[JMS3GTL]

anyway i could get this in laymans terms?

 

[EvilGenius]

[quote author=BLUNTFUNK420 link=topic=84487.msg1597787#msg1597787 date=1185823653]anyway i could get this in laymans terms?[/quote]
Big wheel bad.
Heavy wheel bad.
Big heavy wheel very bad.

 

[myork]

Wasnt there another post a few years back that contradicted this?

The person who wrote it stated that these calculations didnt apply for automobiles (or any motor vehicles) because it didnt take into account the torque being applied at the center of the wheel - these calculations only apply to a free rolling wheel. Its much easier to spin a wheel from the outer circumference than from the center of the wheel.

Or some kinda crap like that.

 

[spinzero]

[quote author=daniyar79 link=topic=84487.msg1597754#msg1597754 date=1185822873]
Does it make me a geek if I did all these calculations on paper without a calculator using my current/future wheel weight?

By the way, excellent write up. I enjoyed physics very much while getting my Comp Engineering degree. :klavergreg:
[/quote]

Physicists admit that we are some of the geekiest people on earth. Can't help it. But it's always nice have the comp sci/eng majors to look down upon. :sarc:

 

[spinzero]

[quote author=myork link=topic=84487.msg1597976#msg1597976 date=1185827123]
Wasnt there another post a few years back that contradicted this?

The person who wrote it stated that these calculations didnt apply for automobiles (or any motor vehicles) because it didnt take into account the torque being applied at the center of the wheel - these calculations only apply to a free rolling wheel. Its much easier to spin a wheel from the outer circumference than from the center of the wheel.

Or some kinda crap like that.
[/quote]

Well, to clear up any potential confusion, the calculation above already assumes that we are applying the torque at the center of the wheel. More exactly speaking, the moment of inertia "I" that I used above is calculated assuming that you are trying to spin the wheel at the center. (with respect to z-axis, in wikipedia) If you want to know what happens when you try to spin it somewhere other than at the center, you have to calculate the "I" again, which will neither be trivial nor realistic.

If you can find a link to that post, I would be very interested to read it. I wouldn't know what to search for though.

 

[mattleegee]

im trying to unlearn things, interesting stuff

So if someone went from a 24lb rim to a 17lb rim
that would be 28lbs total, same size rim, but 0.5" wider

That would be like loseing 56lbs of sprung weight? or am i totally effed up now?

 

[spinzero]

[quote author=Mattleegee link=topic=84487.msg1598021#msg1598021 date=1185827872]
im trying to unlearn things, interesting stuff

So if someone went from a 24lb rim to a 17lb rim
that would be 28lbs total, same size rim, but 0.5" wider

That would be like loseing 56lbs of sprung weight? or am i totally effed up now?
[/quote]

You're correct sir. The effect of going 24lns -> 17lbs would be somewhere between 42~56lbs sprung weight, with the needle pointing towards the 56lbs end.

Width really doesn't play into this, since this is a rule-of-thumb calculation that assumes the same traction for all cases. Obviously if you get a lot more traction by going to heavier rims+rubbers, you may very well improve your 0-60. So I'm not saying this is the only facator or anything like that, but all else being equal, this is what it is.

 

[JMS3GTL]

anyway i could get this in laymans terms?
Big wheel bad.
Heavy wheel bad.
Big heavy wheel very bad.

dude I'm no caveman

 

[EvilGenius]

[quote author=BLUNTFUNK420 link=topic=84487.msg1599628#msg1599628 date=1185863603]

anyway i could get this in laymans terms?
Big wheel bad.
Heavy wheel bad.
Big heavy wheel very bad.

dude I'm no caveman
[/quote]
*grins* Sorry, I was having a little fun.

Really that's it though. Assuming you retain stock outer diameter (OD), any increase in wheel/tire combo weight will behave as though you increased chassis/cargo weight by NEW_WHEEL_TIRE_WT - OLD_WHEEL_TIRE_WT * (some number between 1.5 - 2).

So if I go from 45 lbs wheel + tire to 50 lbs wheel + tire, I'm adding the equivalent of between 5 * 1.5 * 4 and 5 * 2.0 * 4 = 30~40 lbs chassis/cargo weight working against my straight-line acceleration.