Disclaimer

This blog contains some simple tips and advice from two regular guys. We're not accountants, financial advisors, or brokers, so follow, ignore, or discuss our ideas as you see fit.

Wednesday, October 22, 2008

Where the rubber meets the road

Posted by Matt

I just had new tires put on my car and thought I would share the details of my shopping experience, which was much more complicated than I initially expected. Before I get into that, however, I wanted to point out that maintaining your tires properly prolongs their lifespan, which is the easiest way to save money on them. I have recurring reminders on my google calendar to check my tire pressure monthly (see the box on "Tire Inflation" here) and get the tires rotated and brakes inspected (annually, which corresponds to every 7500 miles) at my favorite local shop.

The shop mechanic who last rotated my tires was the person who actually recommended new tires, but I didn't take his word for it. I checked the wear bars and also used the coin tests. My tires hadn't worn perfectly evenly, but they were close and one of them definitely needed replacing.

So, I went back to the tire shop and they gave me a list showing tires from their inventory that were compatible with my car.

I ask whether any of the tires on the list were designated as "low rolling resistance" tires, as I had heard that this could save money by improving gas mileage, but the clerk didn't seem to know anything about this. I also asked about the age of their inventory, but was reassured that the shop sold enough tires that they didn't have a problem with tires aging on the shelf.

The list of available tires was short, but unfortunately, I wasn't quite sure how to comparison shop. I found a very helpful article on HowStuffWorks that helped me interpret the sidewall codes used by the tire industry to categorize their tires.

Here's an example from my shopping list: P195/60R15 87T M+S
P - Type of tire (passenger)
195 - width of the tire across the tread in millimeters
60 - Aspect ratio of the sidewall compared to the width
R - Radial construction
15 - Diameter of the rim in inches
87 - Tire's load rating
T - Tire's speed rating
M+S - Mud+Snow, meaning the tire is suitable for all-season driving

All of the codes my shopping list were similar (because they primarily describe sizing) but I noticed one important variable: the speed rating. The "T" in the code for these tires means that they are rated as safe to drive up to 118mph. The other tires on my shopping list were rated "H", meaning they were safe up to 130mph. This didn't really concern me, as I don't plan on driving anywhere near 118mph, much less 130, but the shop told me that the T-rated tires would last for 70k miles, whereas the H-rated tire sets would last between 40k and 50k miles. The explanation from About.com:

The faster a tire can go, the softer the rubber compound they use to make it (softer rubber grips dry pavement better), so the tire will wear out faster than a "slower" rated tire.
The T-rated tires were priced a little higher, but only until I made the comparison fair by computing how many dollars it would cost me per mile of service life:
Warranty (Miles)PriceMiles per dollar
40,000247.96161.32
45,000307.64146.27
50,000337.80148.02
70,000356.80196.19

Based on this, the high mileage tire looks like a great deal. This is just what the shop clerk told me, but I'm always skeptical of the sales pitch, of course. I also worried that I would sell the car before going another 70,000 miles (which equates to about ten years of driving for me) but decided to gamble. Who knows how long I'll have to wait for an affordable electric car?

Next, I decided I should check online prices, but I didn't find any cheaper deals, especially considering that I would have to pay for shipping (around $50) and then pay to have the tires mounted/balanced/installed.

The tire shop also wanted to sell me siping for an additional $50, but I declined based mostly on a Consumer Reports article indicating that siping was most helpful in snow and ice conditions, which I don't encounter often.

The only real bad news in this story is that the quotes that the clerk initially offered me had expired by the time I had finished doing all of this analysis! Luckily, it was very simple to apply the lessons learned to pick from their current inventory list and I'm satisfied that I still found a good deal. Barring any advances in tire technology in the next 10 years (what are the odds?), I should be well prepared for the next set, too.

6 comments:

Anonymous said...

Wow! Thanks for such a thorough report! I'll be needing tires in a few months, so will make the most of your research.

Tiffanie @ welikemoney.com said...

good info! i just had new tires put on my car too...those things were expensive.... :( that's what i get for having 18 inch tires i suppose =P

Matt said...

You're making me glad I never had to buy new tires for my old 4Runner. I don't know how big the tires were, but certainly they were much bigger than 15 or even 18 inches.

Craig said...

Hey Matt nice write up.

Check out the Tire Rack at www.tirerack.com. They have more info on tires than you could possibly find anywhere else on the web. Your mind will go numb with the amount of info they have. They test every brand and type of tire they sell on their own test track in both wet and dry conditions as well as the roads around the test facility. You can also find reviews from customers that have the same car you have and have a similar driving style for every tire they sell. In my opinion, the best place to get info on tires bar none.

I would NOT recommend the low rolling resistance tires. The have zero grip on the road when dry and even less in the wet. This is coming from my wife who drove a Prius for work that had these types of tires. She said that the traction control was continuously engaging when it rained. Since the tire is the only thing that touches the ground, it’s the last thing that you should skimp on. What ever money you save in gas at the pump, you may end up spending at the repair shop. The laws of physics cannot be broken. Low rolling resistance means low friction which mean low grip on the road when you turn a corner.

My advice to getting a few more MPG out of your car is to remove everything in your car that is not needed. The lighter you car, the less the motor has to work to get it to move. Everyone has experienced this at least once. Fill your car with friends and to get the car to go, your right foot goes deep, with just you in the car, that right foot isn’t used as much. Lighter will get you more mpg. It may be fractional but it will. If you can dump a few hundred pounds you will see a dramatic difference in mpg. I have done a test with my MINI Cooper. I removed the spare tire (I DO NOT RECOMMEND this as you will be stuck on the side of the road in the event of a flat) and tire removal kit (car jack and the rest of that stuff). This was a total of just under 30lbs. This translated into 10 more miles over the tank of gas. Do that over the life time of the car and we are talking real savings. But then again, I was lucky, no flat tires, so no call for a tow truck. If it’s not needed, take it out. Empty the glove box, clean out the back seat and the trunk. All the stuff you’re carrying that you do not need, take it out! I have even read an article, I think on the BBC, which said to drive with a half tank of gas. Gas weighs about 6lbs per gallon. I have a 14 gallon tank that’s 84lbs of weight. If I cut that I half, mpg will go up. The point being if you don’t need it in your car, take it out.

A guy in the car club I’m a part of took all the sound proofing out of his car, 20lbs of stuff. If I did that to my car and took the spare out that’s 50lbs. Nearly half a person.

Matt said...

Craig - Thanks for the TireRack link. Another point regarding low-rolling-resistance tires: One article I read suggested just buying OEM tires. The manufacturers are so obsessed with bumping up their fuel economy ratings that they usually pick good tires for just that.

I'm definitely not taking the sound-proofing out of my car. What about the front passenger seat? ;)

rjleaman said...

Nice timing on this write-up - We hadn't planned to buy winter tires for another month, but word just came out of an expected shortage of snow tires here in Canada (supply/demand affected by new legislation making snow tires mandatory in the province of Quebec) and now everyone is scrambling to get equipped before the stores are sold out. Good to have sage and thorough advice on making a tire selection, when there's no time to do our own due diligence!