Aerosol flat fixers should be used only as a last resort

Dear Car Talk:

We were on vacation and got a flat tire that was caused by a screw. A good Samaritan saw our dilemma and offered us a can of aerosol flat fixer and aired up our tire for us so that we could get to a repair shop.

Once at the shop, the mechanic told us that the tire could not be repaired because of the aerosol product that we had used. We had to buy a new tire and were wondering if a tire is really toast once you use this product, or if he just wanted to sell us a tire. -- Rita

RAY: He’d rather sell you a tire than clean out your old tire, Rita. Products like Fix-a-Flat can be helpful in emergencies if you have a small puncture -- like a screw in the tread.

They inject a gooey substance into the tire and then provide some air, from the can, to hopefully give you enough tire pressure to limp to a repair shop. But it’s a temporary solution. That gunk needs to be cleaned out of your tire if you want to repair it and keep using it. The goo gets distributed unevenly, and when it dries, it becomes impossible to balance the tire. It should be cleaned out within about 100 miles of using it.

Cleaning out that goop is a messy, unpleasant job. It’s the tire shop equivalent of changing a diaper after your kid’s been playing in a bouncy house for four hours. And that’s why your repair shop said “no thanks.”

Some shops will do it but will charge you extra for it. Others may just refuse.

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Another disadvantage of Fix-a-Flat, and its ilk, is that they often don’t work on larger punctures, larger than, say, 2-3 millimeters -- or a fat screw.

The best solution, of course, is a full-size spare tire. That allows you to keep driving indefinitely. But fewer cars provide full size spares these days.

The next best option is a mini-spare, which will let you drive 50 miles and does no further damage to your flat tire.

Next on my list is a tow truck. If you have a car club membership or roadside assistance, you can get towed to a repair shop and possibly have your old tire fixed.

If you’re stranded and none of those options are available to you, we prefer flat-tire “kits” that include a liquid sealant combined with a small air compressor that plugs into your car’s power port. Kits, like the Airman ResQ Pro+, tend to do a better job on larger punctures, up to 5-6 millimeters, and allow you to fill the tire with enough air to protect it while you find a repair shop.

Those tires still have to be either cleaned or replaced, but they’re more likely to allow you to drive than the less-effective one-cheap-can approach.

All that said, if you’re not in a safe place or can’t wait, any of those products can be used. But it’s just like throwing a big party. It’s all great, but then you have to clean up.

Better options available in aftermarket warning systems

Dear Car Talk:

I have a 2007 GMC Sierra 1500 pickup truck. It is in great condition and has low miles. I would like to install (or have installed) one of the latest safety options -- blind spot warning.

Are there good aftermarket blind spot warning systems you can install on an older car? -- Dan

RAY: Blind spot warning is one of the great safety inventions of our time, Dan.

The only people who disagree are chiropractors, who are losing business because people no longer have to violently whip their necks around to see what’s in their left lane.

You can get an aftermarket blind spot warning system installed in an older car. They’re not quite as good as factory installed systems, but some are close.

The downsides of aftermarket systems are that they require a lot of work to install and their accuracy varies more than factory systems. By accuracy, we mean that they tend to give you more false positives, detecting things that aren’t always cars coming up in the next lane behind you.

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That said, the best of them seems to be the Brandmotion RDBS 1500. It costs around $600, and you might pay as much again to have it installed professionally.

Installation involves internal wiring, removing the bumper, modifying it to hold the sensors and modifying the interior A-pillars to install the warning lights.

The Brandmotion not only has very good accuracy but also includes rear cross-traffic alert, which warns you -- when you’re backing up -- if a car is coming toward you down the street from either direction.

It can be installed on 2007 and newer vehicles but not vehicles with metal bumpers, so you’ll have to check with them and see if it’ll work on your truck. If not, you’ll have to keep looking.

For installation, I’d check with your dealer or, more likely, a high-quality shop that installs stereo and alarm systems. They’re used to doing that kind of wiring without making the inside of your car look like Apollo 11.

Most importantly, try to find a shop that’s done it before. You’d rather not be Patient Zero if you can help it.

Got a question about cars? Write to Ray in care of King Features, 628 Virginia Drive, Orlando, FL 32803, or email by visiting the Car Talk website at

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