[rich9426]

Hey guys , I am a little surprised about the lack of response on my mileage post . I think it is significant that by putting bigger rims on a car your odometer will no longer give a valid mileage. If one of us were to buy a used car with aftermarket rims on the car and the car had 40000 miles , when in all reality depending on the size of the rims you could be getting a car with as low as 44000 or as much as 48000 with 20" rims. Buy wisely . Rich

 

[RobertCTS]

Hey guys , I am a little surprised about the lack of response on my mileage post . I think it is significant that by putting bigger rims on a car your odometer will no longer give a valid mileage. If one of us were to buy a used car with aftermarket rims on the car and the car had 40000 miles , when in all reality depending on the size of the rims you could be getting a car with as low as 44000 or as much as 48000 with 20" rims. Buy wisely . Rich

Rich,
I think the reason why as the topic has been run thru the forum several times and even recently. It's an old topic and found numerous times in the Search feature. Nobody is ignoring you Pal.

 

[Mbai2]

Yea, what RobertCTS said. It also doesn't really matter as far as engine wear. The main concern with mileage if I were to by a used car is how much life is left in the engine. Going 100 miles on the odometer on stock wheels versus going 100 miles on the odometer with larger wheels still results in the same number of revolutions by the engine even if the actual distance travelled is different. Essentially, the motors are the same age if the odo read the same distance no matter what the actual distance covered by the vehicle was.

 

[rich9426]

Well guys I'am a little concerned , the engine is actually working more than the odometer is saying it is . And as far as the issue being run trough Rob I apologize . You seem to remember them all , and I only found you guys recently . But as always thanks for the quick response. Rich

 

[RobertCTS]

Well guys i'am a little concerned , the engine is actually working more than the odometer is saying it is . And as far as the issue being run trough Rob I apologize . You seemto remember them all , and I only found you guys recently . But as always thanks for the quick response. Rich

Rich,
I had OEM 17" rims and went to 245x45x18". The odometer and speedo is off a tic but not enough to be concerned IMO.

 

[PAW 47]

Here is an example.. you get less revs per mile with a larger wheel then with a smaller wheel.

Specification Sidewall Radius Diameter Circumference Revs/Mile Difference
225/55-17 4.9in 13.4in 26.7in 84.0in 754 0.0%
235/40-20 3.7in 13.7in 27.4in 86.1in 736 2.5%

So as you see if you went from a 17 up to a 20 you would have 18 less revs/mile. So with that said..if you had a car with 20's you would 39000 miles vs 17" with 40000 miles on it.

The odo & mph will always be off once you change rim sizes.. thats a given.

Frankly it really doesn't bother me, cause I drive it like I stole it!

 

[rich9426]

I hope I never come accross your car when I'm looking:thumbsup:

Here is an example.. you get less revs per mile with a larger wheel then with a smaller wheel.

Specification Sidewall Radius Diameter Circumference Revs/Mile Difference
225/55-17 4.9in 13.4in 26.7in 84.0in 754 0.0%
235/40-20 3.7in 13.7in 27.4in 86.1in 736 2.5%

The odo & mph will always be off once you change rim sizes.. thats a given.

Frankly it really doesn't bother me, cause I drive it like I stole it!

 

[PAW 47]

I hit submit the post before I was done..take one more gander at it.

 

[PAW 47]

Now I can use one more example.. my track car. It's street tires are 205/45-16 it's a big wheel considering the stock wheel is a 14" 185/60-14.

Now my slicks for track use are 205/50-14, when I put those puppies on I can tell a big improvement. Consideing the car only has 100rwhp and 90 lbs of torque. You can really feel a change. Now for autocrossing I'm thinking of going down to a 13" 235/40/13 a far wider tire will give me better cornering and a little more accel.

Thats what people don't understand taller rim will only hinder the performance. But, if your only in it for the 'bling' factor there you go.

 

[rich9426]

I am just talking about the odometer being incorrect . If you went to a dealer to buy a new car and it had zero miles , but you found out later that it had 2000 , wouldn't you be pissed .

Now I can use one more example.. my track car. It's street tires are 205/45-16 it's a big wheel considering the stock wheel is a 14" 185/60-14.

Now my slicks for track use are 205/50-14, when I put those puppies on I can tell a big improvement. Consideing the car only has 100rwhp and 90 lbs of torque. You can really feel a change. Now for autocrossing I'm thinking of going down to a 13" 235/40/13 a far wider tire will give me better cornering and a little more accel.

Thats what people don't understand taller rim will only hinder the performance. But, if your only in it for the 'bling' factor there you go.

 

[dkozloski]

I would be way more concerned about who put the miles on the car before I would sweat the pure number. There are owners whose 100,000 mile car looks like a 10,000 mile car and those whose 10,000 mile car looks like 100,000 miles. Why stomp on pissants while elephants are running up and down the halls?

 

[PAW 47]

Why stomp on pissants while elephants are running up and down the halls?

Dat's a good one!

Well you have vaild point but then you would/should notice things like that! But I have to agree with DK. I treat my cars well even more so since they both get driven very hard. In fact they get babbied more then the average Joe takes care of his Toyota.

 

[odysseus]

Actually, 'rim' diameter has zero to do with the odometer being off. It's the tire size. More specfically rolling radius. You can actually put a smaller diameter tire on a 20" rim than what may have come stock on a car with 15" rims. Replacing stock 225/50R17's with 225/60R17's on the same 17" rims will make a 7% difference in the speedo/odo reading.

My new 245/45R18's are mathematically 3% larger than my stock 225/50R17's with 30K miles, but when I got them, they measured almost the same rolling radius. Likely due to having slightly less tread depth than the stockers. Tire pressure also makes a difference in rolling radius.

As discussed on previous threads, tires wear, so they're never the same diameter as the computer assumes they are. I think when we did the math last time, a new tire going bald looses ~2% of it's diameter due to worn tread. So 3% is in the noise.

Now my Jeep is another story. Putting 31" diameter tires on a Jeep that came stock with 28" really throws the speedometer (and odometer) off. Fortunately on that truck, changing speedo gears is very cheap and easy with plenty of tooth selections from the factory.

I agree with Koz, mileage is not a good indicator of the condition of a used car. My last jeep had 230K miles and ran and looked like one with only 30K miles. My sisters Corolla looked like a wreck within a year of her buying it.

 

[Chuck C]

great, informative explanations, PAW & odysseus :thumbsup:

 

[AznPrydeRegalRyde]

Actually, 'rim' diameter has zero to do with the odometer being off. It's the tire size. More specfically rolling radius. You can actually put a smaller diameter tire on a 20" rim than what may have come stock on a car with 15" rims. Replacing stock 225/50R17's with 225/60R17's on the same 17" rims will make a 7% difference in the speedo/odo reading.

My new 245/45R18's are mathematically 3% larger than my stock 225/50R17's with 30K miles, but when I got them, they measured almost the same rolling radius. Likely due to having slightly less tread depth than the stockers. Tire pressure also makes a difference in rolling radius.

As discussed on previous threads, tires wear, so they're never the same diameter as the computer assumes they are. I think when we did the math last time, a new tire going bald looses ~2% of it's diameter due to worn tread. So 3% is in the noise.

Now my Jeep is another story. Putting 31" diameter tires on a Jeep that came stock with 28" really throws the speedometer (and odometer) off. Fortunately on that truck, changing speedo gears is very cheap and easy with plenty of tooth selections from the factory.

I agree with Koz, mileage is not a good indicator of the condition of a used car. My last jeep had 230K miles and ran and looked like one with only 30K miles. My sisters Corolla looked like a wreck within a year of her buying it.

You beat me to it Ody.
To add a little, there really isn't a solid way to know how the car was treated or how accurate the miles are. All you can go on, is the repuation of the previous owner, if you can get it. And driving it. Take a car on a long drive. If theres 200k and it runs smoothly, well...whats wrong?

But I can agree that this could possibly cause problems with value.

 

[pjohnesq]

Here is an example.. you get less revs per mile with a larger wheel then with a smaller wheel.

Specification Sidewall Radius Diameter Circumference Revs/Mile Difference
225/55-17 4.9in 13.4in 26.7in 84.0in 754 0.0%
235/40-20 3.7in 13.7in 27.4in 86.1in 736 2.5%

So as you see if you went from a 17 up to a 20 you would have 18 less revs/mile. So with that said..if you had a car with 20's you would 39000 miles vs 17" with 40000 miles on it.

The odo & mph will always be off once you change rim sizes.. thats a given.

Frankly it really doesn't bother me, cause I drive it like I stole it!

So Paw, can I use the above scenario as a defense then to my speeding ticket? Different size tires, like my 20s, gave an incorrect reading on the cops car since they probably had 17", thus, their speedo was showing a higher speed than I was actually going? Or is it the reverse?

 

[DDS rollin a CTS]

So Paw, can I use the above scenario as a defense then to my speeding ticket? Different size tires, like my 20s, gave an incorrect reading on the cops car since they probably had 17", thus, their speedo was showing a higher speed than I was actually going? Or is it the reverse?

If you put on a larger wheel/tire than stock, your speedo will read slower than you are actually traveling so that wont help you in arguing your way out...although, not everyone knows this so you could always give it a shot. worst case scenario is you still have to pay the ticket.:devil:

 

[nbtesq]

So Paw, can I use the above scenario as a defense then to my speeding ticket? Different size tires, like my 20s, gave an incorrect reading on the cops car since they probably had 17", thus, their speedo was showing a higher speed than I was actually going? Or is it the reverse?

Nice try!!! But, I would suggest that going 90-mph on 20s and going 90-mph on 16s don't matter... the end result is that the vehicle was going 90-mph...

Unless the cop got you not using a radar but compared his own speed with yours... Which is asinine if the cop did that. If so, I would motion for discovery (In Illinois that's what you have to do, I don't know about CA) and see when was the last time the speedometer on the cruiser was calibrated, by whom and how... Chances are the speedometer was never touched and is factory sealed. In which case, you have a good chance in beating the ticket throwing reasonable doubt in the mix--it is reasonable to doubt that two speedometers from two different manufacturers on two different cars on two different tire pressures on two different tire manufacturers on two different tire threads will result in the exact same speed indication.

Take a tire expert with you... lol...

 

[IHIeiniken]

Actually, 'rim' diameter has zero to do with the odometer being off. It's the tire size. More specfically rolling radius. You can actually put a smaller diameter tire on a 20" rim than what may have come stock on a car with 15" rims. Replacing stock 225/50R17's with 225/60R17's on the same 17" rims will make a 7% difference in the speedo/odo reading.

My new 245/45R18's are mathematically 3% larger than my stock 225/50R17's with 30K miles, but when I got them, they measured almost the same rolling radius. Likely due to having slightly less tread depth than the stockers. Tire pressure also makes a difference in rolling radius.

As discussed on previous threads, tires wear, so they're never the same diameter as the computer assumes they are. I think when we did the math last time, a new tire going bald looses ~2% of it's diameter due to worn tread. So 3% is in the noise.

Now my Jeep is another story. Putting 31" diameter tires on a Jeep that came stock with 28" really throws the speedometer (and odometer) off. Fortunately on that truck, changing speedo gears is very cheap and easy with plenty of tooth selections from the factory.

I agree with Koz, mileage is not a good indicator of the condition of a used car. My last jeep had 230K miles and ran and looked like one with only 30K miles. My sisters Corolla looked like a wreck within a year of her buying it.

Learned something new. great explaination! :thumbsup:

 

[DDS rollin a CTS]

Nice try!!! But, I would suggest that going 90-mph on 20s and going 90-mph on 16s don't matter... the end result is that the vehicle was going 90-mph...

Very true, cops and judges tend not to be very leinient when youre going that fast.

Chances are the speedometer was never touched and is factory sealed.

"Calibrated" is printed below the speedo on cop cars. Since they do occasionally use their own speedo to guage how fast another driver is going, cop speedos get calibrated at some point. How often is a different issue.

...it is reasonable to doubt that two speedometers from two different manufacturers on two different cars on two different tire pressures on two different tire manufacturers on two different tire threads will result in the exact same speed indication.

Take a tire expert with you... lol...

Many states (like Indiana) you can request a jury trial. Having been on a jury, I can attest to the fact that most people on juries are damn idiots who just want to get back to their own lives. Show up with a bunch of diagrams with faulty conclusions in your favor and throw around a lot of big words and they'll probably rule in your favor.

On a related note, I tried this strategy with the traffic court judge in Boone county (87 in a 65 on I65, my speedo was reading 82 at the time. I compared this against my friends speedo b/c he'd just had new guages installed and mine was reading...you guessed it, 5 mph slow) but he snubbed it. Of course he was a bit of an a****** too.