The problem is the same as always, we aren't discussing 33's, we are discussing 31.5's.
Gears and lockers
- Thread starter tristan6555
- Start date
Give me a known highway speed in top gear, which transmission and the exact engine RPM assuming the speedo is accurate and I can get you the exact rolling radius.
Mickey Thompson does, and all the other manufacturers do, but that number is always completely worthless. Tires are always about an inch smaller than that number. 31.5-31.7 is typical for "33's."
Ah ok I went to look for that rev/mile figure and they just had that, thought it might have been an actual measurement.
I checked and I don't have any pics of that unfortunately. 70 is just about 3100 rpm I believe in 5th from memory
The number isn't worthless, it just isn't very useful for gearing discussions. If the tires were made from steel like trains use, then we wouldn't struggle so much to get folks to understand that the loaded tire radius is what matters, not the horizontal diameter.
When you get something other than "just about", I'll be glad to get you an answer that is other than "just about".
Right, but the tire doesn't get smaller when you put load on it, it just flattens out and elongates the tread. You still have to travel around the full circle. I don't think that circle is ever the advertised size.
Take a simple Goodyear tire for example: 33X12.50R15 Duratrac
Advertised Diameter: 32.5"
Rev/mile figure: 643
643 comes out to 31.37"
Why would the manufacturer's own two numbers contradict themselves? To me, the rev figure is the only one that is ever accurate. The manufacturer doesn't know how much the tire is going to deform under different vehicle loads and yet for me the distance it takes that tire to travel a mile is always accurate and never changes.
Don't know, don't care. I know how to do it in the gear calculator and that's all I need. And, the result on the vehicle is what matters which is very easy to do in the calculator.
I do too but I'm just explaining why I have always believed and still believe the advertised diameter is worthless and always will be.
You need a point of reference when you buy a tire other than depending on cumulative experience reported by wonky Jeep owners.
And that's exactly my point - the manufacturer gives me two points of reference and they contradict each other so I only use one of them.
You don't normally work this hard to miss a point. A point of reference when comparing various tires from different manufacturers.
Here, try this. I have 33 1/2" of width I can lay a tire down into, length isn't a problem. How many revolutions per mile will fit in that spot?
Something something, when you're a BFH everything is a nail
Don't know, don't care. I drive them, I don't lay them down in confined spaces.
More seriously, my point always has been and still is, that the tire itself is actually smaller than the advertised diameter number from the manufacturer. So even if I'm looking at a tire that claims to be 33.5" (and if that's what my space constraint is), it's probably 32.5" anyways and so what fits between the walls will still be more than what was advertised. So in this case all that number will guarantee is that I end up with a tire smaller than the space I have so long as the advertised number is 33.5" or less.
You ever wonder how folks make it onto my list of folks I ignore?
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