Tire size?

[SpencersGreenTurd]

Ok guys, I'm looking for tires for my wife's car. It's been very confusing. The size on the car and the plaque is 235-65-16 Walmart says it takes 215-70-16 or 235-70-16. I'm looking for something taller and skinner but can't find any thing. Which is taller 235-65-16 or 215-70-16? And why?

[ProDarwin]

215/70-R15 is slightly taller (approx .2")

the width (215) * the aspect ratio * 2 will give you the height. 215 x .70 x 2 = 301mm or 11.85"

Add that to the wheel diameter (16") to get the overall height of 27.85"

[some_other_dave]

Note that those calculated sizes are "notional"--they generally reflect the actual sizes of the tires, but are not necessarily completely accurate. Usually the tire makers will give a "revs/mile" figure, to tell you how many revolutions the tire will make in one mile. Fewer revs means a taller tire, more revs means a shorter tire.

Tirerack shows the revs/mile figures for many of their tires, and those can be used as a basis for comparison.

Of course, inflation pressures, wear, and even rim width can also make some difference in that figure so even those numbers may not be absolutely precise.

-soD

[moonmonkey]

be carful going much taller than stock .depending on what car and what transmission,, i dont have proof but am pretty sure that taller tires took out my transmission (5speed).on my toyota echo.also if it raises the height of the car much it can hurt aerodynamics at highway speeds. overall it might help you though.

[CapriRacer]

Originally Posted by SpencersGreenTurd

Ok guys, I'm looking for tires for my wife's car. It's been very confusing. The size on the car and the plaque is 235-65-16 Walmart says it takes 215-70-16 or 235-70-16. I'm looking for something taller and skinner but can't find any thing. Which is taller 235-65-16 or 215-70-16? And why?

You don't want to be using the 215/70R16's. The 235/65R16's have a higher load rating and that translates into better rolling resistance - about 2% better. This is larger than the 0.6% you get with the diameter difference.

Plus, there is the safety issue using a tire with a lower load rating.

But there is another consideration. The difference between tires is an even larger affect on fuel economy. So look this over very carefully.

[brucepick]

Originally Posted by SpencersGreenTurd

... The size on the car and the plaque is 235-65-16 Walmart says it takes 215-70-16 or 235-70-16...

A quick rule of thumb:
If you DECREASE the first number by 10 (235 becomes 225)
you will need to INCREASE the second number by 5 (65 becomes 70).
That way your tire's outer diameter stays nearly unchanged.
You can work it the other way too, increase the first number by 10 and decrease the second by 5. The last number is the rim diameter and that must stay the same for this rule to work.

Yes a tire size calculator is more precise and more informative. But if you can carry this method in your head, it will always be there when you need it.

Try the info at TireRack.com.
Or do a web search for "tire size calculator"; I think you'll find some.

[SpencersGreenTurd]

Looks like I got my work cut out for me. I was thinking of going smaller. Anyone have any luck with smaller lighter tires?

[oil pan 4]

Originally Posted by SpencersGreenTurd

Looks like I got my work cut out for me. I was thinking of going smaller. Anyone have any luck with smaller lighter tires?

No.
Smaller tires make your engine have to turn faster to maintain speed.
Taller tires are the cheap easy way to alter your final drive ratio to reduce engine speed at cruise.
Now if you put taller differential gears in and smaller tires you will have something.

[brucepick]

Tire size calculator:

Tire size calculator

[SpencersGreenTurd]

Thanks everyone, is tire stuff is difficult... I m still not sure what's the best route to take...taller tires are heavy and raise car height....skinner tiers loose load weight and cause more resistance... What I want I can't find. A LRR, light weight, tall, skinny, with a good load weight tire. I don't think one exists!