Vehicle odometer and tire size

Darkbloodmon

Darkbloodmon

Active Member
Joined
Dec 21, 2020
Location
Concord, NC
I was thinking about this on my way home from work last night. For what ever reason I was fantasizing about a manual swap on my 91' Accords F22A6 and a staggered FWD drag setup for shits and giggles. Then it occurred to me that a larger tire size traveling the same speed as the factory size travels farther with less revolutions.

Less revolutions, less miles, odo readout is incorrect. Weather its an abs sensor reading off a tone ring or a small gear reading off a gear in the transmission/transaxle it's setup for the factory tire size. If the vehicle isn't "Modern" and requiring re-calibration or you just don't do it.

You can keep miles off a vehicle by increasing the tire size over factory. If you really wanted to you could make a mathematical formula for your vehicle and calculate how many miles it really has and what tire and wheelsetups will take it farther for less.

Thoughts?
 
True... but why do you care?

The only time I've ever considered that was making a mileage correction in MPG calculations on the Explorers I drove in college.
 
I think the gains don't out weigh the loss of fuel mileage. Likely only looking at a 6-8% difference for cars, slightly more for a truck depending on factory tire size.

On a side note I had a 93 Accord with the F22A6 and a 5spd, was a fun little car to bomb around end and plenty enough to get in trouble. Still miss that car.
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LBarr2002 said:
True... but why do you care?

The only time I've ever considered that was making a mileage correction in MPG calculations on the Explorers I drove in college.
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Just something to think about.
 
Why not just correct the speedo/odometer with the right size speedo gear like we've done for 50 years, or a calibration device, like we've done for the past 15-20 years?
 
The info might come in to play if you're looking at a used vehicle. I was looking at a 92' Volvo 240 previously, after running a vin check on it I found the Odo had stopped working roughly about 57K miles from what was currently on it little to the sellers knowledge, the aftermarket wheel and tire set increased the mileage aswell. He was selling the car with what he thought was 170K but it was nearer to 235K.
 
jeepinmatt said:
Why not just correct the speedo/odometer with the right size speedo gear like we've done for 50 years, or a calibration device, like we've done for the past 15-20 years?
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You could, It's often something overlooked though when changing a wheel and tire setup. If you're looking at a used car and trying to haggle down a price could be a nice point to mention.
 
Darkbloodmon said:
The info might come in to play if you're looking at a used vehicle. I was looking at a 92' Volvo 240 previously, after running a vin check on it I found the Odo had stopped working roughly about 57K miles from what was currently on it little to the sellers knowledge, the aftermarket wheel and tire set increased the mileage aswell. He was selling the car with what he thought was 170K but it was nearer to 235K.
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If you're worried about 170k or 230k on a 92 Volvo, you're worrying about the wrong things ;)
 
To each their own, my concern was the lack of record keeping. There's an odometer for a reason.
 
I understand where you are coming from. I always think about that when doing the MPG math on my truck. Tires are slightly oversized and my speedometer is off by about 5ish mph. (I have an SCTX4 that can correct the Revs Per Mile but it doesn’t match it exactly, still off by about 1.5mph no matter what I do). I’ve noticed and up tick in Mileage and was always curious about if it was due to larger tires actually helping or just the inaccuracy. Figured there was a formula to tell you exactly the percent error you have vs OE tire size. Would love to know if I really had 83K miles on the truck or 73K or whatever the case may be.

Does it matter? No, but some of us are big nerds and like to think about these things.
 
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