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Discussion Starter · #1 ·
I'm putting together plans to reduce both the static weight of my Z125 and the weight of rotating parts (e.g. wheels, tires, brake rotors, rear sprocket, primary gear, etc). I'm having trouble finding accurate weights for both the OEM IRC tires and aftermarket tires.

Tires are a bIG target, simply because reducing their weight reducing BOTH static weight and rotating moment of inertia ("MOI"), both of which affect speed of acceleration, deceleration, and handling. And, because tires are right at the periphery of the wheels, and since moment of inertia is proportional to mass times distance-from-center SQUARED, the tires are, normally, about the simplest and cheapest change you can make to reduce MOI.

It APPEARS to me that the OEM tires are:
Rear IRC NR77U D tire 120/70-12 (51L) 7.7 lb (speed rated to 74mph) 7.59 lb
Front 100/90-12 IRC NR77U (49J) (speed rated to 62 mph) 6.56 lb

But those weights are not 'certified' in my mind, as I have found that most vendors don't even list tire weights, and those that do often get them quite wrong.

The lowest weight tires I THINK I have found are these:

Rear: Pirelli EVO 22 120/70 = 7.4 lb shown by one vendor. A Pirelli clerk told me it is actually 7.16 lb. The big U.S. tire vendor Dennis Kirk says 7.65 lb. and past experience tells me their weights are usually very accurate. I'd like to think that Pirelli, the manufacturer, knows best . . .

Front: Pirelli EVO 21 110/70 (I know it is less tall but wider than OEM) = 5.8 lb per Leandro on this forum. But the Pirelli clerk told me it is actually 6.65 lb. But Dennis Kirk shows it as 6.0 lb.

Does anyone out there actually have ACTUAL weights for these Pirelli tires, preferably taken on a digital type scale of appropriate weight range (like 30 lb, not 300 lb) for best accuracy?

Jim G
 

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Think twice about putting a lot of effort into lowering unsprung weight and rotating mass of this bike. It doesn't need it like some big bikes do and if you go too far (and carbon fiber wheels on this bike is too far) the bike is going to get more twitchy on you than it already is - and this will be magnified if you do any engine work that makes the bike faster.
 

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Discussion Starter · #3 ·
Think twice about putting a lot of effort into lowering unsprung weight and rotating mass of this bike. It doesn't need it like some big bikes do and if you go too far (and carbon fiber wheels on this bike is too far) the bike is going to get more twitchy on you than it already is - and this will be magnified if you do any engine work that makes the bike faster.
I LIKE twitchy. :)

I call it "nimble". To me, it's a big desirable part of the motorcycling experience!

Jim G
 
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