Car tire on a motorcycle: the honest pros and cons

Most of what you'll find on this topic comes from one of two camps. Magazine writers who've never run a car tire tell you it's a terrible idea. Forum guys who love theirs tell you it's the best thing they ever did. I'm one of the forum guys, so take that for what it's worth, but here's the list as straight as I can give it.

The pros

• Tread life. This is the big one. A Spyder rider reports about 30,000 miles per car tire against roughly 10,000 on the stock rear. Wing and Valkyrie riders tell similar stories.
• Cost. A car tire in a common 16-inch size usually costs a fraction of a touring rear, and you buy them less often.
• Rain. Riders keep bringing up wet roads. A wide, flat contact patch with car-style siping is a big reason people stay on the darkside.
• Braking in a straight line. More rubber on the road when you're upright. A GL1500 rider on GoldwingDocs says he's never locked up the rear braking hard on a car tire, the way he could on a bike tire.

The cons

• It feels different in a lean. A car tire is flat with a square shoulder. The bike takes more push on the bars to stay leaned and wants to stand up over crowned roads and ruts. Most riders adjust. Some never like it.
• Nobody who makes the tire or the bike approves it. Honda has said plainly it considers it inappropriate, and tire makers say the same.
• Finding someone to mount it. Most shops won't put a car tire on a motorcycle rim, so plan on doing it yourself.
• Bead seating. A car tire can take more pressure to seat on a motorcycle rim. A GoldwingDocs rider writes that some riders have cracked wheels from over-pressure, so stay under the limit on the sidewall.
• Inspection states. Some riders report failing inspection with a car tire. It's worth a call before you mount one. More on that in the darkside FAQ.

The one that's mostly myth

You'll read that your insurance won't pay if you crash on a car tire. I looked, and I haven't found a single documented case of a claim denied because of one. It looks like an assumption that got repeated until it sounded like a fact. Policies do differ, though, so a five-minute call to your agent settles it for your situation.

Who it makes sense for

The darkside lives on big touring bikes and heavy cruisers: Gold Wings, Valkyries, Ventures, VTX1800s and Spyders. A rider on the Valkyrie forum put it well. On a sport bike you can easily push past what a car tire was built for, but the classic cruiser and touring class does well on one. If you ride a sport bike hard in the twisties, this probably isn't for you.

My take

I run a car tire on the back of my Gold Wing and a rear motorcycle tire on the front, and I'm very happy with it. That's my call for my bike and how I ride. If you're thinking about it, read up, check what riders run on your bike, and make the decision with your eyes open.

This is one rider's experience and research, not professional advice. Read the full disclaimer.