true tire size thread
JK Super Freak
Joined: Jun 2010
Posts: 1,465
Likes: 0
From: northern virginia
JK Super Freak
Joined: Jun 2010
Posts: 1,465
Likes: 0
From: northern virginia
but, why....The concern most people have, is clearance between the tire and body. I run 37/12.50-17 KX krawlers, and they are actually really true to size. When mounted off vehicle
The outside circumference remains the same whether it has a load on it or not. The diameter only changes at the point of load,on the load bearing radius. Which is different depending on the vehicle weight and other variables.
So, when my 37's are aired down to 8 psi on the trail they are around let us say 35" "tall" and they barely rub at full stuff.......because the radius from the center and the body is the same as if they were off the jeep.....That means I can't run a 39" Krawlers at 8psi even though they would measure 37" "tall" on the jeep....because of the available clearance in the fender well, will not accept a 39" tire.
So, the only measure that is needed is mounted off the vehicle
The outside circumference remains the same whether it has a load on it or not. The diameter only changes at the point of load,on the load bearing radius. Which is different depending on the vehicle weight and other variables.
So, when my 37's are aired down to 8 psi on the trail they are around let us say 35" "tall" and they barely rub at full stuff.......because the radius from the center and the body is the same as if they were off the jeep.....That means I can't run a 39" Krawlers at 8psi even though they would measure 37" "tall" on the jeep....because of the available clearance in the fender well, will not accept a 39" tire.
So, the only measure that is needed is mounted off the vehicle
Super Moderator
Joined: Sep 2007
Posts: 1,750
Likes: 89
From: Arizona
Sooooo many variables. PSI, Hot Tire, Cold Tire, Load Rating, Speed of Vehicle, Weight on Tire, and maybe Phase of Moon. Here's something I found on the web concerning "Static Load Radius". It shows for this example the loaded radius of a tire is only 44% of loaded static diameter (what I think everyone is measuring for this thread) when going slow or stopped, but can be 51% of the static loaded diameter at 70-80 MPH. Your ground clearance increases with speed. Probably makes a difference to what calibration correction you use depending on the speed you were going when you checked with your GPS.
When measuring a tire's radius, use the following as an estimate:
When measuring a tire's radius, use the following as an estimate:
- Enter 44% (Loaded diameter x 0.44) of the static loaded diameter if the vehicle is driven at 0-10 mph while testing.
- Enter 45% (Loaded diameter x 0.45) of the static loaded diameter if the vehicle is driven at 10-20 mph while testing.
- Enter 46% (Loaded diameter x 0.46) of the static loaded diameter if the vehicle is driven at 20-30 mph while testing.
- Enter 47% (Loaded diameter x 0.47) of the static loaded diameter if the vehicle is driven at 30-40 mph while testing.
- Enter 48% (Loaded diameter x 0.48) of the static loaded diameter if the vehicle is driven at 40-50 mph while testing.
- Enter 49% (Loaded diameter x 0.49) of the static loaded diameter if the vehicle is driven at 50-60 mph while testing.
- Enter 50% (Loaded diameter x 0.50) of the static loaded diameter if the vehicle is driven at 60-70 mph while testing.
- Enter 51% (Loaded diameter x 0.51) of the static loaded diameter if the vehicle is driven at 70-80 mph while testing.
JK Enthusiast
Joined: Mar 2011
Posts: 227
Likes: 0
From: Odenton, MD
Posting this here also.
I am running Goodyear MTR Kevlar 285/70/17 (33x11.5x17)
2012 Unlimited Rubicon
Goodyear Kevlar MTR 285/70/17 100% tread
Mickey Thompson Classic II 17X9 wheels
35 PSI
Vehicle was not driven for an hour or so.
I measured 32-5/8 from the ground to the top of the tire. I put a level across the top of the tire and measured up to that.
FYI.
I am running Goodyear MTR Kevlar 285/70/17 (33x11.5x17)
2012 Unlimited Rubicon
Goodyear Kevlar MTR 285/70/17 100% tread
Mickey Thompson Classic II 17X9 wheels
35 PSI
Vehicle was not driven for an hour or so.
I measured 32-5/8 from the ground to the top of the tire. I put a level across the top of the tire and measured up to that.
FYI.
JK Super Freak
Joined: Jan 2012
Posts: 1,611
Likes: 1
From: Pawnee Ok
Tires: Fierce Attitude MTs
Wheels: Ultra Mavericks
Tire size: 305/70r16
Wheels size: 16x9
Tire psi: 35
Tire load range: E
True tire measurement: 33
gotta love the true tire size!
(on a jeep with full tank of gas as well as heavy bumpers ect..)
Wheels: Ultra Mavericks
Tire size: 305/70r16
Wheels size: 16x9
Tire psi: 35
Tire load range: E
True tire measurement: 33
gotta love the true tire size!(on a jeep with full tank of gas as well as heavy bumpers ect..)
JK Newbie
Joined: Mar 2012
Posts: 28
Likes: 0
From: Lake Mary, Florida
Hi everybody. I have a question about wheels and tires. I hope this is the right forum.
I am hopefully getting my JK this weekend. Unlimited sport. Flame red. 2012. I will be installing Ruged Ridge wheels with nitto terra grapplers.
The question is, if I keep the jeep stock (without lift) what is the maximun allowed size and width for the wheels and tires without having problems with rubbing or other problems? I would like to have the maximun allowed width ( I like the look with the tires sticking out of the fenders a little bit).
Now, I would also consider a minimal lift (2 or 2.5 inches). If I do this, then what will me my allowed maximun size and width to achieve the look that I want?
I thank everybody in advance.
Juan
I am hopefully getting my JK this weekend. Unlimited sport. Flame red. 2012. I will be installing Ruged Ridge wheels with nitto terra grapplers.
The question is, if I keep the jeep stock (without lift) what is the maximun allowed size and width for the wheels and tires without having problems with rubbing or other problems? I would like to have the maximun allowed width ( I like the look with the tires sticking out of the fenders a little bit).
Now, I would also consider a minimal lift (2 or 2.5 inches). If I do this, then what will me my allowed maximun size and width to achieve the look that I want?
I thank everybody in advance.
Juan