Wondering if I dun goofed - Toyota GR86, 86, FR-S and Subaru BRZ Forum & Owners Community

Zeezy · 02-28-2017, 01:06 AM

I recently got new wheels and tires for my car and I think I may have chosen the wrong tire size.

Wheels are 18 x 8.5 and Tires are 245/40 R18

This wheel and tire combo increases the overall diameter by ~27mm (~1 inch)

In hindsight I feel like I should have gone with 245/35 R18 or 235/40 R18

Is this 1 inch increase in diameter too much?

What impact will this increase have?

Thanks in advance!

SCQTT · 02-28-2017, 01:36 AM

It will basically increase your overall gear ratio. Which may have a little effect on how quick your car is, but will give it a higher top speed (and higher in each gear)

It will also change the accuracy of the speedometer. Chances are it read a few MPH faster than you were actually going when stock. Now it might read a little slow. Remember this will change depending on speed. For example now you might be going 31 and only show 30 and might show 70 but be going 74.

You can do some measurements and a little math and get a good idea of where you will be.

PandaSPUR · 02-28-2017, 02:57 AM

According to this: https://tiresize.com/calculator/

Your actual speed will be 4.5% higher than what your speedometer reads.

tyler_win_photo · 03-01-2017, 05:59 AM

It'll make the car feel slightly sluggish compared to stock and possibly look a little odd. If you're not tracking your car, you shouldn't have much to worry about. Like others have said, just keep in mind that your speedo is going to read lower than your actual.

nikp · 03-01-2017, 07:49 AM

You'll find that the speedo reading lower from your tire diameter change is pretty much offset by our cars reading faster from factory.

Go download a GPS speed app and drive at a constant speed. Look at your speedo and compare it to the app.

guybo · 03-01-2017, 08:00 AM

It's also going to affect your grip levels and balance. If you have not done any power mods, it'll make the car harder to drift and probably a little more boring to drive.

Shinchu · 03-02-2017, 07:22 PM

In short? Yes. You goofed.

Kendallkab · 03-02-2017, 07:28 PM

Just curious.. did you see the thread under this and then started to think you goofed?

02-28-2017, 01:06 AM	#1
Zeezy Member Join Date: Feb 2015 Drives: Black 86 GTS Location: Adelaide, South Australia Posts: 14 Thanks: 7 Thanked 0 Times in 0 Posts Mentioned: 0 Post(s) Tagged: 0 Thread(s)	Wondering if I dun goofed I recently got new wheels and tires for my car and I think I may have chosen the wrong tire size. Wheels are 18 x 8.5 and Tires are 245/40 R18 This wheel and tire combo increases the overall diameter by ~27mm (~1 inch) In hindsight I feel like I should have gone with 245/35 R18 or 235/40 R18 Is this 1 inch increase in diameter too much? What impact will this increase have? Thanks in advance!

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
I dun goofed into a curb	sittinSideways	Scion FR-S / Toyota 86 GT86 General Forum	17	03-31-2015 12:00 AM
I dun goofed... need help identifying interior wire	Turbowned	BRZ First-Gen (2012+) — General Topics	26	05-17-2014 11:51 PM
Subaru dun goofed: what steering wheel controls?	Turbowned	BRZ First-Gen (2012+) — General Topics	9	03-20-2013 11:25 AM
I dun goofed.. RIP BRZ	thelegaCy	BRZ First-Gen (2012+) — General Topics	90	11-04-2012 05:54 AM
i dun goofed?	Andyx5044	Scion FR-S / Toyota 86 GT86 General Forum	30	10-26-2012 12:19 PM

02-28-2017, 01:36 AM	#2
SCQTT ZWEI KOLBEN Join Date: Feb 2017 Drives: 2017 86 Halo 6MT Location: Mikes Sky Rancho Posts: 245 Thanks: 106 Thanked 163 Times in 88 Posts Mentioned: 1 Post(s) Tagged: 0 Thread(s)	It will basically increase your overall gear ratio. Which may have a little effect on how quick your car is, but will give it a higher top speed (and higher in each gear) It will also change the accuracy of the speedometer. Chances are it read a few MPH faster than you were actually going when stock. Now it might read a little slow. Remember this will change depending on speed. For example now you might be going 31 and only show 30 and might show 70 but be going 74. You can do some measurements and a little math and get a good idea of where you will be.

02-28-2017, 02:57 AM	#3
PandaSPUR PandaPandaPandaPandaPanda Join Date: May 2014 Drives: 2015 BRZ Limited CWP Location: New York City, NY Posts: 1,432 Thanks: 776 Thanked 697 Times in 438 Posts Mentioned: 12 Post(s) Tagged: 1 Thread(s)	According to this: https://tiresize.com/calculator/ Your actual speed will be 4.5% higher than what your speedometer reads.

03-01-2017, 05:59 AM	#4
tyler_win_photo Senior Member Join Date: Dec 2013 Drives: 2014 Scion FRS (Asphalt) Location: Redmond, WA Posts: 559 Thanks: 39 Thanked 173 Times in 143 Posts Mentioned: 6 Post(s) Tagged: 2 Thread(s)	It'll make the car feel slightly sluggish compared to stock and possibly look a little odd. If you're not tracking your car, you shouldn't have much to worry about. Like others have said, just keep in mind that your speedo is going to read lower than your actual.

03-01-2017, 07:49 AM	#5
nikp Junior Member Join Date: Jun 2016 Drives: 2016 BRZ Location: Sydney Posts: 8 Thanks: 0 Thanked 0 Times in 0 Posts Mentioned: 0 Post(s) Tagged: 0 Thread(s)	You'll find that the speedo reading lower from your tire diameter change is pretty much offset by our cars reading faster from factory. Go download a GPS speed app and drive at a constant speed. Look at your speedo and compare it to the app.

03-01-2017, 08:00 AM	#6
guybo Huge E85 fan! Join Date: May 2016 Drives: 2016 Scion FRS Location: Tampa, FL, USA Posts: 1,850 Thanks: 539 Thanked 1,010 Times in 605 Posts Mentioned: 32 Post(s) Tagged: 0 Thread(s)	It's also going to affect your grip levels and balance. If you have not done any power mods, it'll make the car harder to drift and probably a little more boring to drive.

03-02-2017, 07:28 PM	#8
Kendallkab Senior Member Join Date: Nov 2015 Drives: Black MT LMT BRZ Location: Everywhere Posts: 142 Thanks: 159 Thanked 20 Times in 17 Posts Mentioned: 0 Post(s) Tagged: 1 Thread(s)	Just curious.. did you see the thread under this and then started to think you goofed?

User Name		Remember Me?
Password