• From: Hayward, CA
  • Registered: 2010-03-23
  • Posts: 1,762

Re: Ride height question

The radius difference is 1.5" the difference
215/70/15    20.925
225/50/15    19.429

So the car will sit lower by 1.5", but that's not the key.
The circumference will drop from 7.03 ft to 6.25 ft, a difference of 11.1%.
The circumference will be smaller on the 50/15 tire and while you will loose top speed (yeah from 137.4 to 118.9 mph) you will gain in acceleration. Your not going to be hitting that top speed much (or at all), but you will need acceleration out of slow corners, multiple times every lap.

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  • From: Dallas Tejas
  • Registered: 2009-05-01
  • Posts: 527

Re: Ride height question

mackwagon wrote:

The radius difference is 1.5" the difference
215/70/15    20.925
225/50/15    19.429

So the car will sit lower by 1.5", but that's not the key.
The circumference will drop from 7.03 ft to 6.25 ft, a difference of 11.1%.
The circumference will be smaller on the 50/15 tire and while you will loose top speed (yeah from 137.4 to 118.9 mph) you will gain in acceleration. Your not going to be hitting that top speed much (or at all), but you will need acceleration out of slow corners, multiple times every lap.

you mean 1.5 / 2 right?

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  • sac02
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  • Posts: 68

Re: Ride height question

mackwagon wrote:

The radius difference is 1.5" the difference
215/70/15    20.925
225/50/15    19.429

Where are you getting those numbers?  Show your work. 
Those aren't the diameters or radii of either of those tire sizes.

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Re: Ride height question

sac02 wrote:
mackwagon wrote:

The radius difference is 1.5" the difference
215/70/15    20.925
225/50/15    19.429

Where are you getting those numbers?  Show your work. 
Those aren't the diameters or radii of either of those tire sizes.

What you haven't seen those new tires that only appear on half the wheel?

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30 Reply by Jeff G 78 (edited by Jeff G 78 2010-03-30 11:46 AM)

  • From: Detroit, MI
  • Registered: 2009-05-16
  • Posts: 1,594

Re: Ride height question

I'll do the math and show my work so we can end this class.

215/70R15   ((215 x (.7x2)) / 25.4) + 15 = 26.85" diameter
225/50R15   ((225 x (.5x2)) / 25.4) + 15 = 23.86" diameter

26.85" - 23.86" = ~3.0" diameter difference or 1.5" radius difference.  -----> the car will sit 1.5" lower with the 225/50R15

23.86" / 26.85" = 0.889  ------------> therefore the 225 is 11% smaller than the 215

I have no idea where mackwagon got the 20.925 and 19.429 numbers, but the rest of his math is correct.

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  • From: Hayward, CA
  • Registered: 2010-03-23
  • Posts: 1,762

Re: Ride height question

Jeff G 78 wrote:

I'll do the math and show my work so we can end this class.

215/70R15   ((215 x (.7x2)) / 25.4) + 15 = 26.85" diameter
225/50R15   ((225 x (.5x2)) / 25.4) + 15 = 23.86" diameter

26.85" - 23.86" = ~3.0" diameter difference or 1.5" radius difference.  -----> the car will sit 1.5" lower with the 225/50R15

23.86" / 26.85" = 0.889  ------------> therefore the 225 is 11% smaller than the 215

I have no idea where mackwagon got the 20.925 and 19.429 numbers, but the rest of his math is correct.

SORRY, slight math error in my spreadsheet (forgot to divide the wheel diameter by 2)

215/70/15  (15/2+(50/100)*(215/25.4) = 13.43"  and circumference = 7.03'
225/50/15====================11.93" and circumference = 6.25'

Delta in ride height is 1.5" (change in Radius!)

delta in circumference is 9.4" which 11.1%.  This percentage works out for radius, diameter or circumference, since the Radius/diameter is what's changes and the

the

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  • Dave
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Re: Ride height question

Now factor in that a new tire is 10/32 and a worn out tire is.............

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  • From: central ohio
  • Registered: 2009-09-19
  • Posts: 324

Re: Ride height question

Tajracing45 wrote:

76 millimeters = 2.99212598 inches  but who's counting... 
Dude, just go with the smaller rubber, cut the springs down, and we'll follow the sparks around the track.

Hey  maybe you wont need tailights !!!

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