Question for anyone running 12.5s

[CRDPhenox]

How much rubbing on the steering/suspension components are you seeing/have you seen before fixed and what have/will you do to aliviate that? Im not too worried about sheet metal or plastic, just the stuff that you cant cut up and call good.

(Please dont post up too much random warnings about gearing/power/ect. unless you've ran 12.5s before)

Im going with 33/12.5/15 on procomps with 3.75 and its a CRD with 3:73 which will be plenty for offroad use while lowering my rpms onroad. Its on hopefully 4.5"(front) and 5"(rear) of lift when i get the rest of the setup done so also not worried there. And just saw a guy on LOST put 33/10.5 under his stock so again not worried - just trying to get all the random people telling me I cant appeased as to the fact that I allready did plenty of research.

 

[Ry' N Jen]

Rub a dub rub...
Tires rubbing in the wheel tub!
You will notice that the fellow on LOST also cut away a huge part of the inner
fender liner as well as allot of the sheet metal directly in front of the tires.
As well as removing allot of the fender flare material.
Not to mention that he is re-gearing to 4.56...

I find that on our 3.7 liter Heep the stock gearing tends to hunt while on the open road and off road I am usually in 2 nd. or 1 st. gear.

But...

Have fun and let us know how it works out for you.

 

[tjkj2002]

Bye-bye D30A and CV's:Bye:

 

[tommudd]

I could tell you from my observations running 32s and over 4 inches of lift
but since you only want people who have ran 33s
never mind
all I can say is good luck with hacking

 

[J-Thompson]

Is it really worth the headache?
245/75R16's are close to 31" tall
most 33's are really only 32.5" tall
That is only 3/4" more ground clearance
Yes the 12.5's are wider but I have run with a few guys
with 33X10.5 BFG MT's and the did very well in all but deep
soupy mud
Then there is the gearing ,which judging from your post about
lowering your RPM's you don't fully under stand but trust me
even the CRD will get crap for mpg's and be a **** on road
I found that a 3.7L with the 45rfe ,3 to 1 first gear, was "sluggish"
with 245/75's and 3.73's
And I know my TJ with the 4.0L and TF999 ,also 3 to 1 first gear, is
a dog with a 32" tall tire (tire with a measured od of 32") so I could do nothing
bigger with out first going with 4.10's or 4.56's

Yeah not with the headache but good luck

 

[tjkj2002]

Well I run 35x12.50's and 5.13's are almost not low enough gearing for Colorado.You will need to regear to at least 4.56's,even for a CRD.As JL Rockies,he regeared to 4.10's in his CRD with 32" tires and it was a big increase in power/mpg's from the stock 3.73's.

 

[CRDPhenox]

I could tell you from my observations running 32s and over 4 inches of lift but since you only want people with 33s

Im actually asking for people with 12.5" wide tires



@tjkj2002

Im supprised you both had that problem, when i went from 31" on 3:53 to 32" with my Hemi I gained ~1.5 mpg and from 29" on 4:10 to 35x12.5 with my cummins I got a 300 rmp reduction (2200 to1900@65 mph in 6lo and 1700 in double over )and about 3+ mpg maybe Im not getting the difference with the smaller axle as im still learning wit the 1/4 ton/ low power vehicle as this is my first small truck build. Every tire to ratio chart iv ever seen has 33" tires right on the edge of stock/economy range. Im anticipating CV failure and gauging my options for when they go. The main reason im asking right now is how much rubbing the 12.5 tires do at the outside of the tire at full turn/stuff? Im going to trim my fenders up like JeepBumm68 did with his girlfriends CRD as mine are allready cracked/crushed in the vertical sections and Id rather get my turbo kit than drop 1500 for new fenders and flares.

 

[CRDPhenox]

Im wondering where that extra inch of width on either side goes when turned/ stuffed

 

[J-Thompson]

I really doubt you gained any MPG going with bigger tires
I have only lost with bigger tires
and I have been driving longer than you have been out of diapers
I can easily count 6 totally different rigs that I have owned and every one of them lost MPG when the tires got bigger
some only 1 mpg some 4 but still a loss

 

[tommudd]

People give advice on experiences
no matter size etc there are some who do know what they are talking about
You're trying to compare apples and oranges and saying you gained mileage with larger tires:happy175::shrug:
We may as well all save our time trying to explain as you already know what you want the answer to be:whip:

The guy over on LOST did a lot of "hacking" and also went to 4.56 gears and a steel front diff, at least he is using stronger parts and lower gearing. Yours will be useless on the road with stock gearing even if it is a CRD, they're not that much more powerful

 

[CRDPhenox]

http://www.4wheelonline.com/superlift_tiresize.htm

These ones are a little more conservitive but the concepts the same: http://www.jeep4x4center.com/jeep-tires/tire-gear-ratio-chart.htm

http://auto.howstuffworks.com/auto-...wing/maneuvers/gear-ratio-tire-size-chart.htm

I have hundreds of these links built up in my research pages and more that are geared twards hotrods. I understand that your speaking from experience but the data and my experience say otherwise.

So no one out there are running 31/32x12.5 and have seen unusual rubbing that would be an issue?

 

[CRDPhenox]

Last I heard the guy was going to go to the steel diff and 4:10 later in the build and was rolling fine stock for quite a while. I can see the excess strain when rock crawling but im more a sand and mud and speed kinda guy and sos my wife who this is for.

 

[tommudd]

Last I heard the guy was going to go to the steel diff and 4:10 later in the build and was rolling fine stock for quite a while. I can see the excess strain when rock crawling but im more a sand and mud and speed kinda guy and sos my wife who this is for.

The one with the red CRD who just did it just cut the fenders off and hacked up the wheel wells a couple weeks ago, last week he had the steel front diff and 4.56s installed along with a 4 inch lift and lockers so no he has not been rolling fine for quite a while. At least he's doing most of it right.
More strain is also going to come just driving down the road period, and even in sand and mud when it bogs down.
Engines are built to operate at a certain RPM, when installing larger tires and keeping the stock gearing it takes it out of the range and you'll be dogged down quite a bit even on the road.

This comes right from the article you posted
[FONT=Verdana, Arial, Helvetica, sans-serif]Whenever larger-than-stock tires are installed on a truck, it will have a direct effect on the truck's performance. Why? It has to do with the effective gear ratio. Your truck comes from the factory with the optimum axle gear ratio to work with the truck's engine, transmission, and stock tire combination as well as provide a good balance between acceleration and fuel economy. When taller tires are installed on a truck but the axle ratios stay the same; the effective gear ratio is reduced. This means the engine is forced to operate below its power band, and performance and fuel economy suffer as a result. In order to restore the effective gear ratio (and the truck's performance), you'll need to have the axle gears swapped to lower (numerically higher) ratios. [/FONT]