadlines, I for one wouldn't. Start. Seriously. It's harsh advice, but it comes from a good place.

There are so many factors involved in veering but usually it is related to either removing hands from bars or oversteering or maybe unconsciously steering when looking at something or sometimes even while pedaling things get a little uneven. Your body English can have an effect on riding so if you try to steer using just your body and not your arms and the handlebar you can go quite a ways without any input up front. That is why you will see people riding such long distances without hands on the bars. Not saying one should do that but keeping an eye on how your body is moving can help and if you learn how to use your body and the handlebars in tandem you can do some really helpful things.

I recommend practicing in a good safe spot away from so many cars and such and maybe try with some cones and just go for it maybe even remove the pedals and lower your saddle a bit so you can basically "Fred Flinstone" it. That way you can eliminate the pedaling from the equation and just focus more on steering. The more you do it the easier it will be come and certainly at slower speed steering is harder you need some momentum otherwise you can have some less sure steering.

Related to what others have said, practice riding in a straight line first and keep your head looking up out towards the horizon ( try not to look down at the ground any more than is necessary). Also keep your head straight up and down when you ride ( i.e. don't tip your head over to one side ). Keeping your head vertical means your brain maintains perspective relative to the horizon. You can see MotoGP riders doing this even when cranked right over.

Re-reading your post, I'm also wondering if you might be simply riding too slowly for your experience level.

Maybe discuss the issue with your doctor? Sudden loss of balance or dizziness when exercising may be something more serious than your riding technique.

Could also have mechanical issues. Bent fork, wheel in dropout crooked, bad headset bearings. There's probably many more possible causes. If it just happens momentarily and at random, it's probably the component called 'the rider.'

Regarding cycling as exercise, you can get out of it whatever you put into it. Many years ago, Bicycling magazine published a chart of calorie burn based on rider weight and average speed, based on putting a rider on a trainer and measuring O2 usage. Of course it was minimal Calorie burn at 5 mph, but at 18-20 it became significant, like 800+ Calories per hour. Which, if that's at 18 mph, is still only 44 Cal/mi. Overall, I think walking at a brisk pace is still the best exercise for weight loss. And yes it must be done in conjunction with diet.

The OP did mention it happens on different bikes just as an FYI.

I agree. What is happening is not normal. I would suggest seeing a neurologist and undergoing an evaluation. This may be an indicator of something else going on.

I’ve had an occasional attack of vertigo, perhaps once a year. It feels like the room has turned sideways, or like being in a plane which falls a bit in turbulence. It has happened once while I was cycling, but I had no issue keeping the bike up and straight (reflexive riding I suppose). It is an issue you should get checked out. My situation has never been bad enough that I have thought about treatment.

Cycling is efficient transportation, which means the calorie burn is lower than other forms of exercise, but it's also something that with a relatively small amount of training one can keep doing for hours at a time. 30 minutes of running or lifting weights will burn more calories, but it's not hard to train to the point that 4-5 hours on a bike is fairly easy. 4-5 hours of running is pretty much a marathon for a beginner or a slow experienced runner, which is definitely not easy.

It can just be due to momentarily paying attention to something else apart from riding the bike. Like I can ride on the white line (and I mean staying exactly on it for fairly long periods) or just behind it on the right side of it if there is half a foot or a foot of paved road (~under 20-25 mph), but that takes a constant disciplined attention and not relaxing on pedaling effort. Whenever I want to take a sip from bottle, or look back over shoulder, or just ease up on that disciplined push into pedals, I find I stray back over into the road almost automatically, by instinct, a foot or even two left of the white line... generally whenever I relax my attention from that disciplined bike riding.
It also happens if I slow down and dawdle for a bit, I find myself more in the road than I consider safe. Luckily for me, where I ride the roads are mostly empty and most times I can hear vehicles closing in from behind, but that is not a sure thing.

When I was in my twenties, I trained for one season with bike racers and learned to ride in pace line which requires that same discipline in maintaining constant speed and keep in line and close behind the bike in front and now when I am much older, I still profit from that. But your straying from riding line could be for other reasons than what I describe here.

Still I find that moments of inattention to riding generally lead to sideways movement almost automatically and almost always to the left side, because of the constant threat of going off the road to the right... that is more constant threat than that from the vehicles, even if you are bound to sustain more serious injuries from vehicles than from leaving the road into a ditch. Vehicles happen by relatively infrequently for most of us but the ditch is most of the time always there, waiting to receive you.

go to an empty parking lot and practice following a long painted line. Notice when you look down at the line you will meander. Look ahead 50' or so and you'll follow the line much better if not exactly on it. Maybe this will help with your analysis of the veering problem.

I'd start with a lot of practice, in larger unused parking lots, ideally ones without those berms at the head of each parking spot which will just end up being things you could run into. Or a larger hard-packed dirt area. Growing up, we had a couple of very large fields nearby and that's where we learned to hone our cycling skills. Lots of little, unobtrusive impediments (small stones, areas where the rain had washed a bit of a groove) to avoid. If you can, consider making a game out of hitting certain painted lines in the unused parking lot, 'round and 'round, until you're easily able to consistently hit what you are aiming at. Could even drop a few easily-seen stones here and there, as markers to go around. Could do a "figure-8" route, 'round and round', which forces you to constantly manage that ever-changing balance point along the path. Eventually, as you gain confidence, your balance and control of the bike ought to greatly improve.

Remember as a kid there would always be a few kids around who could bunny-hop up curbs and do other similarly "sketchy" maneuvers? Well, a lot of that is good skill-building, for remaining capable of controlling the bike in variable conditions. Keeping your bike on a route, ie along lines. Being able to turn and wheel around a space "hitting" the marks you intend. Handling the less-certain surface of a dirt trail or space.

One thing to keep in mind, as well, is that not all bicycles have a simple, easily-handled balance point. Some are a bit "off" ... and I'd suggest it's more likely that some of the rental bikes will get manhandled to the point things are likely to have minor alignment or balance issues. Which can translate to reduced handling quality for the rider.

As for taking your eyes of the road, it takes practice. Same as with a motor vehicle. Eventually, you learn how to move your eyes or even your head, without changing the directional control of the vehicle or bike. Takes practice.

That'd be my suggestion. Those little "games" to push you to improve your balance and control.

If you're brave, head to one of the local youth cycling parks where the kids typically defy gravity with their BMX bikes. Just to watch, of course. Those little gumbies are, for the most part, experts in control and balance with those things. But it could give you great ideas about the type of route changes and changes in balance you could test yourself with, as you practice on your empty parking lot or hard-packed space.

Of course, the group rides you would partake in wouldn't ride in pace line but more loosely spaced, also maybe two bikes shoulder to shoulder? You should be brave and join them but tell them of your worries, so that they would be aware of it, maybe you should keep in the rear of the group for the start.
It is well possible that the responsibility of riding in a group will impress on you, so that your problem or your worry will not materialize.

Don't get all flustered and anxious... It's always good to start from the simplest explanations and solutions and work into it...
Most folders have smaller wheel sizes than your avg regular bike. Smaller wheels can be more skittish. They may also have shorter 'trail' (bike tech thing) which allows easier or harder (often called 'more stable') turning, depending on design.
Human body balance is somewhat innate, but can be greatly affected by each person's adaptation, depending each person's use/need for balance. Ice skater, gymnast vs sedentary person....
Plus aging does/can affect and deteriorate balance. Aging challenges every aspect of the Human, both physical and mental - you either deal with it or allow decline.
Work on your balance skills - plenty of methods, ways, suggestions out there for improving balance.
Balance can be greatly improved, over not too long a time - but it does take time and consistent, perseverant attention and work.
Along with 'balance', body flexibility works with (or against if flexibility is low). Again, lots of things to improve flexibility.
The Human Body is also Torso Mass Centric, meaning small changes in the movement of the torso will have great affects throughout the body movement. The great the size of torso compared to arms and legs, the more sensitive your balance point becomes.
Then there are bike skills... like a fundamental principle "You will go where you look", meaning where your vision is focus is where your body wants to steer...
it takes work to skillfully disassociate 'vision' from direction, when you wish to or need to.
Simple things to do
Always work to having your attention well ahead of where you are at the moment - Don't stare down at the road/path directly in front of you. Note the path you wish to ride well ahead of getting there. The faster you ride the further forward you should place attention. (same idea for noting obstacles, etc...)
Let your peripheral attention handle the stuff directly in front of you.
Don't lock your elbows, wrists, shoulders - allow them to be soft and flexible - the bike will make minor steering adjustments automatically. Work on a flexible, soft grip on the bars.
make sure your weight is centered on the seat.
A great exercise - find a flatter stretch of path with a painted line of some sort, and try to ride that line with as little veering as possible - employing all the things I mentioned.
DON'T focus on the line ! Allow it to be a part of your peripheral attention. At first you will focus on it, but after time and many attempts it should and will be just something else out there.
It will be difficult, but you will improve - if you pay attention to the things I mentioned...
When I see a line, anywhere, (or imagined line), I ALWAYS ride it !!! LOL ! it's a fun game for me. It feels good to do it. Like a great skate down the ice, like a dance, a difficult run down a tough hill... It's the magic of controlled movement, yet flexible enough to change at any time - It's Great 'Music' ...
Living is a tough thing, sometimes a wonderful 'downhill', sometimes a tough climb 'uphill' - be in the game, and love every minute of it !
Ride On
Yuri

Is this veering off occurring when you are looking at something other than down the road in front of you? That might just be you needing more time to get use to cycling so you don't put false steering inputs to the handlebars or shift bodyweight when you look elsewhere.

Not all bikes have the same stability either. So different bikes can require different amounts of shifting weight or moving the handlebars to maneuver or keep you from veering suddenly. When I went from a very stable and easy to ride with no hands bike to one that was less stable, I had to re-learn how to better keep my bike straight. However the less stable bike is more maneuverable in crowds and definitely more fun to ride.

Thank you so much everyone!!

Yeah, he did, his folding bike, and sharing bike apps, like those that some cities have that you can use a phone app and pay to ride a bike for a specific time period you pay for. So, his problem is on multiple bikes.

While this all could be balancing problem when he tries to look around, if he tries to resolve that issue and it doesn't work, and all the other methods listed won't work either, it could be an inner ear problem for which he will have to see a doctor specializing in that sort of thing.

which is my point. Exactly! Do you have 4 - 5 hours free and clear, every day just for exercise? I don't, neither does DW. We cycle to get places, not to burn calories.

My bike veers on its own when it sees yard sales, especially ones with bicycle parts, but that may be different from the OP's issue.

IF you have the time, cycling allows you to build up much more quickly to a much higher quantity of exercise than other options do.