Is It Worth A Try?

 

It’s a new year, so let’s visit an old controversy! As motorcycle riders, we’re always looking for ways to enhance the ride, both the bike and the experience. We’re keenly conscious of costs as well, as our passion can get quite pricey. Enhancement versus economy- its a tightrope to walk (or ride), for sure.

We’ve done a fair amount of tire testing in the last couple of years, with Ted Edwards and Dave Wensveen logging thousands of miles across the western states. One unconventional option that we’ve never tried but still fuels debate in some circles is using automotive tires on motorcycles. While motorcycle tires are specifically designed for the unique demands of two-wheeled vehicles, some riders still think it’s worth exploring the possibility of installing car tires on their bikes. Most of us respond with, “Are you nuts?!” Yet we still occasionally meet riders who swear by them. My friend Ken Glassman and I were recently discussing this as well. So, let’s take a deep dive into the pros and cons of using automotive tires on motorcycles, and see where we can park this debate.

Car tire mounted on a motorcycle. Looks harmless enough,… photo by Inside Motorcycles.

When talking with proponents of automotive tires on motorbikes, here’s a few of their “pro” arguments.

Cost Savings:

One of the primary motivations for using automotive tires on motorcycles is cost savings. Car tires are generally more affordable than motorcycle tires, making them an attractive option for some riders on a budget. The larger production volume and variety of car tires also contribute to a wider range of budget-friendly options. So, those who “ride the dark side” swear this makes them a viable option.

Longevity:

Automotive tires are typically designed to endure greater mileage than motorcycle tires. The added durability and overall design difference of car tires obviously results in a longer lifespan, meaning riders don’t have to replace them as frequently. This can be particularly appealing for those who embark on long-distance rides or use their motorcycles for commuting purposes. I had a friend who rode a Honda Goldwing that he shod the rear with a car tire, and swore he got 30+ thousand miles out of them at a fraction of the cost of more expensive and more frequently replaced motorcycle tires.

Stability and Traction:

Some riders argue that car tires provide greater stability and traction, especially in wet or slippery conditions. The broader contact patch of automotive tires may enhance grip on the road, potentially improving overall handling and performance. In a straight line. But in a full lean?

Bike in full lean, rear auto tire tread and contact patch clearly visible. Your thoughts? Photo from Iron Butt Forum.

Let’s look at the reasons car tires are NOT a good idea on motorcycles.

Handling and Maneuverability:

Motorcycles are engineered with specific tire characteristics in mind to optimize handling and maneuverability. We’re on two wheels, not four, so obviously the handling characteristics are completely different. We’re leaning motorcycles, not steering them. Automotive tires, designed for three and four-wheeled vehicles, simply cannot offer the same responsiveness and agility as motorcycle tires. This leads to a less precise and more cumbersome riding experience when installed on a motorcycle. And potentially dangerous.

Compatibility:

The overwhelming number of motorcycles are definitely not compatible with automotive tires. They are each designed for completely different types of riding/driving. The rounded construction of motorcycle tires works perfectly with the front/rear wheel design of motorcycles, making diving through corners nearly effortless. The squared profiles of automotive tires are clearly designed for a tri or quad setup on a vehicle, working together for maximum contact with the surface. My friend Mike owned a Harley Tri-Glide with automotive tires on the rear, which works great for a trike as well as a four-wheeled automobile. His Honda NC750X however runs Bridgestone Battlax A41 Adventure tires for on and mild off-road riding, which of course is what these tires are designed for.

Legal and Safety Concerns:

In many regions, using automotive tires on motorcycles violate safety regulations, insurance requirements and/or manufacturer recommendations. This can have legal consequences, and insurance coverage may be affected in the event of an accident. Riders should thoroughly research and understand the legal implications before opting for car tires on their motorcycles. Is it really worth the supposed cost savings and tire life gains?

Closeup of car tire mounted to a bike, on kickstand. Interesting. Photo posted on Quora.

While the idea of using automotive tires on motorcycles may seem tempting due to potential cost savings, longevity and other perceived benefits, riders must weigh the pros and cons carefully. Safety should always be a top priority, and any modifications to a motorcycle really should align with manufacturer guidelines and legal regulations. Before making the switch to “the dark side” as proponents like to call it, you should consult with professionals, conduct your own thorough research, and ensure compatibility to maintain a safe and enjoyable riding experience.

Our opinion? If motorcycle manufacturers thought auto tires were a great idea, they’d build bikes with them in mind, and would install them on their two-wheeled machines from the factory. But they are not compatible and not worth the effort or risk, in our humble opinion. We’ll never use them nor will we ever recommend them. But that’s just us. You do you, friends.

What are your thoughts on the subject? Let us know in the comments below!

Rob

Funny cartoon from years ago, posted by Rider Magazine. Sorry, we couldn’t resist.

 

NE Ga Motorsports

12 Comments

  1. Bo Sills

    My brother-in-law first convinced me to try a Goldwing after years on an H-D. He later convinced me to go darkside on it. I did and after very little riding on it, I was sold. I’ve run the mountains (Tail of the Dragon, etc) and run long distance while towing heavily laden camping trailers. I have nothing technical to offer, other than to say I’m quite happy with it.

    Reply
    • Rob Brooks

      Do you find any handling issues either at slow speeds, or in tighter corners?

      Reply
  2. Dwayne

    So I own a Triumph Bonneville T100 with a Cozy sidecar and I would LOVE to install car tires on it. My question is, can I find car tires to fit the stock 19″ front and sidecar rims and the rear 17″ rim? I’ve searched and can only find emergency spare tires in those sizes. I am aware that the classic sidecar thing is to have car type rims laced up to your motorcycle hubs, for something like 15 inch VW Beetle tires. Obviously I am trying to avoid that cost. Also, flat car tires are ok on sidecar rigs since no leaning is involved while riding.

    Reply
    • Rob Brooks

      Hi Dwayne,
      We’ve not taken a deeper dive into “the dark side” beyond our research for this story. We know there are forums out there pertaining to it, and apparently social media groups dedicated to it.
      It’s not our thing, obviously, but we’re sure you can find sources to answer those questions.
      Thanks for joining in the conversation!

      Reply
  3. Phil Heslep

    Hi Rob! You know I double dark sided my bike for quite a few years. It was cool and interesting to try. Some extra thought on this and why I went back to motorcycle tires eventually. Instability issues can happen. Front tires are self aligned to the rear tire. So having a wide rear contact patch can cause the front tire to hunt for the center of the rear tire patch. This shows itself in handlebar feedback. As the bike transitions into a turn the front tire adjusts and when you get used to it, the initial unsettling feeling becomes the new norm. However when traveling on parallel uneven surfaces the bike can become a bit unsettled in its track. Tire bead and sidewall construction are very different than a motorcycle tire. I had decent results with tires designed to deliver better gas mileage as they have a stiffer sidewall. However to keep from being too long winded, I went back to motorcycle tires for this reason. Think about the difference between worn out motorcycle tires and a brand new set. The new ones are fresh, they handle great and you corner with confidence again. Now go back and look at the old rear tire. Most of the wear is in the center. So why is a 1.5” bald patch so terrible compared to that fresh new bike tire? And now think about why you would want to install 5” of that from the beginning with a car tire! We ride bikes for enjoyment not to save money! Otherwise we would do it on a scooter that got 100 mpg.

    Reply
    • Rob Brooks

      That is VERY well-stated, Phil. Thanks for a fantastic explanation.

      Reply
  4. Steve hawkins

    Hello Rob! I had a riding buddy who dark sided his FJ1300 and he loved it. The savings were quite substantial and the mileage was more than amazing, up to 5 or 6 times what I got on my Dunlops or Michelins. He did a lot of commuting and highway riding which take full advantage of the wide and flat tire profile. The thing that almost pushed me over the edge is that I have gone through 2 sets of premium motorcycle tires in a single season several times. I have never gotten over 7000 miles on a set and have sometimes had to change out at 6000 miles. And these were pilot road 3’s or roadsmart 4’s(hi dollar and supposedly higher mileage tires). Now, every other season, the tire manufacturers come out with their new compounds and tread designs (with what seems like less real tire materials or side wall strength) for more and more money. So, given the mileage and high tire cost, it’s hard to keep up with the demand on my credit card! I have friends who can get almost twice the miles on a set of premium tires, but they don’t ride the same way I do. If you ride your bike trying to get all of it’s potential into your ride, like I do, then the dark side is a dangerous place for you to go. If you ride like my FJ1300 buddy, it can be a nice option to save lots of money and tire changes. I have to laugh whenever I’m following a dark sider…. When they turn, all I can picture is a dog hiked up next to a fire hydrant 😆

    Reply
    • Rob Brooks

      Hi Steve!
      Great thoughts, and yes, I agree, kinda strange riding behind one, for sure.
      We should visit and chat again soon!

      Reply
  5. Vern

    I asked users LOTS of questions over 2 years before deciding to go Darkside. Once I road a dozen or so miles I became acclimated to the different feel, which was rather minimal. The only riding difference was the turns, to me the bikes rear did turn slightly (others call it going straight) but I used it to my advantage. I steered my turns a little less since the back slightly pivoted. You know some Honda cars rear wheels pivot their turns without issue? Once I was hooked I went DDS (Double DarkSide rear bike tire up front).
    SO… stopping was simply amazing, IT… WAS… QUICK!!! Had to start looking behind me before stopping to make sure THEY were paying attention. To be safe I accustomed myself with stopping nearer to either side of the lane AND pointing the bike outward JUST IN CASE I needed to scoot over a few inches from being rear ended. Which happened once so far but by moving a mere foot or so over, the mini truck softly plowed into the car I was behind.
    The DDS tread patch width on the road was nearly doubled, rear & front had 1.75% more rubber on the road. In turns I measured the tire patch at about 1.67% more than bike tires. How did I measure? Rode slowly through a parking lot water puddle upright then in a well leaned turn.
    Overall cost was lower by 1/3 less and longevity was quite a bit higher by nearly doubled up front (about 195%), the rear about 550%. I used Austone Taxi tire and got 80,000 miles 3 times in a row. Yup 240,000 miles on just 3 rear tires. If I used normal bike tires I would have needed 20 to achieve 240,000 miles (I averaged ~12,000 miles on bike tires).
    OK… now for the tire bead difference. Yes there is one, while I never had a flat rear car tire I cannot vouch for said car tire jumping over the “inner rim bead” but I will say installing said car tire on a bike rim that inner bead absolutely need lubrication… it is that tight! Sealing car tire bead to a bike rim. Yes it does seal but at minimum about 90% (tire mfg depending). Is it enough? Yes, I say it is. I had a car hit my trailers rear tossing my bike at expressway speed and sent the bike into a SEVERE wobble where I eventually HAD TO depart off the bike or go over the railing & onto the Tollway below. Shortened story, went to pick up the bike & trailer next day at the towing lot, neither tire never lost one PSI.
    LASTLY (yaaaay) IF you never rode DarkSide you have absolutely no experience of how well it works. All you’re doing is explaining like a bookworm would. In that sense, you don’t use common sense. Naysayers, ask yourself, why are we not still living in caves?
    .

    Reply
    • Rob Brooks

      Thanks for sharing your testimonial and experiences, Vern.

      Reply
      • Vern

        Thank you for recognizing it.
        This article sorta reads like it’s biased against DarkSiding, true or false?
        _One of my many questions B4 changing was how many crashes were caused by car tires on bikes, none. I then went back in modern times (1990 to present) asking the possible accumulation of DarkSide miles on all bikes. While the answer isn’t exact, we came up with (2010-ish) well over a Billion accident free miles. It was that answer that convinced me to try it.

        Reply
        • Rob Brooks

          You are correct, Vern, the article does not endorse it. We are, however, open to the conversation. Thanks for sharing your calculated thoughts on it. The discussion is why we published it.

          Reply

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