View Single Post
Old 01-21-2014, 05:17 PM   #1 (permalink)
bestclimb
Smeghead
 
Join Date: Oct 2009
Location: South Central AK
Posts: 933

escort - '99 ford escort sport
90 day: 42.38 mpg (US)

scoobaru - '02 Subaru Forester s
90 day: 28.65 mpg (US)
Thanks: 32
Thanked 146 Times in 97 Posts
Increased tire pressure and center wear (tread depth checked after 1 year / 30k mi.)

Ok so it's pretty well established that increased tire pressure increases mileage. We often hear about how awful the handling will be if you increase pressure, and how our tires will be worthless in a few thousand miles as the center wears away quickly.

So I measured my front left tire last winter about this time, drove for a year and accumulated a little under 30,000 miles. The tires were inflated to the max inflation on the sidewall, at 44psi. I maintained this once a month never needing to add more than 4psi to bring it back up. Subaru recommends 26psi. I make no claims here about how much the change has effected mileage as that has been tested elsewhere, and my drive cycle is not anyone else's drive cycle.

Front left tire, cooper CS4 mounted on a Subaru forester.
The tire has 3 grooves running the circumference. one center and one about 1.5 inches from each edge. The measurements were taken at the grooves.

at 169,000 miles on jan 29
Inner
.321"
middle
.322"
outer
.314

average tread depth
.319"

then at 195,000 miles on jan 21
Inner
.245
middle
.240
outer
.224

average tread depth
.236

Change
inner
.076"
middle
.082"
outer
.09"

average wear
.082

I'm not going to make any claims that the uneven treadwear is not going to happen as I don't have a large data set but on this 1 data point it does not seem to be an issue. What these measurements do tell me is that I need to rotate my tires and do an alignment.

__________________

Learn from the mistakes of others, that way when you mess up you can do so in new and interesting ways.

One mile of road will take you one mile, one mile of runway can take you around the world.

Last edited by bestclimb; 01-21-2014 at 08:09 PM.. Reason: fix typo
  Reply With Quote
The Following 4 Users Say Thank You to bestclimb For This Useful Post:
Andrei_ierdnA (07-25-2017), brucepick (03-17-2016), MetroMPG (01-21-2014), redpoint5 (01-21-2014)