wheel circumfrances, is there a mathematical genius around?

[stevepeanut]

I started thinking about the wheel sizes on my car, its currently got 15" with 50 profile tyres. My spare 13" wheels have 70 profile tyres. So after some calculation.

 

13" total diameter is 400.2 mm

15" total diameter is 431 mm

 

and if I use my correctly (glad I learned something usefull in school)

 

13" circumfrance is 1257.43 mm

15" circumfrance is 1354.2 mm

 

so the difference between the 2 is 96.77 mm (9.6 cm)

 

therefore my 13" wheels are travelling 9.6 cm less per turn, or the 15" wheels are going 9.6 cm more depending on which way you look at it.

 

Now I know my 13" wheels should give more acceleration, but is there anyone on here that can figure out how much I would gain with the 13" or loose with the 15" compared to each other.

[Fiesta Steve]

No

[Toby]

 

I haven't tried this one but there's lots of these type of calculators on line....

 

http://www.club80-90syncro.co.uk/Syncro ... ulator.htm

[5hane]

dont you get half the diameter, and times it by pye squared

 

I cant find my calclutor bnut im sure thats it

 

 

(and aint done maths in ages )

 

 

o and not a clue about the other bit sorry

[Jiffer]

I got to the 3rd line and had to have a lay down

if you post some pics I can tell you which ones I think look best

[GT_lenny]

just take it to a rwyb and try both sets

[Vista]

I started thinking about the wheel sizes on my car, its currently got 15" with 50 profile tyres. My spare 13" wheels have 70 profile tyres. So after some calculation.

 

13" total diameter is 400.2 mm

15" total diameter is 431 mm

 

and if I use my correctly (glad I learned something usefull in school)

 

13" circumfrance is 1257.43 mm

15" circumfrance is 1354.2 mm

 

so the difference between the 2 is 96.77 mm (9.6 cm)

 

therefore my 13" wheels are travelling 9.6 cm less per turn, or the 15" wheels are going 9.6 cm more depending on which way you look at it.

 

Now I know my 13" wheels should give more acceleration, but is there anyone on here that can figure out how much I would gain with the 13" or loose with the 15" compared to each other.

 

I think your maths is all screwed up mate, a 70 profile tyre doesn't mean it's 70mm tall (I assume that's how you got 400.2mm dia for a 13" wheel with a 70 profile tyre?), equally a 15" with a 50 profile isn't 431mm diameter

 

the 50 and 70 numbers are percentages of the tyres width,

 

i.e. a 175/70/13 has a diameter of 575.2mm and a circumference of 1807.04mm. Try subtracting the 330.2mm diameter of the 13" rim from the 575.2 tyre diameter and then divide the answer to that sum by two. The result will equal 70% of the 175mm tyre width. i.e. the height of the side wall is the profile percetage multiplied by the tyre width.

 

I'm going to guess that you have 195/50/15's on one set of rims and 175/70/13's on the other.

 

The two diameters on those two sets of wheels are very nearly the same. The diameter on the 13" ones will be 575.2 mm (circumference 1807.04mm) and the 15" ones 576mm diameter (circumference 1809.56mm)

 

If those are the correct tyre sizes I've guessed at then you will not notice any difference what so ever.

[over_head_cam]

I thought that Mr. Vista, but couldn't have put it as eloquently

[Andrade]

[bigglesmk2]

I started thinking about the wheel sizes on my car, its currently got 15"

 

No mate you lost me after there

[samurai]

I hate maths!

[Grizzley Dell]

you lot are far to clever, im going to bury my head.

[stevepeanut]

I started thinking about the wheel sizes on my car, its currently got 15" with 50 profile tyres. My spare 13" wheels have 70 profile tyres. So after some calculation.

 

13" total diameter is 400.2 mm

15" total diameter is 431 mm

 

and if I use my correctly (glad I learned something usefull in school)

 

13" circumfrance is 1257.43 mm

15" circumfrance is 1354.2 mm

 

so the difference between the 2 is 96.77 mm (9.6 cm)

 

therefore my 13" wheels are travelling 9.6 cm less per turn, or the 15" wheels are going 9.6 cm more depending on which way you look at it.

 

Now I know my 13" wheels should give more acceleration, but is there anyone on here that can figure out how much I would gain with the 13" or loose with the 15" compared to each other.

 

I think your maths is all screwed up mate, a 70 profile tyre doesn't mean it's 70mm tall (I assume that's how you got 400.2mm dia for a 13" wheel with a 70 profile tyre?), equally a 15" with a 50 profile isn't 431mm diameter

 

the 50 and 70 numbers are percentages of the tyres width,

 

i.e. a 175/70/13 has a diameter of 575.2mm and a circumference of 1807.04mm. Try subtracting the 330.2mm diameter of the 13" rim from the 575.2 tyre diameter and then divide the answer to that sum by two. The result will equal 70% of the 175mm tyre width. i.e. the height of the side wall is the profile percetage multiplied by the tyre width.

 

I'm going to guess that you have 195/50/15's on one set of rims and 175/70/13's on the other.

 

The two diameters on those two sets of wheels are very nearly the same. The diameter on the 13" ones will be 575.2 mm (circumference 1807.04mm) and the 15" ones 576mm diameter (circumference 1809.56mm)

 

If those are the correct tyre sizes I've guessed at then you will not notice any difference what so ever.

 

yes I mistakenly thought 50 and 70 were tyre sizes in mm. So my calculations were utter the round ones lol

 

anyways, I have been out and stood one of my 13s next to a 15 and they do look almost identical in overall height, so you are right, there will be no difference between the 2 sets

[bortaf]

use these

 

 

http://www.miata.net/garage/tirecalcold.html

 

 

http://www.free-online-calculator.com/r ... ator.shtml