Rook, this one is especially for YOU, because of your focus on weight - even to the extent of ounces and fractions of an ounce. This mod is about POUNDS of weight loss and VERY significant drop in rotational moment of inertia, which affects handling, overall weight, and acceleration - a 3-in-1 impact.
I looked up the weight of the OEM Bridgestone tires on my 2017 ZX-14R (HARD to find!), and realized that:
- the front tire = 9.25 lb
- the rear tire = 14.75 lb
- Total = 24.0 lb
I started looking for lighter, high performance replacements for when the OEM tires wear out, and found that a prime contender tire pair is one that I have had great previous experience with on 2 different bikes: Pirelli Diablo.
These are available in the correct same size as OEM, have a "W" speed rating, have the exact same load capacity each as the OEM front and rear, and are relatively inexpensive. Here's the eye opener:
Pirelli Diablo Rear = 12.90 lb
Pirelli Diablo Front = 9.00 lb
Total = 21.90 lb
This is 2.10 lb less than the OEM tires!
The 2.10 lb weight reduction is impressive all by itself, because once we get past installing a Lithium battery and lighter exhaust, we usually struggle to find other mods that are measured in pounds of weight reduction versus ounces.
But the reduction in rotational moment of inertia is even more impressive.
Moment of inertia for a rotating wheel/tire assembly is proportional to the sum of each increment of mass times the SQUARE of that mass's radius from the axle. The tire is usually the heaviest individual component of the wheel assembly - heavier than the chain, the sprocket, the brake rotor, and usually even the wheel. Even more sigficantly, being the outermost component of the wheel assembly, the tire by definition has the largest radius. And that radius gets SQUARED when calculating the rotational moment of inertia.
The rotational moment of inertia (RMOI)is a measure of how HARD it is to tilt the wheel (for turns) and to first accelerate the wheel in order to then accelerate the bike. This means reducing RMOI makes your bike handle more nimbly AND accelerate more quickly.
Notice in this OEM versus Pirelli Diablo weight comparison that the weight difference between the 2 sets of tires is almost entirely concentrated in the REAR tire. You're taking 2 lb off the mass that is concentrated at the outermost radius of the wheel assembly. This is mammoth.
But it gets better. You can supplement this effect with a lightweight rear sprocket, which takes off another full pound from that rear wheel. This has a much smaller impact on RMOI but the one pound pure weight reduction is notable.
Also, the combination of the lighter tires and rear sprocket also moves the center of gravity for the bike as a whole slightly FORWARD. On a high speed bike like the ZX-14R, this is a huge plus, echoning whT kawasaki tried so hard to do in the design of the bike. Ever noticed how far forward the engine, radiator, cockpit, and front fairing are on this bike versus other bikes? Look carefully at a profile shot of a ZX-14R and compare to other sportbikes. You'll see that emphasis on forward weight. (That's why that "gas tank" cover is so looooong, as a result)
I've got the tire on order and already have had the sprocket for may weeks. I just don't want to "waste" the OEM tires by taking them off too prematurely. :)
Jim G