Originally Posted by flipflop
Since you guys are the best I know... here's a question I've been pondering!
With the increasing gas prices I'm seriously considering a moped for longer range transportation. A tomos targa LX to be exact. They weigh in around 80lbs stock, and will be modifyed as much as possible in pursuit of high speeds and "weight weenie-dom."
I'm wondering what you guys think about running bike tires at 35-50 mph for extended periods of time. They work fine on road bikes on the down hills... but the majority of the time they are going less than 20mph. Will they roll of the rims if turns are taken at motorcycle speeds? Will the suspension fork/swing arm prevent a taco at speed if it finds a pot hole?
I'm thinking that the lower rolling resistance and lighter rim would require less horsepower than the normal steel wheel. Deep V rims for strength, high spoke count, laced to disc brake hubs. I'm pondering running a bike chain instead of a moped type chain to save some rotating weight, but it may not be able to take the horsepower. (I don't want to machine a custom sproket...
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Higher speed increases exponentially the stress on a tyre and the chances of losing grip on the road. Engineers carefully calculate the traction capabilities and strength required for particular applications and design accordingly. I think it would be a recipe for failure or even disaster to use a bike tyre on a motorised cycle like you are proposing. Travelling at 50 mph on a bike tyre driven by an engine, when the tyre was designed for human propulsion strikes me as ridiculous. The comparison made above with a cyclist running downhill neglects the fact that the moped is not being dragged to 50 mph by gravity, but by a petrol engine passing stresses through the thin cover they were never designed for. A strong cyclist might put a hundred watts opf power through a tyre, while a moped probably puts out seven to ten times that effort. Take a look at the sidewalls and tread on a moped tyre and then look at the paper thin walls of your cycle tyre. There's a hell of a difference, and that difference is designed in to meet the stresses and not just an example of lazy over design.