Deflating 16.5 tires

[Georick]

The 1987 ford bronco I've bought has 16.5 rims and tires on it.
Does anyone know if you can deflate the tires without them coming off. If so how low of air pressure is safe.
Thank you for any information you can provide me.

 

[oldmopars]

16.5 rims are a big risk when it comes to airing down. I don't think that there is a magic number that will be "Safe". The air is what keep the bead pressed against the rim, on "Normal" rims there is a safety ridge that the 16.5 just don't have. The extra ridge helps make the tire hard to remove even at low pressure. This is what they are talking about when people say they are breaking the bead to remove the tire. It requires a lot of effort to push the tire past this ridge. On a 16.5 rim once you let out all the air it takes nearly no effort to break the bead.
In the end, no matter the tire, it is the air pressure pushing outward that keeps the tire seated. It just takes less force to un-seat the bead on a 16.5 because there is no extra ridge to fight.
I think you will just have to play with it and see what you feel comfortable with. If I had to pick a number I would get very nervous below about 25 psi. The biggest thing to watch out for is side loading. This is where the tire will be most likely to want to come off. The 16in rim can better handle this side load than the 16.5. Also take care when crossing logs and rocks, this can flex the sidewalls and cause the tire to come off.
Its kind of too bad those tires are so nice and you won't need to replace them anytime soon. It would be a good excuse to upgrade to a 16in rim (or 17 if you want).
Until you can replace them, carry a can of starting fluid and an air compressor. Look up on YouTube how to seat a tire with starting fluid and a lighter. Its good to know anyway, but with 16.5's you may get to use this skill more than most. Oh, and a ratchet strap. If you put the strap around the tread of the tire like a belt it causes the beads to push out towards the rim and helps you seat it again.

 

[Georick]

Thanks for the info. I was thinking about try to 30psi and see how that works. The tires are new so I'll have them for sometime.

 

[bgenlvtex]

16.5" wheel is a 15* bead seat angle, 16,17,18 etc. are 5* bead seat angle and have a "safety bead" which the 16.5“ do not have.

16.5 are a blight on all of humanity, I would say if you get under 35psi or so and side load the tire at all it will unseat.

The higher angle bead seat also serves to shovel dirt, debris and trash into the bead seat causing a leak.

 

[Georick]

16.5" wheel is a 15* bead seat angle, 16,17,18 etc. are 5* bead seat angle and have a "safety bead" which the 16.5“ do not have.

16.5 are a blight on all of humanity, I would say if you get under 35psi or so and side load the tire at all it will unseat.

The higher angle bead seat also serves to shovel dirt, debris and trash into the bead seat causing a leak.

Maybe it's best just to stick to dirt roads

 

[bgenlvtex]

Maybe it's best just to stick to dirt roads

16.5 used to be quite common. Their final gasp of practical application was in skid steer loaders and front tires on back hoes where they could serve as the worst possible choice for the application(s).

I would shit can them immediately or as soon as possible. No domestic manufacturer still produces them so in the event you need to replace one on the road your choices will be either none or something produced by the Sum Ting Wong Tire and Rubber company in Wang Dang China.

I hate me some 16.5`s in case you hadn't noticed already.

 

[MMc]

I would learn the the Gas/Ether trick to blow them back on. I wish I could help with pressures but I won't own 16.5s. I show the gas trick to a friend in the middle of Baja however.