Tire Issues?

[TomT]

You will often read that someone will say that their fuel mileage dropped when they got new tires and, therefore, the new tires must not be as efficient as the old... Some things to keep in mind in this regard:

1. New, Full-Treaded Tires Generate More Rolling Resistance Than Shallow-Treaded, Worn Tires

Tire rolling resistance gradually drops by about 20% during the life of a tire as the tread wears from its original molded depth to worn out. This can be attributed to the reduction in tread mass and rubber squirm, as well as subtle hardening of the tread compound during years of service and exposure to the elements.

While this gradual reduction in tire rolling resistance and minor increase in fuel economy may be too subtle to register during the tire's life on a tank-by-tank basis, the virtually instantaneous switch from worn tires to new tires (even if they are the same brand, type and size) will typically result in an increase in rolling resistance of about 20%. Since the automotive industry estimates a 10% increase in tire rolling resistance will result in a 1% to 2% decrease in vehicle fuel economy, drivers should expect to experience a potential 2% to 4% decrease in mpg.

2. New, Full-Treaded Tires Travel Farther per Tire Revolution Than Shallow-Treaded, Worn Tires

Vehicles are programmed with their Original Equipment (O.E.) tire's revolutions-per-mile to allow their odometers to calculate the distance traveled. Unfortunately, vehicle odometers aren't 100% accurate and the tire revolutions per mile will change (increase) as a tire's tread wears. This makes the vehicle to appear to travel further for a given unit of energy expended and increases the apparent fuel mileage even though the actual mileage may not have changed. Thus, again, older tires appear to give better fuel mileage than new tires...

While many of these individual differences may seem insignificant, it is easy to understand that when they are added together, the new tires may appear to reduce vehicle fuel economy. It also means that a Toyota Prius appearing to get 50.0 mpg just before replacing its worn-out tires with new tires of the same brand, type and size, might be reduced to registering just 47.25 mpg afterwards, even if all of the driving conditions were identical.

Remember, "your mileage may vary..."

 

[HIOJim]

My experience: 6 weeks, 1500 miles and I 'nicked' a curb at low speed in a parking lot. The sidewall was compromised and the tire was toast. It wasn't a slow leak, either.

When I got the Leaf I felt comfortable with not having a spare as I had a total of one flat with my Prius over 5 1/2 years of driving. Maybe I was just unlucky but it seemed to me that the Ecotopia's were a bit too easy to damage.

BTW, I will be buying a spare for my Volt.

 

[DaveinOlyWA]

pumping up the tire pressure probably gives a 3-5% boost in mileage on a Prius but when looking at energy expended to get that boost, its relatively small gain due the the ICE's ability to throw away 3 pieces of power for every one that it uses for motivational force.

now go to the Leaf which uses a "slightly" higher percentage of energy towards motivation and the same performance increase will probably only gain a few miles on a charge at best

as far as tires, well, i dunno. seems like the great low resistance tread is not helping the "fragile as glass" sidewall now is it?

 

[goohan]

My wife said she bumped the curb at less than 2000 miles and the tire was ruined. I'm sure we've done the same to other cars we've owned but it never resulted in a tire being destroyed. I think that the tires are not as durable as others, and would be hesitant to buy them when it comes time to replace.

 

[TEG]

7K miles on the original tires with no problems. Seems to have plenty of tread left.

 

[saywatt]

The tire issues I read on this thread and others are disconcerting. Are we Leafers just bad drivers or could there be a manufacturing/design defect with the Bridgestones? I scraped my tire on the curb while parallel parking the other day and a string of past posts drifted through my mind as I got out to look at the tire

Looking at the warranty book on the tires, they exclude so much I can't figure out what they do cover! :shock:

I posted earlier that I've been a Bridgestone fan for a long time and never had an issue. However, most have been on trucks and SUVs so perhaps they were designed without economy in mind. :?

 

[Drivesolo]

For most tires that come OEM on economy cars that are produced in high volume, you will find that the tires are generally poor quality (when compared to others in it's class). They are made at a low cost per unit by a tire manufacturer in high volumes and in some cases usually at only the one size of the OEM. Retailers also charge a slightly higher price than comparable tires not made specifically as OEM. This is intended to take advantage of owners purchasing the same exact tire when there is a need to replace one or more of the original tires (as long as it is not all 4). There are also sales to be had by some owners that feel that they should get the same exact tire when it comes time to change out all 4 tires.

 

[TomT]

Also remember that the tires that come OEM on a car are not necessarily the same as the exact same tire in the aftermarket. Such is the case with the EP422s that come on the Leaf; the exact same tire in the aftermarket is a different tire with subtle differences in specs and manufacturing. Compare the load ratings, for example, and you will see a difference between the two. It could very well be that the aftermarket 422 is a better and more robust tire than the Leaf OEM 422...

For most tires that come OEM on economy cars that are produced in high volume, you will find that the tires are generally poor quality (when compared to others in it's class). They are made at a low cost per unit by a tire manufacturer in high volumes and in some cases usually at only the one size of the OEM. Retailers also charge a slightly higher price than comparable tires not made specifically as OEM. This is intended to take advantage of owners purchasing the same exact tire when there is a need to replace one or more of the original tires (as long as it is not all 4). There are also sales to be had by some owners that feel that they should get the same exact tire when it comes time to change out all 4 tires.

 

[DaveinOlyWA]

well that would suck if they were not the same since i got one from Goodyear to replace the left front. i am thinking i should rotate both fronts to the back (i rotate every 5,000 miles and this would be about 3,000 miles early)

but it does make me think. i had the impression that the replacement tire was wider than the stock. i think i will do some side by sides when i rotate since i will have two wheels off at the same time.

 

[TomT]

The general rule of thumb is that the best tires should go in the back and if replacing only two tires, the new ones too should go in the back...

well that would suck if they were not the same since i got one from Goodyear to replace the left front. i am thinking i should rotate both fronts to the back (i rotate every 5,000 miles and this would be about 3,000 miles early)
but it does make me think. i had the impression that the replacement tire was wider than the stock. i think i will do some side by sides when i rotate since i will have two wheels off at the same time.

 

[saywatt]

For front wheel drive, I would want my best traction and control tires on the front not the rear.

The general rule of thumb is that the best tires should go in the back and if replacing only two tires, the new ones too should go in the back...

well that would suck if they were not the same since i got one from Goodyear to replace the left front. i am thinking i should rotate both fronts to the back (i rotate every 5,000 miles and this would be about 3,000 miles early)
but it does make me think. i had the impression that the replacement tire was wider than the stock. i think i will do some side by sides when i rotate since i will have two wheels off at the same time.

 

[TomT]

The reason for the industry recommendation has to do with stability, spinouts and fishtailing, and is equally applicable to front wheel drive cars...

For front wheel drive, I would want my best traction and control tires on the front not the rear.

The general rule of thumb is that the best tires should go in the back and if replacing only two tires, the new ones too should go in the back...

 

[ENIAC]

I read this very interesting post on the Garage Journal message board from a poster named wormwood. He claims to work for a tire manufacture. If you dont want to read the whole post, the second to last paragraph addresses the specific issue as to why the better tires should be mounted on the back.

You should ALWAYS mount the new tires on the rear. I know there are several people that have mentioned mounting them on the front because the front wear quicker. Yes the front tires wear quicker, but this is for safety and not how to stretch a set of tires. Tires are the most important safety feature on your car and should not be taken for granted.

I am in research and development for one of the large tire manufacturers. My job is to design and analyze tires. There are several things to consider when talking about this subject. There are two phenomenons at play here. There is Hydroplaning and there is viscoplaning. Hydroplaning is where the tire is lifter off the ground by the wave of water in front of the tire. This is directly dependent on Amount of water, Speed, Air Pressure, and the Major grooves in the tire and their ability to evacuate the water.

The other less known factor is viscoplaning. Viscoplaning is the trapping of a film of water under a tread block. The water forms a pocket under each individual block and keeps the block from touching the ground. This is highly dependent on the tread design. Smaller blocks is better. This is not very dependent on speed.

The last factor is the tread compound. This plays a large part in the traction of the tire. There are two ways a tires has traction. One is the formation of molecular bonds between the rubber and the road surface. This "sticking" provides great dry traction. The other traction mechanism has to do with the hysteresis of the rubber. Hysteresis is the loss of energy of a material when it is deformed. As the tire travels over the surface of the road, the texture of the road deforms the surface of the tread on a microscopic level. This deformation causes energy loss from the tire, hence the traction. This is one of the reasons why your car will slow down while coasting, drag and friction.

Now that I have explained the traction mechanisms, back to the original question. If you are traveling on a wet road and the good tires are on the back, this will put you in an under-steer condition and your vehicle will continue to slide straight ahead. The key point is that you can always hit the brakes in an under-steer condition. If the good tires are on the front, you will be in an over-steer situation and you will not be able to hit the brakes if you lose control.

I don't know about you guys, but I would like to be able to hit the breaks when my vehicle starts to slide.
Thank you for your thoughtful comments.

 

[saywatt]

Thanks, that is interesting and makes complete sense. My how things change. Back when front wheel drive was new (no age jokes please) it was the other way around—the idea being that when in a rear end skid, you would point the front wheels the direction you wanted the car to go and tap the accelerator and the skid would dissipate—therefore you wanted the best gripping tires on the drive wheels. So I guess what this tells me is to keep all 4 tires in good shape.

I read this very interesting post on the Garage Journal message board from a poster named wormwood. He claims to work for a tire manufacture. If you dont want to read the whole post, the second to last paragraph addresses the specific issue as to why the better tires should be mounted on the back.

You should ALWAYS mount the new tires on the rear. I know there are several people that have mentioned mounting them on the front because the front wear quicker. Yes the front tires wear quicker, but this is for safety and not how to stretch a set of tires. Tires are the most important safety feature on your car and should not be taken for granted.

I am in research and development for one of the large tire manufacturers. My job is to design and analyze tires. There are several things to consider when talking about this subject. There are two phenomenons at play here. There is Hydroplaning and there is viscoplaning. Hydroplaning is where the tire is lifter off the ground by the wave of water in front of the tire. This is directly dependent on Amount of water, Speed, Air Pressure, and the Major grooves in the tire and their ability to evacuate the water.

The other less known factor is viscoplaning. Viscoplaning is the trapping of a film of water under a tread block. The water forms a pocket under each individual block and keeps the block from touching the ground. This is highly dependent on the tread design. Smaller blocks is better. This is not very dependent on speed.

The last factor is the tread compound. This plays a large part in the traction of the tire. There are two ways a tires has traction. One is the formation of molecular bonds between the rubber and the road surface. This "sticking" provides great dry traction. The other traction mechanism has to do with the hysteresis of the rubber. Hysteresis is the loss of energy of a material when it is deformed. As the tire travels over the surface of the road, the texture of the road deforms the surface of the tread on a microscopic level. This deformation causes energy loss from the tire, hence the traction. This is one of the reasons why your car will slow down while coasting, drag and friction.

Now that I have explained the traction mechanisms, back to the original question. If you are traveling on a wet road and the good tires are on the back, this will put you in an under-steer condition and your vehicle will continue to slide straight ahead. The key point is that you can always hit the brakes in an under-steer condition. If the good tires are on the front, you will be in an over-steer situation and you will not be able to hit the brakes if you lose control.

I don't know about you guys, but I would like to be able to hit the breaks when my vehicle starts to slide.
Thank you for your thoughtful comments.

 

[planet4ever]

I read this very interesting post on the Garage Journal message board from a poster named wormwood. He claims to work for a tire manufacture.

... If you are traveling on a wet road and the good tires are on the back, this will put you in an under-steer condition and your vehicle will continue to slide straight ahead. The key point is that you can always hit the brakes in an under-steer condition. If the good tires are on the front, you will be in an over-steer situation and you will not be able to hit the brakes if you lose control.

Thanks, that is interesting and makes complete sense.

Well, it doesn't make complete sense to me. The conclusion I would draw if I believed that is that I should never rotate all 4 tires at all! Since the front tires get more wear, just leave them there until they are worn out, then move the rear tires to the front and buy two new tires for the rear.

Surely no one is going to argue that is really the best policy.

Ray

 

[DaveinOlyWA]

Well, it doesn't make complete sense to me. The conclusion I would draw if I believed that is that I should never rotate all 4 tires at all! Since the front tires get more wear, just leave them there until they are worn out, then move the rear tires to the front and buy two new tires for the rear.

Surely no one is going to argue that is really the best policy.

Ray

it actually is the best policy safety wise. but financially speaking, its not. rotating tires allows you to get maximum mileage. plus it also allows all tires to wear out about the same time. i used to just replace two tires at a time but that was mostly due to financial reasons. i prefer to do all 4 tires at once which is why i rotate every 5,000 miles. i do it myself so there is no cost involved.

if tires are rotated frequently enough, the difference in stopping power is minimized which lessens any safety issues. i get my oil changed on my Prius at the dealership and they run a multipoint inspection and i have never had tread depth vary more than a single millimeter and that is how it should be

i have been doing this on all my cars for years since my brother recommended it to me. he was a tire store manager and it was his job to sell tires, not get the maximum mileage of out them, but he still knew how to do it.

 

[DaveEV]

I read this very interesting post on the Garage Journal message board from a poster named wormwood. He claims to work for a tire manufacture. If you dont want to read the whole post, the second to last paragraph addresses the specific issue as to why the better tires should be mounted on the back.

I don't know about you guys, but I would like to be able to hit the breaks when my vehicle starts to slide.

I don't know if I can trust a tire guy who can't spell brakes right.

If you follow their advice to the letter, you'll have to rotate your tires ever 1,000 miles - otherwise you'll have noticeably more wear on the fronts and we all now know how that's a no-no.

If 2 of your tires are bald - then yes, you probably want to put the new ones in the front if you experience wet weather. If your tires aren't close to bald - I wouldn't sweat it. Otherwise you are likely to perpetually end up with mismatched tires forever - unless at some point you replace all 4 prematurely.

FWIW - I have found that new tires are typically much more squirmy/slippery than old tires when the road is dry - doesn't this then go against their own advice?

 

[aqn]

I read this very interesting post on the Garage Journal message board from a poster named wormwood. He claims to work for a tire manufacture. If you dont want to read the whole post, the second to last paragraph addresses the specific issue as to why the better tires should be mounted on the back.

I appreciate your contribution to this discussion, but I'm afraid I have some issues with the information from this "wormwood" guy.

You should ALWAYS mount the new tires on the rear.

I don't know... For me, words like "always" tend to disqualify statements about complicated subjects such as tires and vehicle dynamics and driving.

I know there are several people that have mentioned mounting them on the front because the front wear quicker. Yes the front tires wear quicker, but this is for safety and not how to stretch a set of tires. Tires are the most important safety feature on your car and should not be taken for granted.

I am in research and development for one of the large tire manufacturers.

That may be so, but that doesn't say anything about what he knows about driving.

My job is to design and analyze tires. There are several things to consider when talking about this subject. There are two phenomenons at play here. There is Hydroplaning and there is viscoplaning. Hydroplaning is where the tire is lifter off the ground by the wave of water in front of the tire. This is directly dependent on Amount of water, Speed, Air Pressure, and the Major grooves in the tire and their ability to evacuate the water.

The other less known factor is viscoplaning. Viscoplaning is the trapping of a film of water under a tread block. The water forms a pocket under each individual block and keeps the block from touching the ground. This is highly dependent on the tread design. Smaller blocks is better. This is not very dependent on speed.

The last factor is the tread compound. This plays a large part in the traction of the tire. There are two ways a tires has traction. One is the formation of molecular bonds between the rubber and the road surface. This "sticking" provides great dry traction. The other traction mechanism has to do with the hysteresis of the rubber. Hysteresis is the loss of energy of a material when it is deformed. As the tire travels over the surface of the road, the texture of the road deforms the surface of the tread on a microscopic level. This deformation causes energy loss from the tire, hence the traction. This is one of the reasons why your car will slow down while coasting, drag and friction.

This is all very reasonable, but has nothing to do with the myriads of conditions of how one can lose traction at one end: FWD or RWD, on/off throttle, too much/too little throttle/brakes, steering angle, etc.

Now that I have explained the traction mechanisms, back to the original question. If you are traveling on a wet road and the good tires are on the back, this will put you in an under-steer condition and your vehicle will continue to slide straight ahead.

Ummm... wait, so wet road and good tires on the back automatically equals "understeer"?

The key point is that you can always hit the brakes in an under-steer condition.

(There's that word, "always", again!) I hope he never enters a turn too fast, overdoes the braking, and starts to understeer off the road, and still want to "hit the brakes"!

If the good tires are on the front, you will be in an over-steer situation

OK, so again, good tires on front automatically equals oversteer?! I hope he actually meant "more likely to be in an oversteer situation". In which case, I would agree.

and you will not be able to hit the brakes if you lose control.

He's correct of course: the last thing one wants to do in a FWD in an oversteer (which is usually (not "always" ) caused by backing off the throttle too much or braking too hard mid-turn) and un-weighing the rears) is to back off the throttle or to hit the brakes. Stay in the gas, or even hit it, and pray that it will end well, 'cause back off or braking more is certainly not going to end well! Best of all, don't get into an oversteer in the first place: unless you have taken a turn a million times and know it like the nose on your face, always leave some room for error.

I don't know about you guys, but I would like to be able to hit the breaks when my vehicle starts to slide.
Thank you for your thoughtful comments.

Like I said, I hope he never overcooks a turn...

So, all that said, where should one put the newer tires, front or back, of a FWD car? The answer is, "it depends". (Like I said, I don't like "always".) To start with, as drees intimated, unless two of the tires are a lot more worn than the other two, as if two are brand new and two are bald, I wouldn't worry about it much. Certainly, in a LEAF, with its better than average weight distribution for a FWD car, of 56/44 F/R, I would claim that off-throttle oversteer is less of an issue than in a garden variety FWD with the typical 65/35 F/R distro.

If I must answer the question, I would say that if the person has done a fair amount of competitive driving and has experienced a wide variety of "marginal control" situations, I say put the newer/higher-traction tires in the front. For everybody else, the majority of U.S. drivers, I am not sure that it'd be better to put the better/higher-traction tires on the back. While it's true that doing so lowers the probability of encountering oversteer, it's also true that in a FWD car, the front tires do a lot more work: accelerating, braking, and turning, and as such it'd be safer to have the better-performing tires up front.

 

[saywatt]

aqn also makes good points. Yet what about the roles of the ABS & VDC systems. What is it those systems were designed to do in the Leaf and based on their design where should the better tires be placed (the manual does not say, of course)? Though not perfect by any stretch of the means, ABS/VDC can be a big help to the "average" driver. That said, they can be a hindrance to those with much driving experience. It is possible to I/O the VDC which I have done on several occasions in a BMW X5 when I realized the vehicle was not handling as I wanted it to on snow covered roads.

OK, I'm back to putting the better tires on the front (when that time comes) as I always have.

 

[DaveEV]

For everybody else, the majority of U.S. drivers, I am not sure that it'd be better to put the better/higher-traction tires on the back. While it's true that doing so lowers the probability of encountering oversteer, it's also true that in a FWD car, the front tires do a lot more work: accelerating, braking, and turning, and as such it'd be safer to have the better-performing tires up front.

Nice rebuttal - I would probably clarify the above statement to say "put the tires with the most tread on the end that wears tires the fastest" since the goal is to be able to replace all 4 at the same time...