Dawn Nelson wrote:
My 33" Goodrich All-Terrains were getting chunks out of the tread (and they weren't even that old, a year at most??).
It seems that you state that you don't off road the Jeep much, so I don't know if this is entirely applicable, but I'll toss in this.
Do you air down when in the dirt?
I run B.F.Goodrich All Terrain T/A KO tires (started running them in 1997 on my former truck, a '96 Chevrolet S-10 4WD pickup), but I'm sure that the Mud Terrain tires would be even more suseptible to this tendency than the All Terrains since they have larger blocks with wider separation between them for mud removal. In the past, I ran street pressure off road, my first set of All Terrains chunked badly. Chunking in that the tread blocks tear their outter edges and sometimes even entire blocks. When I mentioned something about it years ago and the suggestion to air down was made to me to eliminate that, chunking went away.
Lowering your tire pressure off road allows the tire to flex and mold themselves over sharp edged stones; running street pressures presents a stiff tread face to the stones, maximizing the chance for damage. Lowering tire pressures results in a softer ride off road as well, plus better floatation when encountering sand.
On road I run 35psi in my Toyota Tacoma. Off road I run around 15-18. Sometimes 20psi if I'm only running Class II two track trails with no known hazards.
If you don't want the inconvienience of airing back up when getting back to pavement, I've run 50+ miles with my tires aired down on pavement. My current 12v portable air compressor takes about 35-40 minutes to air back up all four tires, so if I'm not that far from home I simply drive home so I can air back up with my shop compressor. I've found that my All Terrains handle that just fine as long as I don't drive more than 55-60 home (although I've done 75 in winter) with no apparent over heating. However, I do slow down in corners as sidewall flex shows itself if you make sudden steering inputs (nothing scary, but it is a factor that I am aware of and make corrections for). However, southern Nevada summer temps are a consideration you might want to factor in before running home at lower pressures. However, my thinking is that a Jeep Wrangler is far lighter than my Tacoma, so that is a trade-off.
Dawn Nelson wrote:
I decided to get 35" Goodrich Mud-Terrains. Gear ratios didn't enter my mind. I have the standard gears that come on a stock Rubicon. ... the jeep was NOT happy on that hill.
I've got a friend with an automatic transmisson, 2-door JK Wrangler Rubicon with tires about that size (I forget the exact figure) and he went to a 4.88 ratio, the recommended for that size tire by the Dayton, NV off road shop that did his modifications.
Going oversize tire sizes is in effect lowering your overall gear ratio (lowering numerically - i.e. you know have something like 3.85:1 instead of 4.11:1 or whatever your Rubicon has). It also affects your ABS sensor input and operation, as well as your speedometer. And on road your gas mileage suffers as any uphill travel must be done while in lower gears (automatic or manual), higher RPMs or more open throttle settings or a combination of all. Being that modern Jeeps and all other vehicles are far more complex and computer controlled, it may affect other things as well.
As stated before, each modification often presents side effects, which take time and $$$ to overcome. If you go bigger in tires, it is better for your Jeep on and off road to re-gear your differentials.