Tire/Final Drive Ratio question.. - TCCoA Forums
 
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post #1 of 10 (permalink) Old 05-16-2008, 06:47 PM Thread Starter
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Tire/Final Drive Ratio question..

Wow... In my search for a tall, fat tire to stick on the rear, I didnt consider how going from a 225/60-16 to a 255/60 might affect the final drive ratio. I'd assume mileage would be affected?? I'm assuming its negligible, but I'd hate to see the tach spin higher... Anybody got a Formula for this??
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post #3 of 10 (permalink) Old 05-18-2008, 01:15 PM
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Here is the one you want; what size gear do you need to make the speedo read right.

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post #4 of 10 (permalink) Old 05-18-2008, 09:37 PM Thread Starter
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Wow, Ok... Yeah, thats kinda what I thought.... Damn, I love this site...
Thanks for the info, Guys!!!!!!!
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post #5 of 10 (permalink) Old 05-31-2008, 12:06 PM
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Quote:
Originally Posted by HGainiac View Post
Wow... In my search for a tall, fat tire to stick on the rear, I didnt consider how going from a 225/60-16 to a 255/60 might affect the final drive ratio. I'd assume mileage would be affected?? I'm assuming its negligible, but I'd hate to see the tach spin higher... Anybody got a Formula for this??
It will spin lower at the same given ground speed. Taller tire covers more ground each revolution, so fewer revolutions per minute to go same miles per hour. As posted:
Quote:
Originally Posted by JR Tigerstar
225/60-16 to a 255/60-16 = Speedometer Difference: 5.339% too slow
Tire Size Calculator
Your speedometer will read 5.339% slower at same ground speed as before, likewise so willl your tach read lower at same speed. Approximately 3.2 mph slower at 60.... or if you set it on same 60 as before, you'll be going about 3.2 mph faster. It will also affect your odometer which means you need to allow for it when you compute mileage ...
... in which case you may crunch numbers if you did before, and it may even appear that you loose mileage (mpg) until you add the 5.339% back, as your are doing the same work. Motor is turning slower, but leverage available on grades is less due to effectively higher rear gear so works harder to get you up over the grades, but you'll make up for it on the coast side. In other words, don't expect a noticeable change in mileage (it'll take same gas to do same trip IOW).

A fine pair ... ... and whatever you do, Have a Safe Trip!

Last edited by CrystalPistol; 05-31-2008 at 12:16 PM.
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post #6 of 10 (permalink) Old 05-31-2008, 01:05 PM
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Why do you want such a tall tire in the first place?


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post #7 of 10 (permalink) Old 06-02-2008, 07:07 PM Thread Starter
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Why do you want such a tall tire in the first place?
Well, I'm STILL looking for the 'rake' on this bird... I'd like to kick the a$$ of this thing up a bit... I want that offset look of more Meat in the rear and I don't mind if I forgo the handling slightly to get butt bumped up a bit... I dunno...It's more agressive looking to me. I"m sure goes against all logic here, but I like that old school 'Pro Stock/Pro Street stance... I know... Win the lottery, Put in a narrowed 9inch and tub the thing... But I would if I could.....
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post #8 of 10 (permalink) Old 06-02-2008, 11:41 PM
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Well, back in the old days before you were born (probably) we used to just put on Air Shocks, pump em up and put on big ass tires. LOL Course that was "the look" back then. Did it to my 70 Mustang as a matter of fact.

However cars were built different then than they are now though. Tires to. (They used to be measured with letters. My 73 Mustang had F7014's on it.). But I digress... To me aggresive looking is lowered all around with big honkin' tires all the way around. ONE guy had that look back in my day... He had a 75 Trans Am 455 4-speed, with big, wide low profile tires all around.... Looked great.

My point being after all that wandering around.. Some cars have a "look" that goes well with the big n' little tire set up. others look better with 4 big ol tires all around. In my opinion the T-Bird (LOL and that guys awesome 75 T/A) is one of those cars that look better lower all around with big tires. But, you're car, you're call.


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1997 T-Bird GT 4.6
80 MM Mustang GT MAF - P&P'd Mustang GT TB and Intake Plenum - PI Intake manifold - PI Heads
Mark VIII Torque Converter - J-Modded 4R70W transmission - Mark VIII Aluminum Driveshaft - 3.73 gears
PBR Brake Calipers - Eibach Springs - KYB Shocks
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SCT Chip programmed by Lonnie Doll
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True Dual exhaust with Magnaflow DI/DO muffler
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post #9 of 10 (permalink) Old 06-03-2008, 09:17 PM Thread Starter
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Quote:
Originally Posted by Traveler View Post
Well, back in the old days before you were born (probably) we used to just put on Air Shocks, pump em up and put on big ass tires. LOL Course that was "the look" back then. Did it to my 70 Mustang as a matter of fact.

However cars were built different then than they are now though. Tires to. (They used to be measured with letters. My 73 Mustang had F7014's on it.). But I digress... To me aggresive looking is lowered all around with big honkin' tires all the way around. ONE guy had that look back in my day... He had a 75 Trans Am 455 4-speed, with big, wide low profile tires all around.... Looked great.

My point being after all that wandering around.. Some cars have a "look" that goes well with the big n' little tire set up. others look better with 4 big ol tires all around. In my opinion the T-Bird (LOL and that guys awesome 75 T/A) is one of those cars that look better lower all around with big tires. But, you're car, you're call.

Thanks for the input!!!
God bless ya for the warm sentiments Bro, but you've only got 3 years on me!... But I refuse to grow up...or at least grow old....
I've got too many of my own 'good ol days' stories of my own, playing with rear suspension, tweakin' coils and leaf springs in the rear to fit the 'big meats' back there.. You an I will have to pm sometime....
YOU of all people should remember Bill 'Grumpy' Jenkins and Sox and Martin... I absolutely LOVE that Pro Stock look, Skinnys up front, Bigs in the rear....I'll catch 9 yards of 'flak' for saying this, but I'm not personally a fan of the 'lowered' look I see on some of these cars. IMHO these cars look too 'sedan' in stock form.....I see something different thing for my 'bird, and I 'aint got the $$$ to Pro Street-4 link an tub the thing!! I just want some of that profile, the 'rake', when I look down the side of this car... Nothing crazy....Prolly screw my handling up a bunch, but when you gotta have something....
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post #10 of 10 (permalink) Old 07-14-2008, 10:03 PM
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cut the front springs a little bit and leave the rears stock. there is a ton of info on this site about cutting springs. i personally shelled out far too much for eibach's and wish i would have grabbed some sport springs and chopped those instead...which i may do in the future anyway.

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