What I ride and why 20" wheels.

[boyntonstu]

My friends are avid bicyclists that ride $1,200+ folding bikes.
The bikes come with 20" wheels.
I found the bike below for $12.50 at a thrift store.
After adding a stem extension and raising the seat, I am very satisfied with the results.
20" wheels are stronger that larger wheels and will resist spoke bending and breaking better than 26" wheels.
I plan to have another bike with a 80 cc motor mounted in the rear.
Notice how much room is available.

 

[KCvale]

I found the bike below for $12.50 at a thrift store.

Nice score.

I plan to have another bike with a 80 cc motor mounted in the rear.
Notice how much room is available.

Just to be clear, there is no such thing as a Chinese 80cc 2-stroke, they are all ~66cc and ~3HP and should be referred to as such to end the silliness associated with that marketing claims of 4-5HP 80cc BS.

Anyway, back to the topic of putting a 2-stoke bump start engine on the back of that bike...
You might want to re-think that as a motorizing option unless you are a skilled welder with engineering skills because you won't be able to mount it to it basic rack, the torque will twist it apart.

An electric is the best option and lowest center of gravity, but there are little pull start 4-strokes with decent rack mounts that will work.
I don't mess with those myself but if you don't mind getting a second kickstand or tripod or something to keep it upright when you are not riding it they seem to work well.

I think a $300 36 or 48V 'water bottle' LI battery and electric shift kit like SBP sells for $400 would be your best option.
It will use you bikes gears, allow you to pedal with no resistance, and be a very low center of gravity for romping around off-road.
Just my take.

 

[wheelbender6]

Many adults that ride on 20inch wheels add riser (ape hanger) handlebars and a banana seat for a more comfortable seating position. Just remember that the smaller wheels can make handling twitchy when your speeds reach and surpass 20mph.

 

[boyntonstu]

Faster speeds offer more stability on any bike.
http://www.commutebybike.com/2012/12/12/alex-moultons-answer-to-dont-those-small-wheels-slow-you-down/

http://www.rodbikes.com/articles/650-speed.html

Are smaller wheels just for the ladies? How about something for the guys? Are there any tall guys who choose to ride smaller wheels professionally? Yes! Some of the worlds fastest bicycles were piloted by men and have really small wheels.

What the heck?
Obviously if bigger wheels were faster, one would expect to find bigger wheels, not smaller wheels, on record setting bicycles that are ridden at speeds of over 150mph. Yet, these guys chose really small wheels. Maybe they didn't talk to the guy at the shop.

Don't believe me? Ask these guys.
World Record holding Bike with small diameter wheels

Al Abbott sets the world record riding past 138 mph in 1973
Laurent Jalaber climbing on a 650c wheeled bike during the Tour de France

Famous sprinter Laurent Jalaber becomes a climbing champion on a 650c bike in the 2001 Tour de France
Another World Record Speed Holder with tiny wheels on his bike

John Howard sets the world record at 152.2 mph in 1985
Examples like these are easy to find, and number in the thousands. Again, I'm not saying smaller wheels are faster, but just that wheel size isn't determinant of speed.

 

[Timbone]

Bike racers (on the road) are running 700c wheels (~27") because they work best for road races. Tri-guys and some racers will occasionally play with 650c wheels but that is still 26". A 20" wheel is not something we are gonna see in bicycle racing, at least not on the road.

 

[boyntonstu]

Bike racers (on the road) are running 700c wheels (~27") because they work best for road races. Tri-guys and some racers will occasionally play with 650c wheels but that is still 26". A 20" wheel is not something we are gonna see in bicycle racing, at least not on the road.

All below are 20" or smaller see photos:

http://www.moultonbicycles.co.uk/heritage.html

1985-1986 - In the Autumn of 1985, at the International Human Powered Speed Championships, a fully-faired Moulton ridden by Jim Glover broke the 200 metres flying start speed record, at 50.21mph (80.79kph). Then on August 29th 1986, at the same event, he broke his own record at a speed of 51.29mph (82.54kph) which still stands today for the conventional riding position. The Moulton ridden was an AM SPEED with the fairing designed by Doug Milliken of Buffalo, NY.

1987-88 - Dave Bogdan rode the ultra-endurance Race Across America (RAAM) in 1987 on a pre-production AM-Jubilee, and in 1988 on a prototype AM SPEED. His 1987 time was 11 days, 8 hours and 2 minutes. In 1988 he improved on this by completing the 3,073m (4,944km) route in 10 days and 15 hours and 1 minute, averaging 289 miles (465 km) per day. He finished 8th out of 35 starters in what is not only the toughest, longest 'single stage' race in the world, but also the ultimate test of man and machine.

1989- Richard Grisgby of the Bath Cycling Club, riding an AM SPEED, came first out of 180 in the 1990 Fowey Triathlon in Cornwall. He also came third in the cycling split of the Kingswood Triathlon out of some 400 competitors and was only 9 seconds behind a 1st category roadman.

1991 - Gerry Tatrai wins the 24 hour HPV race around the Milwaukee Mile Track, Wisconsin USA.

2001 - Dan Farrell (on NS SPEED) completes the world's longest randonnee, the 1400km London-Edinburgh-London in 100 hours.

2003 - Chloe Williams (on NS SPEED) completes Paris-Brest-Paris, a 1200km randonnee, as youngest female finisher and wins the Audax UK Merit Trophy for most outstanding cycling performance of the year. Dan Farrell rides PBP on prototype TSR.

2007 - Kazuhiro Yamamoto on a NS Double Pylon finishes 6th out of 320 in a 4 hour solo class at Suzuka, Japan.

 

[Timbone]

These are specialty endurance events. Not to denigrate them but they are not professional road racers.

The amateurs are copying the pros, mostly running on cassettes whose biggest gear is 53x11. I have an 11 on my road bike, too, and it is not used very often. It all comes down to math: to win a bike race you gotta outsprint the guy next to you. Running the same gear, I don't want to be turning a 650c when my opponent is turning a bigger 700c because, in order to get a higher top end, I have to spin significantly faster. This is why road racing won't be seeing 20" wheels anytime soon!

 

[boyntonstu]

These are specialty endurance events. Not to denigrate them but they are not professional road racers.

The amateurs are copying the pros, mostly running on cassettes whose biggest gear is 53x11. I have an 11 on my road bike, too, and it is not used very often. It all comes down to math: to win a bike race you gotta outsprint the guy next to you. Running the same gear, I don't want to be turning a 650c when my opponent is turning a bigger 700c because, in order to get a higher top end, I have to spin significantly faster. This is why road racing won't be seeing 20" wheels anytime soon!

Please respond to Park Bikes claim:

Many folks who remember riding their 20-inch bike chasing an older brother or sister on a larger wheel bike ask the obvious question:

Don't you have to pedal more?

The simple answer is, No!

It's all in the gearing. A single turn of the pedals on a Bike Friday will cover the same ground as that of a regular wheeled bike — the small wheel just turns a little more.

 

[butre]

more importantly a 20 inch wheel doesn't hold its momentum for very long. not a big deal for a sprinter trying for land speed records but for an endurance cyclist it makes a huge difference.

of course if you're putting a motor on it, engines don't get tired.

 

[boyntonstu]

more importantly a 20 inch wheel doesn't hold its momentum for very long. not a big deal for a sprinter trying for land speed records but for an endurance cyclist it makes a huge difference.

of course if you're putting a motor on it, engines don't get tired.

Are you aware of these endurance records?

1987-88 - Dave Bogdan rode the ultra-endurance Race Across America (RAAM) in 1987 on a pre-production AM-Jubilee, and in 1988 on a prototype AM SPEED. His 1987 time was 11 days, 8 hours and 2 minutes. In 1988 he improved on this by completing the 3,073m (4,944km) route in 10 days and 15 hours and 1 minute, averaging 289 miles (465 km) per day. He finished 8th out of 35 starters in what is not only the toughest, longest 'single stage' race in the world, but also the ultimate test of man and machine.

1989- Richard Grisgby of the Bath Cycling Club, riding an AM SPEED, came first out of 180 in the 1990 Fowey Triathlon in Cornwall. He also came third in the cycling split of the Kingswood Triathlon out of some 400 competitors and was only 9 seconds behind a 1st category roadman.

1991 - Gerry Tatrai wins the 24 hour HPV race around the Milwaukee Mile Track, Wisconsin USA.

2001 - Dan Farrell (on NS SPEED) completes the world's longest randonnee, the 1400km London-Edinburgh-London in 100 hours.

2003 - Chloe Williams (on NS SPEED) completes Paris-Brest-Paris, a 1200km randonnee, as youngest female finisher and wins the Audax UK Merit Trophy for most outstanding cycling performance of the year. Dan Farrell rides PBP on prototype TSR.

2007 - Kazuhiro Yamamoto on a NS Double Pylon finishes 6th out of 320 in a 4 hour solo class at Suzuka, Japan.