redlobster

i currently have stock limited wheels on my 97 4runner, if i want to go with bigger wheels and tires, is there anyway to correct the speedo so it wont be off, say going to 18's or 19's?

wjwerdna

depends.... you can get bigger rims/wheels, but can keep the same outer diameter of tires if you wanted

redlobster

so if the tire size say 235/55/16 to 235/55/18 will make the speedo read the same? i was using this site http://www.miata.net/garage/tirecalc.html

and it was telling me it would read incorrectly

seanz0rz

no metric tire size does not include the outer tire diameter, and therefore circumference. it is the width of the tire in milimeters/the precent of sidewall R diameter of wheel in inches (go figure on this one...) diameter is therefor a derived quantity.

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

those tires would be about 5mph off at 60, so when the spedo reads 60, youd be going about 65.

wjwerdna

you could go with a 235-45-18... very close in diameter (0.15" larger depending on brand used) (0.57% faster reading on your speedo, considering its probably allready 2-3% slow, not a big deal)
I'm just gonna guess you aren't offroading, and am suggesting the Kumho Ecsta SPT (only one in that size at Discount Tire)

http://www.discounttire.com/dtcs/fin...45&ct=&rf=true

and use this calculator, plugging in different numbers to find variations in what you could do http://www.discounttire.com/dtcs/infoTireMath.dos

HuskyRunner

The tire sizes you listed will throw your speedo off. While the width (first number - 235) and the aspect ratio (55 - as in the side wall in 55% of the width of the tire) are the same the rim size is different which will make the wheel/tire combo 2" taller. In order to have your speedo read correctly, you will have to find a combo that keeps the same overall diameter. Or you can just change to whatever size you want and use a calculator like http://www.paspeedo.com/calculator.htm to figure out your actual speed at any indicated speed you want. It won't be perfect, but you'll have an idea, and you can play with the numbers to find out at what indicated speed you are travelling at the actual speed you want. Exmaple: In my truck, I have to do an indicated 92.5kph to be travelling at 100kph. With your numbers you entered above you could go up to 235/45/18's and only have your speedo off by .57kph at 100 kph

redlobster

i should have said the tires i listed were just an example not what i would actually use, and i really wont be offroading , this is currently our family vehicle as i sold my truck and am looking at an 05+ gto so , wjwerdna i will look into those tires

wjwerdna

ok... those are just the only tires in that size, ive had good experience with other Kumhos in the past... you can do the same thing with other sizes, just plug in numbers to see how it responds in width and diameter...

wjwerdna

265-70-16 (stock) to 265-60-18 or 265-55-19 (another example)

BajaRunner

Get access to a GPS and see how fast your going @ 60 then juts make a mental note. Thats what I do .