Clyde1820

In my own case, I was heavy for a couple years, but had old injuries and severely limited range-of-motion to contend with.

My choice, initially:

• A simple Next LaJolla brand step-through bike -- easy on/off; 26in rims; balloon tires; single speed with coaster brake. Strictly kept it to flatter routes, so it worked for me. Was probably near the limits of the frame. Had it been a quality steel, it likely would have been stronger. As it was, it wasn't an issue. Held up fine. A pretty cheap bike, but simple and easy to use.
• Step-through frame design -- helped immensely, given my ROM issues (leg injury). High stand-over height was an absolute non-starter, for me. Even sloping-TT options weren't nearly easy enough to get onto. A step-through's hard to beat.
• A well-sprung, more-padded seat helped, in my case. But, saddles are highly subjective, in terms of fit. Get your sit bones measured, adjust for your riding position, then shop accordingly. Be perfectly willing to get it "wrong" a couple times before you find "the" saddle that works. Keeping in mind that in another 100lbs and increased strength, you will likely find a different saddle feels even better.
• Balloon tires -- In 26in size, I picked the toughest street-oriented no-puncture type design I could. Helped avoid flats. (Never had one, IIRC.)
• Seat post -- get a very strong one. And ensure the frame size is sufficiently tall so you don't end up with a huge post sticking out above the seat tube. Had a cheapie steel seat post bend on me. Was a smaller frame, and the post stuck out about two-thirds of the length of the post. Bad news, being so heavy. Avoid it, as it'll leave you stranded.
• Alternative: lose another 75+ pounds and get your strength back in a gym. Do sufficient cardio, sufficient leg-strengthening activities (ie, recumbent bike station, stair climbing, ellipticals) to get you strong enough to do the biking with few issues.
• Gearing -- Ensure it's sufficiently geared. In my own case, old injuries require very low gears (in the ~13-15 gear-inches range). And, at least so far, I refuse to get an eBike. You might be different, but it's something to consider.

Want a custom bike that'll be strong enough, fit to your dimensions, with the components and features you prefer? Consider a custom-designed bike ... such as: Rodriguez, in Seattle (WA). They can create a custom fitting, select the "right" steel and tube sizes, to make a bike that'll be comfortable and strong.

ironnerd

Women, Children, and Gentlemen of a delicate constitution may wish to skip this post...

The Topic brought back an old memory.

I was 17, and was driving my High school girlfriend home one warm summer night. It was one of those summer nights they write country songs and RomComs about. We had the windows down in my rusted '68 Chevy, and we were just chatting away about nothing much when in the headlights appeared local "interesting person", Ray. Everyone in my little town knew Ray. He was about 5'6", weighed about 300 lbs (±). He was a really nice guy, but had some developmental problems and sometimes did unexpected things. On this particular night, Ray was riding his red bicycle down the side of a quiet country road... in his birthday suit.

The image of his naked back shining in the headlights is burned into my mind, as well as the sound of my girlfriend screaming. I saw a few references to saddle size, and I wish I could help, but there was no sign of Ray's saddle that night. I'm sure it was there, it was just obscured by surprisingly baby-smooth back-side. I can, however, say he was riding on wide tires. He was also wearing shoes, which I thought quite sensible, given the gravel shoulder and the high instances of broken beer bottles on that lonely stretch of road.

Because there was no paved shoulder, Ray was out in my lane a little, and I started to slow down. My girlfriend started yelling, "Oh my GOD! Pass him! Pass him!" So I sped up a little and went around him (giving him at least three feet of space). As we came along side Ray waved and smiled. I waved back, and said something like "Hey, Ray," and continued on to drop off my traumatized GF.

I do remember that Ray seemed genuinely happy that night. I guess it's true that Bicycles are good therapy - it sure put a smile on my face. Even my GF laughed about it - a few days later.

Wilfred Laurier

300lbs is absolutely not too heavy to ride a bike. In fact, if the bicycle is properly fitted, cycling is probably safer and healthier than walking as it is a zero-impact activity.

Furthermore, as a shorter person, your friend should will fit a small frame, which will be stronger and flex less than a larger frame, all other things being equal.

The one thing that may have trouble meeting the requirements are the wheels (which are not specific to the size of the bike, so 300lb 6 footers often use the same wheels as 150lb 5 footers) - specifically the rear wheel... the most highly stressed part on a bike. Most factory built wheels have a short lifespan under bigger riders. No biggie, though - if the wheel starts to complain or spokes break, you can just get a better, heavier duty, wheel.

Best of luck! Just know that often people get a mindset that is not based on the logic they are using, but on their own fears and frustrations. The obstacles are usually not bicycle strength and leg soreness, but a deep seated negative attitude that has probably been growing for years. Your friend probably knows deep down that taking up regular walking or biking would be good but has convinced themselves that it will be futile, or, more sadly, they aren't worth the effort. Keep it up and keep reminding them that people care about them.

Starting out with 'baby steps' (bike ride to the corner and back, for example) is how we all begin to move forward.