Redundant Tire Pressure Question? - Jeep Wrangler Forum
Jeep Wrangler Forum

Go Back   Jeep Wrangler Forum > General Jeep Discussions > Tires & Wheels

Join Wrangler Forum Today


Reply
 
Thread Tools

Please support our sponsors and let them know you heard about them on WranglerForum.com
Old 02-10-2016, 09:19 AM
Thread Starter
  #1
Jeeper
 
wnbamiamisol's Avatar
 
Join Date: May 2012
Posts: 57
Redundant Tire Pressure Question?

I have had my brand new '15 Wrangler Sport exactly a month.
I upgraded from the factory 225/70R16 on steel wheels to Pro Comp AT Sport 285/70R17 tires on Pro Comp 7005 17x9 rims. To begin with, 2 tires were out of round, yet 4wheelparts installed them, attempting to get a balance with 32 tire weights!?! At 400 miles on the Jeep, they installed 2 new tires in place of the defective ones. I bought an AEV ProCal and recalibrated the speedometer. I am STILL experiencing a rough ride. I had the balance checked at the Jeep dealership (high speed balancing) gratis. I am now up to 800 miles. I have ordered an OME steering stabilizer as per the Jeep dealer's suggestion.
The tire pressure was set to 37 and I have lowered it to 35. So I can eliminate that as an issue for the "bumpy" ride, what would you suggest as a tire pressure?
Stock suspension and I don't want to lift. This will 99.9% of the time be driven on the highway. Suggestions to help get rid of the feel of every crack and bump on the pavement?
Thanks!

__________________
1979 CJ5 (sold); 1984 CJ7 (traded); 1993 YJ (traded) ; 1998 TJ Sahara (traded); 2012 JK Sport (traded); 2012 Grand Cherokee SRT (traded); 2014 Grand Cherokee SRT (traded) ; 2014 JK Rubicon X (traded); 2015 JK Sport (traded);

Current: 2018 JL Rubicon & 2014 Porsche Carrera Cabriolet & 2018 MB GLA45 AMG
wnbamiamisol is offline   Quote
Old 02-10-2016, 09:28 AM   #2
Jeeper
 
Join Date: Jun 2015
Location: Indianapolis
Posts: 86
I've got a similar size tire. 285/75/r16. I run them at 25psi.

Flexy is offline   Quote
Old 02-10-2016, 11:15 AM   #3
Jeeper
 
Join Date: Sep 2012
Posts: 33
Googled the tires and found old Loadindex 103 and new Loadindex 121.
Old 1930 lbs maximum load and new 3200 lbs maximum load.
most likely , but check it , both are standard load , wich carry maximum load up to 160km/99m/h AT 35 or 36 psi .
And because the kind of cars in this forum mosly have oversised tires , of wich one tire can bare the totaal Gross axle weight rating, even for the old tires you could do with about 20 psi , only for savety of tires.
New tires can bare about 1.5 times as much , so needed lowest save pressure up to 99m/h is even lower.

Then at 35 psi I would expect some bumping.

If you can give me the GAWR's , and check if tires are Standard load ( AT pressure 35 psi in USA system ,36 EUR) or XL/reinforced/Extraload( AT pressure 41 USA and 42 EUR) , I can calculate a lowest save pressure for you , and a highest pressure at wich comfort and gripp are still acceptable.
Trickysest part in it all is to determine the actual loads on seperate tires.

But also check if you have offroad-like tires with profile blocks that cover a part of sidewall, they are allowed lesser deflection then a road tire, but tiremakers give same Loadindex/maxload for them as road tire.

Added 2 pictures to show what I mean, one is compare and the other one is an even more offroad tire.

Greatings from a Dutch Pigheaded Self-declared Tirepressure-specialist.
Peter
Attached Thumbnails
Click image for larger version

Name:	onroadoffroadcompare.jpg
Views:	106
Size:	97.8 KB
ID:	2812601   Click image for larger version

Name:	evenmoreoffroadtire.jpg
Views:	106
Size:	99.3 KB
ID:	2812609  

jadatis is offline   Quote
Sponsored Links
Advertisement
 
Old 02-10-2016, 11:55 AM
Thread Starter
  #4
Jeeper
 
wnbamiamisol's Avatar
 
Join Date: May 2012
Posts: 57
Curb weight is 3785 pounds.
Here is a photo of the tire. Definitely more off road looking.
__________________
1979 CJ5 (sold); 1984 CJ7 (traded); 1993 YJ (traded) ; 1998 TJ Sahara (traded); 2012 JK Sport (traded); 2012 Grand Cherokee SRT (traded); 2014 Grand Cherokee SRT (traded) ; 2014 JK Rubicon X (traded); 2015 JK Sport (traded);

Current: 2018 JL Rubicon & 2014 Porsche Carrera Cabriolet & 2018 MB GLA45 AMG
wnbamiamisol is offline   Quote
Old 02-10-2016, 12:04 PM   #5
Moderator

WF Lifetime Member
WF Supporting Member
::WF Moderator::
 
Sinister6's Avatar
 
Join Date: Jan 2013
Location: Colorado Springs
Posts: 9,574
Quote:
Originally Posted by wnbamiamisol View Post
I have had my brand new '15 Wrangler Sport exactly a month. I upgraded from the factory 225/70R16 on steel wheels to Pro Comp AT Sport 285/70R17 tires on Pro Comp 7005 17x9 rims. To begin with, 2 tires were out of round, yet 4wheelparts installed them, attempting to get a balance with 32 tire weights!?! At 400 miles on the Jeep, they installed 2 new tires in place of the defective ones. I bought an AEV ProCal and recalibrated the speedometer. I am STILL experiencing a rough ride. I had the balance checked at the Jeep dealership (high speed balancing) gratis. I am now up to 800 miles. I have ordered an OME steering stabilizer as per the Jeep dealer's suggestion. The tire pressure was set to 37 and I have lowered it to 35. So I can eliminate that as an issue for the "bumpy" ride, what would you suggest as a tire pressure? Stock suspension and I don't want to lift. This will 99.9% of the time be driven on the highway. Suggestions to help get rid of the feel of every crack and bump on the pavement? Thanks!
35psi is way to much!
Try 28-30psi and go from there. Have you done a Chalk test? I run 315/75/16 and for DD I'm at 25-28 psi. The only time I went above 30 was from long road trips but my Jeeps a trailer queen now so not an issue. And a steering stabilizer wound help a bumpy ride. A well set up front suspension doesn't need a stabilizer.
__________________
John
The Wolf is not concerned with the opinion of sheep.
MY BUILD: :
https://www.wranglerforum.com/f322/s...ad-235526.html
Sinister6 is offline   Quote
Old 02-10-2016, 12:20 PM
Thread Starter
  #6
Jeeper
 
wnbamiamisol's Avatar
 
Join Date: May 2012
Posts: 57
Factory, stock suspension, so....
Dealer suggested the steering stabilizer :-(. May just send that back when it arrives Friday.
No chalk test yet. I am having a difficult time finding sidewalk chalk (in the Florida Keys). Agreed that will give me a good idea.
__________________
1979 CJ5 (sold); 1984 CJ7 (traded); 1993 YJ (traded) ; 1998 TJ Sahara (traded); 2012 JK Sport (traded); 2012 Grand Cherokee SRT (traded); 2014 Grand Cherokee SRT (traded) ; 2014 JK Rubicon X (traded); 2015 JK Sport (traded);

Current: 2018 JL Rubicon & 2014 Porsche Carrera Cabriolet & 2018 MB GLA45 AMG
wnbamiamisol is offline   Quote
Old 02-10-2016, 12:55 PM
Thread Starter
  #7
Jeeper
 
wnbamiamisol's Avatar
 
Join Date: May 2012
Posts: 57
Oh, chalk tested. Chalk worn off center of tire with plenty remaining on the outside edge at 35 lbs.
__________________
1979 CJ5 (sold); 1984 CJ7 (traded); 1993 YJ (traded) ; 1998 TJ Sahara (traded); 2012 JK Sport (traded); 2012 Grand Cherokee SRT (traded); 2014 Grand Cherokee SRT (traded) ; 2014 JK Rubicon X (traded); 2015 JK Sport (traded);

Current: 2018 JL Rubicon & 2014 Porsche Carrera Cabriolet & 2018 MB GLA45 AMG
wnbamiamisol is offline   Quote
Old 02-10-2016, 01:41 PM   #8
Jeeper
 
Join Date: Dec 2015
Location: Annapolis, MD
Posts: 22
Quote:
Originally Posted by wnbamiamisol View Post
Oh, chalk tested. Chalk worn off center of tire with plenty remaining on the outside edge at 35 lbs.
To be expected, I suppose, since the high pressure is bowing the tread.

My new tires (Mickey Thompson Baja ATZ P3, 285/70R17) came from the shop at 36 PSI (which is what the stock tires were set at)

Mickey Thompson suggested 42 PSI all around. That didn't sounds right to me at all, but I tried it ...they're the tire experts after all. It felt like I was running on 110 PSI road bicycle tires. Terrible. The guy must have been high.

Aired it down to 29 PSI cold, and it rides great.

FWIW
mmathai is offline   Quote
Old 02-10-2016, 02:39 PM   #9
Moderator

WF Lifetime Member
WF Supporting Member
::WF Moderator::
 
Sinister6's Avatar
 
Join Date: Jan 2013
Location: Colorado Springs
Posts: 9,574
Quote:
Originally Posted by mmathai View Post
To be expected, I suppose, since the high pressure is bowing the tread. My new tires (Mickey Thompson Baja ATZ P3, 285/70R17) came from the shop at 36 PSI (which is what the stock tires were set at) Mickey Thompson suggested 42 PSI all around. That didn't sounds right to me at all, but I tried it ...they're the tire experts after all. It felt like I was running on 110 PSI road bicycle tires. Terrible. The guy must have been high. Aired it down to 29 PSI cold, and it rides great. FWIW
You have to keep in mind that those recommended pressures are typically for a full-size pick up truck. Your jeeps weigh a fraction of that.
__________________
John
The Wolf is not concerned with the opinion of sheep.
MY BUILD: :
https://www.wranglerforum.com/f322/s...ad-235526.html
Sinister6 is offline   Quote
Old 02-10-2016, 04:04 PM
Thread Starter
  #10
Jeeper
 
wnbamiamisol's Avatar
 
Join Date: May 2012
Posts: 57
Copy that. D rated tire is for a Yukon Denali XLT. My Jeep is nearly 1/2 that weight.
__________________
1979 CJ5 (sold); 1984 CJ7 (traded); 1993 YJ (traded) ; 1998 TJ Sahara (traded); 2012 JK Sport (traded); 2012 Grand Cherokee SRT (traded); 2014 Grand Cherokee SRT (traded) ; 2014 JK Rubicon X (traded); 2015 JK Sport (traded);

Current: 2018 JL Rubicon & 2014 Porsche Carrera Cabriolet & 2018 MB GLA45 AMG
wnbamiamisol is offline   Quote
Old 02-10-2016, 05:33 PM   #11
Jeeper
 
Join Date: Dec 2015
Location: Annapolis, MD
Posts: 22
Yeah, I know the tires are meant for heavier vehicles, but I gave the guy the exact specs of my Jeep. Oh well, in the end I'm happier to figure it out for myself anyway.
mmathai is offline   Quote
Old 02-11-2016, 01:38 PM   #12
Jeeper
 
Join Date: Sep 2012
Posts: 33
Curb weigt of 3785 is as I recall not the maximum allowed vehicle weight.
GVWR = Gross Vehicle weight rating.
So I did some estimation and think GVWR=5000 lbs and front GAWR 2500 lbs, and rear GAWR 2750 lbs. These are the axleweights that the car-maker uses to calculate the pressure advice.
Can be that I am way off, so correct me then.

But the weight in normal use can be estimated from this curb weight.
I estimate at front axle 2000 lbs empty and rear rest of 1785 lbs.
2 persons of 200 lbs on front seat with gravity point ( about belly button) half between the axles means 200 lbs adding to both axles.
Then some lugage of say 100 lbs in the back so only on rear axle .
Gives Front 2200 lbs and rear 2085 lbs .

For these axle weight I will calculate.
Tires Li 121/3195 lbs would give F23psi R 21psi.

But I lower the maxload by 20%/8 LI steps because of the offroad story.
then LI 113/2535 lbs would give F 29 psi R 28 psi
Then you can drive up to 99m/h with these loads, you probably wont do that.

for up to 75 miles/h the Loadindex can be lowered by 4 steps so gives
LI 117/2833 lbs would give F26 psi R 24 psi.

My idea of savety is to use the middle of 29 psi all around for R/L misbalance.

Or it must be that I am mistaken about the curb weight , then correct me and I will calculate again.
jadatis is offline   Quote
Old 02-11-2016, 02:52 PM
Thread Starter
  #13
Jeeper
 
wnbamiamisol's Avatar
 
Join Date: May 2012
Posts: 57
Thanks. After the chalk test, I am at 30psi. Seems to have really smoothed out the ride. You are probably pretty close.
I have the rear seat removed and I am alone in the Jeep, weighing 130 pounds. Have added 40 pound rock crawlers.
Going to leave it at 30psi for a couple days to see.
__________________
1979 CJ5 (sold); 1984 CJ7 (traded); 1993 YJ (traded) ; 1998 TJ Sahara (traded); 2012 JK Sport (traded); 2012 Grand Cherokee SRT (traded); 2014 Grand Cherokee SRT (traded) ; 2014 JK Rubicon X (traded); 2015 JK Sport (traded);

Current: 2018 JL Rubicon & 2014 Porsche Carrera Cabriolet & 2018 MB GLA45 AMG
wnbamiamisol is offline   Quote
Old 02-16-2016, 10:19 AM
Thread Starter
  #14
Jeeper
 
wnbamiamisol's Avatar
 
Join Date: May 2012
Posts: 57
Wanted to bump this up as the 4Wheel Parts store has conceded there is definitely a balance issue with the Pro Comp AT Sport 285/70R17 tires on my new Wrangler. As they come with a 60 day satisfaction guarantee, they will get swapped out on Thursday.
My choices are:
Toyo AT2
Nitto Grappler 2
I know same manufacturer. Experiences with either? Smoother ride for a DD?
__________________
1979 CJ5 (sold); 1984 CJ7 (traded); 1993 YJ (traded) ; 1998 TJ Sahara (traded); 2012 JK Sport (traded); 2012 Grand Cherokee SRT (traded); 2014 Grand Cherokee SRT (traded) ; 2014 JK Rubicon X (traded); 2015 JK Sport (traded);

Current: 2018 JL Rubicon & 2014 Porsche Carrera Cabriolet & 2018 MB GLA45 AMG
wnbamiamisol is offline   Quote
Old 02-16-2016, 12:00 PM   #15
Jeeper
 
Join Date: Nov 2014
Location: Armpit of America AKA NJ
Posts: 181
Quote:
Originally Posted by wnbamiamisol View Post
Wanted to bump this up as the 4Wheel Parts store has conceded there is definitely a balance issue with the Pro Comp AT Sport 285/70R17 tires on my new Wrangler. As they come with a 60 day satisfaction guarantee, they will get swapped out on Thursday.
My choices are:
Toyo AT2
Nitto Grappler 2
I know same manufacturer. Experiences with either? Smoother ride for a DD?
If you decide on the Nitto Grappler 2, will you let me know your impressions. I'm thinking about those for myself as well and don't know anyone with real world experience on them.
BZSurfer is offline   Quote
Old 02-16-2016, 01:14 PM
Thread Starter
  #16
Jeeper
 
wnbamiamisol's Avatar
 
Join Date: May 2012
Posts: 57
Quote:
Originally Posted by BZSurfer View Post
If you decide on the Nitto Grappler 2, will you let me know your impressions. I'm thinking about those for myself as well and don't know anyone with real world experience on them.
Will do. I did decide on them. Installation is mid day Thursday and I have an 85 mile drive home. That will be a decent first impression.
__________________
1979 CJ5 (sold); 1984 CJ7 (traded); 1993 YJ (traded) ; 1998 TJ Sahara (traded); 2012 JK Sport (traded); 2012 Grand Cherokee SRT (traded); 2014 Grand Cherokee SRT (traded) ; 2014 JK Rubicon X (traded); 2015 JK Sport (traded);

Current: 2018 JL Rubicon & 2014 Porsche Carrera Cabriolet & 2018 MB GLA45 AMG
wnbamiamisol is offline   Quote
Old 02-16-2016, 01:49 PM   #17
Jeeper
 
Join Date: Nov 2014
Location: Armpit of America AKA NJ
Posts: 181
Quote:
Originally Posted by wnbamiamisol View Post
Will do. I did decide on them. Installation is mid day Thursday and I have an 85 mile drive home. That will be a decent first impression.
Awesome. Thanks.
BZSurfer is offline   Quote
Old 02-18-2016, 05:28 PM
Thread Starter
  #18
Jeeper
 
wnbamiamisol's Avatar
 
Join Date: May 2012
Posts: 57
Quote:
Originally Posted by BZSurfer View Post
Awesome. Thanks.
👍👍👍👍👍
BIG thumbs up for the Nitto Grappler 2 tires. They were put on by 2 pm today. Drove the 85 miles home doing 70 mph on the Florida Turnpike as well as normal 45 mph speed zones and my residential street at 25 mph. Night and day ride (vs. the former Pro Comp Sport AT). I know the 4Wheel Parts chain pushes the Pro Comp tires, but they do not compare with the Nitto tires. They are a comfortable ride and equally quiet (maybe a little quieter?). They seem to grab better, too.
Highly recommended.

__________________
1979 CJ5 (sold); 1984 CJ7 (traded); 1993 YJ (traded) ; 1998 TJ Sahara (traded); 2012 JK Sport (traded); 2012 Grand Cherokee SRT (traded); 2014 Grand Cherokee SRT (traded) ; 2014 JK Rubicon X (traded); 2015 JK Sport (traded);

Current: 2018 JL Rubicon & 2014 Porsche Carrera Cabriolet & 2018 MB GLA45 AMG
wnbamiamisol is offline   Quote
Reply

Tags
bumpy ride , suspension , tire pressure

Thread Tools

Posting Rules
You may not post new threads
You may not 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 Off
Refbacks are Off






All times are GMT -5. The time now is 06:13 AM.


Powered by vBulletin® Version 3.8.8
Copyright ©2000 - 2019, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.1
User Alert System provided by Advanced User Tagging v3.1.0 (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
vBulletin Security provided by vBSecurity v2.2.2 (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.

Jeep®, Wrangler, Liberty, Wagoneer, Cherokee, Gladiator, Mopar and Grand Cherokee are copyrighted and trademarked to FCA US LLC.
Wranglerforum.com is not in any way associated with FCA US LLC.