Flat car tire on a bike?

[exdirtbiker]

There's a Harley-Chopper-thing running around town with (looks like) a P235/40-18 rear tire. Maybe wider / lower.
Motor sounds "healthy" but he doesn't beat on it.
I've seen him lean it to about 45 deg, I was thinking that will soon end badly...
But what's the width of the contact patch on a round cycle tire? Probably about the same.
I just looks really goofy to me. I haven't got close enough to ask if the side stand is now obsolete. :-)

[HiSPL]

I have a Vstrom now and tons of those guys are using car tires. Of all the problems that people talk about "could" happen, those that use the car tire rarely if ever experience any problems. Granted these guys are touring more than racing or canyon carving. But still, they seem to be willing and able to lean them over just fine. The best thing is the seemingly unlimited tire life!

[kingofvenus]

People have been putting them on the rear wheel on goldwings.

[Steve]

Yep, it's a common thing on the 1800 Wings, not so much on the earlier ones. I found a car tire for my (earlier) Wing. The rim is just not wide enough to properly support a radial tire, so I need to inflate it to the max for rigidity. The bigger problem is that it's just a little wider and a little taller than the stock tire, so I have to run the shocks with maximum air, but I still drag the tire on the inner fender. It will be coming off soon, unfortunately it will be LONG before it's worn out. I think I only have about 4-5000 miles on it, so it looks pretty much brand new.

Handling of a car tire on a bike that can wear one properly is quite surprising. There is a guy that goes by the name Yellow Wolf on some of the Goldwing forums. He rides Deals Gap several times a month. In fact, he has also done an Iron Butt ride on the Gap. Logged 1008 miles in about 23 hours, 40 minutes. Had to have every turnaround logged and certified, but kept it up for 24 hours. For those who have ridden the Gap, imagine doing it at night. ALL NIGHT LONG.

Anyway, Yellow Wolf has been seen at the Gap with a car tire on the rear, he claims that it handles just the same as any of the better tires that are intended for the Wing, so he is keeping it.

Video: click here.

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[robertbarr]

This is what's on the rear of my Goldwing. It's obviously a car tire, and it's a run-flat. I don't notice any trouble with handling or traction.

[83GS1100E_Tornado]

This has been a HUGE topic of discusson on several motorcycle forums I frequent, the Honda Valkyrie guys just love them. Some interesting reading here:

https://ridermagazine.com/2016/05/20/tales-from-the-dark-side-putting-car-tires-on-motorcycles/

[Grimly]

You'll always, without fail, find two polarised opinions on it.
1) Those who've never tried it and say it's bad because it's just a bad idea.
You'll find Safety Nazis coming out of the woodwork, left and right, because they just can't help themselves from pursing their lips and preaching to anyone, whether anyone wants to listen or not.
In that lot you'll find a heavy influence of the tyre companies themselves because they a) don't want to lay themselves open to anything, however unlikely and b) the golden goose egg that is motorcycle tyre sales won't come to an end anytime soon, if they can help it.


2) Those who've tried it and got used to it and like it.
I'm firmly in the second camp, having had a car tyre many years ago on a chopped type thing that handled like a bag of spuds anyway, so I was quite used to any quirks or foibles of the car tyre on the rear. That was back in the days when many 'vintage' car tyres were available in really odd sizes that overlapped with many bike wheels. They were all crossplies, of course.
I'm utterly sure I would quickly get used to a modern car tyre, no problem.

I've been looking for ways to fit a 15" car radial to my 850s and over the past couple of years I've collected a Cavalcade wheel and swingarm, just in the process of acquiring a final drive pumpkin to suit. In the European market, fairly narrow car radials of 135 section are available and I have two I snagged just waiting to go on. At some point I'll get around to finalising the project and basically never have to buy another rear tyre.
A similar quest is underway for the rear of the XJ900 - the later XJ900S Diversion rear wheel and swingarm fit straight on, from what I can gather, and apart from a minor welding job of making new twinshock brackets (the 900S is monoshock), I don't see much in the way of a problem there. If necessary, I can fit the V-Max 15" wheel I have under the bench. As far as I know it's the same drive engagement, along almost the exactly the same lines as the GS design.

http://forums.delphiforums.com/darksiding/start

[TxGSrider]

Ive seen people use them (usually on Harleys) and have wondered about the weight of the tire as well as the lean angles.
If Im thinking about this right, maybe it would work best with a tire that's too wide for the rim forcing the tire to bow out in the center of the tread?

[Steve]

The weight of the tire isn't that much more (if any) than a bike tire, and even if it were a bit heavier, what difference would it make?

As far as lean angles: I did a test ride on a bike many years ago that had a well-worn rear tire, but it was pretty much all worn in the center. Almost to the cords, but the outer tread was almost untouched. Setting that thing up for a turn was "interesting". It took a bunch of effort to get minimal response, then all of a sudden, it would lift up over the squared edge of the tire and proceed with the turn. I was sort of expecting that when I put the car tire on my Wing. Even though I was expecting it and waiting for it, I never noticed it. It just handled like it did before. I can's say for sure, but I am guessing it's because the edges are not rigid on the radial tiers and they just bend in, effectively making the profile a bit more round than when there is no load on it.

I am going to have to add a third category to Grimly's statment.
3) Those who have tried it, found no problems other than fitment, and decided to go back to a motorycle tire.
A different tire might fit a bit better, but for all the effort of purchasing/mounting/testing just to find out it doesn't fit, I'll just go with a long-wearing bike tire that I KNOW will fit.

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[robertbarr]

I'll try to find a video I watched a while back -- it was well-made, with (I'm guessing) a Go-Pro perfectly aimed at the rear tire of a Darksider putting the bike through various maneuvers. The tire's reaction to turning input was really interesting, and not what I expected to see. It's buried somewhere on the GLRiders forum. Give me a day or two.

[1978GS750E]

Showing my age here but....Back in the late 70's, we used to re-lace Honda hardtail chopper wheels with wider rims to use a Volkswagen size rear tire. Never had an issue. Never rode them very far in a day either!

[Steve]

I'll try to find a video I watched a while back -- it was well-made, with (I'm guessing) a Go-Pro perfectly aimed at the rear tire of a Darksider putting the bike through various maneuvers. The tire's reaction to turning input was really interesting, and not what I expected to see. It's buried somewhere on the GLRiders forum. Give me a day or two.

I just did a quick search on You Tube for "darkside rear tire" and found SEVERAL.

This one only shows a couple of curves, but great camera angle.

This one shows a BMW K1600 on a race track.

This one is a 15000 mile report on a V-Strom.

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[wymple]

There is a certain tire that is commonly used because it has a more rounded profile. A run thru the Goldwing forums would find it I think.

[Steve]

The Wingers run just about any tire that will fit the swingarm and fender. Yes, there are some preferences, but it is far from "a certain tire". One of the preferences is a run-flat type of tire. It is used because it has stiffer sidewalls, which give a bit more stability. You also have to keep in mind that the GL1800 Goldwing that has been produced since 2001 has come from the factory with radial tires, so the wheels are properly-wide to support them. Our bikes have wheels that are pitifully narrow. Probably too narrow for a radial that is designed for a bike, WAY too narrow to even think of installing a car tire.

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[Grimly]

Our bikes have wheels that are pitifully narrow. Probably too narrow for a radial that is designed for a bike, WAY too narrow to even think of installing a car tire.

I'm finally getting around to putting the pieces together (as mentioned above) to run a relatively narrow section car radial on a GS850. Cavalcade 15" wheel of 3" width and I'm about to obtain a Cav pumpkin to see if it will fit the GS. If it does, that's the easiest way.
I much prefer that method as everything is off-the-shelf and nothing needs specially made, except perhaps the driveshaft, but not sure yet exactly what will be involved there.
If not, I'll shorten the Cav swingarm by about 4" and transplant the whole assembly into the back end - that will definitely fit, but more involved of cutting, welding and alignment issues.
This is greatly facilitated by the latest crop of econo-boxes having some interesting tyres - taller and skinnier than they used to be. If only Michelin had kept making the 15 and 16" Citroen 2CV tyres at an affordable price, I'd have simply slung one of them on long since. Actually, I can get one of the weird metric 400mm tyres easily enough, but they're not cheap and the size is just too short of a 16" rim by about 5mm which is too much of a stretch.
At the moment I have a pair of 135R15 tyres under the bench that will do. Not sure if it's a size that's available across the pond as they might be aimed at the Euro market.