In another thread SOFTBATCH WROTE:

"Using 275/40/17s is like putting 3.73 gears in the back of the '05+ Mustangs."

Is this true. It certainly makes sense that tire size can have a similar effect as gear ratio. If this is true how do my 275 40 18's affect gears. It was my plan to order 4.10's today or tomorrow, but now I hesitate. My car is an auto and I'm already a little nervous about 4.10's (yeah I know don't fear the gear) Is my tire selection going to make things even more aggressive and less everyday friendly? Someone with a calculator and knowlege let me know if I have a potential problem.

 

<div class='quotetop'>QUOTE(eric n @ March 2, 2006, 5:09 PM) Quoted post</div><div class='quotemain'>
In another thread SOFTBATCH WROTE:

"Using 275/40/17s is like putting 3.73 gears in the back of the '05+ Mustangs."

Is this true. It certainly makes sense that tire size can have a similar effect as gear ratio. If this is true how do my 275 40 18's affect gears. It was my plan to order 4.10's today or tomorrow, but now I hesitate. My car is an auto and I'm already a little nervous about 4.10's (yeah I know don't fear the gear) Is my tire selection going to make things even more aggressive and less everyday friendly? Someone with a calculator and knowlege let me know if I have a potential problem.
[/b][/quote]

not really. your 275/40/18s have almost the same overall diameter as the stock 235/55/17s. They're a little smaller than stock, but not much.

first tire calc on google
http://www.miata.net/garage/tirecalc.html

 

I have been running taller than stock street tires (27.8") and shorter than stock track tires (26" drag radials). It's a good combo. IMO, shorter street tires, with 4.10s, will for sure make you "tractionally challenged".

However, after the engine rebuild, I'll be going to taller track tires, too. [img]style_emoticons/<#EMO_DIR#>/thumb.gif[/img]

 

<div class='quotetop'>QUOTE(eric n @ March 2, 2006, 4:09 PM) Quoted post</div><div class='quotemain'>
In another thread SOFTBATCH WROTE:

"Using 275/40/17s is like putting 3.73 gears in the back of the '05+ Mustangs."

Is this true. It certainly makes sense that tire size can have a similar effect as gear ratio. If this is true how do my 275 40 18's affect gears. It was my plan to order 4.10's today or tomorrow, but now I hesitate. My car is an auto and I'm already a little nervous about 4.10's (yeah I know don't fear the gear) Is my tire selection going to make things even more aggressive and less everyday friendly? Someone with a calculator and knowlege let me know if I have a potential problem.
[/b][/quote]


True, sure is. All depends on diameter difference. Simple use of tire calc shows:

235/55 17 = 27.2

275/40 17 = 25.7

A 1.5" decrease in dia a 5" decrease (6%) in circumference. This will have the effect of leaving tire diameter the same and changing gear ratio. 3.55 x 106% = 3.76 so it's even a greater increase!

 

I dont get it...I know all the specs say 275/40/18 is shorter than stock but when I lined up my new 275 toyos next to my new stockers the toyos were taller. I even took a level and placed it on top to make sure. So get the 4.10's and dont look back...

 

RPM WROTE:
True, sure is. All depends on diameter difference. Simple use of tire calc shows:

235/55 17 = 27.2

275/40 17 = 25.7


How tall are my 275 40 18s????

 

<div class='quotetop'>QUOTE(eric n @ March 3, 2006, 8:19 AM) Quoted post</div><div class='quotemain'>
RPM WROTE:
True, sure is. All depends on diameter difference. Simple use of tire calc shows:

235/55 17 = 27.2

275/40 17 = 25.7
How tall are my 275 40 18s????
[/b][/quote]

26.7

 

A tire that's taller than stock will make your effective gear ratio lower numerically. A shorter tire, higher numerically. My 295/45/18 rear tires make my 4.10's an effective 3.90 or so. I'd need 4.30's to have an effective 4.10.

 

Well it's settled then. Pulled the trigger on Ford Racing 4.10's today. Ordered through Summit. Should have them by tues. Also have Steeda Pullies on the way and trying to get jlt cai and switch to sct2 (currently running predator) from Bama.

Seem to have some e-mail problems on my new account though. Hope I'm not missing his mail.

I'd love to be 12.9, but I'll settle (for now) for more zip.

 

<div class='quotetop'>QUOTE(MTAS @ March 3, 2006, 8:38 AM) Quoted post</div><div class='quotemain'>
A tire that's taller than stock will make your effective gear ratio lower numerically. A shorter tire, higher numerically. My 295/45/18 rear tires make my 4.10's an effective 3.90 or so. I'd need 4.30's to have an effective 4.10.
[/b][/quote]

holy moly! where'd you get 295/45's from and what size rim are you using? what do you have up front? Looks f*ing awesome [img]style_emoticons/<#EMO_DIR#>/thumb.gif[/img]

 

<div class='quotetop'>QUOTE(nonsensez9 @ March 3, 2006, 3:43 PM) Quoted post</div><div class='quotemain'>
holy moly! where'd you get 295/45's from and what size rim are you using? what do you have up front? Looks f*ing awesome [img]style_emoticons/<#EMO_DIR#>/thumb.gif[/img]
[/b][/quote]

I'm running 295/45-18s as well and I really love the look, I'm running 255/45-18s in the front. Nitto 555s. Check out my gallery for pics.

Just got my 4:10s in and I love them but like was said before it's more like having 3:90s.

 

<div class='quotetop'>QUOTE(nonsensez9 @ March 3, 2006, 4:43 PM) Quoted post</div><div class='quotemain'>
holy moly! where'd you get 295/45's from and what size rim are you using? what do you have up front? Looks f*ing awesome [img]style_emoticons/<#EMO_DIR#>/thumb.gif[/img]
[/b][/quote]

Thanks!! They're Nitto 555's [img]style_emoticons/<#EMO_DIR#>/thumb.gif[/img] Fronts are 255/45/18

 

so let me get this right?

By changing the tire size you are doing a back door gear swap, correct?

 

<div class='quotetop'>QUOTE(traffic142 @ March 4, 2006, 11:16 AM) Quoted post</div><div class='quotemain'>
so let me get this right?

By changing the tire size you are doing a back door gear swap, correct?
[/b][/quote]

Yeah pretty much - never thought of it like that but that's the deal [img]style_emoticons/<#EMO_DIR#>/icon_mrgreen.gif[/img]