Barry's Tire Tech: New/Revised articles

I learned something...and it is counter-intuitive to me.

"2) Using a wider and larger diameter tire can improve RR by 6%. This might have additional benefits as the effective drive ratio is also reduced!"

cool to know...I always thought wider tires had higher RR.
 
DriveHard said:
I learned something...and it is counter-intuitive to me.

"2) Using a wider and larger diameter tire can improve RR by 6%. This might have additional benefits as the effective drive ratio is also reduced!"

cool to know...I always thought wider tires had higher RR.
Click to expand...
ok what about the larger tire weighing more? That is definitely going to hurt rolling resistance..
 
researcher said:
ok what about the larger tire weighing more? That is definitely going to hurt rolling resistance..
Click to expand...

While weight might effect acceleration and braking in a negative way, I don't think it would have much effect on steady state fuel economy. Any extra fuel used in getting the tire rolling is gotten back on a longer coast out due to the greater rotational inertia. My guess is as far as fuel economy goes, the weight is a wash, or small enough of an effect it doesn't register.

I don't think the weight of the tire would change RR hardly at all...probably not even enough to measure.
 
researcher said:
ok what about the larger tire weighing more? That is definitely going to hurt rolling resistance..
Click to expand...
Naw. wheel/tire mass only matters during acceleration. At a constant speed it doesn't matter so much. RR is the degree is "squish" where a section of tire meets the road surface. A wagon wheel has very low rolling resistance because the wheel doesn't deform. Like a wagon wheel, low profile tires have reduced rolling resistance because the sidewalls are stiffer vs a taller tire with the same load rating. A flat tire causes a vehicle to slow down rather quickly. That's an example of maximum rolling resistance.

My two cents
 
I enjoyed reading this article:

Barry's Tire Tech

Barry talks about tire and rim balance, uniformity and runout.
barrystiretech.com

....Side Note: Rims also have harmonics and non-uniformity, but you can directly measure non-uniformity as run out. About 0.001" of runout ~= 1 pound of force variation. Again the 1st harmonic's peak could be in a different location than the composite's peak....
Click to expand...

Have OEMs ever considered manufacturing wheels with a "low spot" of 0.006" (or higher) , to facilitate the effectiveness of match mounting for improving the uniformity of the tire/wheel assembly? If a tire with 18lb of radial force is match mounted to a wheel having a 0.006" "low spot", won't the resulting tire/wheel assembly have a final RFV of 12lb ?
 
SubLGT said:
I enjoyed reading this article:

Barry's Tire Tech

Barry talks about tire and rim balance, uniformity and runout.
barrystiretech.com



Have OEMs ever considered manufacturing wheels with a "low spot" of 0.006" (or higher) , to facilitate the effectiveness of match mounting for improving the uniformity of the tire/wheel assembly? If a tire with 18lb of radial force is match mounted to a wheel having a 0.006" "low spot", won't the resulting tire/wheel assembly have a final RFV of 12lb ?
Click to expand...

It was so long ago, but what I remember is someone telling me that they were doing it and the valve hole was located at the wheel's low spot. I've since been told that what I remember is incorrect - except, how would you make the valve hole the low spot if you didn't already know where the low spot was going to be?

What has happened in the meantime is that the OEM's have lowered the specs so far that it's unnecessary and the normal process to make the wheel is used, then the low spot measured and marked - which means it is usually not at the valve hole. I suspect the reason they still mark everything is because everyone had all the equipment in place so the OEM's just kept the marking requirement even though it shouldn't be needed any more.

But the problem you are alluding to is that in the aftermarket, tire manufacturers set their own specs. They are all trying to lower the values, but it's expensive and requires making major changes to the production process. Of course, the OEM's don't care - they have something that works for them.
 
interest reading for sure, retired + reading on line beats crap TV ANYDAY IMO!!!!
 
DriveHard said:
I learned something...and it is counter-intuitive to me.

"2) Using a wider and larger diameter tire can improve RR by 6%. This might have additional benefits as the effective drive ratio is also reduced!
Click to expand...

This is counter intuitive to me too as I have visited this issue in my choice of car.

When I bought my current car the annual road tax was based on CO2 emissions with a break point at 150g/Km after which the tax went up by 25%. There was a choice of tyre sizes as shown below and the wider tyre option had greater emissions and higher tax. What could cause that except increased rolling resistance as the cars were otherwise identical. There was a 3rd option of 225 tyres and that had even higher CO2 emissions of 159g/Km.

I bought the one with 195 tyres which has saved me a fair amount of tax over 9 years of ownership.

CO2.jpg
 
DriveHard said:
While weight might effect acceleration and braking in a negative way, I don't think it would have much effect on steady state fuel economy. Any extra fuel used in getting the tire rolling is gotten back on a longer coast out due to the greater rotational inertia. My guess is as far as fuel economy goes, the weight is a wash, or small enough of an effect it doesn't register.

I don't think the weight of the tire would change RR hardly at all...probably not even enough to measure.
Click to expand...

Is that why I see semi trucks moving to single large WIDE tires instead of doubles?
 
barryh said:
This is counter intuitive to me too as I have visited this issue in my choice of car.

When I bought my current car the annual road tax was based on CO2 emissions with a break point at 150g/Km after which the tax went up by 25%. There was a choice of tyre sizes as shown below and the wider tyre option had greater emissions and higher tax. What could cause that except increased rolling resistance as the cars were otherwise identical. There was a 3rd option of 225 tyres and that had even higher CO2 emissions of 159g/Km.

I bought the one with 195 tyres which has saved me a fair amount of tax over 9 years of ownership.

View attachment 218399
Click to expand...
I'd imagine the increase in unspring mass due to larger* rims uses more fuel during the acceleration phase of the test cycle.

*Typically lower profile tires come with larger rims which depending on the manufacturing method can weigh more.
 
barryh said:
What could cause that except increased rolling resistance as the cars were otherwise identical. There was a 3rd option of 225 tyres and that had even higher CO2 emissions of 159g/Km.
Click to expand...
Might be air resistance! Pedantic, but it's not the same as rolling resistance. My cars have little spoiler "lips" in front of the tires, on the rocker panels or fenders. Like little mudflaps but on the other side.
 
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