60 PSI,
does your KJ weigh 12,000 lbs?
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| Dunlop Radial Rover R/T http://www.lostjeeps.com/forum/phpBB3/viewtopic.php?f=8&t=32290 |
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| Author: | Bill.Barg [ Wed May 07, 2008 7:36 pm ] |
| Post subject: | Dunlop Radial Rover R/T |
Got some Mud Terrain tires Dunlop Radial Rover R/T 245-75-16 load E speed rated R 10 ply. 2 ply sidewall Measured weight each 40.0 lb !!! This is the lightest MT I could find Running 50 psi now (down from 60 psi initially) see http://picasaweb.google.com/bill.barg/J ... 8398201026 Same road noise as my old BIG O AT bigfoots (very little. can't hear it over the diesel anyway!) Good... perhaps better handling than Big O ATs Lighter than BIG O AT (47 lb measured new) Lighter than the BFG AT (50 lb spec) cost $930 for qty 5 out the door with tax etc. $161 each base price (Discount Tire) I will report on long term fuel mileage change... so far real time EVIC is unchanged (23.6 mpg )after 50 miles |
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| Author: | Pote [ Wed May 07, 2008 7:54 pm ] |
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strange tread for MT...I'd say some average ATs have as deep/aggressive a tread. Not knocking, but those treads seem awful close together for a MT. Really looks like an AT tire. How do they do in the mud?? |
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| Author: | tommudd [ Wed May 07, 2008 7:55 pm ] |
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60 PSI, does your KJ weigh 12,000 lbs?
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| Author: | Guest [ Wed May 07, 2008 8:48 pm ] |
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Tom, you beat me to it. I about shart myself. drop it to 40 or less... |
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| Author: | Bill.Barg [ Wed May 07, 2008 11:51 pm ] |
| Post subject: | Tire pressure |
"On Tire pressure and sharting onself;" I use this website to get good advice from others that know a lot more than I do. Thanks for your input. Below is the way I see it, however. Not claiming any special experise. (keep in mind that I am after the 1 mpg that high pressure tire inflation gives). Not interested in a cushy ride. i do want the tires to wear well. --- I dont think the tire pressure should be tuned to the vehicle weight without considering how much air it takes to keep the 10 ply tire round. For instance; The load range E takes 80 psi at full load (3000lb load per tire). Say the libby is 4000lb , then we have 1000 at each tire. Do we run at 1/3 the pressure? = 26 psi ? No, probably not. At 33 psi, the 10 ply tire tire is visibly deformed at the pavement... buldging.... the pressure unable to keep the tire shape against the 10 plys, I figure. (it takes a lot of pressure to tension up all those plys, no?). A 4 ply P tire of the same size may have a load rating of say 2200 at 44 psi. (maybe this is where the suggested 40 psi comes from?). The libby specs ask for 33 psi on their standard issue P tire... about 3/4 of the max presssure. I figure 3/4 of the 80 psi = 60 psi is about right for the Load E tire. What do you all say? |
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| Author: | Bill.Barg [ Wed May 07, 2008 11:54 pm ] |
| Post subject: | Not a MT |
Pote wrote: strange tread for MT...I'd say some average ATs have as deep/aggressive a tread. Not knocking, but those treads seem awful close together for a MT. Really looks like an AT tire. How do they do in the mud??
Ya... this is not an MT... although the TireRack classifies it as such. I will not often see mud here in the desert. May never get to test it. |
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| Author: | Guest [ Thu May 08, 2008 12:11 am ] |
| Post subject: | Re: Tire pressure |
Bill.Barg wrote: "On Tire pressure and sharting onself;"
I use this website to get good advice from others that know a lot more than I do. Thanks for your input. Below is the way I see it, however. Not claiming any special experise. (keep in mind that I am after the 1 mpg that high pressure tire inflation gives). Not interested in a cushy ride. i do want the tires to wear well. --- I dont think the tire pressure should be tuned to the vehicle weight without considering how much air it takes to keep the 10 ply tire round. For instance; The load range E takes 80 psi at full load (3000lb load per tire). Say the libby is 4000lb , then we have 1000 at each tire. Do we run at 1/3 the pressure? = 26 psi ? No, probably not. At 33 psi, the 10 ply tire tire is visibly deformed at the pavement... buldging.... the pressure unable to keep the tire shape against the 10 plys, I figure. (it takes a lot of pressure to tension up all those plys, no?). A 4 ply P tire of the same size may have a load rating of say 2200 at 44 psi. (maybe this is where the suggested 40 psi comes from?). The libby specs ask for 33 psi on their standard issue P tire... about 3/4 of the max presssure. I figure 3/4 of the 80 psi = 60 psi is about right for the Load E tire. What do you all say? All tires will have a bulge. If anything, my 10 ply 245/75-16s will bulge LESS at the same pressure than a 4, 6, or 8p tire. Just the nature of a heftier sidewall...that's why indirect TPMS doesn't work well with low-profile tires...since there's less deformation of the carcass. Something else to consider...do you have rubber valve stems? I wouldn't run over 50 psi without a high pressure valvestem, or if you have the OEM TPMS valvestems. I don't know what the TPMS valvestems are rated for...but since they don't come on HD trucks that run 75 psi, I doubt it's up to snuff to carry that pressure in the long term. I run my MTR's at around 35 on the road. I have even treadwear across the tread, a decent ride (for a busted ol' Jeep:P), and good traction. Your contact patch is shrinking with that pressure, your traction in an emergency maneuver or under panic braking is going to suffer...and you may have ABS and traction control and stability control...but those systems can only work with how big of a contact patch you have. It's not a fix for poor traction, just an aid when enthusiasm surpasses adhesion. the 1mpg you MIGHT gain by running 60 psi instead of 35 will be offset by having to buy another $700+ set of tires sooner, too. |
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| Author: | Bill.Barg [ Thu May 08, 2008 12:33 am ] |
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Thanks ThunderbirdJunkie. I will look more carefully at the tire contact patch. |
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| Author: | Rush345 [ Thu May 08, 2008 12:41 am ] |
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Those are a little more aggresive tread, I'm running AT's and they are not that agressive. Not to mention I got 4 AT's and an alignment for $550.00. Only been off road with them once so I can not attest to mud and such. But they are a nice street tire and rated for 60,000 miles. |
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| Author: | tommudd [ Thu May 08, 2008 12:43 am ] |
| Post subject: | |
heres a good rule of thumb for example looking at a 30/9.50X15 at 25 psi will carry 1240 lbs at 30 psi will carry 1410 at 35 psi will carry 1570 at 40 psi will carry 1750 at 45 psi will carry 1855 at 50 psi will carry 1990 so at 50 psi this tire would carry a 10,000 pound vehicle |
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| Author: | Bill.Barg [ Thu May 08, 2008 1:24 am ] |
| Post subject: | Tire contact patch |
Okay... I measured the contact patch by rolling the tires over white paper, then measuring the width of the tread mark. I then pushed two papers in from the front and the back, and measured the gap to define the patch length. width length area 60 psi 15.5 cm 15.5 cm 240 cm^2 35 psi 17.5 cm 18.5 cm 324 cm^2 The contact patch area is 35% larger at 35 psi vs 60 psi. It the stopping distance 35% less? What is the patch size on the stock libby? maybe the same as the 60 psi case? Even at 35 psi, I was not able to get a print across the full tread width. |
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| Author: | Bill.Barg [ Thu May 08, 2008 1:50 am ] |
| Post subject: | This topic might get ugly |
I just searched through some other posts on the subject of tire inflation. Yikes ! Seems like there is a wide gap in opinion on this. I think I will take ThunderbirdJunkie's advice to go to 40 psi for a while, given the stopping distance / contact patch relationship. Until someone convices me otherwise.! |
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| Author: | DarbyWalters [ Thu May 08, 2008 3:29 pm ] |
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They are probably considered MTs because of the large "voids" on the outer blocks...ATs (most) would not have those. As for tire pressure, I run 50 psi in my CRDs 235/75/16 ATs and rotate religiously...good wear patterns and better mileage. |
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| Author: | tommudd [ Thu May 08, 2008 4:08 pm ] |
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wow 50 lb? I run 38 in my 255-70x16s and get a flat wear pattern as well doing the chaulk test |
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| Author: | Fulltimer [ Thu May 08, 2008 4:29 pm ] |
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As you can see I have the Dunlop Radial Mud Rovers. Now these ARE Mt's. What you have don't look the same and I guess I would go with them being an AT also. But then again I know squat about tires!  The dealer said to run 40lbs. in them. I e-mailed TireRack with my weight and asked what pressure to run and was told by them to run 34lbs. Interesting isn't it! 
On a side note I went on the beach today to try them out a little. They had posted "4X4 Only" today due to the sand conditions. So, I left it in 2 wheel drive to just see how they would do in deep loose sand. Walked right through! 
Terry |
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| Author: | dog_party [ Thu May 08, 2008 4:48 pm ] |
| Post subject: | |
I kinda like the looks of those tires. I'm interested in a review after you've had them on a while. They are listed on TireRack as "a maximum traction tire designed for the rigors of commercial use." I think it's cool that they make a dual-range comm tire in such a "small" size. |
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| Author: | Bill.Barg [ Thu May 08, 2008 4:59 pm ] |
| Post subject: | High pressure mileage vs safety? |
DarbyWalters wrote: They are probably considered MTs because of the large "voids" on the outer blocks...ATs (most) would not have those. As for tire pressure, I run 50 psi in my CRDs 235/75/16 ATs and rotate religiously...good wear patterns and better mileage.
Darby.... are you concerned about hindered stopping distance, given the contact area will be less? |
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| Author: | fastRob [ Thu May 08, 2008 9:23 pm ] |
| Post subject: | Lock 'Em Up, Test Them Out |
The old way, in old Tucson when I was young and foolish, would be to lock them up, do a power slide and note the air pressure, adjust, do it again. Just looked at those tires, wow, aggressive! Thinking about Michelin SUV tires in 225 75 R 16. Am I still foolish? |
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| Author: | DarbyWalters [ Thu May 08, 2008 10:59 pm ] |
| Post subject: | Re: High pressure mileage vs safety? |
Bill.Barg wrote: DarbyWalters wrote: They are probably considered MTs because of the large "voids" on the outer blocks...ATs (most) would not have those. As for tire pressure, I run 50 psi in my CRDs 235/75/16 ATs and rotate religiously...good wear patterns and better mileage. Darby.... are you concerned about hindered stopping distance, given the contact area will be less? Static contact vs dynamic contact is the difference. Auto-X you use higher psi for sidewall stiffness and to build a little heat up faster for better traction. Yes, in a straight line you might lose a bit of braking distance advantage, but it is not going to be huge. Road Racing you start with lower pressures but you have time to build heat and psi. Street Driving is going to lie somewhere in the middle. My tire temps at highway speeds are pretty consistent across the tread (outside-center-inside) if you factor in the bit of camber for the outside-inside temps. My tires are only C rated and weight only a few pounds more than the stock tires. The extra psi definitely helps mpg and does not seem to affect handling in an adverse way. In fact, they seem more consistent and corner better with the extra psi. The extra weight of much heavier tires would probably affect braking distances more than the extra psi in mine. |
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| Author: | onthehunt [ Fri May 09, 2008 4:48 am ] |
| Post subject: | |
For all the tire experts out there: http://www.nittotire.com/assets/safety/ ... Trucks.pdf |
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