Sunday, March 19, 2017

Darksiders

In one of the Facebook groups I follow a member posed this question: “Anyone tried a car tire on the rear of their bike...lots of info on you tube...just wondering?”

car tire 2

Well that question started a flame war of the like not seen since the PC-MAC conflagrations of the last century. Aside from sidecar rigs (Petunia over at Arizona Adventure Dude, for example) which often sport automobile tires, I’d never heard of anyone putting them on a regular, two-wheeled, motorcycle. Until now. And to say there are advocates for this would be an understatement. The car tire disciples are many, they are vocal, and they even have a name for themselves – Darksiders.



As with many things on the interwebz, there are many opinions but very little solid evidence one way or the other. Some positions make a certain amount of sense (http://www.roadandtrack.com/car-culture/a8606/why-so-called-darksiders-prefer-auto-tires-on-their-motorcycles/) while others rely simply on the passion of their arguments to make their case.

As a lay person with no practical experience other than 40++ years of riding, I find the very idea of putting what is essentially a flat-profiled tire on a vehicle intended to lean to be disconcerting, if not downright frightening. Tire design is not rocket science, but it is complex. Different vehicle types impose different loading factors and forces that determine a tire’s characteristics such as sidewall flex, compound hardness, profile, and so on. So to take a tire designed for one set of conditions and stake your life on it functioning properly under a completely different set of conditions strikes me as idiotic in the extreme.

UPDATE: For anyone who really wants to get into the minutiae of this topic, here's a great link: http://www.goldwingfacts.com/forums/10-reference-faq-forum/400426-design-differences-between-car-motorcycle-rim-tire.html.

13 comments:

  1. I could be a bad example. I did it because of the wear factor pulling the hack, but a bigger reason was because people said it couldn't/shouldn't be done. Well, it can be done and at a 3 -1 ratio of bike tires to car tire I think it should be done. Also, most Darksiders are rolling on those Hondapotamuses, usually tugging a trailer and rarely come even close to leaning them within 50% of their capability. Some love it, some hate it and there isn't much going to change anyone's mind.

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    1. The discussion does seem to take on a religious fervour at times. But I used you as an example (I hope I wasn't out of line) because with your setup it makes a lot of sense to me to go to a car tire, even if it was a nightmare to get mounted. But just two wheels? No way.

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    2. No worries from me and I didn't even know there was a line.

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  2. I can understand the incentive with the cost and short life of rear tires on a heavy bike. And if you primarily travel the interstates then why not. Everything's a compromise...

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    1. To my way of thinking it's just too risky to take the chance. But then I always wear a helmet that costs more than $50 as well, so I suppose I'm more risk-averse than some.

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  3. Here's how we do it: Don't put anything but the technically approved tire on your motorised means of transportation, otherwise you'll lose insurance coverage and your registration will be invalid. Just ask us Germans how to prevent such topic to become a religious war ;-)

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    1. But then the religious war becomes about government interference in people's rights to make their own choices. Don't worry, the religious warriors will always find a way.

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  4. David,
    NZ sounds the same as Germany in this particular case as it's actually illegal to use car tyres. This also means failing the annual warrant of fitness inspection and voiding your insurance. Construction of a car tyre carcass is different from motorcycle tyres which means handling can be compromised under certain conditions, not to mention actual profile issues. I guess on a cruiser that isn't being ridden in a spirited manner, you can get away with it, but the same can be said for not wearing helmets too! For me personally, tyres are critical for safety, particularly for the sort of riding I do. Getting around 10,000 km from a purpose-designed rear tyre is just fine thanks!

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    1. Agreed. And I think it might be illegal in Ontario as well - need to check on that (just curious).

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  5. I have seen this discussion before and I think its not a wise idea at all, bike tires are meant for bikes. I'd hate to put my self at risk trying to get the performance out of a car tire when I am happily tearing up the twisties, and its probably illegal in BC.

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  6. David, you troublemaker you :)

    I heard the other day that Shaq was making his case that the world is flat so I'm thinking that all sorts of conventional wisdom is up for discussion.

    We've got some Iron Butters around here that are total converts. I am and will continue to be a round one rider.

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    1. LOL. Saw that flat earth story as well. Just more alternate facts to ponder I suppose.

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