Low Rolling Resistance Tires...Which is Best?

Rolling resistanve VS inflation

Ernie:
I suspect that your assumptions about rolling resistance VS inflation are not correct. You should check the link below. Their study would indicate that inflation, while not inconsequential, is not as much of a factor as the tire itself.

The quote below gives a good summary"

"For example in Figure 3 below, going from the tire with the highest
rolling resistance to the tire with the lowest rolling resistance within this test group can improve highway mileage by about 3.9 mpg, or about 12%, even at 25 psi, which is typically lower than the recommended tire pressure. On the other hand, going from 20 psi (low inflation) to 45 psi
(maximum recommended inflation) yielded about a 1.5 to 2.0 mpg difference in the fuel economy expected from each set of tires."

See:

http://www.ecosconsulting.com/downloads/2003-01-31_600-03-001CRVOL2.pdf

Also, take a look at the presentation made by Tim J. LaClair of Michelin. He indicates that the overwhelming majority of the rolling resistance comes from the hysteresis of the tire rubber.

http://www.energy.ca.gov/transportation/tire_efficiency/documents.../TIM_LACLAIR_MICHELIN.PPT

For me, the information which has been presented to the California Energy Commision gives a pretty clear picture: get those low rolling resistance tires. Your Energies are probably worth a 10% mpg premium vs the lousy Toyo tires I am currently running.

Which Toyo's are you running?

Toyo tires

Ruking:
they are Toyo "Spectrum". The negative points are that they are noisy, they don't stick all that well, and they seem to hurt fuel mileage. On the positive side they have lasted fairly well with the gravel road driving we do (only one flat last summer ), and the local dealer ( Les Schwab ) does give fairly good service.

I expect that my next set of tires will be lighter and will have a silica rubber tread compound, but because of the gravel road I want a long tread life warranty, which I know I will use. Possibly something from Michelin/Goodrich or Goodyear. Maybe Nokians. A friend who sells tires says tjhey are much better than the other brands he sells.

Using size 195/65/16 will give us 776 revolutions per mile.
Going up a size to 205/65/16 will give us 761 revolutions per mile. This would seem to help mpg, cornering and braking distances as well. I mentioned the friction only because going to a taller yet no wider tire, like 195/70/16 will give us 754 revolutions per mile. This is even better for mpg and reduce friction compared to the other two sizes I listed. If your goal is mpg then this is the best size of the three. If you drive hard and need more traction, then going to the 205/65/16 will not adversely affect mpg and will give you negligible improvements in handling and braking.

Dangerous_Dan said:

Ruking:
they are Toyo "Spectrum". The negative points are that they are noisy, they don't stick all that well, and they seem to hurt fuel mileage. On the positive side they have lasted fairly well with the gravel road driving we do (only one flat last summer ), and the local dealer ( Les Schwab ) does give fairly good service.

I expect that my next set of tires will be lighter and will have a silica rubber tread compound, but because of the gravel road I want a long tread life warranty, which I know I will use. Possibly something from Michelin/Goodrich or Goodyear. Maybe Nokians. A friend who sells tires says tjhey are much better than the other brands he sells.

Click to expand...

Looking on the Toyot site, it appears the Spectrum is an S or T rated tire depending on the size. What were some of the reasons for you going to an S/T rated tire from oem H rating? After much research, I went with a Toyo Ultra 800 on a Honda Civic. It is a T rated tire up from the S rated ones that come oem with the Civic. On the TDI I went with the H rated Toyo TPT's. I have put neither model on either car at this point.

Ruking:

the main reason was that the 800s die very quickly with our gravel road driving. My fuel log says that I got about 44 with the OEM Goodyears and about 44 with the 800s. I get about 40 with the Spectrums. This can easily be explained by differences in rolling resistance.

The OEMs and several sets of 800s lasted about 30K miles. The Spectrums look like they will last maybe 50K at a lower cost. Gravel roads really mangle tires. My experience has been that S or T tires stand up better to the gravel. I am sure that any tires I use will wear out quickly.

Thanks. Other TPT owners have said they had no mpg difference from oem type tires. So on the Honda I suspect I should get slightly better mpg with the Ultra 800's as I have the 30/31 rated Dunlop SP 20 FE's. I truly do not envy your gravel road journey. Based on your and my tire wear the gravel exacts a 3x-4x toll on tires: as I project 110 to 120k from my oem GY's. Best of luck.

I attended a Michelin OEM truck tire seminar at their US headquarters in Greenville SC.

Their bottom line as far as increasing MPG= Thin sidewalls and thin soft tread.

The flexing of the tread and sidewall creates heat which is lost energy.

SO - If you want maximum mileage buy the thinnest sidewalls and use the maxumum pressure.

As to tread- you will need to conduct a heat comparison (uisng a non-contact thermometer) to determine which tread creates the least heatl

Delete the thin 'soft' tread in my post above- minimal flexing is the key not softness

Tires

45,000 miles on 2002 Golf GLS. Put new Goodyear Comfort Treads on about 3k ago. Mileage has been no noticeable differance. Average between 48-50 mpg, 75% highway driving. Trip to NC on GY's got me 54 on the highway thru the mountains. Stock michelins worked well, but the GY's do ride a bit smoother and quieter. I think some of the factors to look at along with resistance is the sidewall stiffness and weight of the tire. I belive stock michelins are about 19 lbs, same as the GY's. Tire rack.com provided me with most of my info. By the way...my mileage gets done averaging about 70 mph highway. I don't baby her. Good luck.

Your suspicion my assumption is incorrect is correct

Well, yes, my assumptions are incorrect, but which aren't?

Thanks, Dangerous, nice to hear from folks that know what they are talking about. It's very difficult to argue against facts, but I will try--

About Tim LaClair's statement-- if you discount pavement effects, then ALL energy loss from the tires (= rolling resistance) is due to rubber hysteresis. But, from the Cummins report (cited in another thread about concrete pavement) we know that pavement properties can make a huge difference.

My viewpoint on rolling resistance may become more understandable if I tell you that I came into this subject from a background in bearing design. There (and in the railroad), you deal with rolling resistance between a metal roller and a metal track. Temperature and contact properties have little or no influence. In this simple case, rolling resistance theory is well worked out. I will describe rolling resistance from that viewpoint, and then we can discuss why it might be wrong.

Let's remind ourselves about the relationship between rolling resistance (force) and energy:

E = F x

So, the rolling resistance is the energy expended per unit distance. You can relate that to the energy loss per unit volume for each flexure of the tire material. (Distance relates to length and width of tire involved.)

The energy loss per volume is expressible like this:

Rolling resistance = C Estrain (1 - Cres)

C is some constant. Estrain is the strain energy, the work that goes into stretching and bending the rubber as the tire rolls through a unit distance. The last factor is the energy fraction lost (1 - what you get back) when the rubber unflexes. Cres is sometime called the coefficient of restitution, and is a function of the internal resistance.

All right, so what is the nature of Estrain? The strain energy is proportional to the load (or the amount of deflection). For a rubber tire, the deflection is inversely proportional to pressure, and essentially independent of rubber properties. But, the strain energy is proportional to the elastic modulus. The amount of strain, as I recall, is theoretically proportional to the fourth power of the wall thickness; however, experiments indicate that a dependence on first power of wall thickness works well for small deflections like in a tire. Putting all these factors together, the strain energy has this form:

Estrain = k W t Em /P

K is just another constant, W is the load (weight) on the tire, t is the wall thickness (could also be tread thickness), Em is the elastic modulus, and P is the tire pressure.

Okay, then you might ask, where did I go wrong? The dependence of rolling resistance on pressure is much less than this. (I did some experiments last summer and posted them here.) I think the answer is that the two rubber properties included, Em and Cres, vary a lot with temperature. When tires lose more energy, they get hotter. With increasing temperature, Em gets smaller and Cres gets bigger. So, lower pressure tires run hotter, that helps to keep the efficiency up.

Did we just discover another reason why you get better mileage in summer? I think so.

Oh, and I heartily agree with the idea that buying efficient tires is about the most important thing you can do.

I hope I didn't make too many mistakes going through that math maze.

Ernie Rogers

Dangerous_Dan said:

Ernie:
I suspect that your assumptions about rolling resistance VS inflation are not correct. You should check the link below. Their study would indicate that inflation, while not inconsequential, is not as much of a factor as the tire itself.

The quote below gives a good summary"

"For example in Figure 3 below, going from the tire with the highest
rolling resistance to the tire with the lowest rolling resistance within this test group can improve highway mileage by about 3.9 mpg, or about 12%, even at 25 psi, which is typically lower than the recommended tire pressure. On the other hand, going from 20 psi (low inflation) to 45 psi
(maximum recommended inflation) yielded about a 1.5 to 2.0 mpg difference in the fuel economy expected from each set of tires."

See:

http://www.ecosconsulting.com/downloads/2003-01-31_600-03-001CRVOL2.pdf

Also, take a look at the presentation made by Tim J. LaClair of Michelin. He indicates that the overwhelming majority of the rolling resistance comes from the hysteresis of the tire rubber.

http://www.energy.ca.gov/transportation/tire_efficiency/documents.../TIM_LACLAIR_MICHELIN.PPT

For me, the information which has been presented to the California Energy Commision gives a pretty clear picture: get those low rolling resistance tires. Your Energies are probably worth a 10% mpg premium vs the lousy Toyo tires I am currently running.

Click to expand...

moondawg said:

This may be true if you change sizes while staying with the same brand/model of tire. If you switch to a tire that has a lower rolling resistance, you may not increase friction overall.

If you go to a slightly wider, moderatly taller tire, the increase in engine efficiency at a given speed may be enough to counteract any increase in friction.

I only had one tank of similar weather/fuel conditions to make a comparison when I switched tires. I did not lose any fuel economy by making the switch, but I'm not sure I gained any either. Also, I have not checked my tire pressure since I got the tires installed, I've just been using what the garage put in there. I may have some gain by running higher psi.

But as I stated earlier, the increase in traction worth a loss in mpg for me. If I find that the larger tire size doesn't help at all, I'll probably go back to stock in 80k when these tires wear out.... but it will definitely be stock sized WRs.

moondawg

Click to expand...

Moondawg - digging up an old one here...

How do you like your Nokian's? Still good?

Mileage still ok?

Will be taking off my studded snow tires soon and looking for what to replace them with.

Would also like to know how the Nokians are doing. I'm thinking of buying them.

Does anyone have a MPG report using the Michelin Pilot Exalto A/S tires?

Fix_Until_Broke said:

Moondawg - digging up an old one here...

How do you like your Nokian's? Still good?

Mileage still ok?

Will be taking off my studded snow tires soon and looking for what to replace them with.

Click to expand...

Sorry... been busy with other sites and things ... I got a camera for Christmas!

The Nokians are freeking awesome. I will never buy another tire for a general purpose vehicle.

They've been wearing great, providing great mileage, and holding air really well. My michellins would need to be "topped up" every couple of weeks. The WRs haven't been filled in 6000 miles! I checked them all the other day and were all above 48 psi. (I started them at 51)

The traction in the wet and the snow has been unbelieveable. I've never used anything other than a standard M/S rating, so I don't know how they compare to dedicated snows. The tires slip alot less in the snow, and when they do slip they seem to keep the car going in the right direction...somehow. I haven't been able to get them to hydroplane yet. We got a buttload of rain the other day... and aside from my camera and my TDI, my favorite hobby is driving through puddles near the side of the road. If you've ever done this, you know that it can nearly rip the wheel from your hand as your car pulls to the right (left in England and Japan) Anyway, it was nearly impossible to get the tires to pull... they were firmly planted on the ground. Nice.

In short: I'm getting them again when these wear out (too soon to tell when that will be) and I'm getting them for my Dakota when those wear out.

moondawg

Soft is good in tire rubber

Hello, JVC,

Are you still out there? I don't know if this is still of interest, but soft rubber makes lower rolling resistance. See my post with the formula for strain energy. Notice that the strain energy, which is what causes rolling resistance, is proportional to the elastic modulus, Em. This is the stiffness constant, so stiff rubber causes more energy loss, all else being equal.

Also, it's important to remember that the tire deflection is essentially independent of how stiff the rubber is-- the tire is held up almost entirely by the internal pressure. And, that is why high pressure is good, it means less tire deflection.

Ernie Rogers

jvc said:

Delete the thin 'soft' tread in my post above- minimal flexing is the key not softness

Click to expand...

Has anybody considered using larger diameter tires on the rear axle only? I know it would look funny but would it lower friction? Fewer rpm/mile = less friction?

cekretkod said:

Has anybody considered using larger diameter tires on the rear axle only? I know it would look funny but would it lower friction? Fewer rpm/mile = less friction?

Click to expand...

No, I think most people just put them on all 4 and deal with the odometer being off. The gain from just replacing the rears would be infinitessimal, I believe. Plus, it would make rotation a pain... especially for directional tires like the WR.

moondawg

Nokian NRH tires ... initial impression

OK, I just went and put a set of Nokian NRH tires on my 740 Volvo, mostly because the light truck tires on it started to come apart...

Initial impressions:
1) These are the quietest tires I have ever driven on!
2) They have very good cornering traction.
3) It poured today and they were very good on wet roads.

I'll know how they affect mileage in a month or so. From my downhill roll test I suspect they are pretty good on that score.

The one remaining question is wear rate. Ask me in two years...

I just put Firestone Affinity LH-30 with Uni-T on my wife's 2003 Jetta last week. WOW!!!!!!!!!! Tires pressure set at 39 all around. The car steers easier, the car handles much more responsively and it rides smoother then a baby's butt! Did I just say that? Seriously, I am very impressed.

I put some Hankook Ventus HII H405 on my car, aparently they have a silica compound and "The stylish unidirectional grooves enhance steering stability, rapid drainage, and reduced rolling resistance." I bet I'm getting 80mpg with these things on in the 225/45-17 size! (I run the fronts at 40psi and the rear at 38psi now).

Seriously though, has anyone run these for a few tanks that has a really good baseline? I've only got two and a half tanks through them so far, and I honestly don't seem to be doing any worse than I was with 195/65-15's on steel rims. (Perhaps my driving style has something to do with this, I never actually try to get the best possible mpg a person could). My "new" rims reportedly weigh in at 23lbs, as do the tires themselves (UPS says so). I know the traction has improved for me, so I can't see how I am going to get the same mpg as I was before these tires, as traction doesn't equate to low rolling resistance does it? Maybe someone can sort me out.

I would love to do a long highway trip to see what I would be able to get with these puppies, but all my long trips are acompanied byt two children, my wife and a roof top carrier...no where near ideal. I think I could handle the roof top carrier though.

Don't get your hopes up!!

MYLittleTDI said:

I just put Firestone Affinity LH-30 with Uni-T on my wife's 2003 Jetta last week. WOW!!!!!!!!!! Tires pressure set at 39 all around. The car steers easier, the car handles much more responsively and it rides smoother then a baby's butt! Did I just say that? Seriously, I am very impressed.

Click to expand...

This is how it works.
Tires wear very gradually as a result the degradation of steering, handling and smoothness is gradual. We do not notice it and if we do not think about it we may think the tires we took off were always like that from new.
They were not.
I have seen the cheapest tires put on a vehicle that had worn tires and the steering etc. is always better..
Its what the tire is like after some use that determines if they are better than most..

For a smooth, easy steering tire, any cheap new tire will temporarily work.. Used car dealers know this trick too..

raybo said:

Does anyone have a MPG report using the Michelin Pilot Exalto A/S tires?

Click to expand...

I just put these on my Jetta. No difference from the stock Continentals. Just turned in 53.4 mpg on the Jetta last weekend (Not due to the tires). Nice tires and very quiet.

Hey Lightflyer1, Please keep us updated as to how these tires handle in the rain as they get older.... Thanks.....

Ernie,

I am just curious on the 205/60 Michilen Energy tires. Were there any clearance issues for this tire on the car since it was approximately 1" taller? Will I have any issues mounting up a tire this tall? I am looking at the 94H SL on Tire Rack. It shows the tire max psi at 50 psi. Is this the same tire?

Also what method do you use to keep track of your miles and mileage since the ODO is now off with the larger tire. Thanks, this has been a very helpful thread.

Longsnowsm

I got the Continental 205/60s and had no problem getting it mounted by the tirerack-recommende guys. Clearance also hasn't been an issue.

I used tirerack's data on the number of revolutions per mile to calculate the difference and it was only like 1.5%, so I'd figure it's not really worth all the extra calculation.

So the the tire has been performing like a dream. According to tirerack, this tire is rated much higher than the Michellin's MXV4 and MXV4+ tires. According to Continental's own data sheet, this tire outperformns my OEM tires in terms of rolling resistance too.

I'm extremely satisfied and so far my mpg hasn't really changed.

Alex

Alex,

Thank you very much for the info. I wanted to make sure I wasn't going to run into any issues. I like the idea of going with the larger diameter tire. How do you keep track of your miles and mileage since the ODO is off? Do you use a GPS or is there something else out there for this? Thanks.

Longsnowsm

I think according my calculations, (# of revolutions per mile of new tire) / (rev of old tire), the difference was only 1.5%, so I just didn't bother worrying about the ODO and Speedo error.

I mean, the speedo is 3 - 5% off from the factory anyway, right? If that's good enough for VW and DOT, that's good enough for me.

Gotcha, What was the diameter of the tire you chose? I went out to the Continental site, but couldn't find any data on low rolling resistance. Do you happen to have a link? I found a link for Green Car Congress, but the data is all from 2003 I think and a lot has changed since then.

Longsnowsm

Here's the website
http://www.conti-online.com/generat...ance_touring/conti_pro_contact/master_en.html

Here's the datasheet
http://www.conti-online.com/generat.../conti_pro_contact/printable_datasheet_en.pdf

The number of revolutions per mile data I got from Tirerack.