Car tires on a motorcycle

Apparently lots of people think it is a great idea to put a car tire on a rear motorcycle wheel, particularly on custom bikes. Some of them pump them up to over 100 psi. This seems absolutely stupid to me. What am I missing?

Cheaper, longer lasting, and supposedly smoother riding. I've only heard of it on cruisers, and only on the rear.

It's still not a good idea, but there are worse things out there.

The tire profile is way too square on a car tire to work on a bike. Check out how bulged out the tire is where this guy is cornering on it. Not good.

When you initiate a turn the motorcycle is going to resist leaning until you clear the flat part of the tire. Once you lean it enough to be on the sidewall the bike will fall over like it's been kicked. All of this happening somewhere in the corner you're trying to negotiate. This might explain why only cruisers have these installed. A sport bike is expected to corner while some cruiser riders see this as optional.

Does that dude have some sort of leather pony tail protector? ATGATT?

I'm pretty sure the argument is that they have to lean less so they don't scrape anyway.

This is a lot like stretched tires on cars. It's far from ideal, but it's been going on for decades and the world keeps spinning.

Reminds me of the Schwinn my cousin had in the 70s. It was a typical 70s bike with a square-shouldered slick on the back. Since we were 10-years old, we thought it looked cool.

I've seen it on large touring bikes aka GoldWings.

If all you are doing is superslab for 1000's of miles and no hard corners, I could almost see it.

10K out of bike tire, 75K out of a car tire

In reply to Grtechguy:

Tires last you 75K?

I've seen threads on this on a HD site. It's interesting. 8K on a $200 bike tire, 20-30?K on a $75 car tire. Yeah, heavy cruisers.

its called the dark side

Otto Maddox wrote: Does that dude have some sort of leather pony tail protector? ATGATT?

I think that's his woman on the back.

And dammitol, that looks like a Wisconsin plate on that bike.

@Otto That's what the Kelly Navigators on the Aurora are rated at.

If you look at bike tires from the 50's they were square tread. My 52 K model harley runs Good years that are stiff wall squares type on both front and rear and let me tell you it takes some getting used to as you feel the bike get tall as you lean in to the corner but after 4 or 5 corners its no big deal.

I'd never run on a car tire on a modern bike just plain silly idea.

The only one I've seen in person is a 1970s era Honda funny bike that belongs to a friend - he's converted it to street use and it runs a humongous drag slick on the back. It's hugely impractical and really only good for taking to shows, but he doesn't need a kick stand to park it.

The only thing silly about it is having to change a rear tire once or twice every year. A modern tire isn't too square shouldered and pressures are no where near 100psi. I've gone darkside w/the Goldwing and the only difference(other than longevity) is the bike wants to straighten up a tad sooner after cornering. After a few curves, you don't even notice. $220-$250 for a motorcycle tire every 10K is unacceptable. As an added benefit my rpms dropped by about 250 @ 70mph. No problems cornering on the Dragon and Skyline Drive either.

This was in the darkside database -

Kumho 195/65/R15 89H At 110 psi IT BLEW UP!

Of course it blew up. Good lord. It looks like most of the successful riders are using far lower pressures.

Otto Maddox wrote: Does that dude have some sort of leather pony tail protector? ATGATT?

Keeps your ahir from becoming a rat's nest. Guys wear them too, or just lots of elastics, every few inches along the pony tail.

PHeller wrote:

That's not a car tire. That is a drag slick. Firestone also makes some cool looking vintage tires with a squarish profile:

Never done it, but seriously have considered it. My old Magna was set up as a heavy cruiser and did many tens of thousands of miles down the interstate. Tires that started out as round were invariably worn flat and square.

Which, btw, corner just fine.

Never was one to run with the canyon racer crowd. Never have worried about wearing out my kneepads or such. Don't fret about getting my tires up to optimal temperature.

You guys ever look at yer average Harley riders rear tire after 10k? The centers are flatter than piss on a plate by that time, so why not start out that way?

And what rocket surgeon decided 110 psi would be required?

Any other states do a motorcycle inspection? VA law requires me to display a valid inspection sticker on my front fork. I could register my old antique as an antique and avoid an inspection, but the way I figure it, it's probably a good idea for another set of eyes to be going over my ride. The first time I had the local bike shop look it over, the guy was like "I'm not sure that your rear tire is going to pass, it looks like a front tire." I assured him it was the right tire and his boss okayed it. Not sure they'd let a car tire pass, but that's just conjecture on my part.

1988RedT2 wrote: ..... Not sure they'd let a car tire pass, but that's just conjecture on my part.

The tire is good enough for a 4000lb car but not an 800lb. motorcycle? It works just fine. I just wish my bike was newer. The 1800 'Wings can run a wider variety than is available for mine.

I read an article once written by Bridgestone (IIRC) about how motorcycle tires are designed to handle loads at angles and how the tread is designed for cornering angles and how car tires are designed for completely different circumstances and how unsafe it was to use them on a bike. It was enough to convince me to use the right tool for the job, although all of the darkside users I have spoken with have not had a problem.

From what little I've read from the darkside sites (it was hard to get through many of the posts), it seems most guys who are documenting this states its only good for a cruiser or some big touring bike that doesn't have a ton of lean angle to begin with. You probably aren't going to overwhelm a tire with one of these things riding down the interstate, but you probably shouldn't attack the dragon with one on either. Horses, courses, and different strokes I say, let 'em run what they want.

I don't believe for a second that there's some great conspiracy among motorcycle companies to sell more tires, I think its the nature of the beast that in a sport where grip is more important for 99% of riders over longevity that tires are designed to grip and roll over smoothly instead of lasting for 100k.