“The man was in such deep distress,” said Tom, “that I could do no less than give him good advice.” Said Jim: “If less could have been done for him I know you well enough, my son, to know that’s what you would have done.”
—Jebel Jocordy (Ambrose Bierce)

If there was one piece of advice that you’d think was universal to all motorcyclists, whether they’re riding dirtbikes, sportbikes, cruisers, tourers or ice racing in Wisconsin in January (as the MO crew once did), it’s this: don’t put a car tire on a motorcycle. This advice is so natural-seeming, so obvious, that I don’t think I’ve ever had to actually type that phrase before, so I’m going to do it again, because it’s so much fun:

Don’t put a car tire on a motorcycle.

You know where this is going, don’t you?

I know it may be old news, but maybe you’re like me a week ago and didn’t know that this is, as they say, a Thing. There are numerous discussion sites and motorcycle shops that are fully supportive of slapping a car tire on your motorcycle’s unsuspecting rear (or even front) rim. But why, Lord, why? Just because you can do something doesn’t mean you should do it. So why do thousands of riders roll over to Pep Boys to do it?

One obvious answer to ‘why’ is – and I’ll bet you could guess – it saves you skrilla. How much? A high-mileage motorcycle tire is what … $150? $200? $250? And you’ll be lucky to get 20,000 miles out of it if you’re really anal-retentive about tire pressure and whatever else it is that conscientious motorcycle owners do. An Arizonian Silver Edition car tire can be had at America’s Tire for a mere $73 (with free shipping) and comes with a 50,000-mile warranty, plus the waiting rooms at car tire shops have vending machines and a barely audible TV from 1998 playing the Steve Harvey Show. Finding a shop with the stones to mount it to your motorcycle rim can be challenging, but they’re out there.

Tom’s rear tire leaning into a turn. Yes, it’s square, but it still leans. You just have to push a little more. If you are old, you may remember motorcycle tires having a much more car-like, squared-off profile than they have today.

Tom’s rear tire leaning into a turn. Yes, it’s square, but it still leans. You just have to push a little more. If you are old, you may remember motorcycle tires having a much more car-like, squared-off profile than they have today.

I found out about this from the latest issue of Iron Butt magazine, the official organ of the Iron Butt Association. If you don’t know, the IBA is “dedicated to safe, long-distance motorcycle riding and sponsors the Iron Butt long-distance rally every other year as well as other smaller events. The IBA has over 50,000 members, and these people ride – a lot.

It’s a surprisingly interesting and readable magazine, with great photography and the sort of articles you really aren’t going to find in other publications unless the editors there are profoundly off their meds, like “Confessions of a Rally Spouse or “Priorities – How to Make Long-Distance Relationships Work along with thrilling shoot-out comparisons between Ibuprofen and Naproxen.

In “Examining the Dark Side (Iron Butt Magazine, Fall/Winter 2015), IBA Chief Technical Adviser Tom Austin not only writes in great detail about mounting car tires (the hipsters call them “CT’s for short), he mounts up a Kumho 195/55-16 Run Flat on his own Gold Wing, with resulting benefits I hadn’t thought of.

For one, the car tire, with its far stiffer sidewall and greater load rating, ran cooler than the moto-specific tire he was using before. Austin points out that anecdotally, there have been no reported heat-related catastrophic failures of a CT on a motorcycle, but such failures are well-known on heavyweight bikes riding at high speeds at high temperatures. Another benefit is (according to posters on Dark Side fora) the availability of stickier-compound rubber in oddball touring and cruiser sizes. Another advantage is long tread life – up to four times what you’d get out of a motorcycle skin. Oh, and you can also use a run flat, which can, in an emergency, let you ride on a flat tire for a few dozen miles.

Did you know there’s an actual Tire and Rim Association that sets standard bead sizes for car and motorcycle tires? Maybe you should listen to them before you try to mount a car tire on a motorcycle or vice versa. Or not. What do they know, anyway? Diagram: Tom Austin.

Did you know there’s an actual Tire and Rim Association that sets standard bead sizes for car and motorcycle tires? Maybe you should listen to them before you try to mount a car tire on a motorcycle or vice versa. Or not. What do they know, anyway? Diagram: Tom Austin.

Of course, there are some disadvantages, too. The main one is strange handling characteristics from the CT. No, really! Yes, it seems that the squared-off profile of the car tire results in heavier steering feel and abrupt transitions from lean to vertical, which unless you live somewhere that’s extremely flat and straight, you probably figured out on your own. The car tire can make the bike hard to hold upright on a sloped road, a problem for those with short inseams and heavy motorcycles.

Also, there’s an issue (according to Austin) with the design of the motorcycle rim vs. that of a car. The car wheel’s “bead hump” – which is behind the tire bead and keeps it from unseating – is a few millimeters farther back from a motorcycle’s, which means the bead will not seat into the motorcycle rim like it’s supposed to. The risks created by this are enough to make a products-liability attorney wet his or her business suit (or slather with greedy anticipation depending on the side of the courtroom he or she is on). “An incredibly bad idea,” writes Austin.

And yet, you don’t hear about motorcycles crashing because of running CT’s. Lo and behold, it turns out that motorcyclists are the kind of people who are willing to take risks and continue doing something that sounds insane to outsiders. And kudos to the IBR for allowing the use of car tires at its sanctioned events, even though a recent Iron Butt Rally finisher set a record of 14,185 miles on Metzeler ME880 motorcycle tires. In the IBA’s view, there’s no data supporting the notion that car tires affect tire safety or motorcycle handling, and there is data supporting the notion CT’s run cooler – so it’s kosher.

How’s this for freaky: to mount a car tire on a motorcycle rim, not only do you have to be okay with this, you also have to mount a size smaller – a 16-inch car tire fits a 17-inch moto rim. What could possibly go wrong? According to Dark-Side riders, nothing. Diagram: Tom Austin.

How’s this for freaky: to mount a car tire on a motorcycle rim, not only do you have to be okay with this, you also have to mount a size smaller – a 16-inch car tire fits a 17-inch moto rim. What could possibly go wrong? According to Dark-Side riders, nothing. Diagram: Tom Austin.

Austin does point out the disadvantages probably outweigh the benefits of running a CT, and I’m with him. In fact, I’m going to state for the record, on behalf of myself, Motorcycle.com, the USDOT, the MIC, UN, and every other organization you could think of, including the Organization of Satanic Temples (which may, in fact, not exist), that you should under no circumstances, ever put a car tire on your motorcycle.

But if you do, I unofficially think you’re a badass. Ride on.


Gabe Ets-Hokin is a product development specialist for SuperKid, a Hong Kong-based toy company. His latest products, Broken Glass n’ Rusty Scrap Iron Discovery Center and Baby’s First Meth Lab, are available at your local toy retailers.

  • JerryMander

    I don’t understand the author’s surname. Is that some kind of nobility title? I would change it.

    • john burns

      I believe that’s Gabe “the Hokin”, which refers to a lost tribe of milliners.

    • Prakasit

      Last names are not meant to be understood.

    • http://www.motou.info Gabe Ets-Hokin

      LOL! My great-uncle Emuel Hartmann claimed he was Hungarian nobility. He wore a monocle and as far as I know never had a job. He offerered to build a small deck for my parents when they were newlyweds at no charge–my mom just had to make him lunch every day. I think it took him two years to complete it.

      Anyway, if you’re really curious, you can read this blog post: http://gabeunchained.blogspot.com/2014/05/what-are-thats-question-i-used-to-hear.html

  • Ser Samsquamsh

    Another way to think about that would be for the same $250 you could get a really amazing car tire instead of an average bike tire. One with computers in it. Or a drifting tire with candy color smoke bombs or something.

    Unfortunately where I live is somewhere “very flat and straight” so my bike’s tires end up square anyway! If I drove a Ural I would definitely try this out.

    • Sayyed Bashir

      Looks like the Ural “Dark Force” already has car tires (and a light sabre too!).

  • Alexander Pityuk

    As if our bikes required even more reasons to crash…

  • spiff

    If you can’t afford the correct gear don’t play. Square tires are for drag racing, and nothing more.

  • Auphliam

    As soon as I saw the title I thought “Oh crap, here we go”. On motorcycle forums everywhere, DarkSide threads are second only to Oil threads in the vitriolic arguments they generate LOL.

  • Tim Sawatzky

    I rode with an old biker who put a CT on his Intruder 800 rat bike. He said he went through 4 rear tires a year and was tired of changing them, so he went to the dark side. We live in the straight and flat prairies, so to him it made sense. We swapped bikes for a stretch on a trip in the mountains and honestly I couldn’t tell a difference in handling. Although his head bearing was also shot and the front end flopped around, so maybe I was more focused on that, lol. That said I was more than glad to get off that thing and back on my bike.

    • Ser Samsquamsh

      Ya but it looks cool on a rat bike! Wrap some barbed wire around it for “traction” and it’s off to the Bullet Farm!

  • Mike Milano

    I mounted a CT (ya, i’m “hipster” like that haha) to a Goldwing back in 2010. It was for an 11k mile summer tour from San Diego to Prudhoe Bay.

    The reason wasn’t due to money. I was thinking it was going to prevent me from having to change tires on such a long trip. Sure people get 11k+ miles on motorcycle tires, but they are generally extremely conservative riders… which I am not.

    After getting used to the slight extra effort at slow speeds to roll the bike, I hardly noticed it. It lasted the entire trip, but not by much.

    Besides lasting a bit longer, it really excelled all the dirt and gravel I traveled on during that trip… the most significant being the Dalton Highway. (about 500 miles one way of dirt/gravel, where you turn around to backtrack that 500 miles at the end)

    In the end, I’m sorta happy I had a CT on that bike for that trip, but I went back to my MC tire for normal riding.

    Here’s a video of the tire in use I made for a little research before I committed to using it on that trip. https://www.youtube.com/watch?v=Mqp3QXhzJmY

    This article recommends against it. I say if you got a big bike, why not try it if you are curious about it… it’s not really as big of a deal as it makes for controversy on the web. Just be prepared to revert in case you end up not liking it.

  • Archie Dux

    This is stupid. Car tires are for cheapass posers.

  • Craig Gibson

    My thoughts are simple. Don’t want a car tire on your bike? Don’t put one on….and if you want to get all emotional and preachy about it, cough up the evidence. If they’re really that dangerous and risky, the crashing/regret will be palpable and evidence in spades that the risk is too great to consider. I don’t run them, but I’m paying attention to people who do and they’re not crashing or experiencing major issues from doing so. Seems like a lot of hand-wringing over nothing.

  • Ray Boone

    I met a guy recently with over 100K on his FJR running a car tire out back. When he pulled up I thought wow…never. Then I realized how many miles he had under his belt and we talked about how many decades he’d been riding–5 to my 2–and figured he may know something I don’t.

    • Vrooom

      100K on sport tourers is pretty much a dime a dozen. I know people who do it, but they aren’t fast in the corners. They are cheap though.

  • mugwump

    These threads never fail to entertain

  • Brian Clasby

    “If once you start down the dark path, forever will it dominate your destiny, consume you it will.”

  • Kirk Harrington

    Gabe’s Superkid gig rocks.

  • R3Stripes

    I have 50 years of riding experience on all types of motorcycles. I figuratively slowed down on riding a while until Triumph invented the massive Rocket 3. Shortly after buying my first one a 2006 I found existing mc tire suppliers did not provide a tire that would accommodate the massive torque and started experimenting with the darkside. I own 3 rockets now and all are darside out of necessity, enhanced performace and efficiency. When attending Rocket 3 meetups always almost half of those in attendance are darkside. I will revert to a mc tire only after the mc tire industry catches up to the performance requirements needed by the R3’s.

  • Vrooom

    I have a friend who runs car tires on his GS. He does admirably off road, but he’s slower than hell in corners even though he wouldn’t admit it. He’s actually about 25 mph slower cornering, but if you rail it in the straights, you can tell yourself otherwise until you get to a really twisty road where you can blame it on your bike, the road conditions, needing a tune up, air pressure, throttle bodies, the Baghwan, etc. etc. Or he can.

  • http://www.mymotorrad.com/ james lagnese

    It’s not ideal, but people do it anyway and the reason 99% of the time is money. It’s not a superior tire for traditional riding on the street (I know of one case where it was a detriment as the guy cranked over too far on a wet road. Not much rubber real estate to purchase at that point), but lasts longer and that is what matters most. Too each his own, but I find it parsimonious and niggardly.

    • Sayyed Bashir

      If car tires were so great for motorcycles, manufacturers would make car tires for motorcycles. First of all they inhibit the leaning motion of the bike which is essential to safe riding. Secondly the rubber is too hard for good traction. Motorcycles need round profile tires with sticky rubber for the best traction, especially when leaned over. The right tire to get the best performance from your bike will cost more, and you will have to replace it more often. No one buys a Corvette or a Ferrari and then puts cheap tires on it to save money. You could also ride a bike with a flat tire, but who would want to?

  • Buzz

    I think it would be ok if you were riding a Wing in the Midwest but I’d never do this anywhere near where I live.

    I remember riding a Victory Hammer in a MO test down the Ortega highway over Lake Elsinore and fighting that giant non-car tire the whole way. I don’t want a motorcycle that wants to stand up when there’s a thousand foot drop-off below me.

  • JMDonald

    A nice nimble bike with a nice sticky tire works for me. It took some getting used to riding on high mileage touring tires. The tires of today weren’t available in the 70’s. I’ll take the tires of today. Motorcycle tires that is.

  • ll

    you buy a 15 – 20 k usd touring or adv bike and try to save a mere 100 bucks by using a car tire on a motorcycle? funny.

  • MARK LOGSDON

    For all of us riders using sidecars, a square tire would be very much appreciated. That is why Ural uses them. Sidecar rigs need square tires because they operate like cars, unless, you constantly “fly the car”, that is. I would LOVE to find a tire to fit my 08 Harley Ultra Classic and TLE sidecar.

    Mark Logsdon
    drummajor@1stmichigan.com