Car vs Bike tire lfie - BMW Luxury Touring Community
 
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post #1 of 14 Old Jul 2nd, 2012, 4:36 pm Thread Starter
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Cool Car vs Bike tire life

Why do car tires last much longer than bikes?

I dont have much experience maintaining my cars because I change them every 2-3 years. but I have atleast put 30K miles minimum on my car while I owned them and the tires were very usable without me having to replace them.

Why do bike tires last only 10-15K while cars last much longer?

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post #2 of 14 Old Jul 2nd, 2012, 7:44 pm
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Re: Car vs Bike tire lfie

I would have to say contact patch size and forces applied. You want a very sticky rubber compound on a small patch that gets significant forces on them. Sticky rubber wears out faster. Put the same compound in an 80,000 mile car tire on a bike tire and you would be lowsiding all over the place. Especially with the loads imposed by the LT. Don't take me to the dark side - I won't go there.

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post #3 of 14 Old Jul 3rd, 2012, 1:09 am
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Re: Car vs Bike tire life

Hell, I'd be thrilled if I could get 10-15K out of bike tires, instead of half of that, or less . . .

John has it mostly right. Larger flat contact patch, plus harder rubber, plus heavier carcass and belting, plus four tires to share the load all contribute to longer car tire life. Heat is the enemy of rubber, and tires flex during normal operation, adding heat. So car tires are built harder and heavier to counteract that, and to deal with the additional weight of a car.

Note that even car tires come in a variety of compounds. You can get sportier tires that stick well but wear faster, and harder tires that last but give less grip and a harsher ride. Most drivers are fine with longer-wearing tires, as they don't usually push a vehicle's limits. But some drivers prefer the sportier tires, and just change them more often, much like some riders do.

By the way, contact patch can affect tire wear, but it doesn't affect traction. The formula to calculate friction is:

Ff = μ Fn

Where Ff is the Force of Friction (usually calculated in Newtons), Fn is the Normal Force (weight of an object pushing down against a surface, also in Newtons), and μ is the Coefficient of Friction, based on the surface treatments of the two objects (but always less than 1.0).

Surface area doesn't appear in the formula at all, and so isn't relevant to the friction calculated, or to the traction we see on a bike (or car) tire. So a larger contact patch when leaned over has more to do with evening out tire wear than it does with increasing traction.

And that concludes the Physics lesson for this evening.

Ken
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post #4 of 14 Old Jul 3rd, 2012, 8:05 am
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Re: Car vs Bike tire lfie

Seriously, I understand that surface area doesn't appear in the formula, so why do race cars have big fat tires?
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post #5 of 14 Old Jul 3rd, 2012, 10:20 am
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Re: Car vs Bike tire lfie

daba
I don't know anything about tires, and formulas, but I would say the race cars have wide tires to keep them flat on the ground on the curves.
One of the nicest cars I had was a 2007 Mustang GT with wide tires. Low profile and wide. Excellent cornering.
I think a lot of it had to do with the wide tires.
dc

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post #6 of 14 Old Jul 3rd, 2012, 10:53 am
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Re: Car vs Bike tire lfie

Quote:
Originally Posted by dabadou2
Seriously, I understand that surface area doesn't appear in the formula, so why do race cars have big fat tires?
Low profile tires have less sidewall flex, meaning the car is more stable and predictable in the corners. And wider tires put more soft rubber on the road, helping with overall tire wear.

Remember that race tires are ultra-soft, which increases traction (by increasing the μ constant in the above formula), but it also increases the wear rate. So you need more rubber to get a tire to last nearly as long. You could go with thicker rubber, but again, that can lead to tire flex which increases tire heat (and thus wear) and adds unpredictability in the corners.

So a soft, wide, low profile tire is the best solution. And even then, they swap out tires many times during a single race.

Ken
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post #7 of 14 Old Jul 3rd, 2012, 5:04 pm
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Re: Car vs Bike tire lfie

Rubber on a motorcycle tire needs to be soft so you can corner. Soft rubber = fast wear.

An indycar has rubber so soft, grass will stick to it when it's heated up. How many tire changes are there in the Indy 500?

Motorcycle tire needs to be soft so you can corner while riding in rain. Have you noted how racecar rain tires wear out almost instantly when rain stops? Too soft.

Tire width is basically meaningless to this discussion. Racecar tires are wide to provide best lateral grip, i.e. when cornering. Wide tires on cars are basically for looks and to enable tire company to sell more rubber. They are a liability in rain and snow, as the vehicle weight is spread over too much area ... plus, you're not going to corner a street car hard enough to need them. They're a liability, too, when it comes to fuel economy, as they're heavier and create more rolling resistance. Look closely at World Rally cars running dirt roads--very narrow tires. Even narrower in snow.

Proportionately, bike tires are wider than car tires but it makes no difference in making them wear less, i.e. it doesn't.

You don't really fall over driving a car and you probably don't need a helmet and body armor. About anything will work on a car and some pretty hard, long wearing rubber can be fitted. Still that won't "handle" as well as a soft rubber tire, but then you're just about 100% likely to never test the tire to its limit in any event.

Dunlop once made a high-mileage motorcycle tire called the 491, and it indeed lasted quite a while, but if you rode in rain you fell down.

The absolute LAST thing you should think about motorcycling is that it's economical. Rather, it's an expensive hobby and tires are a significant expense.

Kent Christensen
Albuquerque
'12 R1200RT, '02 R1100S, '84 R80G/S

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post #8 of 14 Old Jul 12th, 2012, 11:42 am
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Re: Car vs Bike tire lfie

Many years ago I asked my Harley dealer the same question. He advised that the weight per square inch on a motorcycle tire was 7 times that of an automobile tire. I don't know that he was right but it did make me feel better about paying a couple of hundred dollars a tire every year to two years.
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post #9 of 14 Old Jul 15th, 2012, 10:20 pm
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Re: Car vs Bike tire lfie

I'm surprised at the number of people that still believe that M/C tires are softer than car tires. Do some research on the durometer readings and you'll find that car tires are as soft or softer than M/C tires. The wear factors have more to do with the relative weights vs contact patch areas. If you do some research, you'll find that there are some very good factual investigations of this phenomenon that aren't colored by unsubstantiated opinion.
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post #10 of 14 Old Jul 16th, 2012, 1:01 pm
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Re: Car vs Bike tire lfie

Your statement is unsubstantiated as well. YOU provide the links.

Kent Christensen
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post #11 of 14 Old Jul 16th, 2012, 4:49 pm
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Re: Car vs Bike tire lfie

I'll have to do some digging when I get a chance. I had in my head (rightly or wrongly) that I had seen data somewhere that matched what LebanonRider is saying regarding it being not true that MC tire compounds are softer than car tires. I'll see if I can find something if LebanonRider can't - heck I might even prove to myself that my memory is getting worse as I get older...

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post #12 of 14 Old Jul 16th, 2012, 5:33 pm
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Re: Car vs Bike tire lfie

There are a few threads with interesting info. And no, I am not suggesting or recommending a darkside thread - I am simply focused on answering the question of "using typical durometer readings of motorcycle tires versus car tires, are motorcycle tires software than car tires generally", out of interest in why one might last longer than the other, nothing more.

The first post of the thread below looks like a fair shot at trying to use experts.

http://www.vtxoa.com/forums/showthre...out-MC-C-tires

There were many other posts with somewhat unscientific approaches to durometer readings, typically it was one car tire measured versus a bunch of motorcycle tires. Across a number of people measuring, it seems the truth is that there is no solid rule that can be applied to this question as there are just so many tire choices on both sides, so the question itself really is likely not one that can be answered with a "yes or no".

There are several cruiser forums where people measured a specific car tire versus various motorcycle tires, and in those cases the car tire was softer, but the measurement is often stated with an assertion that that one car tire chosen was known to have amongst the hardest car tire compounds - not a very scientific statement without a table. Interestingly the two car tires mentioned most (Goodyear Triple Tread, and Michelin Hydroedge) are ones that are positioned as great in the wet, which would suggest to my mind that they might be building them with a softer, not harder compound, but again, I couldn't find comparative data on this. In the end, it simply wouldn't be correct to make a rule from all this - it would be essentially stating that all car tires are softer because these two car tires are softer.

So I guess I'd have to say, in the end, that my memory is going on me and I now believe that one cannot state that a motorcycle tire is softer or harder than a car tire based on what I've read. That's my 2 cent conclusion from the best that I can find with Google.

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post #13 of 14 Old Jul 17th, 2012, 4:55 am
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Re: Car vs Bike tire lfie

Just to throw more oil on the fire!

We fitted our car with four season tyres, which the tyre place reckoned was a softer compound than normal summer tyres, but not as soft as genuine winter tyres. (They do not make genuine winter tyres for our car.) It was said that they will wear quicker than normal summer tyres, but not as quick as full winter tyres.

I do not think there will be any definitive explanation as to why bike tyres wear quicker than car tyres. Mainly because there are too many variables; Ground pressure, compound, way it is driven to name but a few.

I have seen a motorcycle tyre last for ages, and another wear very quickly, but felt great in all weathers.

Just to be difficult - I think the compound answer goes a long way to resolving this issue, otherwise why would the manufacturers spend so much money on making dual compound tyres? Hard on the centre line, and soft at the sides? That is just my opinion, and until further information / evidence is available I will hold on to it! (Biking is fun but not cheap!)

Best regards
Adam

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post #14 of 14 Old Jul 17th, 2012, 7:14 am
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Re: Car vs Bike tire life

Quote:
Originally Posted by meese
-----------------------------------------------------------------------------

By the way, contact patch can affect tire wear, but it doesn't affect traction. The formula to calculate friction is:

Ff = μ Fn

Where Ff is the Force of Friction (usually calculated in Newtons), Fn is the Normal Force (weight of an object pushing down against a surface, also in Newtons), and μ is the Coefficient of Friction, based on the surface treatments of the two objects (but always less than 1.0).

Surface area doesn't appear in the formula at all, and so isn't relevant to the friction calculated, or to the traction we see on a bike (or car) tire. So a larger contact patch when leaned over has more to do with evening out tire wear than it does with increasing traction.

And that concludes the Physics lesson for this evening.
Yep, all true. However, tread patterns can affect the contact patch's grip, so that one tire with the same compound may grip better than another one given the same contact patch size.

A smaller contact patch will heat faster, even though the traction will be about the same. Same amount of "work" spread over a smaller area.

When in wet though, the smaller contact patch will be better than the large one. The larger patch will hydroplane much earlier.

All our engineering formulas are a great place to start, but the old saying applies:
" In theory, there is no difference between theory and practice, but in practice, there usually is."

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