I bought a brand new car and as an optional extra i had the 17" alloy wheels instead of the standard 15". I went through a radar speed trap at 36mph and got a ticket although my speedometer read just over 30mph. Would the difference in circumference of the larger wheels fitted alter the accuracy of the reading given by the speedometer ???
2007-04-28 10:10:25 · 12 answers · asked by richard999 2 in Science & Mathematics ➔ Other - Science
Yes wheel diameter will effect the spedo if the spedo is not adjusted to compensate for a larger tire diameter.
If you do calculations to show in court remember you don't drive on rims.... The tires overall diameter is what will determine the distance traveled per wheel revolution NOT the rim diameter. You can get tires for use on larger rims which have smaller side wall height. This can result in having the same overall wheel diameter between the two tire sizes.
You will need to do your homework and find out what tire diameters were originally mounted on your car before the swap at the dealer.
Also if you spedo was compensated at the dealer was it done correctly?
2007-04-28 17:42:43 · answer #1 · answered by MarkG 7 · 0⤊ 0⤋
For every inch in diametor, height of tire, the speed will be off by aprox. 5 M.P.H. Speedometer reads 30 your doing 35 with 1" taller tires. Take car to dealer and have them correct speedometer. Take your repair ticket to trafic court and tell the judge you bought the car with larger tires and didn't know speedometer had not been corrected. Most times the ticket will be dismissed if you show prof of repair. This will save you 10% on your insurance per year for 3 to 5 years depending on state. .
2007-05-01 08:06:48 · answer #2 · answered by Anonymous · 0⤊ 0⤋
Yes it will, the circumference of the 15" wheel is 47.1" and the circumference of the 17" is 53.38". This means that with every revolution of your wheel the 17" wheel takes you 6.28" further than the 15", this will make your speedometer out.If your car is brand new the dealer should have altered your new cars speedometer register to suit your 17" option.
2007-04-28 10:25:53 · answer #3 · answered by alec A 3 · 1⤊ 0⤋
If u get higher wheels you'd be going quicker than the speed and smaller your speedometer will slower. one element to seem at is the production unit wheels w/tires diameter. 15" tires are like 22+ inches tall so take into count number that in case you went from a fifteen inch rim with say a 225/sixty 5/15 to a 20 inch wheel with a 225/35/20 you 20" wheel might want to be smaller then you fairly 15". in case you comprehend what wheel and tire you'd be using bypass to the tire internet web site and discover out how tall the tires are and then bypass to the tire internet web site of the production unit tire makers and evaluate...a inch diff wont make a sizeable change in velocity...
2016-12-05 00:53:13 · answer #4 · answered by ? 3 · 0⤊ 0⤋
I'm not sure of the math involved.. but once read that it can indeed affect the accuracy of the speedometer - often speedometers are calibrated for the manufacturer's intended wheel size. In the same thread they were saying that bigger and thus heavier wheels lead to worse fuel efficiency.
2007-04-28 10:17:51 · answer #5 · answered by Joe Bloggs 4 · 0⤊ 0⤋
Yes.
You will have an error of 13%, which is significant.
Legally, you may be able to wriggle out of it, if you can prove the speedo is defective, or maybe claim compensation from the garage which supplied the vehicle.
To prove this, use or borrow a GPS unit, and compare your speed between it and the speedo. Then at least you will know what you have to drive at to stay safe - until you get it sorted out.
2007-04-28 10:40:17 · answer #6 · answered by ffordcash 5 · 1⤊ 0⤋
yes, think about it, if a closk had hands that were 300mm long, how fast would the end of the hand go to go round a full circle, then think if a closk have hands that were a mile long, how fast the hands would have to go round to do a full circle, ie loads faster.
Or in your case, a 15" wheel, which equals 375mm, the length of the tread on your tire would be pi x diameter,: 375 x 3.142 = 1.178m, a 17" wheel would be 425mm x 3.142 = 1.335, therefore to travel at 30mph you tire on a 15" would need to turn around 11.3 turns per seconds, which would cover 13.31m per second, a 17" turning at 11.3 turns per second would be doing 15.08m per second, or 33.94mph
2007-04-28 10:44:50 · answer #7 · answered by mafewoooooo 2 · 3⤊ 0⤋
yup! because your speedometer is mechanically linked to the transmission. so when you get one revolution, the standard tire moves a certain distance if you increase the diameter of the tire, it will move farther due to cercumference of the wheel. it's all a math game of ratios, plus it can get you ticketed. they don't care they want the money
2007-04-28 10:24:42 · answer #8 · answered by Anonymous · 1⤊ 0⤋
Yes and they improve the fuel comsumption. But when you ordered the car with larger wheels the additional size will have been accounted for. Have your speedo checked for accuracy, it seems to me to be faulty..
2007-04-28 10:16:29 · answer #9 · answered by tucksie 6 · 0⤊ 0⤋
yes, it's like altering the gear ratio of the transmission, you can probably bring this up in traffic court and they can have the variance of the indicated speed from the actual speed tested
DON'T GET ANYTHING FIXED UNTIL AFTER THE TRAFFIC COURT HAS ESTABLISHED THAT YOUR INDICATOR IS NOT DISPLAYING THE ACTUAL SPEED
2007-04-28 10:23:14 · answer #10 · answered by Nick F 6 · 4⤊ 0⤋