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66-96 Ford Broncos - Early & Full Size
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EvlFaust

Tire Pressure?

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Okay, so I am pretty sure that this has been talked about before, over and over in fact. But was is everyone's opinion on how tires should be aired up. I have heard people talk about how tires should be aired up based on what the auto manufacturer posts on the door jam. That theory doesn't make sense to me because those numbers are based on the stock tire that comes with the vehicle. I have also heard people say that you should air a tire up to the cold PSI value that is branded on the tire. This would make sense to me, but then I got a set of BFG All-Terrains for my wifes Explorer and it says 80PSI cold. That seems a bit high to me. I have the BFG All-Terrains on my 95 Bronco, it has a 50 cold PSI rating, but I have always kept them at about 44PSI.

 

What do you all think?

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The number molded into the side of the tire is what the manufacturer says is the maximum safe pressure. It has very little to do with how much you should put in it (except that you should never excede that number). The number on the door jamb is based on the weight of the vehicle and is designed to give you the optimum contact pattern with the ground with the least rolling resistance. A tire that is underinflated will ride smoother but with increased rolling resistance and therefore less fuel economy. A tire that is overinflated will have less resistance and better fuel economy but will bounce around over the surface of the road. The underinflated tire will carry more of the vehicles weight on the outer edges near the sidewalls and will wear unevenly. Likewise, an overinflated tire will carry more of the load on the center of the tire and will also wear unevenly. What all that means is that some well paid engineer has taken all of this information into acount to come up with the number on the door jamb. It is the best compromise for all of the different factors and what I recomend you use for everyday street driving with any vehicle.

 

For offroad driving, that all goes out the window. For best performance you will need to air down to give the tire more flexibility and a larger contact area with the ground. You will have to experiment to find the right pressure for how you use the truck. Some of the rock climbing guys go all the way down to single digit numbers, but you will need bead locks to keep the tires on the rims at such a low pressure.

 

Well that's my 2 cents on tires.

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Yup, what he said.

Sometimes (on heavy trucks, 1 tons +) they have the air pressure posted on the door jamb, for when they are loaded.

 

The number molded into the side of the tire is what the manufacturer says is the maximum safe pressure. It has very little to do with how much you should put in it (except that you should never excede that number). The number on the door jamb is based on the weight of the vehicle and is designed to give you the optimum contact pattern with the ground with the least rolling resistance. A tire that is underinflated will ride smoother but with increased rolling resistance and therefore less fuel economy. A tire that is overinflated will have less resistance and better fuel economy but will bounce around over the surface of the road. The underinflated tire will carry more of the vehicles weight on the outer edges near the sidewalls and will wear unevenly. Likewise, an overinflated tire will carry more of the load on the center of the tire and will also wear unevenly. What all that means is that some well paid engineer has taken all of this information into acount to come up with the number on the door jamb. It is the best compromise for all of the different factors and what I recomend you use for everyday street driving with any vehicle.

 

For offroad driving, that all goes out the window. For best performance you will need to air down to give the tire more flexibility and a larger contact area with the ground. You will have to experiment to find the right pressure for how you use the truck. Some of the rock climbing guys go all the way down to single digit numbers, but you will need bead locks to keep the tires on the rims at such a low pressure.

 

Well that's my 2 cents on tires.

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the tire pressures usally made for the brand of tire that they come from the factory and are for the most fuel economy. if u up the tire size or drive in different situactions such as dirt or mud then u will haveto adjust accordanly. me i have 32inch bfg's on my truck and i use 34 psi up front and 38 in the rear. it gives a good firm ride with out too much road crown pull. i also pull a 16 ft car trailer here and their so that is why the rear is up a few psi. also i think the tires last longer with a bit more pressure in them. but thats my .02 cents

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Okay, so I am pretty sure that this has been talked about before, over and over in fact. But was is everyone's opinion on how tires should be aired up. I have heard people talk about how tires should be aired up based on what the auto manufacturer posts on the door jam. That theory doesn't make sense to me because those numbers are based on the stock tire that comes with the vehicle. I have also heard people say that you should air a tire up to the cold PSI value that is branded on the tire. This would make sense to me, but then I got a set of BFG All-Terrains for my wifes Explorer and it says 80PSI cold. That seems a bit high to me. I have the BFG All-Terrains on my 95 Bronco, it has a 50 cold PSI rating, but I have always kept them at about 44PSI.

 

What do you all think?

 

 

everybody has there opinions but as far as 33's go i run 34 up front and 36 in back for daily driving and air down to 20 off road

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Roadkill did a great job in his post. I will only add that you need to look at each set of tires, and check what the max rating is, what ply they are, what loads you are carrying, what roads you are driving, and several other factors. We've all heard about the Firestone tires and Ford Explorers, that was about the worst case scenarion of under-inflated tires and poor performance I know of. The tire may be fine ,but too little pressure can destroy it. The pressure may be within limits, but the tire load rating may be such that you shouldn't even use it on the Bronco. As a rule of thumb, I run at least a 6-ply tire, or 8-ply if carrying any cargo or towing. Add tire pressure for cargo or towing, up to the max, be it 50 or 60 psi. You can adjust the pressure up or down to improve ride quality, but generally not more than 5-10 psi. Start with 40 psi, and work from there, for most 6-/8-ply offroad tires. I have 10-ply Firestone Destination MT's on my '06 Dodge Hemi, and the tire shop is always trying to put 80 psi in them (the max reading). At that setting, I can't hold the truck on the road because the tires bounce all over the road. I run 45-47 psi on the highway. When I go offroad, I don't change the pressure at all. While it's true that a lower pressure of 20-25psi will give you more traction, you risk popping the bead off of the rim the lower you go. THen you have to air bakc up when you get on the road again!!! To get better traction in sand or loose dirt, you can prolly safely air down to 15-20 psi. WHen i go rock crawling with the Bronco, we run 8-10 psi, but I'm running on Hummer Hi wheels with the internal bead lock. Running that low a pressure on a 16.5" wheel is a sure bet to pop the tire off, since that size has no safety bead like smaller or larger diameter tires. JSM84

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tire side wall is max presure at a set load the sticker on the door jam holds the answer regardless what tire size for example inflate a balloon to 35 psi and fill a 200 gallon tank to 35 psi it will take more air so the psi rating does not change when tire size changes BUT after that it is a mater of personal choice myself with 33's I keep all four at 40 psi with the 31's I run 35 at all four ( I try to keep all my tires the same so when I rotate them theres no need to change psi) in addition the reason for "cold tire " presure is that they will heat up while driving and even when sitting over night they are affected by surrounding air temps so when the temp drops you might want to add some and the opposite in summer

 

 

hope that made sense seen way to much of a Jeep gear box today and my head is still spinning

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I run 40 psi in all mine, I prefer a less spongy feel driving but at the same time dont want to be hopping around after hitting variations in the road

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