What should I know about 18" rims

[kxcntry99]

Hi everyone,

I am looking to upgrade from my stock 16" rims. It should first be let known that I want to keep my stock rims and get some all season tires to put on for the winter and the 18's I would like to use as only summer wheels. I am sure you will also need to know about my suspension setup and as of right now I am running with stock shocks and H&R OE Sport springs. I would eventually like to upgrade the shocks but I will probably do that when I get the tires straightened out.

Keeping that in mind...what do I need to know about putting 18's on our cars? Will they even fit? I will be running a "low profile" tire on the rim and I was thinking about the Goodyear eagle F1. If anyone has had experience with these let me know. Basically I am looking for how wide I can go on the rims and anything else I should know I would appreciate the help.


This is the first time I would be getting performance tires so I am new and need some help.

 

[wret]

...what do I need to know about putting 18's on our cars? Will they even fit?

Sure, 18's are an easy fit. The size looks good imo, although perhaps somewhat less practical than 17's. 225's are easy. 235's work with careful selection of offset. Even 245's if you don't lower too much.

 

[DSMSpyder99]

for 18x8 with a 40mm offset would be best. 35mm with a wide tire might hit the fender and 45mm might hit the knuckle

 

[kxcntry99]

although perhaps somewhat less practical than 17's.

Why less practical...my eclipse is my daily driver so do you mean that on a good sized bump I will be rubbing in the wheel well? I am really just looking to fill out the wheel well so would a 17 work best on my application. I was thinking 18 because I have the stock 16 on now and I thought if I went with a 17 and low profile tires I would not see much if a difference.

 

[wret]

I say less practical because:
A) Typically they are heavier than the same 17" wheel and tire.
B) They are a rougher ride and you risk damage if you have rough roads in your area.

 

[jtmcinder]

There are two "excuses" to run 18" wheels: you have gigantic brakes or you're trying to run 285s.

Otherwise, here's most of what you need to know about 18" wheels for this forum: they cost more, they force you to buy more expensive tires, they are more likely to need to be replaced sooner, and - are you ready for it? - they make your car slower.

Oops. Sorry. I got that last one wrong. At least, I forgot to include a proviso. Let me try again.

... they make your car slower under all conditions other than when you are braking.

Yeah. That's better.

- Jtoby

 

[Ballin' GS]

The only benefit to 18's are that they look better. i think they might handle better too, but thats debatable, JTM cinder would know about that than me. I got 18's and love, just for the look, but they are ALOT heavier.

 

[Defiant]

They make the little factory brakes look just darling inside them. Once you can find them.

 

[gsx rated98]

On the topic of wheels and offset. My wheels are 18x8.5 and i think it has a 42mm offset. Whats the widest tire i could put on without haveing to roll the wheel wells?

 

[wret]

Probably 225's on a lowered car which are kind of narrow for those rims. But you must know this already. It looks like you have them mounted.

 

[gsx rated98]

Yea, there already mounted. I bought them when i was first learning about everything(not saying i know alot, but i know alot more) and really didnt know any better as far as the width of the rim. The 225s work, might be able to fit 235s on their, but i dunno.
Thanks

 

[wret]

Yea, there already mounted. I bought them when i was first learning about everything(not saying i know alot, but i know alot more) and really didnt know any better as far as the width of the rim. The 225s work, might be able to fit 235s on their, but i dunno.
Thanks

235/40/18's are what you want. Just roll those fender flanges up and be done with it.

 

[wret]

They make the little factory brakes look just darling inside them. Once you can find them.

Some might argue that large breasts are impractical. Others might prefer them for esthetic reasons.

 

[2nd gen gst]

Depends on how low you want to lower your car. I'm lowered 1.25" all around with 18" rims with 245/35 18 goodyear f1 gs-d3 tires , and I didn't have to roll my fenders. If I decide to go lower, then it will start rubbing. But be prepared to spend more $$$.

 

[ivanr4g63]

I have the Eibachs sportlines who lower my car by 1.6 or 1.7 inches, with a set of 18x8 with 40mm offset and 225/40 khumo tires, no probs... they fit just fine, and i did had rubber hitting the fender everytime I drove thru imperfections on the road, but that was because of bad struts, that problem is gone, and rides pretty good.

then again I have a 1g.

 

[Defiant]

Some might argue that large breasts are impractical. Others might prefer them for esthetic reasons.

D'oh!

A Freudian slip is when you say one thing, but mean your mother.

 

[Defiant]

On the topic of wheels and offset. My wheels are 18x8.5 and i think it has a 42mm offset. Whats the widest tire i could put on without haveing to roll the wheel wells?

http://www.vfaq.com/mods/macross/offsetFAQ.html

 

[BOV]

Right now I'm running 18 x 7 1/2 Primax 922 Rims with Nankang N2 Ultra Sport rubber.
225/40 x 18. I put on H & R droping the front 1.7" & rear 1.4. My shocks are KYB G2's.
The stance of my Talon is looks menacing. The handling is excellent and a much more comfy ride than I anticipated. I'd say go for it!

 

[Jason99DSM]

5 x 114.3 is the lug pattern correct ?

 

[Defiant]

5 x 114.3 is the lug pattern correct ?

Yeah. Which is 4½" in the real world.

 

[paul s]

I have 18/8 with 235/40 and 41mm offset and the rear lip had to be trimmed after the allignment was done. the car is lowered 1.5 inches..

 

[Rice Over Wheat]

Otherwise, here's most of what you need to know about 18" wheels for this forum: they cost more, they force you to buy more expensive tires, they are more likely to need to be replaced sooner, and - are you ready for it? - they make your car slower.

... they make your car slower under all conditions other than when you are braking.

Wheel size with correctly matched tires is far less an important factor in determining impact on acceleration and top end speed than is weight of the combination. You're leaving out way too many variables that are calculated and are oversimplifying this issue which is why saying 18s make a "car slower under all conditions" is false.

Assume that you have the following sets of wheels and tires:

215/50 x 16 = 76.86 inches circumference
225/40 x 18 = 78.81 inches circumference
That gives a 97.5% accuracy at speed per revolution. Because the actual circumference of the wheels are very similar, weight is the more important variable.

Smaller radius wheels require less energy to make a single revolution, however they must make more revolutions to cover the same distance as a larger radius wheel…the latter point is minimized with the above wheel/tire combo. This means that from a stop, the smaller wheels can quickly get up to speed faster, however they have to spin at a faster rate. Larger wheels require more energy to get them moving from a stop because they have more mass.

There's all kinds of formulas for calculating rotational inertia, rotations per second, etc. But now you have to consider what happens once the two sets of wheels are up to a set speed…say 80 mph. Once you achieve a certain speed, now you have to contend with other forces like friction, rolling resistance, and once again mass.

Now smaller wheels are at a disadvantage because the pros of fast rotational speed diminishes in value as you increase in higher and higher speeds. You have to deal with friction that forces the smaller wheels with less mass to work harder (spin faster) to obtain higher speeds, and therefore translate power into acceleration. It's the same as gearing.

Larger wheels now have advantages with the additional mass. Once at speed, less energy is requires for each revolution to keep them turning. This also helps in lessening frictional loss. Larger tires also benefit from lower rolling resistance. The rubber does not deform under speed as much thanks to larger surface area and less revolutions.

Smaller wheels = fast acceleration
Larger wheels = higher top end

When it comes to racing and taking the above into account…I'd determine what your racing goals are and your type of car.

GSX = Smaller wheels for fast acceleration off the line and ¼ mile distance. Good for drag.
GST = Larger wheels for top end, street racing, helps traction. Good for highway.

 

[Injected]

Assume that you have the following sets of wheels and tires:

215/50 x 16 = 76.86 inches circumference
225/40 x 18 = 78.81 inches circumference
That gives a 97.5% accuracy at speed per revolution. Because the actual circumference of the wheels are very similar, weight is the more important variable.

Smaller radius wheels require less energy to make a single revolution, however they must make more revolutions to cover the same distance as a larger radius wheel…the latter point is minimized with the above wheel/tire combo. This means that from a stop, the smaller wheels can quickly get up to speed faster, however they have to spin at a faster rate. Larger wheels require more energy to get them moving from a stop because they have more mass.

I agree with almost everything Rice over Wheat says. However smaller radius wheels require taller profile tires thus making up for the additional radius provided by the larger rim as he says. And tire wall weighs less than the additional surface area added to the rim to accomplish the larger size. It is true that it takes less to keep the momentum of the wheel constant, but under acceleration the smaller tire has the advantage no matter what the speed. Since there is less mass that the engine must accelerate (F=MA thus A=F/M and the lower M is the greater A is) the smaller rim always wins (that's why all serious race cars have smaller rims).

However, again, 18's look much better .