Is this speed possible ???

B

borntofli

Member
I just installed a speedo on my bike and got a top speed of 41mph.......

I have a 39 t sprocket......1/3 to 1/2 throttle reads 22-26 mph...This is the first time ive run wot to see how fast it goes, was waiting for it to explode and send me into the pavement.....

66-80 china girl.....
 
Sure it's possible, but bicycle speedometers tend to not be perfectly accurate, especially at higher speeds. That's almost 8500RPM, definitely pushing your engine hard!
 
it's possible, but...

what other mods to the engine have you done?

what kind of bike?

tire size?

your weight?

flat ground?

wind?

there's a lot of factors. a well built bike with a lightweight rider can get into the 40's (or faster) but if all you've done is change the sprocket, it's unlikely.

my first bike was a stock 26" cruiser with a 36 and i got 38mph.

my race bike is a heavily modified china engine on 20" wheels with a 36 and it tops out at 43.

my old 26" with an insanely modified motor and a 28t blew up at 62.

aleman witnessed it at 54. :)

i've seen and had bikes easily go over 40, but they've all had a lot of work done to them.

all that being said, you mighta got what i call a "lucky motor." sometimes you'll get one that goes fast right outta the box.
 
The first thing I'd do is check against other speedos to ensure it's something like accurate. My van say 34 when it's doing 30.
 
you can get those bike speedos pretty accurate if you measure the hieght of the tire(in inches) then multiply by pi(3.14) then convert the numbers to milimeters. this would be the value you enter into the speedo. that will get you pretty close to correct. but not perfect. my tire measured 2257mm. but to get a more accurate reading i had to enter 2233mm. into the speedo.
 
Time yourself between mile markers with a stop watch and then do the math. Gives you a nearly perfectly accurate result every time and gives you a good average over a mile long section of roadway so you know how much time you need to budget to commute how far via motorized bicycle.
 
Isn't doing it accurately some sort of cheating? How are we supposed to hold pointless arguments if you go around getting things right?
 
My daughters Cavalier speedometer says 65 when you are going 71....I know because I got a ticket last night going to get a bacon sundae at Bogus King.

A 137.49 dollar sundae.
 
P.S., I have never wanted to waste the money on a speedometer for a bike that will not go the speed limit. ;)
 
We're stuck with a regulation for a speedo even on a 1kw classified bike, all 16mph of it. And with built in illunimation.
 
shwnrttr said:
you can get those bike speedos pretty accurate if you measure the hieght of the tire(in inches) then multiply by pi(3.14) then convert the numbers to milimeters. this would be the value you enter into the speedo. that will get you pretty close to correct. but not perfect. my tire measured 2257mm. but to get a more accurate reading i had to enter 2233mm. into the speedo.
Click to expand...
Another method for accurate calibration is to make a mark on the front tire where it meets the floor and a corresponding mark on the floor. Roll the bike forward (must be a straight line) for one wheel revolution then mark the floor again where the tire mark is. Measure the distance from floor mark to floor mark and convert to metric if you don't have a metric tape. This is the number in milimeters that you enter into the calibration.

Example: 2073 is the ball park number most speedometers suggest for a 26" wheel. Due to differences in tires that number might not be exact. Using the method I described above will be accurate for your tire diameter.

Tom
 
... or you can just velcro your GPS to your gas cap and take it for a ride (running on the internal battery of coarse). I had a cheapo speedo on my bike and wasn't sure it was accurate, low and behold it was dead on when I ran with my GPS in place to check it. So cheapo speedo's can be accurate. I did nothing special with mine, just set the tire size and rode...
 
I also checked my bike speedometers with my GPS all three of mine were with-in 1 MPH or dead on after doing as Tom has suggested above, all of mine are wireless models I ordered from main land China for just a couple bucks each, one of them has been working like a champ since 2009, so yes, the cheapo speedo's can be accurate and reliable on the MB's in my experience.

Peace, Map (^)
 
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