Chalk test?? I'm not driving at 16 PSI!!! - Page 2 - JeepForum.com

Reply
 
LinkBack Thread Tools
post #16 of 49 Old 02-26-2012, 03:30 PM
DanZ51
Registered User
2004 TJ Wrangler 
 
Join Date: Feb 2009
Location: Wallingford, VT
Posts: 844
'Just a perspective: a basic M998 HMMWV (curb weight 5200 lbs) runs 20/26 (F/R) PSI for 37x12.5x16.5" Radials.

Bigger tires need less pressure for a given weight. Although 16PSI maybe a bit wobbly for the street


"I will always be an American Soldier"
DanZ51 is offline  
Sponsored Links
Advertisement
 
post #17 of 49 Old 02-26-2012, 03:49 PM
AKGeo
Web Wheeler
2000 TJ Wrangler 
 
Join Date: Feb 2011
Location: Fairbanks
Posts: 1,166
Quote:
Originally Posted by PredatorNC View Post
Good points made by all, and being a noob to the jeep world, there was a healthy amount of fear thinking that 16 psi was a sweet spot...and that 16 psi was optimistic...there was still chalk there so another 2-4 lbs would have probably made it even.

TYVM! bringing the info on the wheel width! Yes, I am running 15x8's. So literally I would have to run a 12" width for it to lay flatter with more psi correct?

Thanks for being noob kind! lol
10". Your tires are 12.5's but the tread is only 10" wide...the width is also counting the sidewall bulge. Tire manufacturers recommend wheel widths for each size tire, and most 12.5's have a 9 to 10" width recommendation.


It's a trade-off. If you want your tires to last as long as possible, get wider wheels. If you want your tires to perform offroad at lower PSIs without blowing beads, get narrower wheels or beadlocks.
AKGeo is offline  
post #18 of 49 Old 02-26-2012, 08:32 PM
Fortune
Registered User
2003 TJ Wrangler 
 
Join Date: Jan 2012
Location: East Lansing
Posts: 15
I understand the chalk test... What's the spray bottle test?
Fortune is offline  
post #19 of 49 Old 02-26-2012, 09:13 PM
rkwfxd
Registered User
2004 TJ Wrangler 
 
Join Date: Nov 2008
Posts: 584
TJ soft top with 35X12.50 on 15X8. I am probably too high but I am running 30 in the front and 28 in the rear. Might drop them all down 2 psi but they look pretty good right now.
rkwfxd is offline  
post #20 of 49 Old 02-26-2012, 09:15 PM
Jerry Bransford
Administrator
 
Jerry Bransford's Avatar
2004 TJ Wrangler 
 
Join Date: Jan 2003
Location: Escondido, California
Posts: 67,026
Quote:
Originally Posted by rkwfxd View Post
TJ soft top with 35X12.50 on 15X8. I am probably too high but I am running 30 in the front and 28 in the rear. Might drop them all down 2 psi but they look pretty good right now.
24-26 is appropriate for that size tire supporting a Wrangler. 28 and 30 is excessive for a 35" tire.

Getting
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
...


When you have a choice, buy American made.

To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
Jerry Bransford is offline  
post #21 of 49 Old 02-26-2012, 10:12 PM
Maverickxeo
Registered User
2002 TJ Wrangler 
 
Join Date: Jan 2010
Location: Wetaskiwin
Posts: 2,415
Garage
I have been trying to find out what I need to run for PSI in my 33x10.50R15 BFG A/T tires, but I cant quite find a good 'balance.' I havent done the chalk test, but I have seen that when Im driving down a dirt road, and come onto the street, the centers of the tires are pretty dirty, but they outsides look relatively clean (basically, they dont seem to be touching all the way). I believe Im running 24PSI right now, on the canyon wheels... Am I set too high for the street?
Maverickxeo is online now  
post #22 of 49 Old 02-26-2012, 10:19 PM
Jerry Bransford
Administrator
 
Jerry Bransford's Avatar
2004 TJ Wrangler 
 
Join Date: Jan 2003
Location: Escondido, California
Posts: 67,026
Quote:
Originally Posted by Maverickxeo View Post
I have been trying to find out what I need to run for PSI in my 33x10.50R15 BFG A/T tires, but I cant quite find a good 'balance.' I havent done the chalk test, but I have seen that when Im driving down a dirt road, and come onto the street, the centers of the tires are pretty dirty, but they outsides look relatively clean (basically, they dont seem to be touching all the way). I believe Im running 24PSI right now, on the canyon wheels... Am I set too high for the street?
Getting the entire tread on the ground is not the goal, that would be underinflated. For a 33x12.50 BFG AT supporting a Wrangler, 26-28 is actually about right.

Getting
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
...


When you have a choice, buy American made.

To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
Jerry Bransford is offline  
post #23 of 49 Old 02-27-2012, 03:08 AM
Necromancer_tat
Where'd all my money go?
 
Necromancer_tat's Avatar
2015 JK Wrangler 
 
Join Date: Jul 2011
Location: Norfolk
Posts: 5,291
Quote:
Originally Posted by Fortune View Post
I understand the chalk test... What's the spray bottle test?
On a clean level driveway, with cold tires, use a spray bottle to mist the tire, then roll forward a few feet and look at the tread pattern left on the ground. If it's darker on the inside than the outside of the tread pattern then the tire is over inflated, if it's darker on the edges, then it's under inflated. Same principal as the chalk test but it's faster.

My newest build:
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
Necromancer_tat is offline  
post #24 of 49 Old 02-27-2012, 03:43 AM
oalali
Registered User
2006 LJ Wrangler 
 
Join Date: Sep 2011
Location: Abu Dhabi
Posts: 788
.... and I'm running 30 psi on my Cooper STT 33x12.5r15 ..

Would having a hardtop and a tire carrier makes any difference ??

I guess that I should lower the pressure to 26~28psi....


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
oalali is offline  
post #25 of 49 Old 02-27-2012, 09:36 AM
ytowntj
Registered User
1999 TJ Wrangler 
 
Join Date: May 2008
Location: Norfolk - Old Dominion
Posts: 2,743
After running 32x1150 and 33x1050 bfg ats on my TJ Id feel safe recommending 26-27 psi. I ran 28 pounds in my 32s and got TONS of life out of them.

Parting my TJ:


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.


My build - Odd approach to 33's

To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
ytowntj is offline  
post #26 of 49 Old 02-27-2012, 09:55 AM
Peterpsc
Registered User
2006 LJ Wrangler 
 
Join Date: Feb 2009
Location: Northern California
Posts: 353
I run 37 in MTR w/Kevlar on Evans Beadlock 17s. PSI for street 26 and off-road 8-10. My jeep is heavy at 5500 lbs loaded.
Peterpsc is offline  
post #27 of 49 Old 02-27-2012, 10:03 AM
Griff1918
Registered User
2003 TJ Wrangler 
 
Join Date: Oct 2011
Posts: 1,625
well, the other way to figure out the psi is a mathmatical equation.
Griff1918 is offline  
post #28 of 49 Old 02-27-2012, 10:57 AM
Peterpsc
Registered User
2006 LJ Wrangler 
 
Join Date: Feb 2009
Location: Northern California
Posts: 353
Quote:
Originally Posted by Griff1918 View Post
well, the other way to figure out the psi is a mathmatical equation.
The formulas I've seen don't work for my jeep. Here's an example of what appears to be a popular formula for tire PSI (cold pressures). It can be found on various forums:

(Axle Weight / 2) / Tire Capacity) x Tire Max PSI = Inflate Pressure

While the formula doesn't work for my jeep it gets real close for my dually.

Which formula are you referencing?
Peterpsc is offline  
post #29 of 49 Old 02-27-2012, 11:00 AM
Tenshots1
Registered User
2005 TJ Wrangler 
 
Join Date: Dec 2009
Location: San Diego
Posts: 934
I run 29psi with my KM2 and I have been getting great wear the past 25k miles

2005 Jeep Sport 4" lift With plenty of goodies
My Build Thread: http://www.jeepforum.com/forum/f22/budget-jeep-1151796/
Tenshots1 is offline  
post #30 of 49 Old 02-27-2012, 11:02 AM
Imped
Web Wheeler
 
Imped's Avatar
2004 TJ Wrangler 
 
Join Date: Feb 2008
Location: Indianapolis
Posts: 20,378
26F/24R psi on the road, 8 psi off.

OlllllllO

To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.

IndyORV
Imped is online now  
Reply

Tags
33 , chalk , tire pressure

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the JeepForum.com forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid e-mail address for yourself.



Email Address:
OR

Log-in









Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.




Currently Active Users Viewing This Thread: 2 (0 members and 2 guests)
 
Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page



Similar Threads
Thread Thread Starter Jeep Forums Replies Last Post
Chalk test results UltimatE YJ Wrangler Technical Forum 5 10-25-2010 05:34 PM
Chalk test rockit TJ Wrangler Technical Forum 17 09-18-2007 04:39 PM
Test Driving: What to look for? chitarra YJ Wrangler Technical Forum 30 05-07-2007 10:52 AM
Test driving a TJ? Marty315 TJ Wrangler Technical Forum 2 08-10-2003 10:24 PM
FAQ or How-to for test driving a TJ? duckyjp TJ Wrangler Technical Forum 1 02-19-2003 09:51 PM

Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome