|
FWIW, the 250 Production folks who race EX250s report that changing from a 5XX (OEM) chain and sprocket to a 410/415/428 size will show a bump of about 1-1.5hp on an inertial dyno. Obviously, that doesn't actually create more horsepower. Rather, it is the lower rotating mass that lets the dyno accelerate quicker making it look like more power.
IIRC the 2.50x18 Bridgestones used by many of the CB160 Honda racers are about half the weight of a set of 80/90x18 Dunlop or Avon race tires. That is significant when you figure the mass is at a 9" radius and the bike doesn't have a lot of power.
When talking about EX250 tires you need to specify if you want 16" (Gen 1 and 2) or the 17"s that came as OEM about 2008 onwards. The Gen 2 EX I had came to me with an Avon Venom on the back and that thing was very heavy compared to the Dunlop (K391?) I replaced it with.
The spec sheets you'll find at most of the manufacturers seldom show the tire weights. You need to take a scale to the local shop and weigh them yourself. In the early 70s even tires that were the same size/brand/model could vary a pound or so. I suspect they've gotten more consistent since then.
Some of the modern sporting street tires are very light. But that's in the sizes for 600/750/1000s, there's not as much attention paid to the small bikes any more.
cheers,
Michael
|