Higher tire pressure -> lower MPG??

[user removed]

I look for tire gauges at yard sales, then match them to those I already have and throw away the ones that are way off. Older made in the USA gauges are best from my experience.
What everyone is experiencing is the "China effect", cheap tools that might be adequate for a very occasional use, nowhere near their design limits. I have tools that I bought in 1969, USA made and still working fine. The most frequent purchase at yard sales are tools.
Anyone know what a "fountain brush" is without looking it up?

regards
mech

[CapriRacer]

cyclopathic,

Below are 2 of my webpages on RR and Fuel Economy. I'll bet most of the answers to your questions are there:

Barry's Tire Tech

Barry's Tire Tech

[cyclopathic]

Originally Posted by CapriRacer

cyclopathetic,

Below are 2 of my webpages on RR and Fuel Economy. I'll bet most of the answers to your questions are there:

Thanks for the links, good summary. Unfortunately it does not answer my question on contact patch. I remember seeing a high speed camera video of contact patch wave a while back, with explanation on how this impacts rolling resistance.

Also have you looked at EU efficiency labeling? Could not find tire database compilation with info on tire ratings.

[cyclopathic]

here is info on EU labels:

Full Guide To The EU Tyre Label

[CapriRacer]

Originally Posted by cyclopathic

Thanks for the links, good summary. Unfortunately it does not answer my question on contact patch. I remember seeing a high speed camera video of contact patch wave a while back, with explanation on how this impacts rolling resistance......

This is a speed related phenomenon and common to all types of tires. Yes, it does impact RR, so to reduce this phenomenon, keep your speed down. There's a chart around somewhere, but you'll have to dig for it, if you are truly interested. But, again, it is common to all tires, so it isn't something you need to worry about.

Originally Posted by cyclopathic

.....Also have you looked at EU efficiency labeling? Could not find tire database compilation with info on tire ratings.

I am not aware of anyone who has compiled a summary on the EU labeling. NHTSA publishes a summary of the UTQG ratings, but that does not include RR as a rating point - perhaps in the future.

[cyclopathic]

Originally Posted by CapriRacer

This is a speed related phenomenon and common to all types of tires. Yes, it does impact RR, so to reduce this phenomenon, keep your speed down. There's a chart around somewhere, but you'll have to dig for it, if you are truly interested. But, again, it is common to all tires, so it isn't something you need to worry about..

I think speed matters not as you still have the same number of revolutions per mile. So your total loss on RR per trip will be the same regardless of speed

[euromodder]

Originally Posted by cyclopathic

For example on LRR tires Bridgestone or Michelin use special more flexible rubber compound in sidewalls, and probably best LRR tires in US market Michelin Energy Savers have the thinnest sidewalls I've seen.

The EU Energy Savers will still roll noticeably lighter @ higher pressure.


Before joining ecomodder, I originally started increasing tyre pressure to cure or reduce wallowing and tram lining effects due to too low OEM pressure recommendations.

[CapriRacer]

Originally Posted by cyclopathic

I think speed matters not as you still have the same number of revolutions per mile. So your total loss on RR per trip will be the same regardless of speed

This says otherwise.



https://www.tut.fi/ms/muo/vert/7_raw...p_image008.jpg

And there is other data to support that RR is relatively the same until you hit about 60 mph, then it increases dramatically - which is probably where the video you looked at was coming from.

[Donahue]

Originally Posted by CapriRacer

This says otherwise.



https://www.tut.fi/ms/muo/vert/7_raw...p_image008.jpg

And there is other data to support that RR is relatively the same until you hit about 60 mph, then it increases dramatically - which is probably where the video you looked at was coming from.

I'm curious of the physics involved in this. On the surface, you would think tire resistance would be linear. What is causing the curve, is some sort of internal dynamics on the tire causing the change? Is is something like heat, or a harmonic vibration or something? Do speed ratings have any effect on when that curve occurs?

[CapriRacer]

Originally Posted by Donahue

I'm curious of the physics involved in this. On the surface, you would think tire resistance would be linear. What is causing the curve, is some sort of internal dynamics on the tire causing the change? Is is something like heat, or a harmonic vibration or something? Do speed ratings have any effect on when that curve occurs?

Best guess = standing wave that grows as the speed increases.

I'm not sure what effect speed ratings have - or more precisely, what affect the change in construction has - but I suspect that the increased RR you get to achieve a higher speed rating is only slightly offset by the softening of the speed effect.

Put another way:

1) Higher speed rating = higher RR (all other things being equal)

2) Higher speed rating reduces the effect speed has on RR, but does not eliminate the effect.