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I wanted to upgrade my wheels, but I just wasn't sure if I could justify spending a bunch of money. So I've set out to quantity how much real world

__impact to__a fancy super light race 1000g (3000 euro) wheelset would make vs just changing the tires for 100$.

**rotational kinetic energy**__A.K.A. How much easier the wheel changes speed or direction for $$$ spent on separate parts of the wheel.__

__TLDR:__

500g (1.1 lbs) wheelset weight reduction makes less of a difference (to rotational kinetic energy) than 150g (0.3 lbs) reduction from tires at 30km/h.500g (1.1 lbs) wheelset weight reduction makes less of a difference (to rotational kinetic energy) than 150g (0.3 lbs) reduction from tires at 30km/h.

Compared rotational kinetic energy at 15 & 30 KM/h (10 & 20rad/s) (≈ 932 & 18.64 mph) for a 29er wheel (approx. 740mm diam./C=~2.35m):

1) 1440g wheels + 1550g tires

2) 1000g wheels + 1550g tires

3) 1440g wheels + 1400g tires

Bonus:

4) 1440g wheels + 1250g race tires

__Calculations__and relevant excerpt from wiki:

30km/h:

15km/h:

__Findings__:

**Tires make up the most**

**(~70% in this example)**

**of the kinetic rotational energy of the entire wheel system. And while rims do make make some measurable change - the hubs, spokes, and disc rotors amount to almost nothing.**

At 30km/h:

1) 500g of wheelset weight reduction makes just 6% difference of Er from 3KG. At the cost of 3000 euros (~3,410 usd).

2) Only 150g tire weight reduction makes a 7% difference of Er from 3KG. For 100$.

3) Race tires, that drop 300g, make a whopping 14% difference Er from 3KG. For 100$.

Or in other words:

__Changing tires can cost as little as ~10usd per 1% of Er savings, but on a wheelset will cost over 500$.__

Turns out there is almost 1500 times more rotational kinetic energy difference between a hub and a tire. (Or 1369, to be precise, when calculated a 100g hub weight at 10mm from axis at 20rad/s, I (mom. of inertia) = 0.00001 kg*m², or 0.002 joules, versus 100g @ 370mm = 0.01369 kg*m², or 2.738 joules).

Now I'm not the smartest zergling in the control group, nor am I a physics PhD, nor have I "discovered" something new. We all know that tires have a huge effect on the bike, and that a lighter rim/tire will make the acceleration / decel. and change of direction faster due to less mass moment of inertia. But I was just shocked that a 0.5kg reduced wheel weight made less difference than shaving 150g from tires (not counting the drag).

__Clarification__:

This is my calculation on the power requirement (joules, or watt per second) to accelerate (and decel.) the wheel. This doesn't mean that on a flat road you will see this, it's probably going to be between wind resistance and tire friction/drag for that.

**I would also like to clarify that this isn't bombproof -**

__I'm just an idiot on the internet__, and all info is just an estimate. If someone sees an issue with this__please correct me__.Would like to know if any of this is what you guys find from experience? Or am I just making a fool out of myself here?

Regards