i just beat my own personal speed record on my 20 inch.
behind my house there are some bike trails, and one of them is this climb that is a little over a quarter mile long. i just rode it in 3 mins and 12 seconds…if i did my math right thats about a 4.6 MPH average…thats not my fastest time on my 20 inch…but it is my fastest quarter mile climb. im pretty stoked about it.
woo endorphin high…haha…its wearing off though and my legs are burning.
The math is correct. The Google Calculator says 4.6875 miles / hour. I love the Google Calculator for calculating mph and other things that require unit conversions.
For a theoretical 20" diameter wheel that gives you a cadence (revolutions per minute) of about 79. You can spin faster. 
Childs’ math sucks. He didn’t even ask you what “a little over a quarter mile” means. It’s hard to get your two decimal point precision with that and he got four.
My math is good. My application of math is poor. That’s why I flunk college physics.
Of course you’ve already calculated that the alleged high speed for that approximate 1/4 mile ride is exactly 20 955 000 000 angstroms / second. It’s more impressive that way.
that google calculator is pretty nifty, i will have to remember that in the future.
man, when you give me the RPM it doesnt sound all that impressive haha…
my goal is to get the time down to at least 2 mins 30 seconds…do you think that is possible?
i love training on my 20 inch, then when i get on one of my bigger unis it just seems sooo much easier