Changing Tire Size

**rael** · January 12th, 2009 05:06 PM

hi, i'm planning to change my toyota revo stock tire size.

i've done quite a research and using the miata calculator, i trimmed down my choices using the following guidelines:

1. i want wider tires for better handling.
2. i want to maintain the sidewall height so i won't sacrifice a smooth ride.
3. i stuck closely to the stock's diameter and circumference to maintain performance, speedo and odo readings.

given all those, here are my choices:

from:

Size Sidewall Diameter Circumference
185/80R14 5.8 25.7 80.6

to one of these:

215/70R14 5.9 25.9 81.2
225/65R14 5.8 25.5 80.2

i might go for the wider/slightly smaller option: 225/65R14.

my questions:
1. do my guidelines and options make sense?
2. these two sizes are not in the user manual. does that mean they are not advisable? and what should the tire pressures (psi) be?
3. will fuel economy be affected though i tried to maintain tire dimensions?
4. when i get a flat tire, can i temporarily use a 185/80R14 spare with these?

by the way, i completely ignored how the wider tires might touch the body (full steering and bumps), coz i know i won't know for sure until i get to a shop and try it on.

thanks in advance, masters!

**Gerbo** · January 12th, 2009 08:52 PM

Consider,not only the rim diameter, but also the rim width inorder to accommodate wider and bigger tires.

Rule of thumb in using the same rim but upsizing the tire: One level increase for tire width and one level below for side wall height, i.e.
185/80/14 to 195/70/14.

A 215/70/14 will probably do among your choices pending tire availability and possibly fender rubbing.

Cons:
Dapat kasi within 3% lang and difference sa tire circumference, more than that there will be:
(1) inaccuracy of the vehicles odometer/speedometer
(2) brake efficiency and compromised effectiveness
(3) increase gas consumption

For more information, search for "tire upsizing" maraming threads na ganyan sa forums.