Hectorm

Hey, guys have you noticed any difference when pulling your car from cero (fast start) after you change the wheels/tires? any drop in performance in this matter?

JeffTsai

iTrader: (1)

Your acceleration will be slower with bigger rims/tires.

Rock-a-Lex

iTrader: (4)

Agreed...but if "overall" diameter (rim + tire) is the same and "overall" weight is the same there should be no difference.

o2GS43o

Bigger rim/tire, slower accel...

bighitbike

I didn't really notice anything except I couldn't chirp the tires at all. But that is most likely because I went from 225's to 275's

aristotle

iTrader: (7)

this is what i also thought when i was plus-sizing my car's rims from size 14' to 16' a few years ago. as long as diameter and weight stays the same, acceleration will not be affected but then somebody told me about 'rotational inertia'.
i'm no scientist so the only way to explain it is by reading this article from mazda6tech.com:

Rotational Inertia

While often considered to be synonimous with unsprung weight, rotational inertia is a different term altogether. It is possible to have a heavy wheel that has little inertia, or a lightweight wheel with lots of inertia. A wheel and tire with a lot of inertia takes a greater armount of torque to slow or accelerate, making the car sluggish.

Have a pencil in front of you? Try this: hold the pencil upright by its eraser. Now spin the pencil in your fingers as if you were trying to make a dot on a sheet of paper. It takes almost zero effort to spin the pencil this way, right? Now hold it the pencil's center, between your finger and thumb. Rotate the pencil back and forth, as if you were shaking it to hear loose parts. Feel how it takes more effort to rotate it this way? That is because the mass you are rotating is further away from its center of rotation. Ever notice how an ice skater or karate man tucks their leg in to rotate faster? It's the same concept. If you don't feel the difference, try the same experiment with a larger object such as a broom handle or a baseball bat. Spinning a broom handle like a propeller will take more effort than turning it like a giant drill.

Likewise, the further a wheel and tire's mass is from the axle, the more torque will be required to accelerate it. If a car has 16" wheels and those wheels are replaced with 17" wheels of identical weight, the amount of inertia that wheel carries will probably have risen between 7 to 8 percent. Going up another inch would add another 7 to 8 percent, and so forth. It adds up quickly.

That's assuming the larger wheels weigh the same, which is often impossible. With a larger diameter wheel comes exponentially more surface area needed to create the outer edge of the rim, which is the worst possible place to add weight. Increasing wheel diameter AND increasing weight (even if only a modest amount) will produce rather noticable drawbacks- you can loose 1-2 car lengths (or more) in a 1/4 mile race. Going with wider wheels raises the amount of metal required too, although it does so only linearly.

However, the largest contributer on the entire car to rotational inertia is the tire. Tires are even further out from the axle than the wheel, and usually weigh more too. Some street tires weigh as much as 4 pounds less than their competitors through the use of lightweight materials. Hoosier racing tires, until recently, were made of fiberglass belts instead of steel for the purpose of weight savings (until new regulations prohibited this). That mere four pounds per tire extra will require about the same amount of force to spin as it would take to carry a date riding shotgun! A small difference in tire weight can make a large difference in rotational inertia.

This is a compelling reason to run smaller diameter tires, as larger diameter tires have more inertia per pound and are heavier due to the increased amount of rubber. The weight and inertia savings of going to a skinnier tires is comparitively smaller than decreasing diameter.

Of course, going to a skinnier, softer wheel and tire combination can sacrifice handling (detailed in another article), so it's up to the tuner to find the proper balance for their car.

Rock-a-Lex

iTrader: (4)

Well put... but the weight of the wheel/tire combo of stock 16" 5-spoke lexus wheels are approx. 44 - 45lbs. My 19" wheels weigh in @ 28lbs.(courtesy of wheelweights.net) and my tires weigh 21lbs (courtesy of frisbyracetire.com) which equals 49lbs.; 5lbs. heavier per corner is not THAT bad for going up 3" in rim size. Oh, and just think I don't even have 3-piece forged wheels that some of these other members have which are MUCH lighter and there are DEFINITELY lighter, better performing tires out there. Oh, and rotational inertia was discussed numerous times on this site...the rotational inertia on a rim/tire combo of the same weight and dimension as another is the same; no matter how you slice it (unless the tires have an outer edge made of lead and the center of the wheels are made of paper mache'.) LOL!

UZ214

i have 3 peice, forged rims, running 275's in the back 19" and 245 in the fronts. i feel my car the same if not quicker than my stock wheels...i was really surprised myself..yea the big wheels will slow you down if the are heavy ..

ICEBERGS

My car is a slug with heavy 20's...My brother has a GS4 as well still on stock 17's, and he walks away from me everytime. Not even close... At least it looks good!!!

tommyGS3

iTrader: (4)

i rather hav the looks of 20''s, and roll like a slug

chuckb

I've been running my stock 16s for a few months again for no other reason than my car feels quicker. I'm ready to race.

Lexmex

When I moved up to 235-70-16 from the stock 225-70-16 on my RX, I noticed takeoff was a little slower (but I need the grip on the roads here).