2005 Outback XT, P235/55R17 & spare

[Michael Aos]

Bought a 2005 Outback XT recently. Put about 1K miles on it so far.

The previous owner had recently put new P235/55R17 tires on on it -- slightly larger than the factory P225/55R17.

Are there any implications to be aware of with these tires and the factory spare? I've read the Subar AWD in sensitive to tire differences.

[1 Lucky Texan]

as long as all 4 are the same model/wear - the AWD would be OK.

refer to the manual for use of the spare.

I THINK those tires will be a few percent smaller in diameter so, your speedometer and odometer will read high.

[rasterman]

matching size is by far the most important. Up or down a few percent in diameter is of little concern to the AWD as long as all four corners are the same.

Yes the temp spare is considerably smaller, which is why it is meant to be VERY temporary on a Subaru, and mind the reduced top speed as well. Slow-cruising a few miles on back roads to get home or to a service station. None of that getting a flat on the way to work Tuesday and deciding to take it to the shop on Saturday stuff.

[John E Davies]

Originally Posted by rasterman

Yes the temp spare is considerably smaller, which is why it is meant to be VERY temporary on a Subaru, and mind the reduced top speed as well. Slow-cruising a few miles on back roads to get home or to a service station. None of that getting a flat on the way to work Tuesday and deciding to take it to the shop on Saturday stuff.

VERY true - the donut is acceptable for use in an urban area, but it's a disaster waiting to happen in the remote West. I flatted due to a sidewall cut in a lonely part of Montana - well, extra lonely, since most of MT is lonely - and had to drive 120 miles to the nearest town that had a tire store. I was able to use the frontage road for maybe 40 miles, but for the rest I was forced to take I-90, and it was hair raising and dangerous to have to drive 55 mph when all the trucks are blowing by at way more than that.....

Be sure to carry a matching full sized spare if you venture far from the cities.....

John Davies
Spokane WA USA

[plain OM]

The previous owner had recently put new P235/55R17 tires on on it -- slightly larger than the factory P225/55R17.

Are there any implications to be aware of with these tires

Go to Tire size calculator, plug in the numbers.

The 235 tire is wider, has a larger diameter, and lower revs per mile. It will cause the speedo to read 1.6% lower than the stock tire. You will be going faster than the speedo indicates.

As noted, as long as all four tires are the same brand, model, size, and tread wear, which implies the circumferences are the same, they shouldn't present any problems for your Subaru's AWD.

However, check the clearance between the front tire inner sidewalls and the suspension strut/spring. I seem to recall posts here suggesting that wider tires might rub on the suspension but I'm not sure if the slightly larger 235 is one of these. The 235 size is not listed in my 2007 Owners Manual on the "Cold tire pressure" page at the back.

The same page shows how different size temporary spares are matched to the various stock tires to minimize impact on the drive train.

[Michael Aos]

I don't have the owners manual.

Sorry my question wasn't clear.

What I meant to ask was if it's worse to run the factory spare with these larger tires.

[rasterman]

I think it's fair to say "yes" because the overall difference is greater, but only very slightly worse. I don't think I would be concerned.

A deflated matching-size spare will fit in the well, so if you carry that + a compressor you'll be ok. Pretty sure it means giving up the foam cargo tray though. I keep a fire bottle, flares, tow strap, fa kit, spare oil filter & a few other goodies in mine, don't want to give that up.

[Michael Aos]

BTW, these are Goodyear Eagle LS P235/55R17 98H.

[Michael Aos]

Also, what pressure should I fill these oversize tires?

[rasterman]

You're kind of on your own for working out ideal pressure. In general it's best to start around 32psi cold and try going up or down in 2lb increments until you get the ride you want, the traction you need, the MPG you're hoping for etc etc. You probably already know the ramifications for treadwear, sidewall temps etc if you go too high or too low. The end result is not likely to be outside the range of 30-38psi for any tire that you can physically fit on an outback, in my experience.