The 45 in the tire size is an aspect ratio which represents 45% of the section width. So when you go wider to a 245 you need to drop the sidewall down to a 40 series to maintain the OE overall diameter. So basically, as you go wider each size you need to go "shorter" in sidewall height. If you go with a 245/45R17 you'll be over the OE overall diameter and that's a def no no.

IMO I'd say run a 245/40R17 as that will be the closest to OE diameter without going over. Its better to be 2" under OE than 1" over. The OE 235 also looks slightly narrow on the 8" wheel IMO and a 245 will solve that problem as well.

235/45R17 = 79.5
245/40R17 = 77.6
245/45R17 = 80.6


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The 45 in the tire size is an aspect ratio, so when you go wider to a 245 you need to drop the sidewall down to a 40 series to maintain the OE overall diameter. So basically, as you go wider each size you need to go "shorter" in sidewall height. If you go with a 245/45R17 you'll be over the OE overall diameter and that's a def no no.

IMO I'd say run a 245/40R17 as that will be the closest to OE diameter without going over. Its better to be 2" under OE than 1" over. The OE 235 also looks slightly narrow on the 8" wheel IMO and a 245 will solve that problem as well.

235/45R17 = 79.5
245/40R17 = 77.6
245/45R17 = 80.6


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Awesome, thanks so much for the reply. I've been reading around and see you replying and giving input on all kinds of stuff, so again... thanks for taking the time!

245/40R17 is what I was leaning towards too after looking at the calculators and taking into account what I've been reading. My initial want was to just get wider 245's to fix the narrow look that you mentioned, but my lack of knowledge coupled with extreme anal retentiveness has led me on a week long search to try and understand the in's and out's of tire size choices.

I think going from 235/45R17 to 245/40R17 would make for a tire that is 0.7" shorter in sidewall height than OEM, which is where my concern about much of a "low profile" look I will have compared to how the OEM's look on the wheel and also within the wheel well. My worn out OEM Dunlop's are probably pretty close to what I would see on new 245/40R17's if I was to somehow measure how much tread has worn off since they were brand new.

So, would this equate to 0.35" less tire sidewall above and below the wheel (I guess "all around" the wheel since it's round)?

Does anyone have any photos for comparison?

 

I'd get new wheels if I were you. If you want to keep the wheels I'd use 235/40R17. The 5-speed is tall. Shorter tires would be better. 245/40R17 will work but that's a very wide tire for an 8" wheel. It actually exceeds the 120% rule for 40 sidewall tires by a very small amount. Certainly safe, but I doubt the added width is going to help much against the added flex. Then again, if the 245/40R17 is cheap then go for it. However, I would expect the 245 would cost a good bit more and have a crappy selection and thus really not be worth it.

 

I would definitely buy new wheels if it was in the budget at this time!

I ended up with the Michelin Pilot Supersport's at 245/40R17 @ $203.00 each. The 235/45R17 OEM size was $175.00 each for comparison, so yeah it's a bit of jump in price but not too much to scare me away.

I'm taking a bit of a shot in the dark, but I really don't like the narrow look on my OEM Dunlop 235's. I'm only speaking about how it visually looks, and I know it's not all about looks so I am taking a minor risk. I'm reading that different manufacturers measure out differently so a 235 width might be slightly different across multiple brands. I hoping the 245 Michelin gives me a nice square look without losing and performance.

 

Exactly OP. so take that height difference and divide that by x4 and that'll give you what you'll actually "notice" in wheel well gap difference from the top of the tire to the top of the wheel well. You'll BARELY, if at all be able to tell the difference in wheel well gap.

Good tire options IMO woul be the below. Tires are the one thing you never skimp on in any way, but seeing you've already mentioned Michelin you're already on the right track. Good luck OP

Michelin Pilot Sport A/S+
Bridgestone RE970 A/S



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Nice choice OP! That's what I plan on going with soon as mine are done. Where'd you buy em at that price? Tire Rack has a promo on Michelin right now and they're $179.50 per after rebate.

And yes all manufacturers specs are slightly different. So no 2 tires will ever be identical. Michelin makes some of the widest specs out there so that 245 is gonna be sitting nice an square ?


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Yep, I got them from TireRack.com. You're right they do have a rebate too! Sweet!

I'll take some pictures and post them once they are installed so you can see how the 245 Michelin sits on the stock wheel.

Now I need to maybe start thinking about better springs and shocks/struts. I would love coilovers, but I can't skimp on those and also can't drop $3000 or whatever on a proper kit. I already can't push in my desk chair because under my desk is storage for a bunch of suspension/chassis goodies. I really want to lock down the chassis and suspension before I start adding power.

 

Suspension was actually a pretty recent convo had on here in another post. Here's the link for some ideas man. You're def going down the right mod path though. Glad to have you be part of the forum.

http://www.wrxtuners.com/forums/showthread.php?t=34834


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then there are the bfg kdw's and Kumho XS that have some of the stiffest sidewalls available... just an idea. 8" wide = 235/40/17 or 245/40/17

Tire size calculator

But Mosc is right....

 

OP I'm replying to your suspension question here rather than in that other thread to help keep forum searches a little more well placed. That thread is a diag thread so others searching would prob be doing so in this section. But....

If you're up for the added costs up front of struts along with springs then complimenting either Eibach or H&R springs with a strut from Koni or GTWorx would be the way to go IMO. Obv lowering the car is going to decrease the life of the struts and paying x2 for the install of struts down the road is kind of silly when thinking of it unless you have your own shop and you're not going to be paying x2 know what I mean. But doing it all at once isn't in the cards for some so riding out the OE struts might be the way to go too. The OE struts could last 5k...or could last 50k you never know really.

For some, running a spring like an RCE Black would be another good option for springs as there's a very slight drop difference and that would "potentially" allow for longer strut life. But again, there's no way to know how long the OE struts will hold up to the lowered springs.

I've personally not done mine yet so hopefully some more forum members will chime back in with their opinion. Reach out to someone like 'brfatal' too if he doesn't notice this thread and give his 2c as he's quite knowledgable on suspension work with Subaru specific vehicles. My opinions on suspension mods/brands comes from conversations with other trusted forum members and conversations with TiC about my own plans and ideas for suspension work. Tires/Wheels is a little more my specialty. But I hope the above helps and just know you're on the only forum worth being a part of. The guys here are top notch! The other guys posting/mentioned in this thread are just a few to speak of when it comes to trusted names.


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Most of the suspension options on the market are designed to achieve an astetic drop and function safely with the stock suspension. Handling improvement is not a concern whatsoever. If you want that type of thing, lowering springs and stock struts are perfectly safe. They will degrade your handling slightly, your ride quality will be completely destroyed, and your struts will not function correctly. Again, safe but astetic only is an understatement.

Correct suspension design is to raise the spring rate in proportion with a corresponding drop as well as a stiffer strut that can handle the new spring rate. Your stock setup is balanced with these three factors: springrate, ride height, damping. To actually improve things, you must change all three and you must also keep all three in balance. In other words, you need higher spring rate springs with only a reasonable drop and much better struts.

Or, you know, just slap on some lowering springs and do some burnouts in the pep boys parking lot. Your call.

 

Specific brand recommendations for achieving all 3 of these things Mosc?


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WRX struts are pretty junky. For many years, they were the same as the Impreza struts. All impreza's also use a tall strut design in the front which allows for more throw (important in off-road rally). These factors mean your stock strut is just not going to cut it, especially up front, if you plan on either a drop or increasing spring rate or both. The STi struts are considerably better but many years have compatibility issues between the WRX and STi (04 STi is compatible with 02-07 WRX only. 05-07 STi is not compatible with any WRX, for example) and they're also not that cheap. I'd recommend D-spec struts to all who want to improve performance on a street car. They can handle a ton of spring rate and still function.

Assuming a strut like D-specs, you have several spring options. A classic lowering spring would be silly as their spring rate increases over stock are fairly mild (since they are designed for stock struts). A correct spring rate for that much drop would be quite stiff, but with the D-specs would be functional and a great performer on level surfaces. Swift is one company that makes both lowering springs and performance springs. Their performance springs are called R-spec I believe, and are well in excess of the stock STi springrates and have a similar drop to most WRX lowering springs. The ride quality of having a functional strut with that much spring rate will still be better than an overwhelmed WRX strut dealing with the drop of a "lowering spring".

RCE makes two very nice spring choices as well, their "yellow" and "black". They say both can be used with stock STi struts but they're a little much. D-specs or similar struts would be better. The Yellows are like the Swift R springs, designed around a very high spring rate and the corresponding drop. The Blacks are a hybrid spring, more graduated than the stock design. The springrate is fairly high but the drop is only moderate. This delivers a lot more ride quality than the all out racing springs while only sacrificing a fraction of the handling. It does, however, keep more "wheel gap" in the front if that's a concern.

The Impreza's frame and suspension geometry is purposely designed for rally. That means 15" wheels with 25" tires and lots of room for throw. That way you can keep both wheels down on uneven terrain and deliver power to the front wheels around a turn. Driving around with your wheel at the fender level looks cool on a flat asphalt road but would be a severe hindrance on a bumpy dirt road.

 

Thank you very much for detailed info ?


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I would add that an overwhelmed strut is basically a blown strut. They similarly fail to damp the bound and rebound of the spring. You don't need a strut to do any damping to drive safely. This however will be very bouncy and will not stop weight from shifting the tire out of contact with the road. Particularly on non-level surfaces this is disastrous to your grip. There are minor issues like additional wear on wheel and drive elements from slamming around without sufficient damping but for the most part, struts are about improving the performance of suspension from springs alone along with improvements in ride quality.

I am pointing that out because I've seen lots of guys with lowering springs on their car and stock struts drive around for tens of thousands of miles. They check their strut and they're not only dead, they never felt them go. They were not doing anything useful even when they still had some life.

EDIT: Some techincal notes. RCE blacks and yellows are for STi struts (or better yet aftermarket struts). There are now "RCE Regular Guy" springs, which are colored black but not the same as RCE blacks, that are specifically made for 09+ WRX struts. The spring rate is lower and the drop is mild but they're fairly balanced if the goal is maxing out the WRX strut. Thanks to Riot for pointing these springs out. Also, the D-spec struts are basically custom made. Turn In Concepts has some pre-made for the 02-07 WRX/STi but for the 08+, they need to be special ordered. Call them directly.

 

Wow! Thanks so much for the input from everyone! You guys already helped a great deal with the initial tire size discussion, and now I'm well on my way to choosing springs and struts.

I've been looking at the RCE options myself, and I think I'm in love.

I already have the following ready to be installed (some of the stuff was cheap and/or randomly asked for on my Christmas list, so I'm not sure if I will be installing everything):

Beatrush Forged Pitchstop Mount
Kartboy Short Shifter
Turn In Concepts Shift Linkage Bushings
Turn In Concepts Wide Shift Lever Pivot Bushings
Kartboy Rear Shifter Bushing
Beatrush Shifter Link Bushing
JPM Coachworks Shift Boot (Black Alcantara / Red Stitching)
JPM Coachworks Armrest Cover (Black Alcantara / Red Stitching)
Whiteline Steering Rack Bushings
Cusco Steering Rack Power Brace
STI Group N Transmission Mount
Whiteline Gearbox Positive Shift Kit
GoodRidge Stainless Steel Coated Clutch Line
Stoptech Stainless Steel Brake Lines (Front & Rear)
Whiteline Rear Differential Positive Power Kit (KDT905)
Whiteline Rear Differential Positive Power Kit Bushings (KDT906)
Whiteline Front Inner Lower Control Arm Bushing
DeatschWerks DW65c Series Fuel Pump
Dimple Magnetic Oil Drain Plug

On the way:

Kartboy Front & Rear Endlinks
Eibach 25mm Front Swaybar / 22mm Rear Swaybar (Adjustable)
Nameless Performance Axle Back Muffler Delete Exhaust
Cusco Front Lower Arm Bar Type II

Installed (easily a 20WHP gain with these parts alone... !Laugh!):

RallyArmour Mud Flaps
Cusco Short Antenna
Michelin Pilot Super Sport Summers Tires (245/40ZR17)

I had my new tires installed this morning and they look and feel great! I can't wait to drive home! I'll post pictures of how they look on the stock 8" wide WRX wheel when I get home. I thought the tires would be way too wide when looking at them off the wheel, but I think they are just right for looks and I'll give them a performance test on the way home (33 mile drive back up the mountain).

Thanks again for the input from everyone! I think I like it here...

 

My goal is to install as many useful bits as I can before I start with the motor. I want all of the surrounding suspension and chassis components (brakes too) to be rock solid and not be "lacking" or holding me back when I add power. I also feel, although I don't really know if it's true, that upgrading my mounts and reducing flex should allow power to be delivered to the wheels more efficiently and therefore any future horsepower gain will be "that much more" pronounced (whatever "that much more" means is currently beyond me).

 

Hmu with a PM anytime you'd like some input or just to mix ideas OP. Glad you're part of the forum. Some pics would be nice ?


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I have no idea idea what's going on, but here's some pictures of how the tires look.

 

Gravity and the laws of physics in general don't apply where I live, as my pictures show. ROFL

How do I rotate attachments? These were taken and uploaded from my cell phone (Galaxy Note II).

 

Those look perfect on there! Glad you're happy too.

You should be able to rotate them with your cell camera app though.


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The photos looked okay on my phone... meh, I'll figure it out later. Yeah the tires felt really nice too on the drive home.

Now I have to think about winter wheels and tires, or getting new summer wheels and tires when the Michelin's wear out and keeping the OEM wheels for winter... something like that. I kind of want 16x6.5 wheels for the winter with meaty rubber.

 

VaughanJer,

Its time for me to replace the stock rubber on my 2012 WRX and a quick google search got me here. I am considering the exact same thing (going with 245/40/R17 tires) and I am looking at Michelin Pilot AS 3.

Now with probably a few thousand miles on them, would you care to share your experience with the wider tire?

Thanks in advance!

Juan