easy way to check for low rolling resistance

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I have low rolling resistance tires in all my cars now and I noticed that sidewalls are cold (near ambient temp) and treads are slightly warm (~10F over ambient at front tires, less at rear) after driving at moderate speeds. I didn't take measurements with old tires, but remember them much warmer.

Makes sense as low rolling resistance means less energy converted to heat in tires.

Anyone has tire temp measurements to compare?
 
Why not find a flat parking lot (like at work) where you can leave your car in neutral, all warmed up (for warm wheel bearings etc) then push your car with a bathroom scale.
 
Isn't rolling resistance at some higher speed more important? I tested various tire pressures by starting at a dead stop at the top of a hill. When you coast (standard tranny in neutral) down you spend two miles around 40 miles per hour. I found that 40psi worked best. Over 40 showed no increase in distance. I don't know if this is the best test but it's the best I could come up with.
 
Originally Posted By: eljefino
Why not find a flat parking lot (like at work) where you can leave your car in neutral, all warmed up (for warm wheel bearings etc) then push your car with a bathroom scale.


I guess I should have made it more clear I was talking about tire rolling resistance. That is a fraction of total rolling resistance.
 
Originally Posted By: eljefino
Why not find a flat parking lot (like at work) where you can leave your car in neutral, all warmed up (for warm wheel bearings etc) then push your car with a bathroom scale.



crackmeup2.gif
Good one - best post of the Month!
 
You're assuming that friction is the source of rolling losses (hence heat could be an indicator of rolling losses). It's not--hysteresis is the main source of rolling losses.

I haven't done this sorta test with car tires, but I have with bicycle tires (when you're dealing with 1/3 to 1/2 of 1HP, you have to sweat this stuff...); bottom line, temperature really doesn't tell you much about Crr. Short of getting on a dyno and measuring losses that way, you'd have to do some coast down tests to measure the difference. Coast down tests are tricky, though, when trying to control for all of the other variables.
 
Reminds me....my wife wanted something for her birthday that went from 0 to 200 in under 5 seconds. I got her a bathroom scale.
 
Originally Posted By: eljefino
Why not find a flat parking lot (like at work) where you can leave your car in neutral, all warmed up (for warm wheel bearings etc) then push your car with a bathroom scale.
Don't let your boss see you doing that.
 
Originally Posted By: Boomer
Reminds me....my wife wanted something for her birthday that went from 0 to 200 in under 5 seconds. I got her a bathroom scale.


How did she take that one? lol
 
Originally Posted By: JOD
You're assuming that friction is the source of rolling losses (hence heat could be an indicator of rolling losses). It's not--hysteresis is the main source of rolling losses.


Wouldn't hysteresis also result in heat?

BTW, I'm enjoying all the jokes here.
 
Energy can be transformed, but not lost.

So if rolling resistance is caused by hysteresis, it MUST come out measurably elsewhere, heat, light, sound are some options, heat being my most probable.
 
Rolling resistance is not just in the tires, but also in the wheel bearing seals. You'd be introducing another variable.
 
Originally Posted By: motor_oil_madman
Originally Posted By: Boomer
Reminds me....my wife wanted something for her birthday that went from 0 to 200 in under 5 seconds. I got her a bathroom scale.


How did she take that one? lol
I'm waiting for the attorney's ad that says, "To lose hundreds of pounds of ugly fat phone 1-800-div-orce."
 
Trying to measure rolling resistance is pretty difficult without the proper tools.

If you measure the amount of heat given off, you're missing the mass portion.

If you use the bathroom scale idea, all you are measuring is the force to accelerate.

The coasting idea has merit.
 
Originally Posted By: CapriRacer

If you measure the amount of heat given off, you're missing the mass portion.


What is the mass portion?
 
Originally Posted By: friendly_jacek
Originally Posted By: CapriRacer

If you measure the amount of heat given off, you're missing the mass portion.


What is the mass portion?


The volume of the tread rubber. For example, an all terrain tire would have more tread rubber than an all season tire, yet if they were made out of the same rubber, the temperature given off would be the same.
 
Originally Posted By: CapriRacer
Originally Posted By: friendly_jacek
Originally Posted By: CapriRacer

If you measure the amount of heat given off, you're missing the mass portion.


What is the mass portion?


The volume of the tread rubber. For example, an all terrain tire would have more tread rubber than an all season tire, yet if they were made out of the same rubber, the temperature given off would be the same.


OK, I hear you. I thought maybe you meant inertia.
I was comparing same size and same type tires.
I believe between comparing weight of tires and difference in tire temp one can get some good ideas about whether rolling resistance is going up and down after tire change.
 
To account for mass, you use Einstein’s theory of relativity: E=MC2

E = Energy
M = Mass
C = Speed of light (in this instance, squared)

You start with your car in neutral in a large, flat parking lot. Then, detonate a moderately-sized nuclear device, say, about 10-20 kilotons …
 
Originally Posted By: motor_oil_madman
Originally Posted By: Boomer
Reminds me....my wife wanted something for her birthday that went from 0 to 200 in under 5 seconds. I got her a bathroom scale.


How did she take that one? lol


I would think this would introduce HYSTERICAL rolling mass.
 
Originally Posted By: CapriRacer

The volume of the tread rubber. For example, an all terrain tire would have more tread rubber than an all season tire, yet if they were made out of the same rubber, the temperature given off would be the same.


I think that the temperature rise would be a function of the heat production and the effective radiating area. I expect that area would not be fully proportional to the rubber volume. So I think that the temperature would be a useful indication of rolling resistance.
 
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