No, the axle doesn't "see" the wheel. But the engine will "feel" it and not be able to spin it up as fast.

2003.5 G35 Sedan Desert Platinum/Graphite Premium/Sport/Aero/Nav/Winter

 

No, the axle doesn't "see" the wheel. But the engine will "feel" it and not be able to spin it up as fast.

?


2003 G35 Coupe 6mt Diamond Graphite
1992 Jeep Cherokee Blk 5.5 RE lift /w 33s
AIM= bkchang79

 

If anyone with a stock g35 coupe on 20's outruns a stock g35 on stock rims in the 1/4 mile, i'd be very suprised....

 

Not to flame, i just dont want someone to make a desision on faulty info. But by that logic (the axel can't see the wheel width) then a light flywheel would not see any performance gains either. Granted, the flywheel will not change in size, but it will take less power to spin it. Obviously the flywheel with have a lot more to do with performance because it is affixed directly to the engine.

With bigger wheels of the same weight, a difference could be measured. This is because the weight is further out from the center. Imagine an axle connected to a pole with a weight on the end of it. If that pole is long, it will take more power to spin it.

Even better, imagine holding a hammer horizontaly, and spinning your wrist to position the hammer vertically, that task would be harder if the hammer were to have a longer handle.

I also understand that being that the weight of the wheel is spread out, and not only at the outer edge of the rim, but more or less, the analogy makes sense.

When it comes to a 11 sec GTO, I might assume that 550 foot pounds of torque might mask the unsprung weight advntage/disadvantage.

That's my $0.02... or maybe more like $0.04

 

SammyJL I thought the same thing as you. If the 18" setup vs. the 20" setup were the same weight it didn't matter. It just effects the tire flex. So does it matter if the weight is in the rim or tire? It all comes out the same when it hits the ground right?
My tires weighed more then the rims. I weighed everything seperate, then the overall 20" setup vs. the stock 18's.


BS G35C 6spd navi/aero/prem

 

Exactly, finally someone understands what I am trying to say. The only weight difference would be between the 2" of rubber vs the 2" of aluminum. I think that the weight difference would be neglegible between the two, especially when the 20" wheels are lighter than the 18" stock wheels.


Silverstone 6MT Maya DTM 20's

 

I personally think for performance - 18" is the limit - that is if you are truly interested in performance. 18"s are also a nice balance between looks and performance. If would like to go with 17" rims... but instead decided on 18"s for the SOLE purpose of having abig-brake kit upgrade path for later. I in fact may still go with nice 17" GT1's (SSR) or Volk TE/LE37's (only 1bout 14 lbs)... and go with a smaller diameter brake kit later.... Not sure

Gurgen

 

Sammy.... no. Even if the 20 and the 18 were the same weight, the 20 would still have a negative effect on performance. By spreading the weight farther out, you increase the required torque by the axel. It has to push harder than it would with the 18, which would take up more power from the engine, making it slower to accelerate.

Physics tells us that rotational inertia is related to the square of the radius of the wheel/tire setup. If you have 2 discs of equal mass, but one has a radius 2 times that of the other, it will experience 4 times greater angular accerleration than the larger disc. Now, the 1 inch increase in radius size between the 18 and 20 is not going to have a HUGE effect if they are the same weight. But, throw in the weight savings of the 18 (smaller, not chrome), and you will have a noticible difference.

Ah, the power of physics.

The bottom line, size and weight both have an effect on performane. An increase in either of the 2 or both will have a negative effect.

Is it E-ffect or A-ffect? I cant ever remember.

 

2k2MaximaRIP - you're right on the money. Must be the Maxima blood

Sorry guys:

http://www.maxima.org/shoptalk/sub_r...ns/index.shtml
I say read the whole thing, but if you want to see the part that disproves most of the crap spewed here, go to the section in red called <font color=red>"Wheel and Tire Weight!!!"</font color=red>

I know I'm a newbie to G35c's, but I'm no newbie to reading and research. And I'm certainly no newbie to Maxima.org

Edit - BlueGen2 - perfectly said. And, you're right, it's effect.

-Big_Ham
'98 SE 5MT
'01 SE 5MT
<P ID="edit"><FONT class="small"><EM>Edited by big_ham on 12/08/03 04:47 PM.</EM></FONT></P>

 

Awesome material big_ham. That really expains the whole concept of wheel/tire size and weight.

The only thing that I am still unclear of, and I'm sorry for being a nuisance but I just can't seem to get my question answered here, is that what if my 20" wheels weigh less than the stock 18's???? Will the weight difference even out the negative effect of the larger diameter wheel?

Heres another analogy, what if the 1" diameter difference between the two wheels weighs the same whether it is rubber or aluminum because the wheel material is lighter, how does the axle know if the wheel diameter is 18" or 20"?

Maybe I'm stretching for this one, but I am just curious.


Silverstone 6MT Maya DTM 20's

 

I have chrome 20s on my G and I have not really noticed any dip in power. I wanted the sweet look of the 20s and didn't mind giving up any minimal performance, but to be honest I have not felt a drop in power or speed.

Just my two cents...

afsarzad
'03 G35 Coupe Caribbean Blue/Blk
Sport / Areo / Nav etc...
Chrome GF-1 20s / 35% Tint / Clear Corners

 

Same here. I can tell a "slight" difference, but a new exhaust made up for any potentially felt losses in power. All the mumbo-jumbo talk around here is just theoretical. I think the actual loss of speed is very minimal. Hell, I have nitrous anyway, so I can laugh as I smoke G's on 17's with my super heavy 20's.

 

Rotating mass is truly a big deal. Getting these 20's to start moving takes more "oomph". They will also generate more drag at speed. So undoubtedly your car is now slower. I have proven this fact on the dyno with my Camaro SS. I went in on my stock 17x9 wheels with 275-40-17s. 53lbs combined. Made a run, then switched to my 17x11s with 315-35-17s that I take with me to the track. 62.7lbs. That 10lbs cost me 9rwhp. Just to make sure it didnt lose the hp due to being hotter I swapped back again just to gain that power back...which it did.

Now, in my case 400+rwhp, the 315s...regardless of extra mass, help me. The extra traction of the 315s far outweighs the loss of HP. Im sure that is not your situation though.

Thank you,
Discount Tire Direct
(888)459-4080 mention G35driver

 

Your question, Sammy, comes down to rotational force.
By making the center of wheel/tire mass further from the axis of rotation (with 20's), you're increasing your moment of inertia which will tend to slow the car down. All this "theory" (as someone else put it) is mostly true and it seems is most noticable off the line. Highway acceleration will not change as much as a rolling start or standing start b/c the wheels are really not moving at all (or not very much in the case of rolling starts). On the highway, the wheels have inertia of their own already and the wheels are not working against you as much. That said, with 20's that are lighter than stock 18's, you can overcome the moment of inertia and effectivey have or feel no difference. Chrome 20's are bound to slow you down a little bit.

That said, I have put this theory to work. My wife's Maxima has the boat anchor 17's that are referred to in the link I provided and I'll tell you that my car certainly has MUCH better acceleration off the line while she can walk me on the highway. While this has a little to do with the differences between the VQ30DE's used from '98 to '01, it has just as much to do with the wheel/tire weight/size analysis.

And, FYI, the axle doesn't "know" anything. It's all physics and how a larger diameter wheel will increase the moment of inertia. Kinda like an apple doesn't KNOW the acceleration of gravity, but it sure as hell accelerates at (9.8m/s)2 when it falls.

-Big_Ham
'98 SE 5MT
'01 SE 5MT

 

I give up !!!!

Maybe I'm just not explaining myself very well. It seems that everybody has the 20" number stuck in their head and will not look at this with an open mind. I will try once again and then that's it, I will not ask anymore.

Remember that I am saying that both the 18" and the 20" setups are exactly the same diameter with the tire included. Where does the cutoff point come into effect between where the outer edge of the wheel ends and the inner edge of the tire starts if the weight difference is neglegable between the metal and the rubber.

Does anybody understand what I am trying to ask here??

I've included a quick picture of what I am asking for.


Silverstone 6MT Maya DTM 20's

151778-Wheel.JPG