Optimal Wheel Size for Stock Power
 

I suppose I should be able to answer this on my own, and maybe I have, but I want your opinions.

Because of the ride height, size, and power of the FT86, I am seriously considering going to a smaller wheel size. I have some 18x9 Work XD9's, but after putting them on the car and driving a few miles, I really think they feel a little bit too big for the car. I know I don't have the car lowered (yet), but you can still get a feel for the wheel/ tire size without being lowered.

Here they are when I test fitted them:

http://sphotos-a.xx.fbcdn.net/hphoto...08848988_n.jpg

Honestly they are probably a great sized wheel for this car aesthetically, but I can't decide if I like the feel of them.

So I know that we all have our own opinions, but is there an optimal performance size for wheels and tires for this car? Where are the limits of too big vs too small if you are keeping the car near stock power? I am mostly going to daily drive the car, but I will be getting a couple of track days here and there as well.

I am thinking that a 17x9 would probably be that perfect size, and I could get take offs in that size as well for the occasional track day in the car.

Thoughts?

For a stock car and keeping performance, 17x7 or 17x7.5 with better rubber is the performance bet. You can probably go with 17x8 but a wider rubber selection will increase diameter and likely slow the car down a few tenths for certain situations. If its a track day it may help, but for street driving it'll be slower. Most might not notice or not care.

^Thanks. My thought was maybe a 17x8 for a daily, then save these work 18x9's for track rubber, or something along those lines.

This should help too:

[ame="http://www.youtube.com/watch?v=r_IWa_qlt3g&feature=player_embedded"]2013 Scion FR-S - YouTube[/ame]

Yeah, it sucks. You want to keep the performance yet look good. That's why I'm having a had time picking out wheels. I wanna stick with stock rubber size (215/45), but I want a light weight wheel that has some decent offset without looking too bad. Maybe some Work Emotion 17x7 or 7.5 and 32? Offset? I don't remember the exact size. Or go cheap and get some Rota Torque 17x7.5 for the time being until I decide if I want the Enkei RPF1 17x9 +45 that will be coming out in November.

I think I will do the 17x8 TE37's. I just wish the offsets were a bit lower. I am having a heck of a time deciding on wheels for this car. Usually the choices are pretty easy.

Yeah seen that video. I should of kept my MS3! Hehe This FR-S is a fun car. Someday I'll turbo it. Just waiting for the dust to settle and see how reliability is on this engine. I won't jump the gun like I did my Mazda.

I actually dont want FI. MAYBE if they release a factory supercharger with a warranty, but honestly I have had lots of turbo cars, big and small, and I have always enjoyed my NA cars more. My M3 was probably the best so far. The superchargers on my mini coopers were rockin' though. Anyway I want my engine to gain some power, but I don't anticipate going to a turbo.

That's why I'm going with the Visconte tune first. Just wish they had a local E85 station around here!! Bastards!! Haha

The problem is not that they are 18's, it's that you bought 28+ lb. wheels. Get a 18x9 that weight 18 lbs and I guarantee you'll see a huge difference. I believe the stockers are 20-22 lbs so you added alot of extra weight to rotate.

Obviously a 17" wheel can be lighter and have less rotational mass, but there's no reason you can't get the great aesthetics of an 18" wheels without destroying your cars performance.

some lightweight 16x8 with some Star Spec or something along the lines.

Less weight = more powah.

I might do SSRs type F in 18X8.5. or in 17s.

Just wish they made them in a wider size :(

a light 17x9 with a 245/40/17 will be ideal for a car that sees the track and autocross as well as the street, if it's more of a street car, go with 235/40/17.

18's look better but the 17 will be better for performance.

I didn't buy the works for this car in particular, and I think they are closer to a 22-24lb wheel, probably not a 28+, but I get your point. I think the front tires contact patch is a balancing act as well.

I think the size is just a matter of opinion. I think 18s make the brakes look ridiculously small. I'm running 17x8 RPF1s with 255/40 Star Specs. I'll probably go to 245/40 next time just to see if I can feel the difference.

The 255/40 works as well, but with an 8" wide wheel you can't really utilize it. When I was doing time trials in miatas, a 225 on a 9" wheel would be faster than a 225 on an 8" wheel, The 235 is abour as big as I'd want to run on an 8 before running into diminishing returns (excluding autocross, which I'm not really into)

My setup is for autocross, so there ya go. 245 may be the sweetspot for me.

P

I will be looking for a 18x7.5 with a 42-45 mm offset

OEM
17x7 5-100 48mm offset with 215/45-17 tires
Sidewall 3.8 in
Radius 12.3 n
Diameter 24.6 in
Circumference 77.3 in
RPM 819.0

Option 1
18x7.5 42-45mm offset wheel with 235/35-18 tires
Sidewall 3.2 in
Radius 12.2 n
Diameter 24.5 in
Circumference 76.9 in
RPM 824.0

Option 2 = Expensive as all Hell
19x7.5 5-100 42mm offset 235/30-19 tires
Sidewall 2.8 in
Radius 12.3 in
Diameter 24.6 in
Circumference 77.1 in
RPM 821.0

I learned over the years that if you keep the RPM close and the weight down you only lose by the drag created from the width, any deviation from this has direct effect upon gearing and power bleed.

How will it affect the trip/odom/mpg comp reading?

The problem with this is that almost no one makes a 235/35/18. 245/35/18 will be a lot more readily available or 225/40/18

It depends on the diameter of the tire. If you go with a 235/40/17 the speedo will read just a smidge high, where if you go with a 245/35/18 it will read a bit low.

Google a tire calculator and you can input different tire sizes to get an idea.

Better yet, use this calculator. Just type in stock spec on the left, and what you want to try on the right. Remember stock is:

215/45-17x7+48

Here is the link:
http://rimsntires.com/specs.jsp

Falken makes the Ziex, probably the least expensive.
FALKEN ZIEX 912 ALL SEASON 235/35R18 140-165$ per
and the
BFGoodrich g-Force T/A KDW-2 approx 180-195 per

18x7.5 ET 45
When speedometer reads 60mph (96.6km/h) actual speed will be 61.8mph (99.5km/h): 3% faster.

19x7.5 ET 45
When speedometer reads 60mph (96.6km/h) actual speed will be 59.9mph (96.4km/h): 0.2% slower.

Thanks for the info on those calculators.

Seriously a smidge?, you sound like the guys that tried to sell tires with me when I was at DTC. I retired (sorry about the pun) from DTC, three words " I know Tires"

http://www.miata.net/garage/tirecalc.html

BFGoodrich g-Force T/A KDW 2 235/35-19 XL Tire $175.00 Tire Rack

It is safe to assume that Toyota and Subaru spent considerable time and money coming up with this answer.

I think the key word is almost. There aren't any tires I would choose from the list in that size on Tirerack.

No. They did what would be the least expensive for them while yielding the best all around wheel they could. BMW is about the best sub 100k car company for wheel fitment and factory options imo.

Like this: http://i800.photobucket.com/albums/y...eering/187.jpg

Well the wheels I am thinking of getting are 17x8 +44. I hope they fall right into that performance range. I believe they are around 14lbs per wheel as well.

Nice!

I replied to your post on the fb page but I'll post this here for the sake of discussion:

TRD makes two wheels for this car both sized at 18x7.5 +46 and the recommended tires are 225/40-18 MICHELIN Pilot Super Sport.

The STI Concept has 18x7.5 +48 at each corner with Dunlop Direzza ZII, 215/45R18 at the front, and slightly wider 225/45R18 at the rear. The consumer version of the STI wheels are 17x7.5 +48. Best tire match is 225/45-17.

Toyota had a few demo cars marketing 18" BBS wheels on 215 tires (not sure on the rest of the specs).

Lastly, Team86 tuned this car for 4 months on the Nurburgring using 17x7 +48 STI/Enkei wheels from the Forester. I suspect the tire size was 215/45-17.

And you've seen the R&T video where they proved the stock 215/45-17 dimensions on better compound performed better than 235/40-18 on the same compound. Also, be mindful of the effect of weight when you increase wheel/tire width. The rule is 1.7 lbs net saving (0.7 lbs rotational) for each 1 lb saved in the wheel/tire combo assuming you maintain the same overall diameter. It's questionable whether the added rotational mass of 235+ wide tires is worth the added grip. Try to aim for lighter than stock because power on this car is scarce. Nobody knows this car better than Subaru/Toyota so I'd stick to their sizes specified above. 17" for thicker sidewall (more comfort) or 18" for flatter contact patch (more grip), 225 width for balanced grip/aesthetics.

Great, Thank you!

I put on 17 x 8 +48 with 235 40 17's
It's working out real well, great looks and improved performance

Those are both crap tires and awfully expensive for what they are.

0.9% is a pretty damn small margin so yes, a smidge. at 100 mph his speedo will be reading 101.

Those will fit very well, run a 235/40/17 for the best performance with those.