I was browsing the pictures in the "member's pride and joy" section
and came upon a Coupe with 13" wheels (second from left on top row).
The owner said that "getting it to speed was a real chore" with the
13" wheels. If a car has bigger wheels on it than standard, wouldn't
the wheels rotate fewer times per mile, showing a slower speed on the
speedometer than correct? Is this correct??
picture in "pride and joy" section
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dealadayray
- Posts: 1
- Joined: Sun Aug 18, 2002 12:08 am
Re: picture in "pride and joy" section
It really has to do with unsprung weight. The overall size of the rim with
50 series tires put more rubber to the ground and weight to each wheel. It
caused the engine to work harder to achieve the same speed although he said
his speed increased it was just getting there.
Bill
50 series tires put more rubber to the ground and weight to each wheel. It
caused the engine to work harder to achieve the same speed although he said
his speed increased it was just getting there.
Bill
Re: picture in "pride and joy" section
But, but...if the 13" tires are say, 20% larger in circumference than 10"
tires, wouldn't the speedometer (and odometer) run 20% slower? They both
measure revolutions of the wheels, and if the wheels are making
few revs per mile...
For example, if the above is correct, then the person driving on 13" wheels
might believe he is going only 50mph, when in fact he is going 60,
accounting for the "getting it to speed was a real chore" effect.
Please have a look at this "speedometer error calculator" and punch in the
numbers for the stock and 13" tires...
http://www.paspeedo.com/calculator.htm
Steve
tires, wouldn't the speedometer (and odometer) run 20% slower? They both
measure revolutions of the wheels, and if the wheels are making
few revs per mile...
For example, if the above is correct, then the person driving on 13" wheels
might believe he is going only 50mph, when in fact he is going 60,
accounting for the "getting it to speed was a real chore" effect.
Please have a look at this "speedometer error calculator" and punch in the
numbers for the stock and 13" tires...
http://www.paspeedo.com/calculator.htm
Steve
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dealadayray
- Posts: 1
- Joined: Sun Aug 18, 2002 12:08 am
Re: picture in "pride and joy" section
Ok Steve, if this is true then use the same formula and measure the wheel
from the bottom to the outer most edge of the tire (while is off the
ground). With a 10in rim and a 145X10 tire you will achieve a diameter of
20.5 inches. Now measure a 13in rim with a series 50 tire and the over all
diameter will be 21 inches. a gain of how many revolutions? At 50 miles
per hour compared with the stock rims and tires you will gain at most,
depending on the inflation of the tire, 3 miles per hour with the series 50
tire. And at 60 and additional .35 miles per hour. However you have added
an additional 8 pounds of weight per wheel with the 13in rims if they are
alloy aluminum. This does not even take into account the added width of
the series 50 tire as apposed to the 145X10. I have driven with them on,
it is not worth the trouble, but they sure do look nice.
Bill
from the bottom to the outer most edge of the tire (while is off the
ground). With a 10in rim and a 145X10 tire you will achieve a diameter of
20.5 inches. Now measure a 13in rim with a series 50 tire and the over all
diameter will be 21 inches. a gain of how many revolutions? At 50 miles
per hour compared with the stock rims and tires you will gain at most,
depending on the inflation of the tire, 3 miles per hour with the series 50
tire. And at 60 and additional .35 miles per hour. However you have added
an additional 8 pounds of weight per wheel with the 13in rims if they are
alloy aluminum. This does not even take into account the added width of
the series 50 tire as apposed to the 145X10. I have driven with them on,
it is not worth the trouble, but they sure do look nice.
Bill