Originally Posted By: redtrucker610
I recently put some tires on my nissan frontier that are slightly bigger then the stock tires. Stock size is a 215 65 15. I wanted some all terrain tires so I had to go with 225 70 15. Door stick says 26 for the front and 35 for the rear. Should I use these pressures in the new tires?
thanks
There are 2 schools of thought when replacing tires with something larger.
1) Larger tires could use less pressure to manintain the load carrying capacity. This would be advantageous for the guy who needs a better ride.
In this case, A P225/70R15 has the same load carrying capacity at 26 psi as the P215/65R15 does at 35 psi - so that's the calculation result for the rear tires
- BUT -
If we do the calculation for the front tires - which starts off with 26 psi - well...... the chart doesn't go that low. And my experience says that 26 psi is the lowest to avoid problems with the tire being forced off the rim during emergency manuevers.
Plus, it is a good idea to maintain the front to rear pressure split to maintain the handling balance.
- which leads me to the other school of thought:
2) Once the load carrying capacity issue is satisfied, then matching the spring rate of the tires is of next highest importance - and that is pretty much tied to inflation pressure. The theory behind this is that the vehicle was set up for a certain spring rate and damping coefficient in the tires and the springs, sway bars, and shocks were specified based on that.
Based on all of that I would suggest that same pressure be used.
