50 mph ?? (Down hill doesn't count)

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BarelyAWake

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Though not a true speedometer, a correctly calibrated digital bicycle speedometer will match a GPS for accuracy.
Not to bust yer chops - but somehow the first half of yer statement kinda nulls the second ;)

It's commonly accepted that even the factory speedometer in a car has a comparatively large margin of error: Speedometer error, Wikipedia whereas even the basic modern GPS has only about a 0.1 knot (about 0.1 mph) variance if tracking four satellites: Global Positioning System, Wikipedia.

Throw in the problem that it's simply impossible to have a "correctly calibrated" bicycle speedometer with the fact that when discussing MBs we're often bickering over even 5mph increments - such speedometers are really only good for "ballparking" speed estimates at best. Even the "radar trap" signs aren't nearly as accurate as we've been lead to believe (target size and vibration have huge effects): Radar gun, Wikipedia, to the point where speeding tickets have been contested successfully with GPS data: GPS Data Used To Disprove Radar Gun In Speeding Trial


For just $10-20, sure a digital bicycle speedometer is a fun toy to give ya an idea of your speed - IF you can manage to get it set even vaguely correctly, but remember the faster you go - the larger the error, whereas the opposite is true with a GPS as it'll get more and more distinct tracking information beyond say a slow walking speed (about 3mph).
 

stv1jzgte

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Amen to the above post, if you throw around ridiculous mph claims like 50 and even 60mph without proof and not electronic wallmart or mechanical speedos, said person sounds like a tool.
 

civlized

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How ironic that there is a tixnix ad in this thread with big print, "Fight Your Ticket!" That's great. I can't wait to get my bike back together and make you guys a video. It's not a kit engine, but it will haul butt. The tires start to bounce pretty bad around 45mph, so it is scary. I'm very anxious to see what it will do WOT.
 

Bikeguy Joe

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How ironic that there is a tixnix ad in this thread with big print, "Fight Your Ticket!" That's great. I can't wait to get my bike back together and make you guys a video. It's not a kit engine, but it will haul butt. The tires start to bounce pretty bad around 45mph, so it is scary. I'm very anxious to see what it will do WOT.

Time to balance the wheels before you bust your yaya's.
 

stuartracing

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hey otis, here's a video of mine doing 45ish. you can see how little i pedal off the line. as long as i'm moving, i don't have to pedal much.

66cc starfire, 30t sprocket, reversed barrelled motor...

YouTube - me and happy playing in traffic
Pretty dang smooth....Glad to see someone else pull the clutch in on decel. instead of letting the motor/chain, drive train rattle/jump around with the motor still engaged.....
 

Bikeguy Joe

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The first and last time I decellorated (sp?) from a higher speed without pulling in the clutch I thought I was about to be consumed in exploding bike, chain, and engine parts.
 

Bikeguy Joe

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Seriously though?

50 mph on a cheap wal mart bike with crappy tubes and tires from china and an engine cranked down tight on your frame complete with a plastic chain tensioner and a quality chain to tie it all together?

Suicidal and I mean in a graphic face hammering, head splitting, femur compound snapping way.
 

civlized

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Time to balance the wheels before you bust your yaya's.
Yeah, I have no intentions of riding at that speed, normally. I have thought about balancing because if it will go that fast, why not make it smooth. But, I seriously won't be cruising at that speed. My goal was to cruise 35-40mph without the engine about to explode from all of the rpmies. I accomplished that, so I'm happy like Dan's old avatar.
 

BarelyAWake

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Pretty dang smooth....Glad to see someone else pull the clutch in on decel. instead of letting the motor/chain, drive train rattle/jump around with the motor still engaged.....
The first and last time I decellorated (sp?) from a higher speed without pulling in the clutch I thought I was about to be consumed in exploding bike, chain, and engine parts.
I'ma guessin' ya'll know this - but I'm gonna throw it out there in case there's ppl who don't :p

There's two reasons sudden and prolonged engine compression braking is tough on these bikes, the first is that bdanged tensioner takes the full load of tryin' to slow the bike - the strain on the chain switches orientation when doin' this and the second is a lack of lubrication to the engine. As alla oil is in the fuel yer not gettin' any if ya cut throttle but yer still at full RPMs... well, ya get the picture lol

Still - I gotta admit that although I don't make a habit out of it, engine compression braking is just too handy to avoid when I'm driving like an idiot. It balances the braking nicely in the ice and snow and helps a ton in the appropriately named "panic stop" - so long as ppl know what the consequences can be and have made sure their tensioner can take it and are willing to accept the wear & tear on the engine... *shrug* sometimes ya gotta do whatcha gotta do lol

Ima gonna miss it a bit with my new build, shiftkit = no can do :(
 

Bikeguy Joe

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if somebody donates a 30-27 tooth sprocket i guarentee i can go 50

If some one dontes a 27-30 t sprocket all that is going to happen is that some one will be a fool.
If you could gear up and go faster, why not just put a 50cc engine in everything and just gear up to go as fast as you wanted?

It won't happen unless you can somehow defy the laws of physics.

I know people alreayd deny the laws of physics...
 

BarelyAWake

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