Physics question

[Lawman]

Excluding acceleration and deceleration, is speed a factor in tire wear for straignt line travel? I'm thinking yes for the rear becuse it's powering the bike but how about the front?

[OoPEZoO]

I have no math to back it up, but I would think speed definitely has an effect on tire wear.

 

Higher speed = higher operating temps = more rubber left on the road

 

To what extent......beats me, I haven't seen a physics book in over 10 years

[jpalamar]

Interesting question! In a perfect/theoretical world the adhesion between road surface and tire would be perfect. But, since we are not in a perfect world... beats the heck out of me!

[Mister Tee]

higher temps = higher pressure = less contact patch, so that could offset the heat factor of the rubber. And tires are vulcanized anyway, so they are relatively unaffected by normal operational temperatures.

 

I suspect that while speed may be a factor, it's probably minimal. On the track, at very high speeds (150 mph+) my tires wear quickly, but mostly on the sides. And race tires are run at low initial inflation pressures to allow for heat cycling, which causes a LOT of wear.

 

On the freeway, where I might commute an average of 80 - 90 mph (yeah, there are sections of I-5 where the flow of traffic actually goes that fast) I'll still get 15,000 miles out of a set of Pilot Powers on a sportbike.

 

I think that by far, the biggest factor in tire wear is pressure.

[smiller]

is speed a factor

There you go again...

[Firefight911]

I would think that speed, in and of itself, would not be a factor. But, with speed in the real world comes increased friction due to resistance to air. The engineer types will be able to confirm/correct this but isn't it with a doubling of speed there is a fourfold increase in resistance or friction?

 

This would thereby cause an exponential increase of horsepower to overcome the resistance and would thereby require more "push" against the roadway and tire interface. This push is increased friction which would speed the wear of the tire.

 

It might have been easier to ask dino or synthetic!

[tallman]

Don't the wheels go round more times when you go faster?

There you go.

 

Just kidding.

 

Slide your hand slowly across the street.

Now slide your hand rapidly.

With the change in force, there is a resultant change in friction.

More friction, more wear.

Not convinced?

Climb a rope wearing gloves, slide down.

Now take off the gloves and climb the rope.

Mitch will now explain why I'm wrong.

[Albert]

My guess is speed will be a factor. I suspect that the major contributor to tire wear in a purely straight line situation would be the flex in the side wall at the contact patch location. There will be an attendant "squirm" of the tire in the patch area due to this distortion. Higher speeds would mean a higher frequency for the distorted portion of the tire. Is fatigue in the cords involved? I dunno.

 

Probably heat will build up more quickly due to a greater rate of local tire distortion (but I dunno). I guess I'm just throwing out more questions since I'm no hyperelastics expert nor a tire guy of any way, shape or form. I can tell you there's a bit of black art that goes into truly understanding tire technology and analyzing tire performance is no trivial undertaking. Maybe one of those types is hanging here.

[Joe Frickin' Friday]

I would think that speed, in and of itself, would not be a factor. But, with speed in the real world comes increased friction due to resistance to air. The engineer types will be able to confirm/correct this but isn't it with a doubling of speed there is a fourfold increase in resistance or friction?

 

Correct.

 

Maintaining a higher forward speed for the vehicle as a whole requires more power/torque at the rear wheel, which will accelerate wear on the rear tire.

 

Front tire isn't used for power delivery, but it experiences increased aero drag and increased rolling resistance at higher speed. Both of those factors tend to slow the wheel's rotation; the fork pushes the wheel forward, but it is friction with the road surface that induces rotation, and so you can reasonably expect more front tire wear too at higher speeds. How much more? Hard to say. Probably not a lot when compared with the effects of acceleration/deceleration on wear.

[T__]

Excluding acceleration and deceleration, is speed a factor in tire wear for straignt line travel? I'm thinking yes for the rear becuse it's powering the bike but how about the front?

 

 

Billy, speed in & of itself (within reason) probably doesn’t add much measurable tire wear.. As mentioned the power from the drive train into the rear tire to keep it at higher speeds would probably add some added rear tire wear.. But you said speed ONLY so assuming the speed was attained from other than driving the rear tire probably not a lot of extra wear.. Probably higher speeds would add some tire heat & that could help or hurt the tire wear depending on the tire pressure to start with..

 

I would imagine how constant of a straight line you could ride with very little handlebar input would decrease tire wear & lots of side to side movement or lane changes would measurably increase tire wear..

 

Probably the big factor would be road surface abrasiveness & road camber.. A very flat very smooth road surface would vastly improve tire wear & a very course highly cambered road would lead to earlier tire wear.. (way more than speed itself would)

 

Slow SPEED could be a factor as the motorcycle isn’t real stable at low speeds so would take more front wheel input to keep the bike on line.. If you look at the cross-section of a motorcycle tire you would see it is round not flat across like a car tire.. That basically means the you have many side by side tires hooked together with each of those side by side tires spinning the same speed (RPM) but covering different distances for every revolution.. So as you lean the bike to steer it you keep going from one circumference to another & that means scrubbing of rubber as one section speeds up or slows down to match the one on either side of it.. Motorcycle tires wear as they lean just no way around it..

 

Very high speeds could accelerate tire wear as you would probably get tread distortion & tread walk (those would both add to tire wear)..

 

Obviously braking,, accelerating,, cornering,, low tire pressures,, overloading would be the biggest offenders.

 

 

Twisty

[RFW]

Excluding acceleration and deceleration, is speed a factor in tire wear for straignt line travel? I'm thinking yes for the rear becuse it's powering the bike but how about the front?

Yes. Increased speed results in increase wear, and because the rear is powering the bike, there is tire to road slippage at the rear...a small amount to be sure, but it exists and gets worse with increasing speed, because increased speed requires increased thrust.

[velomoto]

Excluding acceleration and deceleration, is speed a factor in tire wear for straignt line travel? I'm thinking yes for the rear becuse it's powering the bike but how about the front?

As others pointed out - increased speed means increased friction and higher temps which leads to faster wear. Also as others pointed out, the front is much less affected than the rear if the bike is traveling a straight line. Driving a MC in a straight line at high speed is boring so the reality is that this situation seldom occurs for extended times. Instead the fast moving motorcycle is thrown thru curves where the front tire wears as fast or faster than the rear tire!

[ShovelStrokeEd]

Yes, speed plays a big part. Aerodynamic forces increase as the square of the change in velocity. The motor's power requirement to maintain that speed increases likewise. Below about 60 mph, it is not all that dramatic but, above that, it becomes significant. The only way to transmit that power requirement is through the rear tire. Increased slippage can and does result.

 

At the extremes it really gets hairy. When I worked with Luftmeister back in the bad old days, we ran 207 mph on the salt according to the certified clocks they were using but, our data logger indicated an RPM equivalent to 217 mph. That's 10 mph of wheelspin. Granted, the traction on the salt is not what you have on pavement and that had some bearing on it. Again, the data logger showed next to no wheel spin till about 180 mph and then it steadily increased.

[Joe Frickin' Friday]

Yes, speed plays a big part. Aerodynamic forces increase as the square of the change in velocity. The motor's power requirement to maintain that speed increases likewise.

 

Power is drag * speed, so power goes as the cube of speed; if you can do 100 MPH on 50 HP, 200 MPH will require 400 HP.

[ShovelStrokeEd]

You are right, of course. I could have been clearer about the relationship.

 

One of the reasons, btw, that very few motorcycles can manage >200 mph speed given that even the slipperiest of them has a drag coefficient similar to that of a school bus.

[T__]

You are right, of course. I could have been clearer about the relationship.

 

One of the reasons, btw, that very few motorcycles can manage >200 mph speed given that even the slipperiest of them has a drag coefficient similar to that of a school bus.

 

 

Ed, aerodynamic drag increases with the square of speed,, using drag coefficient is a very poor way of comparing vehicles or power to reach speed.. All that is is the comparison of frontal area to the air resistance (well sort of)..

 

 

 

Using drag coefficient is very misleading.. If you hold a paint stirring stick (with a drag coefficient of (.9) out a car window traveling 60 mph & also hold a 4ft X6ft tapered wedge with a drag coefficient of (.4) out the same window which one will take more power to push through the air? Yes that large 4x6 piece.. It has a lower drag coefficient so why would it take more power? That is just drag coefficient not the actual air drag..

 

 

 

A much better way to look at the ACTUAL air drag (not just the ratio or frontal area to air resistance) is to use DRAG AREA.. We use that lot on the auto industry as a true measure of what it takes to push an object through the air.. A smaller compact vehicle will be somewhere in the 5 area with a large pickup truck somewhere in the high 20's..

 

 

 

Having the drag coefficient of a school buss isn't too bad if the thing you are sending through the air is the size of a pin.. Even though a motorcycle has a higher drag coefficient than a sleek car it still has a much smaller frontal area..

 

 

 

I know just nit picking but true..

 

 

 

Twisty

[BFish]

Again, the data logger showed next to no wheel spin till about 180 mph and then it steadily increased.

 

know what you mean, gawd i hate that!

 

[Matts_12GS]

Again, the data logger showed next to no wheel spin till about 180 mph and then it steadily increased.

 

know what you mean, gawd i hate that!

 

 

And that's just his 4X4 truck!

[ShovelStrokeEd]

I'm aware of all that. My point being that at speeds above 60 mph, the power to overcome aerodynamic drag becomes a major component of the power required to get the bike down the road. The other probably being pumping losses in the engine itself. These diminish as the throttle is opened though. Point is, my bike is just about as slippery as any out there and would have a pretty low, comparative frontal area if I was willing to tuck in more. With all that, the difference between a 65mph cruise and an 83 mph one is nearly 3 mpg in fuel consumption. Not a perfectly good indicator of course as engine efficiency is different at 3900 RPM compared to 5000 but it works for me. At a steady 100, I'm down to about 30 mpg. I haven't been able to find a place to run a sustained 175 yet but just getting up there and back down will move me a bar or so on my fuel gauge, probably somewhere in the low 20's.

[UncleJetski]

Not being a physicist, but considering how you asked the question, here's my "dumb" answer: The faster you go, the sooner you'll wear out your tires.

 

That is, if you go 100 mph for an hour, you'll put 100 miles on your tires in an hour. If you go 50 mph, you'll put only 50 miles on your tire. Ergo, twice the wear in the same amount of time. (I told you I wasn't a physicist!)

[waylap]

Worrying about tire wear based on speed or anything else is like worrying about your turn signals bulbs burning out so not using them unless really really needed. Use them both, often and with deliberation.

[JustKrusen]

I met a guy last weekend that had an identical RT to mine including color. After talking for a while I asked how many miles he had on his. He had 7500. The rear tire looked like new so I asked if it was the second tire. It was the original Road Pilot. My Road Pilot was replaced at 7500 because it was worn out. We live and ride in the same neighborhood but I take many trips at 80 mph. He did mostly local riding and never went over 70.

[notacop]

But of course. Rub your hand slowly over a surface, no heat, nice!

Rub your hand quicly over the same surface and you build up heat, heat eats tires.

Had a truck driver tell me once that Big rig tires go away more quicly in the rail though. Why would that be?

[velomoto]

I met a guy last weekend that had an identical RT to mine including color. After talking for a while I asked how many miles he had on his. He had 7500. The rear tire looked like new so I asked if it was the second tire. It was the original Road Pilot. My Road Pilot was replaced at 7500 because it was worn out. We live and ride in the same neighborhood but I take many trips at 80 mph. He did mostly local riding and never went over 70.

Ed, there lots of other factors besides speed which could have a much greater impact on tread life than the 10mph difference you listed. His riding style could be much easier on the tire. Perhaps he rides a greater amount of time on roads where the pavement is smoother or with many fewer trafic lights or stop signs. Another consideration is that I've read that the color for the RED 12RT's raises the tire temperature by 5 degrees...

[JustKrusen]

Actually my point was that he does most local riding with very little interstate. My miles are mostly interstate.

[motoguy128]

Had a truck driver tell me once that Big rig tires go away more quicly in the rail though. Why would that be?

 

Do you mean rain? Intersting scenerio. You would think that wear would reduce because the water reduces the coeffecient of friction with the road surface. However, a big rig can weigh as much as 100,000lbs with 18 tires, that's still just over 5500lbs per tire, about 8-10 times the loading as a motorcycle tire, and 4-6 times that of a passenger car. Rain will increase drag, so more power is needed to maintain speed. More often, with rain there is wind. Windy conditions will also increase drag and add more steering inputs and trailer sway.

[doc47]

Ed, what are "pumping losses"??

 

Seems a big factor here is whether one is going in a straight line or turning. More turns at a given speed = more acceleration (maintaining angular momentum) = more deforming of tire, etc., etc.