Input for my Rim/Tire Setup - Subaru WRX Forum
 
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post #1 of 10 Old 03-25-2017, 12:04 AM Thread Starter
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Question Input for my Rim/Tire Setup

I use my '17 WRX Limited as my daily driver. I'm around the NY area daily, and the roads here are absolutely terrible.
There are countless possibilities(maybe not) for rims. I'm not adding any camber, or spacers(yet), but I am going to do a .8" drop with my new coilovers.

I'm looking to make the car comfier, without sacrificing too much performance. I'm not sure if it's possible, but heres the list I have right now:

I'm looking to get the Continental ExtremeContact DWS06, unsure what width I should get.
Are there any benefits to going 18x9.5 or 18x9, from the stock of 18x8.5?

After reading a few threads, I was informed that for a WRX the stock offset is +55, and the general rule of thumb is to stay within 5mm or else risk rubbing.

A lot of the rims that I'm looking at are around the +48mm offset. So with that, if I were to get rims with:

18x9.5 or 18x9, with an offset of around +48mm, with a .8" drop, what kind of tire height and width should I get? Would I get any rubbing from it?

What do I want? Less rough travel, minimum impact on performance.
This is all making my head hurt, so seriously, thanks for the help.

*Edit
How about O.Z. Ultraleggera 18x9 +55mm, with 265/35/18, is this possible with the .8' drop? I could possibly pick up the Pilot Sport AS3 as it isn't that much of a price difference.
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post #2 of 10 Old 03-25-2017, 02:10 AM
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Downsize rim...that's what I did for my winter tires. Winter roads in ny are horrible...
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post #3 of 10 Old 03-25-2017, 08:36 AM
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First of all it's not a "rim", it's a wheel. The wheel has a few components, the drop center, the face or "spokes", the lip or "rim", and a few other little things.

Now that we have our learning for the day, if you think having coilovers is going to be comfortable then you need to research more. Coils are on average 3-10 times stiffer than a factory spring, have more harsh valving, and simply put were never meant for comfort.

As for wheels, if you searched you would have found a site that lets you compare your current wheel/tire combo to what you're thinking about running with. I know you didn't search because we've answered this question within the past 7 days at least once before. There's even a link to said site in said post.

I really don't want to bash newbs, but most of you make it so damn annoying when there are over 10 sites with over 2 decades of solid info from the GC chassis up to the 2015 wrx chassis. Google is your friend, and if you think this little nag is bad, don't even think about joining Nasioc if you get your feelings hurt often lol. We have great info and are willing to help, but life isn't about giving out free stuff, you gotta earn some of it HA.

"Search for yourself" is not a tolerated answer around here. If you don't want to answer the question, don't reply. -mosc

Last edited by mosc; 03-30-2017 at 08:49 AM. Reason: mod voice
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post #4 of 10 Old 03-25-2017, 07:46 PM Thread Starter
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I recently got my car a few months ago, and before then I really had no idea about ANY of the specifics about a car. I recently just got promoted, so any time that I should have for my car is instead focused on work. Really just overworked out of my mind right now, and researching, working on my car is one of the only pleasures I have right now. I feel you though, the info is out there, I know it's there, but to me there is TOO MUCH info, some of it dating back to threads as early as 2004. Is the information reliable? Is this what I'm looking for? What if it isn't what I want? It's a lot of specifics.

I completely understand though. But this is a learning progress. I don't mind being bashed, in fact I rather like it. It shows how passionate people are about their cars, and I can totally respect that.

Also, about the coilovers. I've never had a set myself, and I'm looking at the HKS Hipermax IV GT; I've read several threads saying the ride quality is much better, as these coilovers have a wide range of settings to accommodate all aspects of driving.
Thanks for the information though, I'll run through the forums again and see what I can find.
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post #5 of 10 Old 03-29-2017, 12:10 AM Thread Starter
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*REMOVED*

Did a bit more research and it's hard to distinguish myself from what other people have.

A lot of builds dig the 18x9.5 +38 offset, with usually something on the 265/35R18 Tire size and above; with that in mind, they probably don't mind rolling their fenders to make clearance possible. I'd like to avoid that, so the obvious answer here for me is probably try to stick to stock measurements as closely as I can.
I'm just trying to find the sense in it. Why is the market for 18x9.5 +38 so big? Is it clearing most coils/brakes? Is it the perfect wheel for the car? Tirerack on the other hand, doesn't even show anything above 18x9, and even then they only have the O.Z Ultraleggeras with +48, and +55. I don't mind running them if it'll make my life a little easier now that I understand which tires to get.

Would my safest bet be getting +55 offset to make sure everything clears on the inside?

Last edited by mosc; 03-29-2017 at 08:30 AM. Reason: removed quote - mosc
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post #6 of 10 Old 03-29-2017, 10:11 AM
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18x9.5 +38 is popular because people want the spokes of a wheel to point outward towards the wheel's lip (convex wheel). They also want the wheel's upper lip to be flush with the exterior trim of the car (which generally exposes the bottom of the tire which previous was within the fender well). The look has many names, typically things like "hellaflush". Most of the time it's paired with excessive camber angle to try and fit the far lower than factory offset wheel within the stock-ish fender. It can also require coilovers to create a near-zero throw suspension (completely stiff) to prevent rubbing between tire and fender at close proximity. The only positive of this is the look. The negative is handling, ride quality, turning response (think schoolbus, not sportscar), tire wear (with enough camber it can be 10x normal), and even a real risk of catastrophic tire blowout.

The stock suspension, even if you change to a coilover, has a set geometry. It's expecting the center of the contact point with the road to be 55mm inset from the mounting point (hence +55mm offset). Changing this number adversely affects the suspension geometry of the overall car. A small deviation is not that noticeable. 5mm is considered small. More than 5mm is progressively detrimental. Track cars, who care little if the fenders are stock or not, balance suspension geometry detriment that comes with lowering offset with the increased tire width it helps facilitates.

In short, stick close to stock offset. +48 is fine. +38 is an entirely different conversation. At +48, you'll notice your turning radius has increased dramatically but the handling of the car should be pretty similar. Is more offset preferable? Yes. And I do drool over those 18x9" +55 OZ's often too.

The main purpose of changing wheels (beyond looks) is because you want to increase tire width. The tire then dictates the wheel width you need and to some extent the desired offset.

The 17 WRX has pretty good strut clearance from the factory. I haven't messed around with mine nearly as much as I did on the GD but everyone I talk to tells me the clearance is better towards the strut than it was on the GD. On my 04 I ran 255 wide tires at +48 without strut issues. I think on your car you could actually run that width +55 (say 255/35R18 on those 18x9 +55 OZ's) and clear. Don't hate me if they hit your front struts but I really don't think they would. If you want to be extra clear on this point you're going to have to "test fit" or put it on a lift and do a lot of complicated measuring.

Fender clearance is much easier to measure. You jack up the car in the front corner and look at the diagonal wheel that's now compressed and measure fender to tire (usually closest point is around 10 and 2, not straight up). The aformentioned 255 +55 would work (10mm less clearance than stock). 245 at +48 is commonly done (12mm less than stock). I'd do 15mm less than stock at most. When you get to 20mm, I'm pretty sure you're rubbing. 265 wides at +38 as you discussed are a whopping 32mm less than stock.

2015 STi: Still Stock
04 STi, 04 WRX: SOLD
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post #7 of 10 Old 03-29-2017, 10:28 PM Thread Starter
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That's exactly what I was looking for! You're right, that does seem like the ideal size, especially since I can keep the +55 offset. There are definitely not that many on the market.

I think I'm going to try and find something at +48 or +45, at 18x9. Wouldn't this actually give more clearance for my coils as opposed to +55s? I've heard of a few people not clearing their coils because of the offset.

So If I did my math correct, if I grab 265/35R18, on the +48s, I'm looking at about 27mm less than stock?
Would 265s run ok with the +55 OZs? I've heard that they're a perfect fit for them.

I'm getting really close to what I want, so I'll try and find some more wheels.
Thanks again
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post #8 of 10 Old 03-30-2017, 08:47 AM
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265/35R18 +48 vs 235/45R17 +55 would be a difference of 30mm of tire width, half on either side (30/2 = 15mm), shifted out by 7mm (55-48). So your math is a little off it's 22mm (15+7) closer to the fender than your stock wheel+tire. It's also 8mm (15-7) closer to the strut. I think 265 width at +48 would require a fender roll, as I said. I'd go to 15mm at most if you don't want to push the fenders. My opinion on interior clearance is there's at least 15mm there as well. Changing to coils will generally improve that number but it is pretty dependent on the specifics of the coil. If you really want 265 wide I'd say those 18x9" +55 ones are you're perhaps only hope of NOT rolling the rear fenders. It's 15mm less strut clearance than factory but everyone I've talked to seems to think that's fine on the 08+ cars with the double wishbone rear suspensions (it wouldn't be fine on the 02-07, that's more like 10mm MAX).

You also have to consider total tire diameter and it's effect on gearing. The WRX generally benefits from a shorter gearing setup so purposely staying a % or two under stock total diameter is good. With that in mind I'd point you more towards 255/35R18 on those 18x9 +55. You could get away with 18x8.5" at that tire width as well so you also have a few more wheel options (like say, stock 08+ STi wheels). Big tires are great on a track but do have disadvantages on the street, particularly in the wet. Comparing the stock wheels+tires to say 255/35R18 18x9" +55 Pilot Sport 3's or something is going to feel... much more planted and resistant to turn in. That setup vs the 265 +48 type deal will offer ever so slightly less ultimate grip (you'd never notice) but should give far easier driving behavior and give you less clearance fears (cringing when you hit a bump that your tire just destroyed itself on your fender and never letting anybody big sit in back).

Personally, I much prefer the slightly thicker sidewall you get with 17" wheels and when/if I change wheel's I'll be looking for something 17", not 18". My winter wheels are off an 06 STi which are 17x8" +53 (forged monoblock BBS and less than 20 lbs each) which work fine with 245/45R17 tires for an STi's slightly higher total diameter.

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post #9 of 10 Old 03-30-2017, 09:16 PM Thread Starter
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The 17 limited runs 245/40R18 Dunlops, but your point still stands.

I did a bit more research and there are a ton of people who back you up on your statement.
"Aside from the implications of going to low of an offset (reduced steering response, heavier steering feel, tramlining, reduced tire contact patch, increased wear and tear on everything between the steering rack and the hubs, etc), it's really too wide of a setup for non-track use"

There are a few peeps, who have tried and tested the 18x9.5 +38, they say it fits with no rubbing issue with a 265/35R18 on a 15' wrx

I don't even want those anymore so, I'd probably want to stick with something like:

18x9 with +42 to +50 offset
or
18x8.5 with +45 to +55 offset

Next up would be suspension components clearing.
From what I know, the 18x9.5 at +44 will clear the stock struts on a 15'
And that coilovers will generally have a bit less clearance than stock springs.

Assuming I go 18x9, I think anywhere between 42 and 50 offset would be okay right? Assuming a 255/35R18 tire
Also good news! I found some SSR GTV02s that are +45 Offset, 18x9. It's within my range

I know there will be a slight chamber with new wheels/tire, I think the alignment will fix that; so assuming that I can put the coilovers/wheel+tire myself, is it possible to drive to get my setup aligned? Still need to grab a lowprofile jack, and some jack stands.

Last edited by Bojango; 03-31-2017 at 01:23 AM.
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post #10 of 10 Old 03-31-2017, 08:40 AM
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Yeah you can drive on a (moderately) bad alignment it just burns some extra rubber and the handling will be destroyed. If you're being safe about it there's no harm in driving it to an alignment shop.

I don't think +55 is a problem at 255 wide tire (8.5", 9" or even 9.5" wheel) . I'd avoid +42. Generally the recommendation for Impreza suspension geometry is +48 or higher.

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