Going up a tire size - Toyota GR86, 86, FR-S and Subaru BRZ Forum & Owners Community

julzbrz · 07-03-2021, 11:50 AM

Hey guys! I’m new to this forum and to cars as well (just got my brz back in january).

I have a question about going up a tire size/width. As you know, the stock tire dimensions are 215/45/17. I’m planning on sticking with 17in rims, but want to know if there will be any issues if i go up to 225/45/17.

What are the pros and cons? And will it throw off my speedometer?

Sorry if these are dumb questions, I’m such a newb lmao but I want to learn the most that I can! Any and all feedback will be much appreciated!

NoHaveMSG · 07-03-2021, 12:10 PM

225/45/17 is fairly common to use. Your speedo will read lower then you are actually going.

soundman98 · 07-03-2021, 12:44 PM

per wheel-it-fit.com, changing to a 225/45/17 means the tire diameter will increase from 625mm to 634mm, which would result in a speedo difference of -1.4km/h, which simply means at 60mph, the car will read about 0.5mph slower than actual.

which, my car and others in my families fleet consistently measures around 2mph slower according to speed signs anyways.

julzbrz · 07-03-2021, 12:50 PM

Quote:

Originally Posted by NoHaveMSG

225/45/17 is fairly common to use. Your speedo will read lower then you are actually going.

idk if im replying to this right but is there anyway to fix that or is it just something you gotta deal with? thank you for your reply!

julzbrz · 07-03-2021, 12:52 PM

Quote:

Originally Posted by soundman98

per wheel-it-fit.com, changing to a 225/45/17 means the tire diameter will increase from 625mm to 634mm, which would result in a speedo difference of -1.4km/h, which simply means at 60mph, the car will read about 0.5mph slower than actual.

which, my car and others in my families fleet consistently measures around 2mph slower according to speed signs anyways.

thank you so much for the reply! i will take that into consideration. a wider tire is grippier correct ?

Grady · 07-03-2021, 02:24 PM

Quote:

Originally Posted by julzbrz

idk if im replying to this right but is there anyway to fix that or is it just something you gotta deal with? thank you for your reply!

EcuTec can and I believe OFT will also. I have that tire size and a there is about a 1 to 2 MPH difference between Speedo and GPS at 70mph.

soundman98 · 07-03-2021, 03:55 PM

Quote:

Originally Posted by julzbrz

thank you so much for the reply! i will take that into consideration. a wider tire is grippier correct ?

Tire compounds are like girlfriends. And try to say that any one of them are better based only on size!

Tire compound grip is more based on other factors in the rubber and tread. Yes, there's going to be a slightly larger contact patch, but 10mm extra width isn't going to have a significant difference either way. I doubt one could even get much different in track times with that change. Might be good for 1/10 of a second at best

julzbrz · 07-04-2021, 01:45 PM

Quote:

Originally Posted by Grady

EcuTec can and I believe OFT will also. I have that tire size and a there is about a 1 to 2 MPH difference between Speedo and GPS at 70mph.

that’s not bad honestly, and seems like something i could deal with😂

julzbrz · 07-04-2021, 01:46 PM

Quote:

Originally Posted by soundman98

Tire compounds are like girlfriends. And try to say that any one of them are better based only on size!

Tire compound grip is more based on other factors in the rubber and tread. Yes, there's going to be a slightly larger contact patch, but 10mm extra width isn't going to have a significant difference either way. I doubt one could even get much different in track times with that change. Might be good for 1/10 of a second at best

i like that analogy

thanks for the helpful info! everyone on this forum seems so nice

tarzan_nojane · 07-04-2021, 04:16 PM

With a new set of Continental ExtremeContact 225/45-R17s my speedometer was right on the money (speedo gets more optimistic as tires wear). Manufacturers almost always calibrate speedometers to be 1-2 mph optimistic at 60mph to make sure they aren't responsible for you go over the speed limit.

Capt Spaulding · 07-10-2021, 06:49 PM

On 7" wheels the 225 may be slightly pinched and as a result be a wee bit squishier on turn in. It may also ride a little smoother.

Ernest72 · 07-12-2021, 11:46 AM

If it’s just for DD, keep stock size for light weight and playfulness.

07-03-2021, 11:50 AM	#1
julzbrz Member Join Date: Jul 2021 Drives: ‘14 brz Location: connecticut Posts: 15 Thanks: 0 Thanked 0 Times in 0 Posts Mentioned: 0 Post(s) Tagged: 0 Thread(s)	Going up a tire size Hey guys! I’m new to this forum and to cars as well (just got my brz back in january). I have a question about going up a tire size/width. As you know, the stock tire dimensions are 215/45/17. I’m planning on sticking with 17in rims, but want to know if there will be any issues if i go up to 225/45/17. What are the pros and cons? And will it throw off my speedometer? Sorry if these are dumb questions, I’m such a newb lmao but I want to learn the most that I can! Any and all feedback will be much appreciated!

07-03-2021, 12:44 PM	#3
soundman98 ProCrastinationConsultant Join Date: Sep 2013 Drives: '14 Ranger, '18 Tacoma 4Dr LB Location: chicago-ish Posts: 11,330 Thanks: 35,240 Thanked 13,675 Times in 6,782 Posts Mentioned: 98 Post(s) Tagged: 0 Thread(s)	per wheel-it-fit.com, changing to a 225/45/17 means the tire diameter will increase from 625mm to 634mm, which would result in a speedo difference of -1.4km/h, which simply means at 60mph, the car will read about 0.5mph slower than actual. which, my car and others in my families fleet consistently measures around 2mph slower according to speed signs anyways. __________________ "The time you enjoy wasting is not wasted time"

07-10-2021, 06:49 PM	#11
Capt Spaulding Persona Non Grata Join Date: Nov 2015 Drives: '15 BRZ (WRB) Location: On the Border Posts: 1,882 Thanks: 2,016 Thanked 2,781 Times in 1,200 Posts Mentioned: 10 Post(s) Tagged: 1 Thread(s)	On 7" wheels the 225 may be slightly pinched and as a result be a wee bit squishier on turn in. It may also ride a little smoother. __________________ Slow is smooth, and smooth is fast

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07-12-2021, 11:46 AM	#12
Ernest72 Senior Member Join Date: Jul 2016 Drives: 16 Silver BRZ, 04 Silver WRX wagon Location: Rockland county, NY Posts: 1,417 Thanks: 183 Thanked 771 Times in 442 Posts Mentioned: 1 Post(s) Tagged: 0 Thread(s)	If it’s just for DD, keep stock size for light weight and playfulness.

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