35x12.50 GY MT/R tire pressure
04-02-2016, 05:35 PM
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35x12.50 GY MT/R tire pressure
Purchased some brand new 35x12.50x15 Goodyear MT/Rs and I'm having trouble getting the PSI correct.. Mounted on a 15x8 Wheel. Attached picture is a rear tire and you can see the outer edges are dry after driving after a rain storm.. Currently at 25psi but don't know where to go from here.. Started around 27-28 and don't see much difference. My apologies if this is the wrong section
04-02-2016, 05:49 PM
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Keep trying, but you may need a wider rim. You should really have a 10" wide rim for those tires.
I had a dually I ran 25 psi in the rear tires unloaded, and even then, it didn't have full contact. When I towed, I'd bump them back up to 50 or so.
I had a dually I ran 25 psi in the rear tires unloaded, and even then, it didn't have full contact. When I towed, I'd bump them back up to 50 or so.
04-02-2016, 06:00 PM
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That's what I was thinking/not looking to hear lol. I ran 33x12.50 MTZs on the same wheels previously and didn't run into this..
'Trail master' 15x8 d Windows with 3.75 BSing
Last edited by NateJeep93; 04-02-2016 at 06:03 PM.
04-02-2016, 08:53 PM
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I wasn't sure if going down that low is good for driving on the road so I didn't go down below 25.. I'll try that tomorrow and see how they go.. I'd like to stay with an 8 wide though for the airing down reasoning.
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04-03-2016, 09:25 AM
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You have the correct wheel width for a 12:50 wide tire, try about 20# and see what you get. As stated above on a 10" wheel when you air down off road with that size tire you will pop a bead, to wide.
04-03-2016, 10:20 AM
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Well, based on google, every chart I pull up says 10" rim for a 12.5" tire is recommended, but an 8" up to an 11.5" will work. But it's your rig, so you get to decide.
I never lost a bead from airing down on a 10" rim with all the wheeling I've done, but hey, I guess I am the exception. I did run a 10" rim on some 39.5 x 15 TSLs, but I had no choice, no one made a rim in 12" wide on a 5 on 4.5 bolt pattern back then. When I aired them down, I did get some mud in the seat, and lost a bead that way. I was also never able to get a full contact patch with them.
Based on your having issues with getting full contact, you need a wider rim or much, much lower pressures. The lower pressures on the highway & daily driving will give you soft sidewalls, and squirrelly driving. The tires will act like they are flat. Sounds like the stiffer sidewalls on the MTRs are not letting you get a full contact patch, whereas tires with softer sidewalls will.
Yes, an 8" rim will work, but YOU have to decide which is better for you, airing down occasionally, or safer driving daily.
Personally, I think the 8" is better for airing down is bunk, as it puts the lock bead at an angle already to the rim surface from the get go, and if you get in a sidehill situation, it will pull off faster on the downhill side of the rim. The 8" rim will protect the rim better, and help with getting mud/dirt/rocks between the bead & rim.
See this cut & paste below:
Every tire has a range of rim sizes that will offer the best performance and wear. The rim diameter is a given. A 15 inch tire has to go on a 15 inch rim. Period. With regards to width, the tire manufacturer list a range for a given tire. A 12.50-inch wide LT tire, for example, might show a range of approved rim widths from 8.5-11 inches. Some will show a measuring rim width (MRW), which is the rim size used to obtain the section width specification. A narrower rim will make the tire narrower and a wider one will fatten it up a bit. A good rule-of-thumb is that for every half-inch of rim width larger or smaller than the MRW, the section width will change approximately a quarter inch. This can be useful in fitting a tire that almost fits but rubs a little.
The ideal is to make the rim width equal to the MRW, where the manufacturer designed the tire to run. At least stay within the recommended width. If you don't, squirrelly handling and increased wear could result on the highway. A narrow rim tends to pull the edges of the tread up and away from contact with the road. Too wide tends to make the tread pull up in the center. On the trail, either of these extremes could make the tire more vulnerable to rock damage or being rolled off the rim at low trail pressures.
Some Jeepers like to run at the minimum end of the width spec to help protect the rim on the trail. Others think the wider end of the spec is better as it lets the tire flex better. This is one of those controversies where both sides are right... as long as the rim is within the recommended width range.
I never lost a bead from airing down on a 10" rim with all the wheeling I've done, but hey, I guess I am the exception. I did run a 10" rim on some 39.5 x 15 TSLs, but I had no choice, no one made a rim in 12" wide on a 5 on 4.5 bolt pattern back then. When I aired them down, I did get some mud in the seat, and lost a bead that way. I was also never able to get a full contact patch with them.
Based on your having issues with getting full contact, you need a wider rim or much, much lower pressures. The lower pressures on the highway & daily driving will give you soft sidewalls, and squirrelly driving. The tires will act like they are flat. Sounds like the stiffer sidewalls on the MTRs are not letting you get a full contact patch, whereas tires with softer sidewalls will.
Yes, an 8" rim will work, but YOU have to decide which is better for you, airing down occasionally, or safer driving daily.
Personally, I think the 8" is better for airing down is bunk, as it puts the lock bead at an angle already to the rim surface from the get go, and if you get in a sidehill situation, it will pull off faster on the downhill side of the rim. The 8" rim will protect the rim better, and help with getting mud/dirt/rocks between the bead & rim.
See this cut & paste below:
Every tire has a range of rim sizes that will offer the best performance and wear. The rim diameter is a given. A 15 inch tire has to go on a 15 inch rim. Period. With regards to width, the tire manufacturer list a range for a given tire. A 12.50-inch wide LT tire, for example, might show a range of approved rim widths from 8.5-11 inches. Some will show a measuring rim width (MRW), which is the rim size used to obtain the section width specification. A narrower rim will make the tire narrower and a wider one will fatten it up a bit. A good rule-of-thumb is that for every half-inch of rim width larger or smaller than the MRW, the section width will change approximately a quarter inch. This can be useful in fitting a tire that almost fits but rubs a little.
The ideal is to make the rim width equal to the MRW, where the manufacturer designed the tire to run. At least stay within the recommended width. If you don't, squirrelly handling and increased wear could result on the highway. A narrow rim tends to pull the edges of the tread up and away from contact with the road. Too wide tends to make the tread pull up in the center. On the trail, either of these extremes could make the tire more vulnerable to rock damage or being rolled off the rim at low trail pressures.
Some Jeepers like to run at the minimum end of the width spec to help protect the rim on the trail. Others think the wider end of the spec is better as it lets the tire flex better. This is one of those controversies where both sides are right... as long as the rim is within the recommended width range.
Last edited by TRCM; 04-03-2016 at 10:34 AM.
04-03-2016, 05:32 PM
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Well, based on google, every chart I pull up says 10" rim for a 12.5" tire is recommended, but an 8" up to an 11.5" will work. But it's your rig, so you get to decide.
I never lost a bead from airing down on a 10" rim with all the wheeling I've done, but hey, I guess I am the exception. I did run a 10" rim on some 39.5 x 15 TSLs, but I had no choice, no one made a rim in 12" wide on a 5 on 4.5 bolt pattern back then. When I aired them down, I did get some mud in the seat, and lost a bead that way. I was also never able to get a full contact patch with them.
Based on your having issues with getting full contact, you need a wider rim or much, much lower pressures. The lower pressures on the highway & daily driving will give you soft sidewalls, and squirrelly driving. The tires will act like they are flat. Sounds like the stiffer sidewalls on the MTRs are not letting you get a full contact patch, whereas tires with softer sidewalls will.
Yes, an 8" rim will work, but YOU have to decide which is better for you, airing down occasionally, or safer driving daily.
Personally, I think the 8" is better for airing down is bunk, as it puts the lock bead at an angle already to the rim surface from the get go, and if you get in a sidehill situation, it will pull off faster on the downhill side of the rim. The 8" rim will protect the rim better, and help with getting mud/dirt/rocks between the bead & rim.
See this cut & paste below:
Every tire has a range of rim sizes that will offer the best performance and wear. The rim diameter is a given. A 15 inch tire has to go on a 15 inch rim. Period. With regards to width, the tire manufacturer list a range for a given tire. A 12.50-inch wide LT tire, for example, might show a range of approved rim widths from 8.5-11 inches. Some will show a measuring rim width (MRW), which is the rim size used to obtain the section width specification. A narrower rim will make the tire narrower and a wider one will fatten it up a bit. A good rule-of-thumb is that for every half-inch of rim width larger or smaller than the MRW, the section width will change approximately a quarter inch. This can be useful in fitting a tire that almost fits but rubs a little.
The ideal is to make the rim width equal to the MRW, where the manufacturer designed the tire to run. At least stay within the recommended width. If you don't, squirrelly handling and increased wear could result on the highway. A narrow rim tends to pull the edges of the tread up and away from contact with the road. Too wide tends to make the tread pull up in the center. On the trail, either of these extremes could make the tire more vulnerable to rock damage or being rolled off the rim at low trail pressures.
Some Jeepers like to run at the minimum end of the width spec to help protect the rim on the trail. Others think the wider end of the spec is better as it lets the tire flex better. This is one of those controversies where both sides are right... as long as the rim is within the recommended width range.
I never lost a bead from airing down on a 10" rim with all the wheeling I've done, but hey, I guess I am the exception. I did run a 10" rim on some 39.5 x 15 TSLs, but I had no choice, no one made a rim in 12" wide on a 5 on 4.5 bolt pattern back then. When I aired them down, I did get some mud in the seat, and lost a bead that way. I was also never able to get a full contact patch with them.
Based on your having issues with getting full contact, you need a wider rim or much, much lower pressures. The lower pressures on the highway & daily driving will give you soft sidewalls, and squirrelly driving. The tires will act like they are flat. Sounds like the stiffer sidewalls on the MTRs are not letting you get a full contact patch, whereas tires with softer sidewalls will.
Yes, an 8" rim will work, but YOU have to decide which is better for you, airing down occasionally, or safer driving daily.
Personally, I think the 8" is better for airing down is bunk, as it puts the lock bead at an angle already to the rim surface from the get go, and if you get in a sidehill situation, it will pull off faster on the downhill side of the rim. The 8" rim will protect the rim better, and help with getting mud/dirt/rocks between the bead & rim.
See this cut & paste below:
Every tire has a range of rim sizes that will offer the best performance and wear. The rim diameter is a given. A 15 inch tire has to go on a 15 inch rim. Period. With regards to width, the tire manufacturer list a range for a given tire. A 12.50-inch wide LT tire, for example, might show a range of approved rim widths from 8.5-11 inches. Some will show a measuring rim width (MRW), which is the rim size used to obtain the section width specification. A narrower rim will make the tire narrower and a wider one will fatten it up a bit. A good rule-of-thumb is that for every half-inch of rim width larger or smaller than the MRW, the section width will change approximately a quarter inch. This can be useful in fitting a tire that almost fits but rubs a little.
The ideal is to make the rim width equal to the MRW, where the manufacturer designed the tire to run. At least stay within the recommended width. If you don't, squirrelly handling and increased wear could result on the highway. A narrow rim tends to pull the edges of the tread up and away from contact with the road. Too wide tends to make the tread pull up in the center. On the trail, either of these extremes could make the tire more vulnerable to rock damage or being rolled off the rim at low trail pressures.
Some Jeepers like to run at the minimum end of the width spec to help protect the rim on the trail. Others think the wider end of the spec is better as it lets the tire flex better. This is one of those controversies where both sides are right... as long as the rim is within the recommended width range.
I'm going to slowly go down to 20 PSI and see if there's any difference.. GY recommends a 8.5 minimum for these tires but I ran 33x12.50s with no issues on these wheels. I do daily drive it but I don't do much highway driving.
04-03-2016, 07:06 PM
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I agree with everyone saying stay at a 8" wheel. I just bought 33x12.5, and they did exactly what yours are doing now. What helped me was breaking in the stiff ***** sidewalls. Air them down to like 10psi and drive around town that way for a few days. Then air them back up to 25 and see where your at for contact. Obv don't go on the highway when aired down like that (it's doable but unsafe, gives you a "floating" feeling) but around town speeds will be fine.
I did this and dd my MTR's at 26 with full contact now.
It's also worth noting that the whole point of these tires is to have the center section (that weird tread pattern) having contact for dd duties while when aired down the outer lugs take over and thus becomes your mud terrain. An inch or so of non contact on the outer lug is not going to kill the tire, prob even help it.
I did this and dd my MTR's at 26 with full contact now.
It's also worth noting that the whole point of these tires is to have the center section (that weird tread pattern) having contact for dd duties while when aired down the outer lugs take over and thus becomes your mud terrain. An inch or so of non contact on the outer lug is not going to kill the tire, prob even help it.
04-03-2016, 08:02 PM
#14
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I run 35 12.50s on a 8 inch wide wheel with about 20 psi. I have even tread wear. I air down to 12 front and 10 rear without bead issues.
You will be perfectly fine with a 8 inch wheel.
You will be perfectly fine with a 8 inch wheel.
04-03-2016, 08:34 PM
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Depends on the weight of your rig. I'm running 25 psi in my. Same tire and rim size also. Use the chalk method and figure out what the highest psi you can run with full contact
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