William Posted November 18, 2012 Share Posted November 18, 2012 Hi Guys. I am currently running 33x12.5R15" BFG tires on a 15x10 MT with the correct backspacing. My truck is a V6 A/T with 3" BL + 3" SL from AC (4x4Parts.com) I will be SASing the front of my truck in the near future. Still researching the best AXLE to use considering that Dana44 from old Wagoneers are not common in my area. My current differential Gears are still factory (HG43) which I believe stand for 4.365 Rear (H233B) and Front (R200A). Not sure about the Front and Rear Spline count but can safely assume they are 31 Rear and 29 Front. Q: Which Ring and Pinion should I shoot for? 5.13? Q: What is the difference and how can calculate the one needed to return to factory settings considering that I running 33" tires now. William Link to comment Share on other sites More sharing options...
ahardb0dy Posted November 18, 2012 Share Posted November 18, 2012 http://www.alloyusa.com/gear-ratio-calculator Link to comment Share on other sites More sharing options...
silverton Posted November 18, 2012 Share Posted November 18, 2012 XE, so it came stock with 235/75's right? A rear end ratio of 4.99 would return you to stock. so a little over 5 would be great! If it came stock with 31's you'd be looking for a ratio near 4.65 to return it to "stock" gearing. Link to comment Share on other sites More sharing options...
William Posted November 18, 2012 Author Share Posted November 18, 2012 XE, so it came stock with 235/75's right? A rear end ratio of 4.99 would return you to stock. so a little over 5 would be great! If it came stock with 31's you'd be looking for a ratio near 4.65 to return it to "stock" gearing. Well actually mine came with 215x75R15 (not even 235's )!! The driver door TAG is below. Does that mean I need I need something higher than 5.13?? William Link to comment Share on other sites More sharing options...
William Posted November 18, 2012 Author Share Posted November 18, 2012 http://www.alloyusa....atio-calculator Hummm ... I am currently running 33x12.5r15 (which means in METRIC: 318x72R15) So according to the formula below that calculates my overall tire diameter, I have a 35"? (CROSS SECTION WIDTH x 0.ASPECT RATIO x 2 ÷ 25.4) + WHEEL DIAMETER = OVERALL TIRE DIAMETER (318 x 0.72 x 2 / 25.4) + 17 = 35" Does that mean I need 4.56 Gears to return to NORMAL OEM? William Link to comment Share on other sites More sharing options...
AndyC Posted November 18, 2012 Share Posted November 18, 2012 Are you going to stick with 33's after the SAS? Link to comment Share on other sites More sharing options...
AndyC Posted November 18, 2012 Share Posted November 18, 2012 And no, your calculation is off because you added 17, if you have a 15in wheel you add 15, so 33in. Link to comment Share on other sites More sharing options...
AndyC Posted November 18, 2012 Share Posted November 18, 2012 Closest metric measurement is 315/70/15 Link to comment Share on other sites More sharing options...
William Posted November 18, 2012 Author Share Posted November 18, 2012 Closest metric measurement is 315/70/15 Oops. You are right. Sorry.I used the sample given below the formula on the URL and left the wheel diameter at 17 . Thx Link to comment Share on other sites More sharing options...
William Posted November 18, 2012 Author Share Posted November 18, 2012 Are you going to stick with 33's after the SAS? Yes. Will stick with the 33" as this is also my DD and I don't want to go higher than 33". William Link to comment Share on other sites More sharing options...
William Posted November 18, 2012 Author Share Posted November 18, 2012 Closest metric measurement is 315/70/15 I agree. However, I used the following site for the calculation. It is not a commercially available wheel size but probably the exact metric size ..... "mathematically" speaking: http://www.extremeterrain.com/wrangler-jeep-metric-tire-conversion-calculator.html Link to comment Share on other sites More sharing options...
AndyC Posted November 18, 2012 Share Posted November 18, 2012 Ok, so your new tire is 16.8% larger than stock, we multiply that by your stock 4.3 and get 5.0224 as a final drive ratio. 5.13 sounds ideal for wheeling. Link to comment Share on other sites More sharing options...
silverton Posted November 19, 2012 Share Posted November 19, 2012 With 215/75R15 stock tires, a 5.21 gear ratio would put you at "stock" gearing. So a 5.13 would be close. Link to comment Share on other sites More sharing options...
William Posted November 19, 2012 Author Share Posted November 19, 2012 With 215/75R15 stock tires, a 5.21 gear ratio would put you at "stock" gearing. So a 5.13 would be close. How did you come up with 5.21 please? William Link to comment Share on other sites More sharing options...
silverton Posted November 19, 2012 Share Posted November 19, 2012 a website I know of, takes gear ratio, stock tire size, and new tire size, and shows you the speed difference and what gearing you would need to make up for tire size. 1 Link to comment Share on other sites More sharing options...
William Posted November 19, 2012 Author Share Posted November 19, 2012 a website I know of, takes gear ratio, stock tire size, and new tire size, and shows you the speed difference and what gearing you would need to make up for tire size. What is that Website's URL link please? Link to comment Share on other sites More sharing options...
pathybuilder Posted November 20, 2012 Share Posted November 20, 2012 you could use the site, or just do the math as Andy had done above. There's many ways to do it. Your 215/75/15 Tires are 27.6" Tall (http://www.offroaders.com/tech/AT-MT-Tires/pmetric-inches.htm) 27.6" (existing tire) / 4.365 (existing gear ratio) = 6.323 Therefore 33" (new tire) / 6.323 = 5.219 (New Gear Ratio) The math matches what Silverton posted above, but I have a hard time trusting a site without calculating it myself. A 5.13 Gear Ratio will slightly lower your RPM on the highway and may give some increase in gas mileage, but I doubt it would be noticable. This is what I went with although haven't installed them yet, so can't provide any feedback. My truck came with 235/75R15 and same HG43. 5.13 Gears will put me slighter higher than stock. I would imagine that you must have reved pretty high on the highway on those 215's. I'm pretty sure Auto or Manual Tranny also makes a difference in where you rev on the highway. If I were you I would run 5.13 as well. Link to comment Share on other sites More sharing options...
SteeevO Posted November 20, 2012 Share Posted November 20, 2012 (edited) Woah this thread got way more complicated than it needs to be. Simple math fellas. (Stock Tire Diameter)/(Stock Gear Ratio) = (New Tire Diameter)/(New Gear Ratio) Just a little cross multiplication will do the trick. OR Throw all that math out the window and take it from me. For a DD on 33's with an Auto Trans, Run 4.9's For a DD on 33's with Manual Trans, Run 4.63's -You will get better gas mileage on the highway with this as it will slightly lower your RPM's at highway speeds. I was getting 21MPG Hwy in the Pathfinder on 35's and 4.9's w/ manual trans. Edited November 20, 2012 by SteeevO Link to comment Share on other sites More sharing options...
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