[jl001300]

Does anyone know if it can be done or how low you can lower your car with 18x8 rims. I believe the offset is 51. I would like to get 18x8s but I also do not like the large gap between tires/fenders.

 

[RNN14]

Do you intend to actually drive this vehicle to work everyday and race it or just waste hp trying to turn the over sized things and show off? I'm just not getting the novelty sized rim and tire thing in the US.

 

[iceNine]

RNN
Are you refering to wasting horsepower just because the wheel diameter (not the overall tire diameter) is larger or because most larger wheels are heavier? The SSR wheels (the Competition model anyway) in 18 inch are slightly lighter than stock US OEM 16 inch wheels.

Dale

 

[RNN14]

Both diameter and the weight. Almost all the guys who go with the big rims seem to be after looks and not any true performance gains. That being said the stock rims could use a lighter 17 in replacement if that is all he is after. I think the need for the 18 is probably just a visual appeal.

 

[Sunkist]

I like the way body and rims flow together with no large gaps distracting from the uniform look. True having large rims can alter performance but not everyone is shooting for a drag car here, a car can still be fast with big rims, people get new rims for looks mostly if they didn't then there wouldn't be such a large variety and only small light models would be on the market.

 

[schischwein]

While I agree that most people buy large rims for the looks and don't mind sarcrificing output, I also believe large rims are prove beneficial under certain conditions. Take for example 18"(7.5-8" width) rims...less sidewall flex and wider stance for corner carving ability is a possible gain in cornering. SSR type Cs aren't heavy wheels, I believe 17x7.5s are just under 13lbs per wheel. I personally think that in most instances 17's prove more useful as not every road is silky smooth and you still get quite a low profile for lower sidewall flex. By the way, my car will have 15's for a good part of the year....that is, they will be Compomotive TH2 rally wheels.

 

[RNN14]

If your refering to the low sidewall flex of the sidewalls with 18's then that is true but your also talking about a street driven car with roads that are far from ideal use for a 18in rims and tire combo. It just increases the odds of bending one and having that crappy shake in the front from a wheel that's no longer balanced or sometimes too bent that it has to be replaced. If over all cornering was your concern you would be after a set of coilovers and camber plates as well as a host of other suspension upgrades and brake upgrades long before a 18in rims and tire.

 

[Penguinking]

RNN
Are you refering to wasting horsepower just because the wheel diameter (not the overall tire diameter) is larger or because most larger wheels are heavier? The SSR wheels (the Competition model anyway) in 18 inch are slightly lighter than stock US OEM 16 inch wheels.

Dale

just because SSR 18s may be lighter than OEM 16's doesn't neccesarily mean they reduce pwr or waste less hp. because the weight of the SSR is distributed across a larger radius, there is more rotational mass, ie heavier weight on the circumference of the wheel. so while the wheel may weigh less on the scale, the power it takes to rotate the wheel may be more than a 16in.

if you play golf you know what im talking about

 

[Sherb]

Good observation Mr. Penquin about the rotational torque. But if one wishes to get larger diameter rims, the SSR Competitions is a good choice since its pretty light. Just imagine those other heavier, and larger diameter rims. Not only will they deal with the extra weight, but the extra rotational torque as well.

 

[dark_rex]

but what's wrong with getting 18's? whatever the person wants whether it be looks, cornering, reducing parasitic loss, or auto X, those are the wheels he wants.

whether you understand the tastes of "americans" <another nice little stereo type RNN, you do that a lot>, whatever. just because you don't like it doesn't make a difference to jl001300.
have one of you given the guy an answer yet? there have been 7 replies to the thread, and all by smart avid posters, yet no one helps? get off your horses and help the guy for god's sake. if you don't know the answer, don't resort to insulting the guy's taste or wants just to sound smart or taking the topic into a new direction.

no offense ladies, just making an observation.

jl001300,

becasue you're going with the 8 width on top of the 18" diameter, i think lowering is going to be a touchy mod. i would run a search. there are some members running 19x8's but with no lowering, and some running 18's with coilovers, but at 7.5 without the lowering you should be fine, perhaps with some minor adjustments. i'd also drop Dan a PM and pick his brain.

i'm moving this thread to the suspension forum. there are some other recent threads asking very similar questions, and some people that are in your shoes now. i'm sure you'll get the info you need there.

take it easy.

dR

 

[jl001300]

Thanks DR

 

[Big Sky WRX]

With a 51mm offset and 8" wide wheels, if you rub- it will be against the suspension. As one lowers a vehicle the camber generally becomes more negative. This will aggrevate a situation where you may be rubbing against the suspension. Four ways to possibly alleviate this potential problem:

1. you may have to use narrower tires than you want

2. increase positive camber at all four corners (moving the top of the tire away from the suspension).

3. wheel spacer- effectively lowers you offset (moves rim away from suspension).

4. decrease the amount of drop in your suspension

If no one has run this particular setup, then the only way to know for sure if it will work is to try it. But I'm guessing someone has tried this particular combination.

By the way Prodrive is actually advocating 18"'s to be used w/ their suspension (lower springs for know) that got better results than w/ 17". Interesting.

Big Sky

 

[FoamDonuts]

RNN,
just wondering but do you have Speed Channel in Japan? If you do then you can watch the best drivers in the world race on tarmac in rallies across the globe in the WRC. AND they ALL race on 18" wheels. Just a thought.
IKE
P.S. why couldnt you just let the guy get what he wants and not be so negative? Different strokes for different folks. Practice a tiny bit of tolerance and maybe you will live longer.

 

[FoamDonuts]

Now, to answer the original question. I have seen several people do it. I think with the +51 offset it will work. I run an 18x8 SSR Comp. wheel and I think it is somewhere around 42mm offset and it fits fine. I use the TEIN coilovers and I have yet to have any rubbing issues. Also, to address the overall height comment. When you start looking into buying larger diameter wheels go to www.ring-pinion.com and they have a tire height calculator in there that is very fast and a no-brainer thing to figure overall tire height. Hope this answers your question somewhat.
IKE

 

[bbrewer]

The issue of rotational mass always comes up when choosing larger rims. Can anyone define the equation that would allow optimizing weight vs mass when choosing larger wheels?

 

[PlatinumWRX]

The issue of rotational mass always comes up when choosing larger rims. Can anyone define the equation that would allow optimizing weight vs mass when choosing larger wheels?

Mass Moment of Inertia = I = | r^2 dm, where
| = the integral of
r = the distance of each particle mass from the axis of rotation
dm = particle mass



-Jim

 

[neoxman]

All right time for some specs....

jl001300,

I've been battling with this issue too of 18x8" wheels. I have the same goals (pretty much) as you do. I am design minded but also concerned about performance.

I have created a site, modWRX http://www.schulerdesign.com/wrx , hopefully to fill in the blanks of information for wheels and other mods to the WRX.

There is a lot of mis-information out there and lack of knowledge as to the affects of wheel width and wheel offset. What a lot of people don't know is that the width affects offset and vice-versa. When width changes so must the offset in order to maintain proper fit. In the case of the WRX sedan, the stock wheel is offset to "high" or inwards to my taste. This affects the look and design of the car in my opinion. After seeing the turbo magazine article on the White WRX with 18x8 SSR wheels I felt it was the best example of how the WRX should look (offset wise) see http://www.turbomagazine.com/archives/features/0102_features01.shtml

So to hopefully put this issue to a rest and give us rex owners some options I created the modWRX site. In the future I would like to expand this to other mods like suspension and engine mods. Let me know what you guys think.

 

[neoxman]

My previous post doesn't address lowering the WRX but believe the offset issue is still very important to preventing rubbing problems. Does anyone know who owns that Turbo magazine featured article, maybe we could gain some good insight into this issue.

 

[DoctorBob]

18 inch = 25% rotational mass penalty

Mass Moment of Inertia = I = | r^2 dm

And when you complete the integral, you get I = mr^2.

In short, when you increase the size of the wheel by 12% (16 to 18 inch), you increase the moment of inertia by more than 25%. So, if the 18 inchers are 25% lighter than stock, you won't notice the negative effect on your acceleration.

Here's a link that may be useful: www.dac.neu.edu/physics/a.cromer/Physics1192/Dynamics.html

Note: none of the above is a thumbs up or down for big wheels. The tradeoff of sidewall stiffness for increased rotational mass is up to the driver.

--
Your mileage will vary.

 

[Buglight]

wo0ow

And when you complete the integral, you get I = mr^2.

In short, when you increase the size of the wheel by 12% (16 to 18 inch), you increase the moment of inertia by more than 25%. So, if the 18 inchers are 25% lighter than stock, you won't notice the negative effect on your acceleration.

Here's a link that may be useful: www.dac.neu.edu/physics/a.cromer/Physics1192/Dynamics.html

Note: none of the above is a thumbs up or down for big wheels. The tradeoff of sidewall stiffness for increased rotational mass is up to the driver.

--
Your mileage will vary.

LEAVE THIS FORUM AND GO TO A SMART! SCHOOL. ...


and am too looking to find off sets and combos that work for these
18''x8.5'' with 38 offset(link): http://cgi.ebay.com/ebaymotors/18-3...012QQitemZ220154900505QQrdZ1QQsspagenameZWDVW