It seems to me that there's a MAJOR disconnect between wheel manufacturers and tire manufacturers. Have you ever noticed that the standard 17" wheel width is 7"? Check it out for yourself. 90% of all the 17" wheels made come standard with 7" widths. If you want wider wheels, you usually have to pay a premium for them.

Having said that, most performance tires require AT LEAST 7.5" wide rims and prefer rims even wider. WHAT'S UP WITH THAT? Don't these manufacturers ever bother talking to each other? What do they think . . . tires will magically shrink to fit on wheels not designed for them and rational people will purposely buy tire/rim combinations that are out of spec?

I just don't get it.

 

dunno.. but why does the larger the tire.. for example stock is 215/50/17 and u buy a tire 235/45/17 set the speedomater off less then 225/45/17?? the width makes the car speed change? since when?

 

It doesn't have anything to do with speed, AznWontonboy. It has to do with safety.

 

i dunno, i think you were the one with the spread sheet, but i entered in a wider tire, and the speed changed..?

 

Yes. But what does any of that have to do with rim width?

 

I made the spreadsheet. The speed doesn't change. It is the speedometer reading that changes. By going to a different size tire, the overall diameter changes. By changing the diameter, the reading on the speedometer will be off. That is waht the spreadsheet calculates....how far off the speedometer will be....

 

Using an undersized wheel width causes a bit more curvature to the sidewall. So handling won't be as precise. The sidewalls are so stiff on these low series tires that the additional curvature doesn't compromise the safety significantly. Personally, I think going to a 17" wheel is more for cosmetics than performance anyway.

 

The second number (ie profile) of the tire is a percentage of the width of the tire. In otherwords, the 235/45/17 tire's sidewall is 105.8mm high (45% of 235mm). The 225/45/17 has a sidewall height of only 101mm compared with the stock tire sidewall height of 107.5mm. So yes, the 235/45/17 is a better match than the 225/45/17 for our car.

And BTW, a good rule of thumb for rim/tire sizes is that the rim width should be at least 75% the width of the tire. So, on our stock 17x7 rims, the widest tire you should use would be a 235mm (75% of 235mm is 6.94"). Keep in mind that these are just guidelines. I'm sure many people have used 245mm tires on 7" wide rims with no problems.

 

So are you suggesting that people disregard the tire manufacturer's guidelines for minimum rim width?

 

uhhh nevermind, i found the answer out on the miata tire calculator. when thestock tire size, 215/50/17 is changed to 235/45/17, the tire is wider, but also the area from the rim to the ground is thicker, changing the speed. so 225/45/17 would set the speedo off differently then 235/45/17.

 

y2kse: I completely agree with you. Since Maxima's need wider tires than those 7" wide rims can hanlde, it really limits our choices if we want to use the best fit larger tire size (235/45/17). Most of the manufactures must anticpate more sales to smaller cars that have smaller overall wheel diameters and use narrower tires (up to 225mm width). Sure it stinks but there is nothing that we can do about it other than try our luck with an out of spec tire or go with a narrower one that doesn't match the original diameter as well. How many front wheel drive cars out there that use a 235mm width tire? Not many. That is the problem for us.

 

beagle max u spelled ur cars color wrong.. check out my link.

 

i mean signature woops

 

Thanks. How did that "n" get in there?

 

magic

 

Now that were on the topic of rims and tires I have a few QUESTIONs:

1) Will a 18x8.5 rim with a 34-offset OR 45-offset fit withOUT ANY problems?

The online website says a 17x7.5 with a 39-offset and a 18x7 with 42-offset will fit. However, I want 18x8's, but they ONLY offer the 18x8.5 size.

2) What would happen if I went with the 8.5's with either a 34-offset or 45-offset and which would be better? Why?

3) What would be a "reasonable" good weight to try for in an 18" rim?

The 20x8.5's weigh in at a HEFTY 33lbs., but I don't know what the 18's weigh.

4) How much difference in weight should I be concerned with or should I be concerned at all?

Damn, I sound like my girlfriend after she checks her a$$ out in a mirror!

 

I wouldn't advocate disregarding the manufacture's reccomended wheel widths. I would say keep them in mind and try to follow them. As you go outside the fitment range the tire will behave differently, but there won't be any catastrophic failure. Just don't stray too far.

 

Color me conservative, brubenstein, but I'm not prepared to simply keep a manufacturer's recommendations in mind. When they say "minimum", I believe them. And every tire manufacturer will tell you that for best performance, you should use a rim width that falls midway between the minimum and the maximum. For 235/45's, that means using an 8" rim width in most cases.

But that still doesn't get to the issue I raised at the beginning of this thread. Why do wheel manufacturers manufacture rims that are too narrow for the tires they're designed to support? Nobody's touched that question yet.

 

I drove an AE with no mods and compared it to my SE with 16" rims, FSTB and RSB. I can definately say that the 17" rims made a big difference vs. my 16s. Plus I think the stock Toyos on the 16s are lame. They look low on air pressure (bulging sidewall) even when inflated to 35 psi.

 

According to a diagram I seen on the Tire Rack, for a 225/50-17 tire, the rime width could be 7"-8". The wider the rim the more of the same tire exposed to the ground.

= better traction!

 

When I recently got new tires I wanted something a little wider than stock (205/65 to 215/60). My rims were 6" wide. I though it was on the small side, but it was within spec. I got a used set of SE rims (6.5" wide), because I knew it would work better. (I couldn't afford $1200 for a decent set of wheels.) So I agree with you that proper rim width is important. I just think that most wheel makers figure that people getting big wheels are doing so for fashion. For looks, a half inch too narrow is no big deal.