40+mph isn't that uncommon a speed to hit even with a HT (peak downhill ofc) & sure, it's a lil sketchy on a bicycle but all you really need are good rims, tires, spokes & hubs properly trued with well packed bearings and definitely some good brakes. Wheel tracking front & rear is also defo a priority - if it's even a lil off you'll start "wagging tail" (back of bike starts to oscillate) which is bad enough but worse yet it usually starts to happen in a turn, particularly long, gentle curves... bad news lol
It's a lil different than the dreaded "tank slapper" which is usually caused by out of true/unbalanced wheels, usually the front. It's more common on motorcycles with heavier wheelsets and speeds in excess of 60mph, this problem will happen even going straight & worse yet, won't stop until you're well below the speed it started at. All controversy about the effectiveness of balancing bicycle wheels, if you are considering a build that might consistently go in excess of 40mph, I'd defo recommend balancing them anyway - better to do something you think is unnecessary than to find out it is necessary at speed.
Now... about this 70mph business... forgive me but that I'm gonna need to see some hard evidence to accept even with the 9hp Morini lol, wind resistance is an unforgiving exponential equation and custom recumbent salt flat bikes with full aerodynamic shells, six-speed transmissions, & fueled by methanol and nitrous oxide aside - you're talking about record speeds for the limited A-G (altered-gasoline) 50cc class heh, while they've reached it - I just don't see it happening with a retrofitted bicycle... yer talkin' about playing w/the big boys now heh: COBRA KING 50 SETS CLASS SPEED RECORD
Ofc, I'd love it if ya'll proved me wrong
I'd like to add that all the above is assuming good paved conditions - hit any irregularity at 40mph+ with a bicycle and it could be all over, there's just not enough weight & gyroscopic force to insure stability...
It's a lil different than the dreaded "tank slapper" which is usually caused by out of true/unbalanced wheels, usually the front. It's more common on motorcycles with heavier wheelsets and speeds in excess of 60mph, this problem will happen even going straight & worse yet, won't stop until you're well below the speed it started at. All controversy about the effectiveness of balancing bicycle wheels, if you are considering a build that might consistently go in excess of 40mph, I'd defo recommend balancing them anyway - better to do something you think is unnecessary than to find out it is necessary at speed.
Now... about this 70mph business... forgive me but that I'm gonna need to see some hard evidence to accept even with the 9hp Morini lol, wind resistance is an unforgiving exponential equation and custom recumbent salt flat bikes with full aerodynamic shells, six-speed transmissions, & fueled by methanol and nitrous oxide aside - you're talking about record speeds for the limited A-G (altered-gasoline) 50cc class heh, while they've reached it - I just don't see it happening with a retrofitted bicycle... yer talkin' about playing w/the big boys now heh: COBRA KING 50 SETS CLASS SPEED RECORD
Ofc, I'd love it if ya'll proved me wrong
I'd like to add that all the above is assuming good paved conditions - hit any irregularity at 40mph+ with a bicycle and it could be all over, there's just not enough weight & gyroscopic force to insure stability...
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