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NDT tire pressure

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    Posted: 24 Apr. 2018 at 10:44pm
I have 6 ply (load range C) 7.00x16 NDTs on my '48. On the side of the tire it's says 45psi max at 1900lbs. That seems like way too high for this light little jeep that may have 600 - 700lbs on each wheel. I currently have them at 25psi for around town highway use. Does that seem about right? If not, what do you recommend?
Thanks,
Steve
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Jerry45 Quote  Post ReplyReply Direct Link To This Post Posted: 24 Apr. 2018 at 11:04pm
KI run my NDT's at about 12 PSI. It helps with shock absorbing. I filled them up to the rated 32PSI once. Teeth rattling ride!!
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Post Options Post Options   Thanks (0) Thanks(0)   Quote smfulle Quote  Post ReplyReply Direct Link To This Post Posted: 24 Apr. 2018 at 11:22pm
Originally posted by ndnchf ndnchf wrote:

I have 6 ply (load range C) 7.00x16 NDTs on my '48. On the side of the tire it's says 45psi max at 1900lbs. That seems like way too high for this light little jeep that may have 600 - 700lbs on each wheel. I currently have them at 25psi for around town highway use. Does that seem about right? If not, what do you recommend?
Thanks,
Steve

25 psi seems to work pretty well for me on the street. Jerry’s 12 psi is a lot softer, but I don’t like how squishy they feel in corners at speed when they are that soft. 

On the trail I run them at 8-9 psi. Makes a big difference in ride comfort and traction.
Stan
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Post Options Post Options   Thanks (0) Thanks(0)   Quote ndnchf Quote  Post ReplyReply Direct Link To This Post Posted: 25 Apr. 2018 at 11:58am
Thanks guys, glad to hear I'm in the right ballpark.  I might try 20 psi to see how it feels.  My thinking is that 20 might allow just a little larger contact patch with the pavement, and thus a tad more traction for braking. 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote oldtime Quote  Post ReplyReply Direct Link To This Post Posted: 25 Apr. 2018 at 3:40pm
I feel that street tire pressure is an important issue unless you simply don't care about tire wear.
You're right, these little jeeps are all just about over kill concerning tire load ratings.

What one needs to do regardless of chosen tire is to get the tire inflated for the specific load that it will carry.
In the end, what you are seeking is even tire wear. 
This implies that the full  width of tread must contact the road.

It's not hard to determine specific air pressure for your tires.
Place loaded vehicle on a dry, flat, smooth, non slick cement surface.

Wet a portion of  the tire tread down with a sponge. 
Roll the wetted tread across the dry cement.
The tread contact patch will show up as you roll the jeep across the flat.
Start at  high pressure (maybe 32 PSI) and then lower tire air pressure till you achieve a full contact patch pattern.
Most skinny jeep tires will come into full contact patch pattern somewhere around 25 PSI.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote ndnchf Quote  Post ReplyReply Direct Link To This Post Posted: 25 Apr. 2018 at 5:34pm
Good idea Ken, thanks.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote athawk11 Quote  Post ReplyReply Direct Link To This Post Posted: 25 Apr. 2018 at 6:36pm
I like 25 PSI for NDCCs...around town. 

16 PSI when we are on the trails.  Frankly, I get a little nervous with the pressure down as low Stan.  That said, he does have Rank on me out in the wilderness.Smile
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Post Options Post Options   Thanks (0) Thanks(0)   Quote smfulle Quote  Post ReplyReply Direct Link To This Post Posted: 25 Apr. 2018 at 8:29pm
Originally posted by athawk11 athawk11 wrote:

I like 25 PSI for NDCCs...around town. 

16 PSI when we are on the trails.  Frankly, I get a little nervous with the pressure down as low Stan.  That said, he does have Rank on me out in the wilderness.Smile

Not sure about rank.

Some added information.
On our last little jaunt up Cliffhanger I got a flat tire. Haven't checked it out fully yet, but it looked like the valve stem might be cut. Don't know if running at 9 psi let the tire slip a little on the wheel and cut the stem, or if it was just one of those things. With the help of my trail mates I was able to swap the spare over in just a few minutes and off we went. 


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Post Options Post Options   Thanks (0) Thanks(0)   Quote ndnchf Quote  Post ReplyReply Direct Link To This Post Posted: 27 Apr. 2018 at 8:36pm
It rained a little while ago, so I backed the jeep out onto the wet driveway and back into the garage. Looking at the wet track and wetness on the tread, it seems 25lbs may be too much. It does not appear that the full tread width is making contact. I assume full tread contact is optimal?


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Post Options Post Options   Thanks (0) Thanks(0)   Quote oldtime Quote  Post ReplyReply Direct Link To This Post Posted: 27 Apr. 2018 at 10:02pm
Just my opinion but....Yeah I think you need more contact than that. 
Or else you'll just just end up running the center off the tread.
The bigger the tire and a stiffer ply = greater load rating.
The bigger and stiffer it gets the lower your PSI needs to be.

It's kinda hard to tell when NDCC tires get full contact so try to get 5.5 to 6" of tread on the ground.
I looked up STA NDT and NDCC 7.00 x 16" are supposed to be 5.8" tread width.

Try maybe 22 or 23 PSI.....

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Post Options Post Options   Thanks (0) Thanks(0)   Quote ndnchf Quote  Post ReplyReply Direct Link To This Post Posted: 28 Apr. 2018 at 2:59pm
I repeated the test today, but dropped the pressure from 25 to 20. This gives notably better surface contact. 25 on top photo, 20 below. I'm hesitant to go any lower for street driving, I don't want it to get mushy in the turns. 





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Post Options Post Options   Thanks (0) Thanks(0)   Quote oldtime Quote  Post ReplyReply Direct Link To This Post Posted: 28 Apr. 2018 at 3:58pm
Yeah,  20 PSI definitely looks like full tread contact..
Don't go any lower on pavement than what it take to achieve full tread contact.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Ol' Unreliable Quote  Post ReplyReply Direct Link To This Post Posted: 29 Apr. 2018 at 1:46am
You might want to experiment with the Jeep unloaded, fully loaded (whatever that might mean for you) and in-between, just to obtain full data.  Make a chart, keep a record.  Thomas Jefferson would love it.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote ndnchf Quote  Post ReplyReply Direct Link To This Post Posted: 29 Apr. 2018 at 6:41pm
I took it out for a nice test drive today. It handled and felt just fine. I did notice a little more tire noise. It wasn't objectionable, but I could hear it. 20psi seems to be the sweet spot for this set upSmile
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