Magic tires?

layoutshooter · Sep 17, 2011

OK, I got 6 new gumbies on the truck.

I put Bridgestone R280's on the steers and Bridgestone M720's on the drives.

I was running Michilen XZA3 tires all around. I got 10 to 10.5 MPG with those. The XZA3 is a "rib" tires. New they have a 19/32 thread depth. The rolling resistance number is 101.

The Bridgestone M720 has a 26/32 thread depth and a rolling resistance of 110. The R280 has a 18/32 thread depth and a rolling resistance of 109.

I expected when I put these on to see a drop in MPG. I ran one load, typical for us, no reefer and 1200LBS. We got 10.85MPG.

NO drop in MPG. Why would this be? Could they be "magic tires"? I really expected a drop in MPG. Could the cooler weather offset the new tires? Any ideas?

Moot · Sep 17, 2011

layoutshooter said:
I expected when I put these on to see a drop in MPG. I ran one load, typical for us, no reefer and 1200LBS. We got 10.85MPG.

You don't state the mileage of the load. I would think a small change in rolling resistance of a tire either +/- would be imperceptible on fuel economy measured on just one load. Even the addition of Airtabs or some other aerodynamic device's performance could not be measured in one trip. No matter how typical.

layoutshooter · Sep 17, 2011

Moot said:
You don't state the mileage of the load. I would think a small change in rolling resistance of a tire either +/- would be imperceptible on fuel economy measured on just one load. Even the addition of Airtabs or some other aerodynamic device's performance could not be measured in one trip. No matter how typical.

It was almost 900 miles. I was under the impression that just the fact that they were new and had deeper thread that mileage would go down some. Two fill ups, 10.85 on the first, 10.55 on the second. The second had several hours of APU time on it.

OntarioVanMan · Sep 17, 2011

I would give it some more time ...see if it is consistent..

Moot · Sep 17, 2011

Way too many variables; wind, weather, terrain, highway surface, etc. to attach any significance to a 900 mile run. New tires with deeper tread should also run cooler. Give it a full year to make a meaningful comparison.

layoutshooter · Sep 17, 2011

OntarioVanMan said:
I would give it some more time ...see if it is consistent..

Yep, not like I have any options! LOL!! I was just surprised that I did not see a marked drop when I put them on. The MPG I am seeing so far is consistent with what I have been seeing for the past 3 years. I HOPE it continues. I like having deeper thread. I am looking to get more life out of my tires than I have been.

OntarioVanMan · Sep 17, 2011

layoutshooter said:
Yep, not like I have any options! LOL!! I was just surprised that I did not see a marked drop when I put them on. The MPG I am seeing so far is consistent with what I have been seeing for the past 3 years. I HOPE it continues. I like having deeper thread. I am looking to get more life out of my tires than I have been.

I guess that was kinda obvious eh? lol

I put on the magic tires too...I THINK I am seeing an improvement over time....I am hitting low 23's mpg more often at 66 mph then the high 22's...and at 62-63 the mid 25 mpg....

layoutshooter · Sep 17, 2011

OntarioVanMan said:
I guess that was kinda obvious eh? lol

I put on the magic tires too...I THINK I am seeing an improvement over time....I am hitting low 23's mpg more often at 66 mph then the high 22's...and at 62-63 the mid 25 mpg....

The old drives had 4/32 left on them. I would have thought that the jump to 26/32 would have made things drop a bit. Not that I am complaining mind you, just trying to understand things that I don't understand all that well.

Like what makes a tire "Smart Way"? I was looking at that and some SmartWay tires have HIGHER rolling resistance numbers than some that are NOT SmartWay. Confusing to say the least.

Slacktide · Sep 17, 2011

A couple of things to think about... Your new tires are taller at this point, 11/16 of an inch taller thuss covering more ground with each revolution. Cooler temps and accurate tire pressure will play a part as well.
With the deeper tread on the drives keep a watchfull eye for cupping from the flex of the drive lugs, frequent rotations will help keep it at bay, once it starts you can't stop it. Unless you can do a burnout with your truck of course.

Posted with my Droid EO Forum App

layoutshooter · Sep 17, 2011

Yep, rotations will occur. I will be watching my MPG's. I always do.

RETIDEPXE · Sep 17, 2011

The new XZA3 '+' is supposed to be gauranteed to go 30% further, although not sure how they will document, the dealer did not have a clue (stiffer compound they say). Just replaced my XZA3 steers with 170k mi.s. Should have gone further since they had 8/32nds left but developed a couple flat spots before I realized the wheel lost it's weights.. Went with the new '+' so we shall see. I would be curious how well the Bridgestone 280's hold up on edge wear down the road.

It has been quite windy the last few days with the cold front and all, which way were the flags blowing for you on your 900 mi. run?

My M2/C9 best the last couple months is 10.80mpg I believe, but only with a tail wind a couple times. 10 is doable at slower speeds, 9.48 overall. Did a 10500 lb. load out of Petersburg, WV to Adrian, MI and was lucky to pull 8.9 out of it with the mountains, man-o-man, 3 stretches of 9 degree grades 8 mi.s long each along with 90 miles of switch backs. The motor was struggling but kept it's cool by selecting the right gear in the slush-a-matic Allison, wishing I had a pyrometer but we made it without incident. Live and learn.

layoutshooter · Sep 17, 2011

RETIDEPXE said:
The new XZA3 '+' is supposed to be gauranteed to go 30% further, although not sure how they will document, the dealer did not have a clue (stiffer compound they say). Just replaced my XZA3 steers with 170k mi.s. Should have gone further since they had 8/32nds left but developed a couple flat spots before I realized the wheel lost it's weights.. Went with the new '+' so we shall see. I would be curious how well the Bridgestone 280's hold up on edge wear down the road.

It has been quite windy the last few days with the cold front and all, which way were the flags blowing for you on your 900 mi. run?

My M2/C9 best the last couple months is 10.80mpg I believe, but only with a tail wind a couple times. 10 is doable at slower speeds, 9.48 overall. Did a 10500 lb. load out of Petersburg, WV to Adrian, MI and was lucky to pull 8.9 out of it with the mountains, man-o-man, 3 stretches of 9 degree grades 8 mi.s long each along with 90 miles of switch backs. The motor was struggling but kept it's cool by selecting the right gear in the slush-a-matic Allison, wishing I had a pyrometer but we made it without incident. Live and learn.

I got 171,000 out of my first set of XZA3. Only 151 out of these. That is with rotations and Centramatics.

I had a heavy cross wind most of the way, right to left.

10-10.5MPG is our norm. We get that on all but the steepest terrain, with or without the reefer with any load under 5000lbs.