Determining the proper width size of the tire - Toyota GR86, 86, FR-S and Subaru BRZ Forum & Owners Community

CyberFormula · 10-04-2011, 06:37 AM

How would you go about determining the perfect width of the tire in the front/rear relative to your application and power of the car.

I'd imagine for a car like this going any wider than 8inches in width would be too much unless you're hitting 330+hp.

I'm thinking a 7 inches in the front and maybe 8 inches in the back.
However, I have a feeling this car will come stock at 7 inches front and back.

Dave-ROR · 10-04-2011, 07:55 AM

Staggered is fine if the suspension is setup or it (ie setup for oversteer). If not having a traction bias in the rear is going to mean understeer. I'd wait until you were traction limited due to power then change rear tires and then change springrates/sway bars/alignment etc

ichitaka05 · 10-04-2011, 11:45 AM

Quote:

Originally Posted by CyberFormula

How would you go about determining the perfect width of the tire in the front/rear relative to your application and power of the car.

I'd imagine for a car like this going any wider than 8inches in width would be too much unless you're hitting 330+hp.

I'm thinking a 7 inches in the front and maybe 8 inches in the back.
However, I have a feeling this car will come stock at 7 inches front and back.

That's not fully true. I used to know one Mx5 that was only 200whp-ish and using 9" on the rear and it was perfect size (don't oversteer or understeer). Like Dave state, it's all up on suspension setup.

Fortunate Few · 10-04-2011, 11:51 AM

I'm not gonna be staggered unless the car comes staggered.

no_name · 10-04-2011, 12:28 PM

Quote:

Originally Posted by Fortunate Few

I'm not gonna be staggered unless the car comes staggered.

+1
I'd rather keep it simple, hopefully Toyota agrees.

suprachica79 · 10-04-2011, 12:33 PM

Quote:

Originally Posted by no_name

+1
I'd rather keep it simple, hopefully Toyota agrees.

another +1. I like the look of staggered, but I think it's overkill unless I make some serious HP in this car, anything near stock I think should be kept the same, alot of engineering went into this car, and I trust that Tada-san and his cronies know more about correct engineering than I do

chulooz · 10-04-2011, 12:41 PM

Id agree that 7 all around in stock form should be ok, but it wont take much more power to reach the limits of that size. I would probably get rims to accomodate future plans.

SUB-FT86 · 10-04-2011, 12:45 PM

With the 370z when you upgrade to the 19" wheels and tire grip increases from .92g to .98-.99g with the width only increasing by .5. I wouldn't go too aggressive with the width if I wanted to.

Dave-ROR · 10-04-2011, 12:47 PM

Quote:

Originally Posted by no_name

+1
I'd rather keep it simple, hopefully Toyota agrees.

Subaru's PR already said 215/45/17 tires, so they will not be staggered. Since the tires aren't staggered then the wheels won't be either. OEM's tend to fit tires to the correct wheel size provided by the tire manufacturer.

For that size tire the appropriate wheel widths would be 7.0-8.0 for most performance tires. I honestly doubt they'd issue a 17x8 wheel so my guess would be 17x7 all around.

oneday · 10-04-2011, 01:03 PM

215/45-17? Ugh. Why an oddball size, I wonder? At least mfgs are starting to make some decent tires in this size now...though they can cost more than the larger, more common 225/45-17.

The other factor to consider when contemplating changing tires/wheels is the weight of the package. A car this light (2600ish lbs) and with this amount of power (190ish HP) will definitely feel different with just a 5lb per corner change.

ichitaka05 · 10-04-2011, 01:24 PM

Quote:

Originally Posted by oneday

215/45-17? Ugh. Why an oddball size, I wonder? At least mfgs are starting to make some decent tires in this size now...though they can cost more than the larger, more common 225/45-17.

The other factor to consider when contemplating changing tires/wheels is the weight of the package. A car this light (2600ish lbs) and with this amount of power (190ish HP) will definitely feel different with just a 5lb per corner change.

Oddball size? That's common size. I use that size for my DD wheel.

Matador · 10-04-2011, 02:04 PM

Car is built around the tyres, not vice versa.

suprachica79 · 10-04-2011, 02:07 PM

Quote:

Originally Posted by oneday

215/45-17? Ugh. Why an oddball size, I wonder? At least mfgs are starting to make some decent tires in this size now...though they can cost more than the larger, more common 225/45-17.

The other factor to consider when contemplating changing tires/wheels is the weight of the package. A car this light (2600ish lbs) and with this amount of power (190ish HP) will definitely feel different with just a 5lb per corner change.

I would have preferred 225/45-17 as well but there are enough options for the 215/45-17 that I'll be able to find something.

Dave-ROR · 10-04-2011, 03:03 PM

Quote:

Originally Posted by oneday

215/45-17? Ugh. Why an oddball size, I wonder? At least mfgs are starting to make some decent tires in this size now...though they can cost more than the larger, more common 225/45-17.

At least there are RE11s, Star Specs, AD08s, RS3s and XSs in that size.. and some closeout R comps that are likely pointless to use at this point..

10-04-2011, 06:37 AM	#1
CyberFormula Senior Member Join Date: Dec 2009 Drives: gti, nsx, integra type r,porsche911 Location: garage Posts: 536 Thanks: 1 Thanked 17 Times in 15 Posts Mentioned: 0 Post(s) Tagged: 0 Thread(s)	Determining the proper width size of the tire How would you go about determining the perfect width of the tire in the front/rear relative to your application and power of the car. I'd imagine for a car like this going any wider than 8inches in width would be too much unless you're hitting 330+hp. I'm thinking a 7 inches in the front and maybe 8 inches in the back. However, I have a feeling this car will come stock at 7 inches front and back. __________________

10-04-2011, 07:55 AM	#2
Dave-ROR Site Moderator Join Date: Dec 2010 Drives: Stuff Location: Florida Posts: 10,317 Thanks: 955 Thanked 5,965 Times in 2,689 Posts Mentioned: 262 Post(s) Tagged: 8 Thread(s)	Staggered is fine if the suspension is setup or it (ie setup for oversteer). If not having a traction bias in the rear is going to mean understeer. I'd wait until you were traction limited due to power then change rear tires and then change springrates/sway bars/alignment etc __________________ -Dave Track cars: 2013 Scion FRS, 1998 Acura Integra Type-R, 1993 Honda Civic Hatchback DD: 2005 Acura TSX Tow: 2022 F-450 Toys: 2001 Chevrolet Corvette Z06, 1993 Toyota MR2 Turbo, 1994 Toyota MR2 Turbo, 1991 Mitsubishi Galant VR-4 Parts: 2015 Subaru BRZ Limited, 2005 Acura TSX Projects: 2013 Subaru BRZ Limited track car build FS: 2004 GMC Sierra 2500 LT CCSB 8.1/Allison with 99k miles

10-04-2011, 01:03 PM	#10
oneday Opinionated Join Date: Dec 2009 Drives: Something Red Location: Holland Posts: 311 Thanks: 0 Thanked 9 Times in 6 Posts Mentioned: 0 Post(s) Tagged: 0 Thread(s)	215/45-17? Ugh. Why an oddball size, I wonder? At least mfgs are starting to make some decent tires in this size now...though they can cost more than the larger, more common 225/45-17. The other factor to consider when contemplating changing tires/wheels is the weight of the package. A car this light (2600ish lbs) and with this amount of power (190ish HP) will definitely feel different with just a 5lb per corner change. __________________ Most of the cars I drive have nets for windows.

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10-04-2011, 11:51 AM	#4
Fortunate Few will photoshop for ft86 Join Date: Mar 2011 Drives: 07 Mazda RX8 Location: Upland,CA Posts: 281 Thanks: 10 Thanked 15 Times in 12 Posts Mentioned: 0 Post(s) Tagged: 0 Thread(s)	I'm not gonna be staggered unless the car comes staggered.

10-04-2011, 12:41 PM	#7
chulooz Registered you sir Join Date: Feb 2010 Drives: 99 impreza coupe Location: DC / CT Posts: 1,666 Thanks: 259 Thanked 380 Times in 207 Posts Mentioned: 3 Post(s) Tagged: 0 Thread(s)	Id agree that 7 all around in stock form should be ok, but it wont take much more power to reach the limits of that size. I would probably get rims to accomodate future plans.

10-04-2011, 12:45 PM	#8
SUB-FT86 86 Member Join Date: Dec 2010 Drives: 2013 Toyota 86 2.0T (Asphalt) Location: Atlanta, Ga Posts: 3,129 Thanks: 126 Thanked 527 Times in 296 Posts Mentioned: 2 Post(s) Tagged: 2 Thread(s)	With the 370z when you upgrade to the 19" wheels and tire grip increases from .92g to .98-.99g with the width only increasing by .5. I wouldn't go too aggressive with the width if I wanted to.

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