Since this topic has come up a time or two in this forum, I thought some would find this interesting...

Don't worry, it isn't a long read. Worth having a look!

http://www.caranddriver.com/features...sted-tech_dept

 

Interesting read. Although there are obviously a lot of variables that can be put into the equation, it's still good info.

 

Certainly makes sense. I didn't see any comments in the article about bigger wheels needed to clear bigger rotors, but other than that, the assertion that bigger wheels are on modern vehicles for more than styling reasons may have been laid to rest here.

Braking is slightly better with the 19" wheel compared to the 15" wheel, but since all they changed were the wheels I would have to guess it is due to the wider tires that are not available on a 15" wheel.

 

Interesting data indeed. Tks for posting!

 

Pretty cool. Results are as expected in terms of the trends. Nice to get a quantity as well. I wish they had the same compound for all the tires, but still a pretty thorough experiment.

 

i think on a daily driver, sedan these big wheels are a really bad thing for tire costs. i know someone that has a newer malibu. a set of average 4 tires cost him $1000(according to him). i think the wheel size is 18". now i bought some replacement tires for my 91 cavalier recently, tire cost $150 for 2, wheel size is 14". i also put new tires on the camaro last year. 16" iroc wheel with 245/50/R16's, set cost me $530. i dont mind $530 for a set of tires on a car like a camaro, being a performance car. for an average daily driver/grocery getter these bigger wheel just make the replacement tires too expensive. i like to stay in the $70-80 range or less per tire on an average commuter car

 

It's just tire prices keeping up with OE equipment. It's been this way for quite a while.

In the early 1990's when 13,14, and 15" wheels were very common, 16" was still somewhat of a performance option. Our 1990 Lumina Euro had them, and a set of tires was somewhere around $800 back then for the standard Goodyears that it came with.

Now even a Ford Focus comes with 16" wheels, so "commuter car" tires are now cheap again. And it's the 19-24" tires that are buku-bucks these days.

 

I don't understand the big wheel fad either. Sure its the new thing aesthetically for some, but what about the effect on mpgs, rolling mass etc... just dumb.

 

He either bought something real fancy or got ripped off. 18" OEM Goodyear tires on tirerack.com are $98 each.

Everything looks better with a 45 or 50 series tire.

 

Agreed. I love my 275/50/15's on the back of my Cobra.

 

The results seam to make a case for "lightweight" large diameter wheels as they would negate most if not all of the downside the article mentioned. Namely acceleration and fuel economy.

It was very nice to see how much the 18's increased lateral grip.

See, its not all for show Bob!

 

FWIW, back in the late 1980's while I was in college studying civil engineering, I took an elective course on transportation engineering. At the time I was also taking a graduate level technical writing course for engineers and my thesis was on four-link suspensions, which was all the rage in the pro-street world at the time. Needless to say, I was heavily into musclecars and modifying them for maximum performance as well.

A couple of us "car enthusiast" engineers got into a debate with our professor on the effects of tire width vs. diameter and how it impacts skid resistance and braking. As you may or may not know, when designing roadways we use super-elevation (banking) to assist with how a vehicle travels through a curve. The formula to determine the banking required is based upon design speed, curve radius and what is called a side-friction factor. What got the debate going was we were arguing that wheel radius, tire tread/material and tire width had to play a role in all this while the professor was saying that not only was it negligible but that it didn't even factor into the equation. Needless to say, he showed us examples of contact patches of tires in various conditions and went on to prove the formula correct.

This study does nothing more than affirm what most highway designers already know, the frictional forces that effect cornering, are related to speed, curve radii and the banking of the roadway, and that tire diameter, width, etc. is never factored into the equation. (as it applies to roadway geometric design.)

 

Re-read the article. They state the 18s were of a stickier compound, hense the improvement in lateral grip.

 

Bah. I saw this a week or so ago but sat on it, saving it for future use.

There goes my "Gotcha" card.

 

Can you tell me why those numbskulls are in love with decreasing radius onramps where one needs to be building speed in order to merge?