35's= new gears?
JK Super Freak
Joined: Sep 2007
Posts: 1,623
Likes: 5
From: Lawrenceville, NJ
Thanks all.
Just trying to help people get some perspective on all the tire/gear talk...
There's so much new info for the newbies to absorb, their heads are exploding....and at times, it seems they try to relieve the pressure by lightening their wallets.
Just trying to help people get some perspective on all the tire/gear talk...
There's so much new info for the newbies to absorb, their heads are exploding....and at times, it seems they try to relieve the pressure by lightening their wallets.
JK Newbie
Joined: May 2011
Posts: 21
Likes: 0
From: WINOOSKI,VT
Thank you , amazing!
ABSOLUTELY PERFECT! I ESPECIAL ENJOYED THE CLOSE.
A huge amount depends upon where you drive.
People in CO, etc...NEED lower gearing to manage the steep hills even with stock tires.
People who are mostly on flat areas (Kansas, etc...) can get by with higher gearing, and everyone else is in the middle somewhere.
For example...the stock gear set gives you a 3.21 diff, and that is turning stock 32" tires....and provides the best fuel economy.
If you go from 32's, to 33's...as the stock 32's are 32.1" in diameter, and most 33's are closer to 32.0 - 32.8" in diameter....there's almost no real difference in performance, the new tires might be as little as zero inches larger in diameter, and generally, less than one inch larger overall.
32/33 = 0.9696
That means the difference is about 3% or LESS.
3% just happens to be the accuracy of a stock speedometer as per gov stds.
So - if driving along at 2,000 rpm on 32's, and you swap on 33's...your rpm will drop all the way from 2,000 rpm to 1,940 rpm ( A 60 rpm drop...)
Not enough to notice.
If you jump from 32's to 35's...
32/35 = 0.914
So the difference is more like 8.6%...enough to notice...but not earth shattering.
The same 2,000 rpm on 32's is now down to 1,828 Rpm (A 172 RPM drop).
172 RPM is ~ chump change...maybe ~ half the drop from 5th to 6th, etc....
A half gear drop essentially means you need to down shift from 6th to 5th ~ 50% more....to get the rpm back. (Conceptually)
If you ran 37's...
32/37 = 0.865, or a 13.5% drop in rpm....dropping you from 2,000 rpm down to 1,730 rpm (A 270 RPM Drop)....enough to notice, and enough to increase the down shift to 5th on a frequent basis.
Add to that, the proportionally greater mass of a 37" tire, and the amount of rubber than must change shape to be flat on the bottom, round elsewhere, a few hundred times/minute, etc....THAT resistance adds up, plus, the wind resistance needed to lift high enough to FIT 37's, etc....make the mpg plummit after 35's.
------------------------------------------------------------------------------
I strongly recommend that people drive on the existing gears when they upgrade the tires...and SEE for themselves what they feel like.
People are saying "Get 5.13's for 35's"....and, you may want to...but, its a lot of $ to re-gear....plus:
3.21/5.13 = 0.626....so you are RAISING your rpm (In EVERY GEAR) by a whopping ~ 37% .......to compensate for a 8.6% tire change.
3.73/5.13 = 0.727...so you are RAISING your rpm by 27% to compensate for a 8.6% tire change.
4.11/5.13 = 0.801...so you are raising your rpm by ~ 20% to compensate for a 8.6% tire change....
....etc.
If you had 3.21 diffs...adding 8.6% yields a new diff to compensate of 3.49 (More like the 3.73-ish range...)
If you had 3.73's....adding 8.6% yields a new diff to compensate of 4.05 (more like the 4.11-ish range....)
If you had 4.11's....adding 8.6% yields a new diff to compensate of 4.46 (more like the 4.88-ish range....)
Etc.
-----------------------------------------------------------------------------
So - that said....Lower gears, whether you are COMPENSATING or not, really do give an amazing boost in performance, as the lower the gearing, the better your acceleration, power on hills, etc....so, its a really effective way to make the rig leap on an as needed basis.
AND
With gas closing in on the $4/gal mark....remember...you're that many RPM higher ALL the time....including on the freeway.
If you were cruising at 2,000 before, and getting 20 mpg, or whatever with your 3.21 diffs....and you go the same speed with 5.13's instead, you are adding 37% more rpm, so, now you're cruising at 2,740 rpm instead of at 2,000 rpm, etc.
Guess what guage ALSO moves faster now?
Yeah, that's right, the one that says its time to fill that 21 gallon tank at $4/gallon....again. (21 x $4 = $ 84)
----------------------------------------------------------------------------------
If you are in the mountains, or are more or less never doing high speed cruises of any distance....or just want more than the stock ooomph from the rig, and are willing to pay AT THE PUMP TO GET IT...the low gears make sense....if you're down shifting anyway, the rpms are going to be the same anyway too, etc.
If you ARE happy with the stock feel/ratios...adding 35's probably will not be enough to justify the higher rpms, and associated costs in gears and gas, etc.
Of course, you CAN re-gear for free if you have the 6 spd...just down shift....works every time on the hwy.
------------------------------------------------------------------------------------
If off roading, especially rock crawling, the lower the better...so, if you rock crawl, and CAN afford it....the lower gears are wonderful.
-----------------------------------------------------------------------------
Food for thought -
MOST (not all) people who get larger tires forget that the speedometer is wrong...and pull out into traffic, and accelerate to what ever speed on the speedometer they always did, and drive at what ever speed they used to before the swap...based upon the speedometer reading...
That means that the JK is accelerating to say 76 mph, but, you THOUGHT it took that long to get to 70 mph, and were thinking, DAMN! The larger tires SAPPED my accelleration! (Time to get up to 76 vs 70 mph...)
And
The JK used to be able to maintain 70 mph on this hill, but, NOW I have to down shift! The larger tires KILLED my ability to maintain speed on hills! (Ability to hold gear at 76 mph...compared to 70 mph...)
And
Damn, I used to go X miles per tank! (The odometer is off by the same error...)
My MPG Gauge says I have a huge drop in MPG! (Ditto above...)
And so forth.
------------------
IE: People are speeding, accelerating to, and driving at higher speeds, going further than they thought, faster than they thought....and complaining about a loss in performance and MPG.
SOME people have GPS, etc...but, its rarely used to see your speed when pulling off an exit ramp into traffic, etc...so, the overall "SEAT OF THE PANTS" experience, for most people, is that the larger tires slowed them down worse than they actually slowed them down.
People in CO, etc...NEED lower gearing to manage the steep hills even with stock tires.
People who are mostly on flat areas (Kansas, etc...) can get by with higher gearing, and everyone else is in the middle somewhere.
For example...the stock gear set gives you a 3.21 diff, and that is turning stock 32" tires....and provides the best fuel economy.
If you go from 32's, to 33's...as the stock 32's are 32.1" in diameter, and most 33's are closer to 32.0 - 32.8" in diameter....there's almost no real difference in performance, the new tires might be as little as zero inches larger in diameter, and generally, less than one inch larger overall.
32/33 = 0.9696
That means the difference is about 3% or LESS.
3% just happens to be the accuracy of a stock speedometer as per gov stds.
So - if driving along at 2,000 rpm on 32's, and you swap on 33's...your rpm will drop all the way from 2,000 rpm to 1,940 rpm ( A 60 rpm drop...)
Not enough to notice.
If you jump from 32's to 35's...
32/35 = 0.914
So the difference is more like 8.6%...enough to notice...but not earth shattering.
The same 2,000 rpm on 32's is now down to 1,828 Rpm (A 172 RPM drop).
172 RPM is ~ chump change...maybe ~ half the drop from 5th to 6th, etc....
A half gear drop essentially means you need to down shift from 6th to 5th ~ 50% more....to get the rpm back. (Conceptually)
If you ran 37's...
32/37 = 0.865, or a 13.5% drop in rpm....dropping you from 2,000 rpm down to 1,730 rpm (A 270 RPM Drop)....enough to notice, and enough to increase the down shift to 5th on a frequent basis.
Add to that, the proportionally greater mass of a 37" tire, and the amount of rubber than must change shape to be flat on the bottom, round elsewhere, a few hundred times/minute, etc....THAT resistance adds up, plus, the wind resistance needed to lift high enough to FIT 37's, etc....make the mpg plummit after 35's.
------------------------------------------------------------------------------
I strongly recommend that people drive on the existing gears when they upgrade the tires...and SEE for themselves what they feel like.
People are saying "Get 5.13's for 35's"....and, you may want to...but, its a lot of $ to re-gear....plus:
3.21/5.13 = 0.626....so you are RAISING your rpm (In EVERY GEAR) by a whopping ~ 37% .......to compensate for a 8.6% tire change.
3.73/5.13 = 0.727...so you are RAISING your rpm by 27% to compensate for a 8.6% tire change.
4.11/5.13 = 0.801...so you are raising your rpm by ~ 20% to compensate for a 8.6% tire change....
....etc.
If you had 3.21 diffs...adding 8.6% yields a new diff to compensate of 3.49 (More like the 3.73-ish range...)
If you had 3.73's....adding 8.6% yields a new diff to compensate of 4.05 (more like the 4.11-ish range....)
If you had 4.11's....adding 8.6% yields a new diff to compensate of 4.46 (more like the 4.88-ish range....)
Etc.
-----------------------------------------------------------------------------
So - that said....Lower gears, whether you are COMPENSATING or not, really do give an amazing boost in performance, as the lower the gearing, the better your acceleration, power on hills, etc....so, its a really effective way to make the rig leap on an as needed basis.
AND
With gas closing in on the $4/gal mark....remember...you're that many RPM higher ALL the time....including on the freeway.
If you were cruising at 2,000 before, and getting 20 mpg, or whatever with your 3.21 diffs....and you go the same speed with 5.13's instead, you are adding 37% more rpm, so, now you're cruising at 2,740 rpm instead of at 2,000 rpm, etc.
Guess what guage ALSO moves faster now?
Yeah, that's right, the one that says its time to fill that 21 gallon tank at $4/gallon....again. (21 x $4 = $ 84)
----------------------------------------------------------------------------------
If you are in the mountains, or are more or less never doing high speed cruises of any distance....or just want more than the stock ooomph from the rig, and are willing to pay AT THE PUMP TO GET IT...the low gears make sense....if you're down shifting anyway, the rpms are going to be the same anyway too, etc.
If you ARE happy with the stock feel/ratios...adding 35's probably will not be enough to justify the higher rpms, and associated costs in gears and gas, etc.
Of course, you CAN re-gear for free if you have the 6 spd...just down shift....works every time on the hwy.
------------------------------------------------------------------------------------
If off roading, especially rock crawling, the lower the better...so, if you rock crawl, and CAN afford it....the lower gears are wonderful.
-----------------------------------------------------------------------------
Food for thought -
MOST (not all) people who get larger tires forget that the speedometer is wrong...and pull out into traffic, and accelerate to what ever speed on the speedometer they always did, and drive at what ever speed they used to before the swap...based upon the speedometer reading...
That means that the JK is accelerating to say 76 mph, but, you THOUGHT it took that long to get to 70 mph, and were thinking, DAMN! The larger tires SAPPED my accelleration! (Time to get up to 76 vs 70 mph...)
And
The JK used to be able to maintain 70 mph on this hill, but, NOW I have to down shift! The larger tires KILLED my ability to maintain speed on hills! (Ability to hold gear at 76 mph...compared to 70 mph...)
And
Damn, I used to go X miles per tank! (The odometer is off by the same error...)
My MPG Gauge says I have a huge drop in MPG! (Ditto above...)
And so forth.
------------------
IE: People are speeding, accelerating to, and driving at higher speeds, going further than they thought, faster than they thought....and complaining about a loss in performance and MPG.
SOME people have GPS, etc...but, its rarely used to see your speed when pulling off an exit ramp into traffic, etc...so, the overall "SEAT OF THE PANTS" experience, for most people, is that the larger tires slowed them down worse than they actually slowed them down.
JK Freak
Joined: Oct 2010
Posts: 965
Likes: 4
From: Red deer, Alberta
I think it's a matter of opinion and also where and how you drive. I have a Rubicon Unlimited automatic with 35's and stock gears and although the gas mileage isn't great (then again...it's a Jeep), I have no problem getting around. I don't do a whole lot of highway driving and not a lot of mountains either. I'd rather spend the money on new rims than new gears.