30 inch 33 inchers

Joined
Mar 21, 2005
Messages
1,225
Location
Central Oregon
Just measured from the center of my hub cap to the floor with my old BFG 33X9.5 mud Ts on. these tires still have @least 40%.. the measure from the center of the Hub to the ground was 15". I guess that means I'm running 30" tires? tell that to the gearing in my rig..feels more like 35" tires under there.

Anybody else want to go out and measure what they got?

Anybody want to explain to me how the 15" measurement I got dosen't mean I'm running basically 30" tires?

Just stirring it up on a Sat night..

JON
 

2mbb

SILVER Star
Joined
Sep 1, 2003
Messages
5,295
Location
WC, CA
I just checked mine. I have 33x12.5x15 bfg AT/KO. 3/8" tread depth. Center of hub to ground was 15 inches. I checked the tire pressure and it was a little low (25 psig). I increased the pressure to 30 psig and measured 15.25" hub to ground.

The tire diameter is probably a "nominal" diameter, and the actual diameter under load will be less and is dependent upon your tire pressure.

I wouldn't worry too much about it. All other things being equal, if you were running 30" tires the would probably measure out at 27" and you'd still be disappinted.

One way to check "rolling" tire diameter is measure on the ground the distance for one tire rotation. divide this number by pi (3.14) and you have the rolling diameter.
 
Joined
Mar 1, 2007
Messages
1,229
Location
Knoxville
I just measured mine. Brand new 33x10.50 BFG MT on factory rims.
Tires have 200miles on them. They measured 15 1/2" hub to ground.
 
Joined
Apr 7, 2006
Messages
137
Location
Winnipeg
the rubber's going to be displaced due to the weight of the vehicle. If you take them off the truck you might get a more accurate reading. Also, pressure does make a difference.:grinpimp:
 
Joined
Mar 21, 2005
Messages
1,225
Location
Central Oregon
Of course pressure, wheel width, wieght all make a difference...

so with 40# of pressure and a pretty much empty rig..my wheel tire combo is 30inches...don't matter what it is off the rig...

I'm not worried about it..I am worried (sic; concerned) that when I put the new 33x10.5 at's on..I'll have even more lag in the git-up-and-go department cause the new ones will for sure be closer to the 33" I thought I was already running...

like I said..just a Sat night topic ...
 
Joined
Feb 20, 2006
Messages
5,698
Location
calgary
try throwing a level over the top of the tire and measure to that, i think if you actually marked the tire and moved the vehicle to get exactly 1 revolution of the tire to get a measurement, blah blah blah, youd find the result to be closer to 32.
even the the tire doesnt sit as high off the ground you still cover the same distance. however its the clearance that is really the disadvantage.

swampers will be almost exactly the indicated size, sometimes bigger.
 
Joined
Apr 15, 2004
Messages
2,863
Location
Larkspur, CO
This is really 2 issues: ground clearance & rolling radius.

If you want to be sure you're going to clear your favorite 12" rock (remember axle radius & all the crap hanging down below it) you need a different tire/wheel combo.

If you're concerned about gear ratios and/or speedo accuracy, 2m's observation is key.
 

Users who are viewing this thread

Top Bottom