Ride Height and Tire Pressure - Add pressure for more ground clearance

I was measuring tire height prior to installing my TRD springs and I noticed that the front tires were over 1/2" shorter than the rear when measured from the ground to the top of the tire tread. I used a long file placed flat on the top of the tread to obtain the measurement. Interestingly, the tires despite being exactly the same, were much shorter in the front and the measurements were consistent from right to left. Backing up to a few months ago, I remember adding air to my 15" tires and I watched the front end of the car rise while adding air from 35psi to 44psi. I didn't bother to measure the difference at the time but in hindsight I think I should have. The 15" tire will likely experience even more growth than my 17" tires.

The reason for this post is to point out something that may be obvious to most but was not so obvious to me. Tire air pressure can affect ride height even when the lower pressure is within spec.When I measured my tires I found the rears to be 25" as I expected. The fronts, however, were just below 24.5"! The manufacturer specified diameter is 25.1". With The Critic as my witness I re-measured the front and rear tires. I then added pressure to the fronts until we hit almost 25" in height. This height was achieved at 55psi. At 60psi we estimate the full 25" would be achieved but I'm not going that high. I dropped the pressure back down to 46/44psi to test the ride and handling characteristics. I need to settle on a pressure before I get the car re-aligned.

In practical terms - If you need an extra bit of height to clear sped bumps or driveways, try adding air pressure. This could effectively add 1/2" or more to your ride height. For Prius Five (V) owners, replace your tires with a 205/50/17 instead of the OE size of 215/45/17. This will add approx. .20" of height and added air pressure can provide another .30"-.50" for a total max rise of almost 3/4". This could also help folks who want to lower their car for better appearance and/or handling but don't want to scrape on every driveway. Another option is to go with a 215/50/17 which is .50" taller than the OE 15" tires and .70" taller than the 215/45/17.

I'd be interested to see what you observe when adding pressure to your tires. As always, keep an eye on tread wear to ensure you are wearing the tires evenly at whatever pressure you choose.

 

I didn't bother taking them off to measure them because I know the reduced height is due to the extra weight on the front end. This is the reason Toyota recommends the pressure difference in the front vs. the rear.