16 inch tires on 16.5 wheels?

[Mike C]

Based on the shape of the 16.5 bead, the older aluminum wheels might be able to have a 16" safety bead machined into them. Would need a big lathe though.

People wanting big rig wheels on HD trucks will take a 19.5 and turn it down to take a 19" tire. But right size/right tire that scenario. 19.5 tires don't exactly ride smooth on a 1 ton pickup since they are made for about 3 times the weight at least.

22.5's are turned down to 22's as well. But those big rig wheels have a LOT of extra meat to work with.

[wilkin250r]

Everybody is tell you not to, but I haven't seen many people post WHY. You're thinking "It's just a little half inch, and the tire is rubber, it will stretch. Heck, it will probably be BETTER, since it will fit tighter."

You're wrong, but let's run some numbers to show you and prove it.

Pi is the ratio of diameter to circumference, and it's 3.1415926535... we'll just call it 3.1416. So the innermost circumference of the bead on a 16-inch tire is:

16 x 3.1416 = 50.2656 inches.

The circumference of the bead surface of a 16.5 inch rim is:

16.5 x 3.1416 = 51.8364

of which the difference is :

51.8364 - 50.2656 = 1.5708 inches.

Now, in order to get a consistent bead diameter and a good seal that won't break loose, the bead area of tire is reinforced with a ring of steel cable. And what you are suggesting, my friend, is that you want that steel cable inside that bead to STRETCH AN INCH AND A HALF!!!!

Steel will stretch, but not that much. You might get as much as 1/4 inch of stretch in a cable 50 inches long (one half of one percent) before it deforms and weakens, but you want to increase that by SIX TIMES, and you're asking if it's safe?

And just to be clear, 35psi is Pounds per Square Inch. A typical 9.5 x 16.5 tire has a diameter about 31 inches, which gives a sidewall surface area of 541 square inches on just one sidewall. Multiply that by 35 pounds on each square inch, you've got 18,935 pounds. THAT'S NINE TONS OF FORCE.


So you're asking a 50-inch cable around the bead area of a 16 inch tire, to stretch not just double, or triple, but six times it's safe limit, and then ask that same cable to hold back nine tons of force? It won't work. That cable is going to break at about a half inch of stretch, which will cause the bead and the rest of the sidwall to split, and that nine tons of force is going to blow that tire apart.

[jjzepplin]

I was a tire jockey back in the nineties and about once a month my company, General Tire, would send out a memo to NOT-NOT-NOT try this. It was accompanied by a photo or two of the latest gent who DID try it. Pretty gruesome stuff. I was never hurt cuz I didn't do anything I shouldn't have. There are a million reasons to not do this but safety should be the first. It's not safe-your truck won't be safe-and others drivers will subsequently not be safe by your actions.

[special-K]

Originally Posted by wilkin250r

Everybody is tell you not to, but I haven't seen many people post WHY.

Why sure I did. I gave as detailed an answer as necessary:

Originally Posted by special-K

The answer couldn't be more simple: No, they are different sizes.

No is the answer and they are different sizes is why. Further explanation:Tires are made to fit same size wheels. Problem: You have different size tires than wheels. Result:They won't fit. Solution: Get tires same size as wheels.

[ryanroo]

Originally Posted by special-K

Why sure I did. I gave as detailed an answer as necessary:

No is the answer and they are different sizes is why. Further explanation:Tires are made to fit same size wheels. Problem: You have different size tires than wheels. Result:They won't fit. Solution: Get tires same size as wheels.

the most accurate and easy answer.

you dont do it because the TIRE manufacturer doesnt recommend that you dont, they flat out tell you not to, in such seriousness that they cast it into the casing of the tire. would you try to shoot a .357 out of a .44 mag pistol? no.

that there is ever a question about the legitimacy of this is deeply concerning to me. as individuals interested in changing vehicles from OEM specs, we need to be concerned for the safety of everyone on the road. saving a few bucks is the most worthless excuse i can think of for making an illegitimate modification that will endanger many people outside of yourself if you manage to actually get the tires and wheels on the truck. your convenience in finding tires is even less of a good reason. you want some obscure sized tire on your truck? prepare. have a spare tire in your garage that you can toss in the bed for a long trip. in addition to your mounted spare.

i am not sure what constitutes a valid reason not to do this if the demands of the manufacturer isn't enough.

[Stocker]

Originally Posted by Smogmonster

i ALSO have a tire machine and HAVE removed many 16,s from 16.5 wheels i have scrapped. so i KNOW they fit.

Originally Posted by Redcap

I have a real hard time believing that.

Ditto that, Redcap. Every time this thread re-appears, I tell myself there's just no way. Not only it defies all logic, you also have people who have worked in the tire business for many years and have never seen it. I cannot imagine some guy with a tire machine at home has seen it many times.

[jocko]

Originally Posted by Mike C

Uh.....
The real horror stories from 16.5" rims are the split rims with the retainer that comes off and kills you when inflating without a cage.

I believe the split rims were 16", not 16.5" - concur, they are a bit dangerous for installers without proper equipment and that most shops won't mess with em these days.

I guess you've kinda gotten an answer to your original question by now (old thread to boot), so I won't pile on, but, DON'T DO IT

For what it's worth - regarding the solid 16s and the 16.5s, I've had both and they both look and work just fine with the right size tire. As stated above - a few less tire options for 16.5s - but I had a 71 with 16.5s and a 72 with 16s - put Firestone TransForces on both. Looked fine and ran fine. Personally, I prefer the 16" wheels off of a mid-70s-87 C20/30. Better profile for the bead, better (but very close) looks, larger tire selection.

For ref - 16.5 Kelsey slots, then greenie with 16.5s and whitey with 16s...