I have a 2001 Honda Accord (silver) which I bought “pre-owned” from a Honda Store in Tucson in 2006. I just recently found out that the car has 14-inch wheels while having been designed for 15-inchers. This helps explain why I frequently scrape the street coming out of our driveway and bump up over curbs when parking front-in.
All that, however, was less concerning than realizing, on a 7-hour drive from Ohio to Michigan last week, that my speedometer’s display is approximately 5-6 miles in excess of my actual speed. So, even though the (analog) display showed, say 75 mph, my GPS showed 69 mph, which I later verified on an iPhone app. I guess this makes sense, given that a smaller wheel has more revolutions than a larger wheel.
My question to the Car Talk community is whether this is also excessively driving up the odometer’s counter? And are there any other side effects I’m not considering. This could conceivably mean I’m going in too frequently for service and losing resale value.
What would the formula be to determine the mileage difference between a 14-inch and a 15-inch wheel, and could that help determine the cost/benefit of replacing the wheels with the correct size? Thank you!
Yes, a smaller tire and wheel combo will make more rotations per mile and incorrectly inflate your speed and odometer readings.
You’ve already measured the discrepancy, so it’s up to you to decide whether it’s worth buying a set of 15" wheels and tires in order to reduce you future odometer readings by the 8% discrepancy you measured. If you drive another 100,000 miles, that’s a discrepancy of 8,000 miles on the odo, and by that time the effect of the discrepancy on resale value will be non-existent.
But if you’re tired of scraping bottom, you can go back to 15" wheels. i’d just buy a set of used wheels and get a good set of new tires. Tirerack.com says your stock tire size was 195/65-15.
circumference of a circle = 3.14 x diameter
for a 15" wheel with 195/65-15 tires:
195 = tire width in millimeters = 7.7 inches
65 = aspect ratio in percent, so 65% of 7.7 = 5" tire height
15" wheel + (2 x 5" tire height) = 25" overall diameter
so this is the overall diameter of a stock tire/wheel combo
You can go out and measure the diameter of your existing tire/ wheel combo, and if your GPS measurements were correct, it should be about 8% less than the stock diameter above, or about 23".
The TIRE size, not the wheel size, will determine its revolutions per mile.
Your car may be limited on the overall outer diameter that can go on it without rubbing while turning.
A taller 14 could be bought to meet that need as well.
Ken is correct that a larger 14" tire could also correct the discrepancy, without changing back to 15" wheels. For example, a 195/75-14 tire would reduce the discrepancy to about 2%… but you’d have to get tires that match the width of your existing wheels. The width is the first number on the tire size, e.g. “195,” as measured in millimeters.
Thanks for the feedback. Apologies for any confusion. The tires are 14" and should be 15". I don’t know much about cars, so wasn’t sure if there was an assumed connection between wheels and tires, etc.
“the car has 14-inch wheels while having been designed for 15-inchers. This helps explain why I frequently scrape the street coming out of our driveway and bump up over curbs when parking front-in.”
“But if you’re tired of scraping bottom, you can go back to 15” wheels."
Fifteen inch wheels might help to a certain extent, but the reality is that Honda Accords of that era have very poor ground clearance. Whenever I used to drive my '92 Accord, and also when I later drove my friend’s 2001 Accord, it was not unusual to scrape the support underneath the radiator when pulling up to one of those concrete tire barriers in a parking garage.
Even with the standard 15" wheels, the Accord would bottom-out on these little “tire-stoppers”, which was incredibly annoying. That characteristic, coupled with Honda’s practice of mounting the seats VERY low to the floor (which led to incredible back and leg pain after ~30 minutes of driving) turned me off on Hondas.
Here’s a tire size calculator. If you know the original tire size and the size that’s currently on the car this calculator will tell you the percentage the speedometer/odometer is off by and will tell you whether the speedometer/odometer is fast or slow. If the diameter of the tires are smaller than the originals the speedometer will be fast therefore racking extra miles. If the tires are larger it will register less miles.
Check the sticker on the door or doorway to see what size the car had from the factory. Some of the cheaper Accords may have had 14" wheels from the start.
According to Tire Guides, some 2001 Honda Accord’s came with 195/70R14’s - and that’s less than 1% different than the 195/65R15 that came on other Accord models.
So it is possible that the problem isn’t the tires at all, and the problem is in the speedo!