Could a 55 to 75 be to wide
55 too wide? 75 too wide? a 75mm tire would be like what you have on your wheel barrow? Maybe narrower? Ha
The only thing in a tire today that is relative in 2-digit is the sidewall..
They call it the aspect ratio,
aspect: •a distinct feature or element in a problem
If you have a 215/55, sitting next to a 315/55, for example, the sidewall is way taller on the 315 than the 215. 55 is referring to tire height in relation to width (or aspect ratio) (the easiest way to understand though probably not politically correct: 55 is 55% of the width, so depending on width, depends on what "55" means.)
If you're thinking about like a ''60 series tire'', that is referring to tire thickness, or height, or whatever, .. the distance from wheel to ground.
You know, if you guys would read through the links I posted, there's tire size/ rim size calculators for pretty much every country, every explanation on them, wheel offset calculators, etc. There's alot of info there, and it explains all this stuff rather well..
According to the calculator, Icarus is right about the 285/30., Your speedo would only be .27 mph off at 70 mph.;
But, according to the calculator.. that size is recommended for a minimum rim width of 9.5", max of 11". You have an 8.5" wheel, so, you want a narrower tire.
Width is the first number "285".
So, go back to the tire size to rim width calculator, decrease your width, hit calculate, see what it says.
It says a 275 is recommended for a minimum of a 9" wheel.
So, decrease to 265, which says is still recommended for a min. of a 9" wheel.
(Granted at this point, you can get it on with a bit of bulge if you like tire bulge)
(Keep in mind different tire manufacturers seem to do things different, some run ''wide'' and some run ''narrow'', BFG for ex. has a history of running ''wide'')
Anyways, decrease to a 255, voila! Minimum rim width: 8.5". Max: 10".
So now go to the calculator, put in your factory tire size on the left, 225/60/16, and put in "255" for the first number, skip the second number, and put "20" for the third number, and play around with the middle number until the calculator says you pretty much match.
A 255/30/20 is short, when your speedo reads 70 you're really only going 68.4 mph. So, bump ''30'' up to ''35", and you get ~71.04 actual speed at 70. So it's taller. If you don't like this, you can dip down to a 245 or up to a 265 until you find something appealing.
It's a good idea to write down all that are close, because prices can be drastically different depending on production volume of certain sizes.
So look at prices, and decide where you want to sacrifice. Once in awhile, you'll get lucky, and find one exact. for me I believe it was a 275/40. But that is on a 9" wheel.
Good luck.
Use the calculators, and read through the info. Knowledge is nice to have.