This is quoted from Tire Maniac:
Rear motorcycle tires are responsible for certain bike functions, such as:
Power The rear tire has a flatter profile, to provide the majority of the acceleration and stability for your bike, and wouldn’t handle as well if put on the front.
Weight The rear tire carries the majority of the weight of the bike, calling for special design elements to keep you upright & safe at all times.
Lean Since the rear tire does not turn, it is subject to the lean of the motorcycle. This requires a sturdier tire with a flatter profile to accommodate this requirement.
Front motorcycle tires have specific characteristics, as well as limitations, including:
Braking The front tire provides up to 80% of the braking power for your motorcycle. It’s shaped to provide this, rather than acceleration like the rear tire
Turning The most obvious function of the front tire is turning right & left. A front tire is more triangular shaped for better handling. You would notice this if you were to try to put a rear tire on the front, as they aren’t shaped for turning and you’d have a hard time turning your bike properly.
Tread Because the front tire’s main purpose is braking, the tread isn’t going to be as thick. This would become very obvious if you were to run a front tire on the rear of your motorcycle. You would notice that the tread would wear down very quickly due to the thinner tread on a front-specific tire.
This is quoted from the Maxis web site:
Can I use a tire designed for the front on the rear of a motorcycle?
Answer
Tires marked as front or rear tires should only be used in their designated position. Correct matching of front and rear tires is critical to obtaining optimum performance and handling.
Front and rear tires have different handling needs. A front tire has a more triangulated profile for steering control, while a rear tire has a flatter profile for bike stability. Using a tire in a position for which it was not designed will result in reduced handling capability, putting the rider in danger.
Combining a new front tire with a worn rear tire or vice versa may cause instability. Always consult your vehicle’s manufacturer before modifying your motorcycle’s tires from stock.
I am running two REAR designated Diablos on my ZX-50. I did so because I only intended the bike to go in a straight line at 80+ MPH. I never had any intention of riding the bike on the street, and it has sat for about a year because of the way it is set up.
On a 50cc / 45MPH bike I don't think I would be overly concerned w/ what goes where, but as Dee Dee pointed out we are talking about 70+MPH on larger bikes.
Stick w/ what the PSTU figured out. (people smarter than us)
At .02 cents per opinion I figure I have 220.00 US invested here on the forum.
