195/65/15 to 215/60/15

"Clete" wrote in news:ihsrau$dnb$ snipped-for-privacy@speranza.aioe.org:

The new size will be just fine as far as the speedometer goes (speedo will read about 2% too slow), but the new tires are 3/4" wider. That's NOT a good thing in winter, and will negate some of the advantage of the winter tread.

"Clete" wrote in news:ihsrau$dnb$ snipped-for-privacy@speranza.aioe.org:

yeah,but your speedometer/odometer will be off,not reading accurately. Not by much,though. it will read higher than actual speed,and odometer miles will be less,because of the slightly smaller circumference. I suppose you could measure them both to find the difference,and calculate the error.

you might have wheelwell clearance problems with the wider tread.

"Clete" wrote in news:ihsrau$dnb$ snipped-for-privacy@speranza.aioe.org:

Sure you can. The difference in circumference is about 1/2 inch and as Tegger noted...your speedo reading will be off only a miniscule amount. The difference in height is about 3/10 of an inch so clearance in that plane shouldn't be a concern. The difference in width is about ,8 of an inch. However, as Tegger pointed out, the wider tire will not perform as well in winter conditions as the narrower tire, given all other factors are comparable.

DaveD

Jim Yanik wrote in news:Xns9E7AC98F816EEjyaniklocalnetcom@216.168.3.44:

that should be "actual miles driven will be less than the odometer indicates".

Actually, 0.7% too slow. The circumference of a tire is based on its radius, not its sidewall alone. At 60mph, the nominal difference would be around 0.4mph.

Recall that the rim is 15", so its radius is 7.5" or 190.5mm.

Paul wrote in news:ii1mog$gpd$ snipped-for-privacy@news.eternal-september.org:

Yep. My bad, as they say these days. I must have hit the wrong keys on my calculator, then not bothered to double-check.

The correct arithmetic:

(15" wheel = 381mm diameter.)

215 * .60 * 2 = 258mm 195 * .65 * 2 = 253.5mm 258 + 381 = 639mm tire diameter 639 * 3.14159 = 2007.4mm rolling circumference 253.5 + 381 = 634.5mm tire diameter 634.5 * 3.14159 = 1993.3mm rolling circumference 2007.4 / 1993.3 = 100.7%

Therefore, the 215 is 0.7% larger than the 195.

As far as the speedometer and odometer go, the tires are the same.

Paul wrote in news:ii1mog$gpd$ snipped-for-privacy@news.eternal-september.org:

But your not dealing with the circumference of the wheel. You have to figure in the tire as well. As I posted earlier, the difference in circumference of the two tires was about 1/2 inch.

DaveD

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Dave Dodson wrote in news:Xns9E7DE8F1781CFDaveD@

209.112.128.246:

Which is an insignificant 0.7% on the speedometer, as Paul pointed out..

Thanks to all.

Yeah, but you can find the percentage difference from the radius of the tire directly. The percentage difference should be less than 3% either way, with practical considerations factored in. Most people do not even know what the numbers on their tires mean!

William Burrow wrote in news: snipped-for-privacy@molokai.burrow.ca:

And you find that by knowing the diameter of the wheel. You can't find ANYTHING without knowing the wheel diameter. You can get a 215 for a 15" wheel, or a 16", or...

We've already confirmed that the difference in this case is 0.7%.

William Burrow wrote in news: snipped-for-privacy@molokai.burrow.ca:

actually,going from a 65 profile to a 60 will make the speedo read HIGH; the smaller tire circumference means you are travelling LESS distance over the same time/RPM,and thus the car will be slower than INDICATED speed,and actual miles driver will be lower than indicated miles.

a 60 profile tire has a smaller circumference than a 65 profile tire.

of course,that adds in with whatever OTHER errors your speedometer/odometer already has.

Jim Yanik wrote in news:Xns9E7EE18254EA8jyaniklocalnetcom@216.168.3.44:

No! You are mistaken. If the tire diameter did not change then you would be correct. However, in this case, the 215/60/15 has a greater diameter than the 195/65/15 ///snipped///

Dave Dodson wrote in news:Xns9E7FE942037DDDaveD@209.112.128.246:

You mean if the tire WIDTH did not change, then Jim would be right.

195 * .65 = 126.75 215 * .60 = 129 20mm wider but 5% shorter means a LARGER diameter.

Tegger wrote in news:Xns9E8056AA3ED28tegger@208.90.168.18:

Right. Sorry 'bout that. Fingers were going faster than the brain. Not too uncommon fer me

DaveD

Not to mention tire pressure which also is also can be a factor in effective tire diameter...

Y'all r quibblin' with much about nuthin...

JT