What difference will tire size difference of 3" have on gear ratio?

[XS29L9Bxxxxxx]

So my tires are 195/60/14 and look really small / short

Talking with others, It was suggested I go with a 225/70/14

The new tires would be 26.4 to 23.2 inches tall.

As I recall, the shorter tire will make the effective gear ratio shorter, which explains why my car SCREAMS at 60 mph.

Looking for input, and any other suggested tire sizes, but think 26" tall sounds about right for this car. What do you think? Thanks!

[c00nhunterjoe]

a 26 inch tall tire is what the gear ratios are "measured" by. Your 23 inch tires would lower the ratio. For instance, if you have 3.55's in the rear, running a 23 inch tire would make it act like a 4.10.

[XS29L9Bxxxxxx]

a 26 inch tall tire is what the gear ratios are "measured" by. Your 23 inch tires would lower the ratio. For instance, if you have 3.55's in the rear, running a 23 inch tire would make it act like a 4.10.

Hey, no kidding? I didn't know that  about 26" tires...

I haven't checked the ratio, but the car is  G-code 383. Was one ratio more common than another? 

[Back N Black]

I have 275/60/15 on the rear of my charger, its 27 inches tall with 3.23 gear. I checked with the GPS when cruising and the speedo is dead on with the GPS. So no change with the bigger tire.

[XS29L9Bxxxxxx]

With GPS, my speedo reads 90 in a 60 (on nav)

[Chryco Psycho]

http://vexer.com/automotive-tools/speed-rpm-calculator
plug the info in here

[John_Kunkel]

a 26 inch tall tire is what the gear ratios are "measured" by.

Gear ratios are "measured" by dividing the pinion teeth into the ring gear teeth. That 26" (it's actually 26.2) dimension only relates to '66 and later speedo pinions...IOW, with a 26.2" tall tire the speedo pinion tooth count will be the same as the gear ratio IE 4.10=41 teeth, 3.91=39 teeth etc.

[kab69440]

Not much. Going from stock tires to 35x12.50 made my speedo read 4mph low on my Power Ram.

[cdr]

its a percentage off,the faster you go the more its off

[kab69440]

Percentage or not, going from a 235/ 75 or whatever it was... I can tell you the change was significantly more than 3 lousy inches of diameter. How far over 65 mph do you intend to cruise on a regular basis? 

[XS29L9Bxxxxxx]

Percentage or not, going from a 235/ 75 or whatever it was... I can tell you the change was significantly more than 3 lousy inches of diameter. How far over 65 mph do you intend to cruise on a regular basis? 

I'd like to go 80 without fear of an explosion  The 23" tall tires look dorky, too    Found a place that will buy them for $10.00/pc. And the new ones are $94.00 at Tire Rack

[smallhurst]

Or you could put Polyglas on and be COOL!!!!!

[XS29L9Bxxxxxx]

Percentage or not, going from a 235/ 75 or whatever it was... I can tell you the change was significantly more than 3 lousy inches of diameter. How far over 65 mph do you intend to cruise on a regular basis? 

I'd like to go 80 without fear of an explosion  The 23" tall tires look dorky, too    Found a place that will buy them for $10.00/pc. And the new ones are $94.00 at Tire Rack

I actually got a deal on the tires, only $86/per tire. Love 'em