Discussion on tire efficiency

[tasdrouille]

Originally Posted by Ernie Rogers

Hello, Racer,

I think I will try logic, and you point out the errors--

1. Low rolling resistance tires never wear well.
2. Tires with hard tread material always wear well.
3. Therefore low rolling resistance tires never have hard tread material.

What do you think?

Ernie, what do you base your assumptions on? LRR tires usually wear well provided adequate inflation pressure is maintained. Said inflation being usually higher that placard recommended pressure.

[CapriRacer]

Originally Posted by Ernie Rogers

Hello, Racer,

I think I will try logic, and you point out the errors--

1. Low rolling resistance tires never wear well.

..........

Remember it's a triangle and traction is the third leg.

So it is possible to make a tire with good RR and good wear properties, but it will suffer somewhat in the traction department.

This might be a good example of the complexity.

Originally Posted by NeilBlanchard

Hi Ernie,

The upcoming Michelin HydroEdge "Green-X" tires are LRR and they are rated 800 on the treadwear estimate.

When Michelin says these are good for RR, are they comparing these tires to regular replacement tires? If so, then they may get good wear, but their RR would be only be better than regular replacement ires, but not as good for RR as some OEM tires - which would have either wear or traction complaints (or both).

Also, keep in mind that most tire wear occurs in the cornering mode. So if most of your travel is in a straight line, even potentially poor wearing tires will wear well.

Originally Posted by Ernie Rogers

......

2. Tires with hard tread material always wear well.

.............

Again, keeping in mind that it's a triangle, harder rubbers tend to wear well.

Originally Posted by Ernie Rogers

.........


3. Therefore low rolling resistance tires never have hard tread material.

What do you think?

I think that is a good rule of thumb. The problem would be comparing tires with different families of rubber chemistry.

For example, different manufacturers will have slightly different rubber formulations - and the rule would apply within that family, but will have some variation between families.

This also means that even within a given tire manufacturer, if different families of rubber compounds are compared, you'll get different hardnesses compared to the wear / traction / RR triangle - such as the difference between an all carbon black formulation vs a silica / carbon black mixture.

Another factor to consider is that there are tricks that can be employed to improve the wear. Tread elements using large blocks wear better than those with small blocks. But this hurts snow traction.

Another trick would be to use more non-skid depth. An increase in original tread depth from 11/32nds to 12/32nds appears to increase the usable tread aby 11%, but you will get something less than that (Wear rates are not linear relative to tread depth.)

[Ernie Rogers]

Originally Posted by NeilBlanchard

Hi Ernie,

The upcoming Michelin HydroEdge "Green-X" tires are LRR and they are rated 800 on the treadwear estimate.

Thanks, Neil, for the info.

I don't know how you feel, I find it maddening that they didn't have the guts to give us the rolling resistance coefficient. How am I to know how this tire compares with the Michelin Energy MXV4 S8 tires they are putting on the high-mileage VW diesels?

Ernie

[Ernie Rogers]

Originally Posted by tasdrouille

Ernie, what do you base your assumptions on? LRR tires usually wear well provided adequate inflation pressure is maintained. Said inflation being usually higher that placard recommended pressure.

Hello, Tas, and all you Prius II drivers,

A Prius-driving friend was complaining about getting only 25,000 miles on a set of tires. (He drives like a maniac in my opinion.) I told him he would be much happier if he raised his tire pressure. I just got an email from him saying he has been running at 45 psi the last year, and he has been amazed by the increased fuel economy (Duh!) and the last tire set lasted for 7,000 miles past the tire warranty.

I think I get 30,000 miles past the tire warranty, but then my wheels and tires are sized more appropriately to the size of my car (a Beetle TDI). I bet Toyota will have that problem fixed on the next design.

Oh, about my assumptions--well, I don't know about the tire "triangle". I think it is an eternal law that if it's good for you, then you won't like it. Here's the same rule for food--

If that food isn't good for you, you can be darn sure it's delicious.

Despite Racer's learned remarks, I still believe--

Soft rubber = poor wear = good efficiency.

Just seems biblical to me. ("the meek will inherit the earth" sort of)

And, of course high pressure is kind of like one of the ten commandments.

Ernie

[Ernie Rogers]

Yes, Racer, I can see the triangle principle.

And, I think you have an excellent discussion here, that I can subscribe to. I appreciate your patience-- that's needed sometimes with me.

Ernie Rogers

Originally Posted by CapriRacer

Remember it's a triangle and traction is the third leg.

So it is possible to make a tire with good RR and good wear properties, but it will suffer somewhat in the traction department.

This might be a good example of the complexity.



When Michelin says these are good for RR, are they comparing these tires to regular replacement tires? If so, then they may get good wear, but their RR would be only be better than regular replacement ires, but not as good for RR as some OEM tires - which would have either wear or traction complaints (or both).

Also, keep in mind that most tire wear occurs in the cornering mode. So if most of your travel is in a straight line, even potentially poor wearing tires will wear well.



Again, keeping in mind that it's a triangle, harder rubbers tend to wear well.



I think that is a good rule of thumb. The problem would be comparing tires with different families of rubber chemistry.

For example, different manufacturers will have slightly different rubber formulations - and the rule would apply within that family, but will have some variation between families.

This also means that even within a given tire manufacturer, if different families of rubber compounds are compared, you'll get different hardnesses compared to the wear / traction / RR triangle - such as the difference between an all carbon black formulation vs a silica / carbon black mixture.

Another factor to consider is that there are tricks that can be employed to improve the wear. Tread elements using large blocks wear better than those with small blocks. But this hurts snow traction.

Another trick would be to use more non-skid depth. An increase in original tread depth from 11/32nds to 12/32nds appears to increase the usable tread aby 11%, but you will get something less than that (Wear rates are not linear relative to tread depth.)