Generally speaking, a rim with a fixed width can accomodate tires having section widths that vary plus or minus 1 inch.

With that in mind, logic seems to dictate that is it best to buy rims and tires that have identical widths, BUT, I wonder if there are any advantages to mounting a tire with a section width slightly wider or thinner than the rim width?

 

Very general. I run 245-45-17 on 17x7.0 nissan rims. 245mm x .03937 = 9.64". Ideally I should have 7.5", however.... Your tire should be wider than your rim width. Most rims have a recommended tire size. The recommedation will useualy give you a + or - one tire size. But, your tire will still be wider than the rim width.
REMEMBER...WIDER IS BETTER!

 

When you talk about tire width, you mean the section width, right?

BTW, do you know what are the widths of the stock 15" and 16" alloy wheels that go on 4th Gen and 5th Gen I30's and Maximas?

I think it's 6.5" for both. I'm thinking of putting a tire with an 8.85" section width on them. That should fit them because the specs for the tire recommend a wheel width of 6"

 

The recommended relationship between section width and rim width will change with the tire's aspect ratio. If you're talking a huge 75-series tire, you can easily fit a 275/75 on a 7.5" rim, but if you're talking rubber band 35-series tire you probably wouldn't want to go beyond a 225/35 on the same wheel. This is partially because of the bulbous geometric properties of tires in general (i.e. the tread width on a 275/75 will be less than on a 275/35 of the same tire) and partially because of the extra sidewall play you have with the taller tire.

For our application, with 50-series tires your section width should stay ~2 inches or so beyond your rim width. More width will give you better straight-line traction but sloppy handling, and obviously going the other way will have the opposite effect. I wouldn't go below a 215 on a 4th gen, 225s should be ok on the stock SE wheels but wouldn't really do much in terms of performance.

If you want to go wider, get some wider wheels--Z32 NAs are 16*7.5 and the TTs are 7.5F/8.5R. I have four TT rears and am running 245/45s all around, perfect width for this wheel. Also look into FD wheels at 16*8 and light as hell if you find the right ones, but you'll possibly need spacers. All can be found for dirt cheap and look at home on a 4th gen.

Keep in mind that wider wheels/tires usually means both more unsprung rotating mass and more rolling resistance, both decreasing gas mileage a bit.

 

8.85" = 225mm. that is fine for a 6.5 rim. When I get to work I'll look up the stock 15"and 16" rim width.

 

15"-6.5
16"-6.5
17"-7.0
18"-7.5

 

Thanks for the info!

 

Well, I can attest to the differences in the effects of both unspring weight and more rolling resistance between my original 215/60 x 15 Fuzion HR's on 15*6.5 rims and the 215/55 x 16 Goodyear RS-A's on 16*6.5.

There are many things I like about the larger rims and tires, but the one thing I do not like is how much more effort is needed to move the car around.

The 16" tires give the car a more stable ride, and they are harder to break loose than the 15's...but they seem to require a lot more throttle to get the car moving at the same pace that I could with the 15's. Passing rate is also an issue.

By comparison, chirping the 15's was fairly easy to do, and a thing that needed to be controlled...especially when the roads were not clean and dry.

During hard U-turns, the 15's used to knuckle under, whereas the 16's refuse to do so. Instead, they will require me to follow a wider turn arc; that is, unless I dial in a lot more oversteer.

It's amazing just how much body lean is a function of one's tires.

I'm not sure on the difference in weight between the 15*6.5 wheels & the 16*6.5 ones, but, combined with the larger tires, each 16" wheel & rim feels about 10 lbs heavier than the 15" wheel & rim.

I'd love to know what is the actual weight differential.

All in all, I guess it comes down to a choice between more stability (and safety?) versus quickness and maneuverability. I also think that larger tires might take longer to wear out.

Thoughts?

 

There are advantages to be had by changing the tires width. They are similar to increasing or decreasing the tires profile. As you reduce the width you get sharper turn-in and a more stable contact patch, you also get a harsher ride and faster breakaway when you exceed the traction limit. Increasing the width improves ride comfort, but slows the turn-in feel and makes the car feel softer when loaded in a corner. Breakaway is more progressive reaching the limit, but may be harder to gather up once sliding.
It really depends on how you use the tire. For most people on the street they won't notice anything beyond the ride. On the track you start to notice initial turn in, how the car feels loaded, transitional feel, and balance under braking.

 

In making comparisons on my car between the 15's and the 16's, I have the added factor of going to a different style of tire. The 15" Fuzions were more of a performance tire and the 16" Goodyear RS-A's seem more like a touring tire.

I remember one time switching from Bridgestone 950's to Turanzas -- both 215/60 x 15", and noticed a big difference in their handling characteristics. The Turanza is more of the touring type tire with deeper treads and straighter grooves that seemed more at ease with straight-line driving. The 950's, on the other hand, liked taking curves and had triangular-shaped grooves in them to help with grip on turns and wet roads.

The amount of sidewall flex was also different -- probably as a result of their design. The 950's had rounded tread grooves on the edges while the Turanzas were squared off...thart is, until I rounded them off after several thousand miles.

So, I switched back to a more, performance-oriented all season tire.

I cannot explain why my car feels like it needs to work harder with the 215/55 x 16 RS-A's versus the 215/60 x 15 Fuzions on getting the tranny to downshift into a passing gear..but it does. Seems like its greater rolling resistance and mass might be the reason. The RS-A's do a good job of taming the torque steer on dead-stop accelerations, especially on wet roads.

Even if they break loose, they keep the car going straight until it recovers. Same thing on turns. If they break going into a turn, the car does not veer off to the side, but stays in its trajectory and spins until grip is restored.

Getting the 15's Fuzions to not break loose on dead-stop accelerations required a bit of pedal modulation. Passing felt a lot quicker and easier to obtain. On wet roads, when the tires were fairly new, the Fuzions did a good job of reducing hydroplaning and losing traction...assuming, of course, that judicious use of the gas pedal was made. Otherwise, they would send the car sailing off to the left until I either lifted off the gas or gave it some brake.

When new, I liked their responsiveness. Makes me wonder what if I was running 16" Fuzions instead of the GS-A's (which came with the rims when I bought them).

In any event,. I decided to keep the 16's on the car and hold onto the 15's, and, at some later date, try putting wider tires on them (like 225/60 x 15, or maybe even 265/50 x 15 if I get wider rims) and see the differences they might make.