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Unread 06-04-2013, 05:33 PM   #16
lucdog
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Quote:
Originally Posted by bajaviking
A narrow wheel is less likely to loose a bead than a wide wheel when running the same airpressure. This is a well known and well proven fact.
Show me where it says that. Without solid facts, this means nothing.
From either a rim or tire mfg.
Bill

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1957 WILLYS pickup, needs work.
1973 J 4000,
1978 CJ7 DD.
1979 CJ7 360, TH400/Quadratrac trail Jeep.
1979 J20
1980 CJ5 trail Jeep.
1983 CJ7 pretty weekend and sometimes to work Driver in the summer, My first rebuild, if the Q-trac and 5 are broke, this one is the one to take. its just as capable as the other 2, except nice paint.
1984 Grand Wagoneer, 1 ton axles, great 360/727, and a big a$& tree fell on it .
1989 YJ the CJ to YJ conversion.
2005 TJ Rubicon.
2011 Grand Cherokee Laredo 4x4, Mrs. LUCDOG's DD.
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Unread 06-04-2013, 07:39 PM   #17
bajaviking
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Really? Try and ask the same question on every other forum and see what answers you get.
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Unread 06-04-2013, 08:06 PM   #18
lucdog
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Quote:
Originally Posted by bajaviking
Really? Try and ask the same question on every other forum and see what answers you get.
Yea really, if you can't produce solid proof, from a tire or rim Manufacturer to dispute me, it's all just off the top of your head.
And a forum, be it Pirate or any other isn't solid proof. Links to tech articles from reputable sources would be.



Bill
__________________
1957 WILLYS pickup, needs work.
1973 J 4000,
1978 CJ7 DD.
1979 CJ7 360, TH400/Quadratrac trail Jeep.
1979 J20
1980 CJ5 trail Jeep.
1983 CJ7 pretty weekend and sometimes to work Driver in the summer, My first rebuild, if the Q-trac and 5 are broke, this one is the one to take. its just as capable as the other 2, except nice paint.
1984 Grand Wagoneer, 1 ton axles, great 360/727, and a big a$& tree fell on it .
1989 YJ the CJ to YJ conversion.
2005 TJ Rubicon.
2011 Grand Cherokee Laredo 4x4, Mrs. LUCDOG's DD.
Lots of parts not for sale, i'm a hoarder.
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Unread 06-04-2013, 09:26 PM   #19
bajaviking
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Ok whatever, opinions from people that actually go wheeling has no value Again, try and back your opinion up on other forums and see what you get. I'm out.
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85 CJ7 4.3L FI/700R , 4:1 Dana 300 and 3/4 ton diffs.
76 CJ7 6 cyl/t18/Dana 20 pretty much stock
"It ain't been so easy but I guess I shouldn't complain,
I've always been crazy but it's kept me from going insane"
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Unread 06-05-2013, 07:33 AM   #20
jadatis
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I asume here a low vehicle weight with oversised tires , but correct me if I am wrong.

For that low pressure is enaugh, probably even that 20 psi, wich gives then the best gripp and comfort and is still save for the tires.
But you have to calculate that with my formula wich even comes to lower loads for the pressure then the European calculation , wich America yust as late as 2005 stept over to for SL and XL tires , and dont look in American old lists, that still wonder around on the internet.
those list are made with a formula that gave to much deflection of the tire at lower pressure/load combinations.
Europe ETRTO gives 21 psi as lowest to go in official advice, America gives on that older lists 26 psi as lowest, to my opinion because of the calculation that gave to much deflection beneath that.

If the deflection is to much the edge of the tire that is in the bead of the rimm bends , and can cource pressure loss.
It is not because of the sideward forces in curves, that the tire comes loose from the rimm, that low pressure has a border .
Most rimms nowadays have 2 humps wich hold the tire in its place.

Long time ago I read an article of an Canadian Vehicle wich could drive on the yust defrosted plantmud in the norht ( had a name I forgot) .
they had special rimms that hold the tire on its place at the low pressure of 0,8 bar/12 psi. I think that special rimms yust had humps , wich was not much used in the 1970's. This gave a verry lange surface on the ground , wich took care that the vehicle did not sink in the mud, and had the best posible gripp.
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Unread 06-05-2013, 08:43 AM   #21
Jeeper44mag
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Quote:
Originally Posted by lucdog View Post
Yea really, if you can't produce solid proof, from a tire or rim Manufacturer to dispute me, it's all just off the top of your head.
And a forum, be it Pirate or any other isn't solid proof. Links to tech articles from reputable sources would be.



Bill
LOL

It's simple physics dude. If an unmounted tire (12.5x33 for example) has a ~ 9.5" bead to bead width then its going to grip an 8" rim much tighter than a 10" rim even before the tire is inflated. It should be obvious that at 25 lbs pressure (or any pressure for that matter) the 8" rim will have a better grip on the tire bead than a 10" rim does... ie. The 8" rim needs less pressure to achieve the same grip as a 10" rim.

Luis
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Unread 06-05-2013, 09:04 AM   #22
lucdog
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Quote:
Originally Posted by Jeeper44mag

LOL

It's simple physics dude. If an unmounted tire (12.5x33 for example) has a ~ 9.5" bead to bead width then its going to grip an 8" rim much tighter than a 10" rim even before the tire is inflated. It should be obvious that at 25 lbs pressure (or any pressure for that matter) the 8" rim will have a better grip on the tire bead than a 10" rim does... ie. The 8" rim needs less pressure to achieve the same grip as a 10" rim.

Luis
There isn't any "grip" involved here, its Pounds per square inch holding the tire bead to the bead mounting surface of the rim. That's it, no more no less.

Bill
__________________
1957 WILLYS pickup, needs work.
1973 J 4000,
1978 CJ7 DD.
1979 CJ7 360, TH400/Quadratrac trail Jeep.
1979 J20
1980 CJ5 trail Jeep.
1983 CJ7 pretty weekend and sometimes to work Driver in the summer, My first rebuild, if the Q-trac and 5 are broke, this one is the one to take. its just as capable as the other 2, except nice paint.
1984 Grand Wagoneer, 1 ton axles, great 360/727, and a big a$& tree fell on it .
1989 YJ the CJ to YJ conversion.
2005 TJ Rubicon.
2011 Grand Cherokee Laredo 4x4, Mrs. LUCDOG's DD.
Lots of parts not for sale, i'm a hoarder.
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Unread 06-05-2013, 09:13 AM   #23
Jeeper44mag
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Quote:
Originally Posted by lucdog View Post
There isn't any "grip" involved here, its Pounds per square inch holding the tire bead to the bead mounting surface of the rim. That's it, no more no less.

Bill
You are wrong. There is also the pressure of the tire caused by the "bent" rubber. If you don't believe me, go mount the same tire on an 8", and then a 10" rim, and see for yourself. After you have done this, you will understand what I am attempting to explain to you.

Luis
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Unread 06-05-2013, 09:18 AM   #24
Balvar24
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The only thing holding a tire on a bead is force, or Pressure x Area. The less area, the more pressure you need and vice versa.

Geometry of the tire and bead itself comes into play at some point.

I would think the max/min wheel width v/s bead space is a technical point that is stipulated by the tire manufacturer. I mean, I've spent less money on shoes and still got instructions in the box.
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