Car tire on motorcycles - an opinion

[cactusjack]

Okay guys, don't shoot me - I am only the messenger here. This is a transcript of a letter in the May 2009 edition of Motorcycle Consumer News and the response from the editor. I am only passing this along for your consideration.

Car Tires On Motorcycles

I would like to know your opinion on using car tires on motorcycles. I vaguely remember reading about it, but I can't remember where. Was it in MCN? If so, what issue? I've checked all my back issues, to no avail. I'm missing March and May 2008. I'd like to research the subject very well before acting on it.

The reply:

We did address this a year or two ago. It is very simple: Just don't do it! Car tires are not designed for the leaning and side loads generated by motorcycles. If you don't believe me, call a few tire manufacturer tech lines or visit the Q&A sections of their web sites. With the exception of sidecars and special sidecar conversions, there is absolutely no safe or proper way to use a car tire on a conventional motorcycle.As Forrest Gump said, "That's all I have to say about that."

[ballast]

HHHMMMMMM

[strobe]

I am by no means a complete believer yet, but I am going to give it a shot.

All I will say is that there are a lot of actual users that have opinions that would differ. Tire companies are of course going to say that for the usual liability issues same thing for magazines, articles, etc. I think the lower weight on the bike also compensates for some of the issues they discuss with the sidewall strength. Most the bike guys against it have never tried it either and won't even give it a shot.

I am going to try it, tire was supposed to be here today, but if I can get 20-30K like some guys on a tire, I will gladly replace it before it is even worn out just to be safe. I may end up back on a MC tire...who knows, but thought if I am replacing the tire, I may as well try it.

I thought this was an interesting document on the contact patch that you get on a MC vs CT at various angles.

http://bikes.nmsolutions.ca/dl/mcintroe.pdf

Document has points both ways I think. I also think that a CT on a cruiser is an easier sell than on many other types of bikes simply because of the type of riding. I could not imagine anyone trying a CT on a sport bike.

[dougster]

Kinda sounds similar to the "What is the weight limit on the Nomad" question. Do you go with what the manufacturer says (especially considering some of the nutty ideas manufacturers come up with, such as 405 lbs., max, so that you and your passenger can only bring along a 10 or 15 pound bag of something in your hardbags!) or use wisdom (a mixture of what the specs of the product are and wisdom of experience)? Especially when safety is of the utmost importance.

[Kawhead]

Thanks CJ, I appreciate any cons anybody brings to this idea. So far I haven't found anything concrete that would lead me to believe these car tires are unsafe for our bikes. By concrete I mean blood teeth and eyeballs, and a lot of 'em on the road as a result of hard headed people not listening to the Tech Lines.


I wish I had a nickle (or a dollar) for every time I've proved a Tech Rep wrong. If I were for a second convinced a car tire was not capable of handling the side stress and and leaning of a motorcycle, I'd have motorcycle tires on my car!

I'd like a Tech Rep to install for bike tires on a car and follow me through the Dragon!

[Cajunrider]

My questions are not meant to imply that I am against using car tires. I don't know enough about the subject to form an opinion one way or the other but do any bike manufacturers sell their products with car tires mounted? I'm not familiar with any that do so domestically but what about in Europe or Asia?

[dkdixie]

Originally Posted by Cajunrider

My questions are not meant to imply that I am against using car tires. I don't know enough about the subject to form an opinion one way or the other but do any bike manufacturers sell their products with car tires mounted? I'm not familiar with any that do so domestically but what about in Europe or Asia?

Boss Hog did at one time. Not sure if they still do since m/c tire manufactures came out with bigger sizes, IE: 300 series Avon.

I read every article I could find on the subject of putting CT on motorcycle. As in the M/C Consumer news letter, I did not find one that would recommend car tire, nor did I really expect to. Why would they? With liability issues and advertising revenue, no m/c mag will ever recommend a car tire.

There are individual riders out there that have logged hundred of thousands of miles on car tires. Don't believe it, get on some of the Darksider forums. M/C Darksiders has almost as many members as KawaNOW, most of which are running CT. Just too many positive comments from these riders not to give it a try...IMO.
I debated for years about it. Decided couple months ago to try it and wish I had done it years ago. In the last 8 years, have never got more than 9,000 miles out of a rear tire on three different bikes. Most rear tires less than that. Usually replaced front as well since it was almost as bad as the rear. Stock Stone rear lasted 5,050 miles and were cupped so bad were totally junk.

After logging almost 2,000 miles on a car tire, I have almost forgot "there's something different back there."
Yes, it is a different feel and takes time to get use to it.
Yes, it does handle sightly different.
Yes, you do have to try different air pressure and shock settings to find the sweet spot.

But after you do.....you can scrap boards, if that's your desire, with the best of them as I did yesterday. Wasn't trying to, but sure did.

No way am I trying to talk anyone into going with a car tire.
Its obviously not for everybody. If you are interested, I suggest you do the research and make up your own mind.

[dank]

I am very interested. I run about 20,000 miles per year, so just about two rear tires per summer. Sounds like a car tire greatly increases braking power. Big plus. My concern has always been on cornering. Not how well they carve corners. I wouldn't have a cruiser were that my big joy in life. Rather, how unstable does the bike feel due to the two tires having such different geometries in the corner, with the front leaning over on a curved surface and the rear apparently staying flat and flexing the side wall. (Based on pictures on various sites) I wonder about this because even those who use them on a cruiser say they wouldn't do so if they had a sport bike or sport tourer. So there must be a performance issue of some type on corners. I'm not saying that means don't go to the dark side. I'm just trying to understand what it is before I take the leap.

[macmac]

Nice Cj. Nothing but the straight facts. lets see a bile doesn't weogh 1/2 what a car does, and the cornering is an issue some how because?

Maybe the guy is talking sort bike, where there is a lean angle.

Anyway I didn't lock n load...

[nomad561]

The cornering issue is what I worry about too not the stress on the sidewall of the tire but the ability of a car tire to grip. Think about the stress on a car tire on the front of a car as it starts into a corner.What kind of stress do you think is on the sidewall of the outside front tire of a 3500 lb car at that time? There isn't a doubt in my mind that you can run a car tire on a bike without any problems,I just worry about my occasional jaunt through the twisties.

[blowndodge]

Those statements have to be made by all manufactures of tires and/or motorcycle manufactures STRICKLY for liability. I'm hesitant to think its based on "straight facts".

Kawasaki warns against modifying the intake and/or exhaust because it will damage the engine. CJ did that stop you? Doesn't seem to stop a lot of people from what I've read?! If I came out and quoted Kawasaki as the "Authority" on the subject I would think most would dismissed their warning with a smirk. True?

A 4000lb sports sedans "side load" going around a high speed corner is pushing the sidewalls far harder than the weight of a motorcycle leaning. If you've ever seen a high speed camera filming say a BMW going around a track on street tires it looks like the rim is almost touching the pavement the tire rolls on it's sidwall that far. I seriously doubt a motorcycle applies even 1/3 the side load pressure at speed as a car does.

CJ, give MaKaw a call and ask them their opinion about your Nomad towing a trailer and ask if they will give their approval!? Let me know what they say.... ;)

[ringadingh]

I would like to know how different the rubber compounds are between the car tires and the bike tires. If the bikes tires use a softer rubber compound, how much different is it from the car tires compounds. Touring tires obviously are a different rubber than a sportbike tire. Ive never heard of guys with car tires, complaing that they slide out from under them. From what Ive been reading here and on other places is that they feel different but do the job as good as any.

[trip]

I'm thinking along the same lines as BD here........and I thank CJ for bringing it up. I think it's good that we all take a look at all angles. I'm of the opinion that you can't really believe everything you read, as BD put it, it has to be there for liability sake.

I prefer to look at an issue like this as "pushing the envelope". Where would we be if we didn't get out of our box and take a calculated risk every now and then?

And Ring, you bring up the compound issue. I read somewhere several years ago that Metzler as well as other moto tire manfactureres were playing with a dual compound tire, that had a harder compound in the middle of the tire and softer on the sides. In the past the two compounds couldn't be manufactured together. Anymore news on this?

[blowndodge]

There are some rubber out there now trip that state they have a "dual compound". These are I believe almost exclusively high performance tires for the big HP boys.

[cactusjack]

I just posted the letter from MCN to illustrate the "company line" on running a car tire on a motorcycle. It was not my opinion, nor do I buy into the belief that it is inherently dangerous to do so.

To answer BD, I paid a lot of money for my Nomad. Of course I'm not going to do anything to intentionally damage it. You are correct, Kawi wouldn't recommend towing a 300-pound trailer with a Nomad. As far as I know, no manufacturer endorses towing a trailer with a bike. Would I tow a trailer if I felt the Nomad couldn't handle it or it wasn't a wise thing from a safety point of view? Hell no.

I have done a lot of reading on the subject of car tires on motorcycles. I have yet to hear of even one crash that can be attributed to running a car tire. In fact, every first-person account I've read (or heard) has been overwhelmingly positive. Everyone who has gone to the darkside has been very satisfied with their choice.

All it would take is some motorcycle magazine to put in print that running a car tire is a good idea and the first person who does so and crashes would try to sue the pants off them. This is why they all say the same thing: "don't do it!" This response is most likely mandated by their legal counsel rather than by experience and common sense.

I plan to switch over when my still-new Cobra wears out. I spit in the face of danger! I wouldn't be considering it if no one else had ever attempted it, but this practice has been going on for years with proven results.