Matt Harwood Posted October 30, 2022 Share Posted October 30, 2022 I have a weird shimmy in my 1950 Chevy tow truck that I'm not entirely convinced is coming from the steering. I feel it more through the seat of my pants than through the steering wheel. I suspect the tires are out of round or something. It was up in the air this weekend while I was rebuilding the steering system, so I looked carefully at the wheels and tires. I couldn't see anything obviously wrong with the tires, which are 255/70/16 radials on standard dually deep dish wheels. But one of the rear wheels (passenger side, inner wheel) looked different than the others. The edge of the wheel was far less defined than the other wheels--there was less of a "step" from the wheel rim to the edge of the bead, but the outer lip is much more pronounced. Check it out: Weird wheel (left) vs. standard-looking wheel (right) I did some looking and found a few photos and discussions about 16-inch tires on 16.5 inch wheels. Most of the discussion is about "don't do it!" and the accidents that people have heard/seen, but there weren't many posts saying it couldn't physically be done. I would think that it would be impossible to stretch a 16-inch tire an extra 1/2 inch (which, in terms of circumference, is more than 1.5 inches of stretching a steel-reinforced tire bead) but I think that's what's going on with my tire/wheel here. I think the hillbilly who owned this truck was so cheap and such a hack that he figured out how to do it and risked life and limb to save a few pennies. What do you think? I don't know what a 16.5-inch wheel should look like, but here are some other photos of actual 16.5-inch wheels that I found on the internet: Any idea what I have? I suspect I need to find a new 16-inch wheel and get a new 16-inch tire, and that this is what is causing my side-to-side shimmy as I drive. What say you, collective wisdom of the AACA? Link to comment Share on other sites More sharing options...
edinmass Posted October 30, 2022 Share Posted October 30, 2022 Yes, hammer mechanics have got 16 inch tires on 16.5 rims. Bad idea. Every 16.5 rim I have ever seen is stamped on the rim. But I have never worked on truck rims from the era you are working on……..so earlier it may not be marked. Link to comment Share on other sites More sharing options...
Oldtech Posted October 30, 2022 Share Posted October 30, 2022 You should be able to measure from the bottom of the bead across the diameter. Wheels with the .5 designation have a sloping bead instead of the flat step of a regular rim. a 16 inch tire is likely seated lop sided on the sloping bead and giving you the vibes. Link to comment Share on other sites More sharing options...
Bloo Posted October 30, 2022 Share Posted October 30, 2022 That ain't right for a standard bead, and I would expect your 255/70-16 radials have a standard bead. Back in the 60s and 70s a lot of 3/4 ton pickups had a weird wide tapered bead. This may have been at the switch to tubeless radials on 3/4 ton, or more likely just the switch to tubeless on 3/4 ton. Maybe 1 ton too. The details escape me. I think those were half inch sizes. In any event you don't want to mix 16" and 16.5". That's a recipe for disaster. Here's a graphic of a similar change on bigger trucks. 1 Link to comment Share on other sites More sharing options...
Rusty_OToole Posted October 31, 2022 Share Posted October 31, 2022 16.5 truck tires were first put on the market about 1968. I believe they added the extra half inch because the new tires were significantly wider than the old 16s and did not interchange, they did not want people trying to use the new wide tires on old skinny rims. A few years ago (20?) went back to 16 for wide tires. Tire diameter is measured at the bead. You may be able to detect the difference measuring the rim at the outside allowing for the thickness of the metal. 2 Link to comment Share on other sites More sharing options...
Matt Harwood Posted October 31, 2022 Author Share Posted October 31, 2022 Guess I need to find a new wheel, or probably two just to keep things symmetrical. New tires, too, I suppose. Sigh... Link to comment Share on other sites More sharing options...
TerryB Posted October 31, 2022 Share Posted October 31, 2022 Just now, Matt Harwood said: Guess I need to find a new wheel, or probably two just to keep things symmetrical. New tires, too, I suppose. Sigh... It’s only money, Matt. Remember, all people who own antique autos are exorbitantly rich with tons of disposable income. 😀 1 1 1 Link to comment Share on other sites More sharing options...
rocketraider Posted October 31, 2022 Share Posted October 31, 2022 3 hours ago, TerryB said: It’s only money, Matt. Remember, all people who own antique autos are exorbitantly rich with tons of disposable income. 😀 Or so our friends in tax and revenue collection believe!😛 Link to comment Share on other sites More sharing options...
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