Is there any point to running bigger wheels in the back?

[jabb]

I've heard of people around the internet running 16s up front and 18s in back or 18s and 20s and so on. I'm wondering if there's any benefit to this other than aesthetics. Also if anybody has some pics of their ride/any ride set up this way I'd like to see them. I don't think thats any kind of look I'd dig, but I won't knock until I at least give it a try.

Edit: I'm also having trouble deciding which I like better: the filled out, big tire look of the boss mustangs or the big wheel low profile tires on modern sport scars (a'la Porsche 911) Convince me!

 

[D.Hearne]

Bigger tires in the rear were for better traction. As for which looks better, the older 15" wheels and tires look better on these older cars. The few I've seen with modern 18+ inch wheels just looks retarded to me. Let the flame war begin...........

 

[jabb]

I know wider tires in the rear give ya better grab (and just look sweet) but do larger diameter tires do so too?

 

[D.Hearne]

Larger tire diameter also gives better traction, via a larger "footprint". But they also reduce the final drive ratio. For instance, a car with a 3.50 geared rear, if shod with a taller tire, would reduce that ratio to something less, like 3.50 to 3.40, depends on how bigger in diameter the tire is as to how much the ratio is reduced. This generally is good for fuel economy, but bad for accelleration. But don't confuse this with a taller diameter wheel, I'm refering to the tire's actual outside diameter

 

[Hack]

The way you have phrased the question you are asking about the rim diameter. No, a change in the rim diameter doesn't do anything. Some people might run a larger diameter rim to clear big brakes. Big brakes can make a big difference if you are using the car for road racing or something, but most brake upgrades that require a rim larger than 15" are overkill for street driving. Edit: also you definitely don't need larger brakes on the rear as the fronts do the majority of the braking, since that's where the weight is.

In fact, larger rims and tires generally weigh more than smaller sizes and actually degrade handling due to the additional weight. In my opinion most people run larger rims for appearance. I think that 14/15 is a little small, but 18s seem a little large on a classic to me.

Another edit: larger rims using shorter/stiffer sidewalls can help cornering if the car is set up to take advantage of them. They can also make the car less comfortable to ride in over the road.

D. Hearne has done a good job explaining the effect of tire outside diameter changes and rim/tire width changes.

 

[D.Hearne]

And in addition to Hack's excellant pointers, shorter siffer sidewall tires can also reduce traction, depending on the tire's compound. The O.E. tires on my 06 GT Stang (17" P-Zero's) give great handling to the car, but absolutely suck, big time in the straight-line traction department.

 

[gsxrken]

It is for looks. It is actually bad for performance, because a 18, 19, or 20 inch rim is much much heavier than a 15 inch rim, and it's heavier where it really counts- out on the circumference. Remember that a wheels weight gets you three ways. You have to start it spinning, (and stop it spinning) and the big rims have all that weight out on the hoop. That much heavier weight has to be controlled by heavier spring and shock rates. And of course they add to the overall weight of the car.
Past 17s, which you usually need with big disc brake packages, you're into bling and not performance.

EDIT- Hack beat me to my thoughts on this!

 

[Hack]

It is for looks. It is actually bad for performance, because a 18, 19, or 20 inch rim is much much heavier than a 15 inch rim, and it's heavier where it really counts- out on the circumference. Remember that a wheels weight gets you three ways. You have to start it spinning, (and stop it spinning) and the big rims have all that weight out on the hoop. That much heavier weight has to be controlled by heavier spring and shock rates. And of course they add to the overall weight of the car.
Past 17s, which you usually need with big disc brake packages, you're into bling and not performance.

EDIT- Hack beat me to my thoughts on this!

Yeah, but your explanation is a good one and worded differently than mine. IIRC F1 cars use 15 inch rims, so you sure don't want/need large diameter rims for high performance.

 

[jlangholzj]

And in addition to Hack's excellant pointers, shorter siffer sidewall tires can also reduce traction, depending on the tire's compound. The O.E. tires on my 06 GT Stang (17" P-Zero's) give great handling to the car, but absolutely suck, big time in the straight-line traction department.

drag tires are an excellent example of this, a little more give, little more traction (from what I understand anyway)

I geuss I never really was a fan of running a larger rim in the rear, only a larger tire. dependingon the rim/tire 16-17 is the largerst i would every DREAM about going. the rest look dorky

 

[bnickel]

i actually prefer my old 15" wheels, the problems with 15's any more is that tire selection is getting extremely limited and a really good high performance tire in more than 2 sizes is totally not going to happen. for my needs the good old radial T/A is just fine since the car will be mostly a cruiser with only the occasional spirited driving outing. my mustang has 17" e'brock 454's right now but i'm going back to 15's on the 69 cougar. if i ever decide to take the car to the track and do some laps i may try to get used set of 16's or 17's with some track tires but for the street i'm staying with 15's.

 

[zookeeper]

Another thing to consider: big wheels, such as 18's and up, weigh MUCH more than smaller wheels like 15's or 16's and it's all unsprung, rotating weight. That means not only will the car ride worse, but it'll be slower. One of the loacl pro builders arond here took a cutomers '70 Chevelle he built to the drags during street race nite. Basically they turn off the timers and it's run whatcha brung. Even though the Chevelle had a healthy small block, it also had 20's in the rear and 18's up front for a truly stupid look. He got his butt handed to him not once, but three times by the Honda Civic crowd due to no traction with those dumb-looking wheels.

 

[1320stang]

There are guys running low 7's in the 1/4 on 28x10.5 slicks with 1500+ hp. You don't need a wide set of meats in the rear thanks to tire technology.

 

[ttop88]

I used 17's to get the look I wanted. I did have 15's on it first and it just wasn't "right"
View attachment 339654

 

[wicked93gs]

I plan on using 16s myself...a bit bigger sidewall in the back though...I for one will never use any wheel bigger than 16" simply because they dont look right and dont add any performance advantage...on my neon I refuse to use anything larger than 15s because the weight simply isnt worth the "look" and besides, contrary to popular belief, wheel gap can be filled with tire just as easily and look just as good, in short, I agree with everyone else...there is no point to running large wheels

 

[65ShelbyClone]

I'm committed to 15s here. Yeah the sidewalls are taller and yes they will squirm more, but I'm after more of a '60s Trans Am style that's the kind of stuff they used. I have a '57 Ford rear end that is narrower than the stock '68 so I could get away with 9" tires in the back, but it's also a street car and I want to be able to rotate the tires.