30 Inch tire pressure

Fitting oversize tires, raising and lowering, suspension modifications...

Moderator: F9K9

30 Inch tire pressure

Postby ApproachMedium » Tue Oct 29, 2013 1:33 pm

What tire pressure should I be running with 30x9.5s on my crew? I have 15 inch ZR5 wheels and the V8 swap so theres a little more weight on the front end. The sidewall of the tire says 50 PSI but the truck door says 32 i believe. My friend who put the tires on for me set them at 40PSi and they look like they are a little low in the front as the truck sits. Im also not getting so great of MPG which is why I asked.

Speedo has been checked at speeds from 40-80mph and it is on the money with my phones GPS system.
Knowledge has no value unless its shared with others.
Exploration Machine- 02' CC V8 swap. 300K+
Portable Roller Coaster- 07' MKV VW GTI
Its another Jeep- 98 TJ
ApproachMedium
Crew Elite
Crew Elite
 
Posts: 969
Joined: Tue Nov 17, 2009 1:20 am
Location: Jersey Shore

Re: 30 Inch tire pressure

Postby roadrunner » Tue Oct 29, 2013 3:49 pm

My sidewalls (BFG 235x75x15 AT tires that measure 29.5x9 I believe) also say 50psi and it has been my experience that running anything much lower than that hurts my fuel economy and my tires are wearing evenly at that pressure as well. Others will argue differently but that is my personal experience.
2001 CC LS, pewter, stock, 4.3,Wait4meperformance, CFM throttle blade, Helix throttle body spacer, 4spd auto, 3button electric 4x4 shift, heavy duty factory suspension, Bilsteins, 1" rear wheel spacers, skid plates.
User avatar
roadrunner
Crew K Elite
Crew K Elite
 
Posts: 1254
Joined: Wed Dec 05, 2007 5:39 pm
Location: NW KS

Re: 30 Inch tire pressure

Postby killian96ss » Tue Oct 29, 2013 6:18 pm

32 psi cold. The 50 psi mark on the tire is the max pressure allowed for that tire, not the recommended pressure.

Steve
2005 ZR2 Blazer / Mods- Spectre CAI, Descreened MAF, Shaved Throttle Blade, 31" Goodyear Kevlar MT/R's, Black Rock Rims, MSD Street Fire CDI & Super Conductor Wires, Accel Cap, Rotor & Coil, Flowmaster 30 Series, Gibson Tailpipe, ES Bushings, Goodridge Brake Lines, Power Slot Rotors - 1996 Impala SS / Mods- Too Many To List - 1988 S10 Blazer / Mods- Too Many To List - 2001 S10 Crew Cab 4x4 / Mods- Too Many To List *Wrecked 12/06*
User avatar
killian96ss
Crew K Elite
Crew K Elite
 
Posts: 2665
Joined: Tue Sep 09, 2003 11:53 am
Location: Rocklin, California

Re: 30 Inch tire pressure

Postby ApproachMedium » Tue Oct 29, 2013 7:27 pm

But it doesnt say max tire pressure on the side of these tires? It says load support at 50PSI in one place and then somewhere else it says 50PSI.
Knowledge has no value unless its shared with others.
Exploration Machine- 02' CC V8 swap. 300K+
Portable Roller Coaster- 07' MKV VW GTI
Its another Jeep- 98 TJ
ApproachMedium
Crew Elite
Crew Elite
 
Posts: 969
Joined: Tue Nov 17, 2009 1:20 am
Location: Jersey Shore

Re: 30 Inch tire pressure

Postby ApproachMedium » Tue Oct 29, 2013 7:52 pm

CORRECTION, i take it back. I just looked it up online on the General tire site. They said for the 30x9.5 Grabber AT2 it is 50PSI MAX. The tire itself does not say max for some reason..
Knowledge has no value unless its shared with others.
Exploration Machine- 02' CC V8 swap. 300K+
Portable Roller Coaster- 07' MKV VW GTI
Its another Jeep- 98 TJ
ApproachMedium
Crew Elite
Crew Elite
 
Posts: 969
Joined: Tue Nov 17, 2009 1:20 am
Location: Jersey Shore

Re: 30 Inch tire pressure

Postby AVTekk » Tue Oct 29, 2013 8:24 pm

32psi is too low, that is for a standard tire rated at 35psi max. Its up to you what you want to set them at, usually I put them 40-44psi when theyre rated for 50, but mostly for comfort. My 31s are D or E rated and i have to run them around 20spi or the truck rides like a brick.
User avatar
AVTekk
Crew Elite
Crew Elite
 
Posts: 106
Joined: Mon Nov 22, 2004 2:09 pm
Location: South Plainfield, NJ

Re: 30 Inch tire pressure

Postby HenryJ » Wed Oct 30, 2013 4:55 am

Tire pressures and airing down for offroad
Find and empty parking lot.

Inflate your tires to the max pressure listed on the sidewall.

Mark the tires accross the tread with a piece of chalk or crayon whatever really.

Drive straight forward several feet, be sure not to turn at all.

Look at the mark across the tread and see which part of mark has worn off.

If the mark has worn off at the center but not at the edges you have too much pressure (duh i already told you max pressure would be too much). Drop the pressure and repeat steps 2-5 until the desired pattern is achived. Be careful too low of a pressure will rub the mark so allways start with too much and work your way down.

"Speed doesn't kill, suddenly becoming stationary does." - Richard Hammond
"Speed is just a matter of Money - How fast do YOU want to go?"-Mechanic from Mad Max-
If at first you don't succeed - Don't take up Skydiving!
- ThunderII KE7CSK
User avatar
HenryJ
Admin K Elite
Admin K Elite
 
Posts: 12691
Joined: Tue Oct 01, 2002 9:14 pm
Location: Ontario, Oregon

Re: 30 Inch tire pressure

Postby roadrunner » Wed Oct 30, 2013 12:03 pm

The 50psi marking on the side of the tires indicates max COLD inflation pressure.
2001 CC LS, pewter, stock, 4.3,Wait4meperformance, CFM throttle blade, Helix throttle body spacer, 4spd auto, 3button electric 4x4 shift, heavy duty factory suspension, Bilsteins, 1" rear wheel spacers, skid plates.
User avatar
roadrunner
Crew K Elite
Crew K Elite
 
Posts: 1254
Joined: Wed Dec 05, 2007 5:39 pm
Location: NW KS

Re: 30 Inch tire pressure

Postby ApproachMedium » Wed Oct 30, 2013 8:36 pm

Thanks for the info guys. I will try the chalk method. I brought the front tires up to 42PSi today and already I can feel a difference. I left the rears alone as they do look ok.

I do understand now fully that the 50 PSi is the MAX Cold inflation rating. I will avoid that at all costs.
Knowledge has no value unless its shared with others.
Exploration Machine- 02' CC V8 swap. 300K+
Portable Roller Coaster- 07' MKV VW GTI
Its another Jeep- 98 TJ
ApproachMedium
Crew Elite
Crew Elite
 
Posts: 969
Joined: Tue Nov 17, 2009 1:20 am
Location: Jersey Shore


Return to Tires / Lifts / Suspension



Who is online

Users browsing this forum: Bing [Bot] and 2 guests