2012 Tire diameters, gearing & tuning. Stock ECU conflicts? - Ford Mustang Forum
 
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post #1 of 10 (permalink) Old 09-12-2013 Thread Starter
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Question 2012 Tire diameters, gearing & tuning. Stock ECU conflicts?

I currently drive a 2012 Mustang V6 Premium auto. I traded in my 4.0 Ranger and my gas milage has doubled! I have been saving so much money at the pump that now have the itch to modify!

One item I would like to do is put new wheels on. I have my eye on some TSW 20" Panoramas but I want to fill my wheel well. I currently run a stock 215/65-17 that has a 28" overall diameter. What is best to my eye is a 275/40-20 in the rear and a 245/40-20 up front on 9.5s and 8.5s respectively. These diameters come in 28.66 and 27.75 respectively. With 27" being the ideal diameter, my desired rear size is 6% larger I don't know if I can handle bogging down the car down even more.

So my problem is compensating the gearing. I already have an auto and 2.73 gears. So here a few questions I hope some of you may be able to help with...

If I swap out my gears for 3.15 or 3.31 ratio can I maintain a 2.73-3.00 gearing with this tire/wheel size? I still need the mpg to be reasonable and 30 mpg at 80 is a beautiful thing.

Can I swap the gears and correct/compensate with a tune? Will a tuner be able to make the car's ECU compensate that much or will my ECU get stuck in a Ford safe mode?

Will I be wearing or stressing the transmission or any other components quicker as a result?

Any good websites to figure out overall gearing ratios?

I could go with /35 sidewalls but I want the car to sit tucked on a tad more rubber.

Thanks in advance for your thoughts.


USEFUL LINKS
.tacomaworld.com/forum/tirecalc.php
.rimsntires.com/specs.jsp
.wheelweights.net
.arb.ca.gov/msprog/aftermkt/aftermkt.htm
.autos.aol.com/
.cargurus.com
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post #2 of 10 (permalink) Old 09-12-2013
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Interesting, subscribing to follow along


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My Mods So Far (in order): VA Legal Tint, Polk DB571 Speakers - Front & Rear, Third brake light pulser, MMD Classic Louvers, GT500 AB, Bondra Performance EZ-Clutch Pedal Extension, resonators cut out - do this!, Steeda shorty black antenna.
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post #3 of 10 (permalink) Old 09-12-2013
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Sadly you will no doubt lose MPG due to the added weight of the 20s alone...

I lost a little just going from my stock pony package tires 235-50-18's to 255-45-18's

Oxford White 2015 Premium GT with 50-Year Pkg | 3.55 Gears | Roush CAI (105mm Velocity tube) | Stainless Works Headers (Jet-Hot ceramic coated), high flow cats, H-Pipe CatBack full 3" with 4" tips| BAMA V2 93 Octane Tune | Baer EradiSpeed-Plus 2-Piece Rotors | JLT 3.0 Oil Separators | FRPP M-20201-M STB | Silver PP Wheels 19x9, 19x9.5 | NITTO G2 255-40-19, 275-40-19 Tires | J&M Jacking Rails & Subframe Alignment Kit | Steeda Subframe Connectors & Bushing Supports | BMR Front Subframe Brace | Cervinis 1232 Functional Ram Air hood | Ford Performance door sills | White Madness Garage Chrome Shifter | Diode Dynamics interior LED conversion stage 1 & XP80 reverse light | 3M Dark Ceramic Tint (25% sides/20% rear) | Lloyds "50 Years" floor and trunk mats...

Performance White 2012 Premium Pony Package | Torsen T2R 4:1 TBR | FRPP 3.73 Gears | GT500 Differential Cover | DSS 3.8" Carbon Fiber DS | Airaid CAI | BAMA 93R tune | Baer DecelaRotors (drilled/slotted) | BMR Adjustable Panhard & Brace | JLT Oil Separator | Boss 302 STB | Nexen N3000 255-45-ZR18Y tires | PP Engine Cover | 25% Tint

All cars should be rated for Smiles Per Gallon!
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post #4 of 10 (permalink) Old 09-13-2013 Thread Starter
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MPG is a consideration - it is my commuter car and I drive it about 500 miles a week.
But I didn't get a new car to look like Im driving the airport rental Mustang. As the miles add up the less I owe and the more it becomes my toy.

The 20" Panoramas are pretty light at 25.5 and 23.5 lbs. The tires are heavier! Bf Goodrich in a 35 series run 31.5 and 27.5 lbs. and in the 40 series run about 33.5 and 30 lbs.

My goal is to make a good looking solid feeling driving car. If I ended up with an overall MPG of 25+ after everything I would like to do, I would be happy. Most of my driving is freeway traffic but stop and go traffic is the worst. Any bit of lower gearing would really help out in not getting cut off while I'm waiting for the engine to do more than lift the front end and make noise to only have to hit the breaks just as the motor starts delivering.

The wheels and tires are not going to be happening anytime soon but in the next few months I wanted a new drive shaft and a Whiteline Watts link installed. I figure that would also be a great time to swap the gears.

USEFUL LINKS
.tacomaworld.com/forum/tirecalc.php
.rimsntires.com/specs.jsp
.wheelweights.net
.arb.ca.gov/msprog/aftermkt/aftermkt.htm
.autos.aol.com/
.cargurus.com
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post #5 of 10 (permalink) Old 09-13-2013
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I'm just talking out of my butt. It does make sense that it is possible, with different diameter tires your Mustang 'might' think it is losing traction and the 'Traction Control' could kick in. Your brakes could be worn out in just a couple thousand miles. Maybe?..............Just saying......

'Little Red'. 2011 V-6 Mustang. Automatic <acronym title="transmission">Trans</acronym>. C&L C.A.I. Ceramic Coated BBK Long Tube Headers and Catted Shorty X-Pipe. Magnaflow Street Series Axle Backs. 3.73 rear gears. GT 500 Lower Control Arms. JLT Catch Can. Axle Exchange Aluminum Drive Shaft. Steeda Watts Link. Several more mods...1991 F150 4X4 61,000 miles. Wifes car, 2014 Ford Edge Limited.
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post #6 of 10 (permalink) Old 09-13-2013
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It can absolutely be corrected with a tune, but check out this little conversation I had with Bama Tunes regarding changing tire sizes on a '12 (and, I have to assume, any 11+)

Quote:
Your original Revs Per Mile was 770. This was when the speed was reading 5% too high (Car says 42, GPS says 40). I originally thought, in order to lower the speedo we should decrease the Rev Per Mile by exactly 5% 731.5. Which would be like running a taller tire and should lower the speedo.

However, I had the wrong thought process going. The PCM was really counting the revolutions and assuming every time it hit 731.5, the car reached another mile. However, the car was short of a full mile, thus calculating the speed quicker than actual time (MPH).

Now, I just had one of my Bama guys email you new tunes. I increased the original 770 Rev's Per Mile by 5%, since this was the original problem number. That gave me 808.5 Rev's Per Mile. This should lower the Speedo to the correct number.
I was going from stock Brembo tires to 255/45/18 Nitto NT555s. My speedo is dead-on now, btw.

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post #7 of 10 (permalink) Old 09-13-2013
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Quote:
Originally Posted by hawkeye18 View Post
It can absolutely be corrected with a tune, but check out this little conversation I had with Bama Tunes regarding changing tire sizes on a '12 (and, I have to assume, any 11+)



I was going from stock Brembo tires to 255/45/18 Nitto NT555s. My speedo is dead-on now, btw.
Weird my 255/45/18s are said to only be 746 revs per mile

http://www.discounttire.com/dtcs/infoTireMath.dos

Oxford White 2015 Premium GT with 50-Year Pkg | 3.55 Gears | Roush CAI (105mm Velocity tube) | Stainless Works Headers (Jet-Hot ceramic coated), high flow cats, H-Pipe CatBack full 3" with 4" tips| BAMA V2 93 Octane Tune | Baer EradiSpeed-Plus 2-Piece Rotors | JLT 3.0 Oil Separators | FRPP M-20201-M STB | Silver PP Wheels 19x9, 19x9.5 | NITTO G2 255-40-19, 275-40-19 Tires | J&M Jacking Rails & Subframe Alignment Kit | Steeda Subframe Connectors & Bushing Supports | BMR Front Subframe Brace | Cervinis 1232 Functional Ram Air hood | Ford Performance door sills | White Madness Garage Chrome Shifter | Diode Dynamics interior LED conversion stage 1 & XP80 reverse light | 3M Dark Ceramic Tint (25% sides/20% rear) | Lloyds "50 Years" floor and trunk mats...

Performance White 2012 Premium Pony Package | Torsen T2R 4:1 TBR | FRPP 3.73 Gears | GT500 Differential Cover | DSS 3.8" Carbon Fiber DS | Airaid CAI | BAMA 93R tune | Baer DecelaRotors (drilled/slotted) | BMR Adjustable Panhard & Brace | JLT Oil Separator | Boss 302 STB | Nexen N3000 255-45-ZR18Y tires | PP Engine Cover | 25% Tint

All cars should be rated for Smiles Per Gallon!
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post #8 of 10 (permalink) Old 09-13-2013 Thread Starter
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So this brings up another question; The stance I am looking for is slightly raked and slightly staggered. Which wheel(s) is the computer calculating revolutions per mile from? Does the tuner get adjusted to the fronts or rears?

USEFUL LINKS
.tacomaworld.com/forum/tirecalc.php
.rimsntires.com/specs.jsp
.wheelweights.net
.arb.ca.gov/msprog/aftermkt/aftermkt.htm
.autos.aol.com/
.cargurus.com
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post #9 of 10 (permalink) Old 09-14-2013
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The speed is based off the rear via output shaft of the transmission.

Obviously all 4 wheels do have ABS sensors but that's a completely separate system.

Oxford White 2015 Premium GT with 50-Year Pkg | 3.55 Gears | Roush CAI (105mm Velocity tube) | Stainless Works Headers (Jet-Hot ceramic coated), high flow cats, H-Pipe CatBack full 3" with 4" tips| BAMA V2 93 Octane Tune | Baer EradiSpeed-Plus 2-Piece Rotors | JLT 3.0 Oil Separators | FRPP M-20201-M STB | Silver PP Wheels 19x9, 19x9.5 | NITTO G2 255-40-19, 275-40-19 Tires | J&M Jacking Rails & Subframe Alignment Kit | Steeda Subframe Connectors & Bushing Supports | BMR Front Subframe Brace | Cervinis 1232 Functional Ram Air hood | Ford Performance door sills | White Madness Garage Chrome Shifter | Diode Dynamics interior LED conversion stage 1 & XP80 reverse light | 3M Dark Ceramic Tint (25% sides/20% rear) | Lloyds "50 Years" floor and trunk mats...

Performance White 2012 Premium Pony Package | Torsen T2R 4:1 TBR | FRPP 3.73 Gears | GT500 Differential Cover | DSS 3.8" Carbon Fiber DS | Airaid CAI | BAMA 93R tune | Baer DecelaRotors (drilled/slotted) | BMR Adjustable Panhard & Brace | JLT Oil Separator | Boss 302 STB | Nexen N3000 255-45-ZR18Y tires | PP Engine Cover | 25% Tint

All cars should be rated for Smiles Per Gallon!
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post #10 of 10 (permalink) Old 09-14-2013 Thread Starter
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Thank You Kindly Sir.

USEFUL LINKS
.tacomaworld.com/forum/tirecalc.php
.rimsntires.com/specs.jsp
.wheelweights.net
.arb.ca.gov/msprog/aftermkt/aftermkt.htm
.autos.aol.com/
.cargurus.com
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