Mostly Harmless

Now that it’s finally Winter it must be time to put the snow tires on the WRX.

I have a preponderance of tools lined up for the event:

• lightweight aluminum racing jack (I think that’s the one)
• electric impact wrench (possibly that model)
• an air compressor that’s way overkill for inflating tires (get a Husky Air Scout at Home Depot instead)
• convertible dolly/hand truck for hauling the wrench, jack and all four tires in one trip
• tire chalk (so I know the tire rotation order next year)
• tire inflator (nowhere near as nice as the one from Griot’s Garage)
• Husky 2 Mil, 45-gallon contractor clean-up bags (for the unused tires)
• gloves, lights, old clothes, etc.

Nice to have a heated garage for this, even though I have a narrow parking space with a brick wall on two sides.

I “had” to buy an air compressor that was beefier than my 12-volt compressor because the 12-volt model takes too damn long to top-off the air pressure of the four tires that have been off of the car for 6 months (which were probably only fully inflated 2-3 months before that). Also it cost me $1 to air up my tires at the gas station up the road (the free one was busy) so to stick it to “the man” I spent about $80 on a compressor and attachments. That’ll show them. Now I can conveniently air-up the tires in the apartment before taking them down to the car. (Note to self: next time get an oil-less compressor, or better ventilation.)

I did a little test and let some air out of a tire (reducing pressure by 10 psi). That would take at least 5 minutes to re-inflate with the small compressor. With the new compressor I did it in about 8 seconds — although technically I had the regulator set 50-psi higher than necessary.

The tires won’t be that low, probably only down 5 psi each, but I’ll save 10 minutes on airing up the tires. I’m intent on keeping them properly inflated because the dealer (combined with the first cold snap) actually did have all of my tires down to 22-25 psi. Thanks for the free alignment and brake job (yay warranty) but where the hell did my air pressure go?

The rule of thumb is that you lose 1 psi per month and 1 psi for every 10 degree temperature drop. So now would be the time to check your tires.

Another rule of thumb is that my car gets 25% better gas mileage on the highway immediately after (slightly over-)inflating the tires. The same thing happened with my other all-wheel drive car (Audi 90). My mechanic inflated the tires to 36 psi once and it made a huge difference in rolling resistance — so much so that I had to back off on the accelerator, it’s like the car gained 30 HP. Same thing happens with the WRX. None of my 2-wheel drive cars ever had a huge MPG jump like that (they just got better mileage all the time, but they were slow…).

I’ve got some of those air pressure indicating valve caps so now I can very easily see that I’ve got good pressure in the tires. I have the ones that are “hardcoded” for 32-psi. Found ‘em at at Radio Shack for $4 on clearance. They’re $10-15 everywhere else. I think the variety with the three color (green/yellow/red) indicator is probably nicer; it automatically adjusts to your air pressure and warns you if the pressure drops 3-4 psi from whatever it was when you put the cap on. I couldn’t find any cheap electronic models that I liked. Eventually the Pirelli K-Pressure system will be available, which looks cool (valve caps that transmit tire pressure to your phone via bluetooth) but is unlikely to be cheap.

(time passes…)

A week has gone by since I started this post. I put the tires on last Sunday night at 10 p.m. One could argue that’s not the best time for such things. I didn’t use my impact wrench for fear of making too much noise down in the garage — besides, I’m He-Man enough to deal with some puny lug nuts. Round trip time was 55 minutes. That’s: new set of tires on the hand truck, down to the garage via the elevator, four tire changes, and back up to the apartment with the old set. I cheated somewhat on the timing because I un-bagged and inflated the tires, put them on the ‘truck, and then started the clock. I stopped the clock when I got back into the apartment, not when I finished bagging the tires and putting everything away — for that has not happened yet. I can make my way past the cart ‘o tires in the hallway easily enough… but, yeah, I should finally put those away or something…

It did “snow” on Monday but there was no accumulation ’round these parts. Still waiting for a proper snowfall to fully appreciate the snow tires -vs- the crappy all-season tires.

Here’s a little visual to illustrate why I don’t use the all-season tires in the Winter:

OEM all-season tires (Potenza RE92):

Winter tires (Dunlop Winter Sport M3):

When people say to me that they use their all-season tires all year long I just roll my eyes and try to point out exactly how crappy the RE92s are for anything snow-related (read the reviews at that link for more). I haven’t swapped them out for proper Summer tires yet because they’ve only got about 10,000-12,000 miles on them. (Current mileage: 25,000) Actually when I replace them I’ll probably get some high-performance all-season tires so I don’t have to worry about changing over to the Winter set the second the temperature dips or at the first sign of snow, or *gasp* I could even use them all year long… that’s crazy talk!

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