11R tires on semi?

[robertglines1]

noticed semi that picked up cat 336 excavator from me yesterday 90,000lb machine plus 40,000 lb rig was running 11R 22.5 tires .18,000lb front axle----we discuss weight all the time and tire choice---I have the charts---so why is it practice and works in this case? yes it has more tires on ground but is 4 times the weight also..would at least 60,000 lb on tractor..This is just a nagging question that doesn't agree with my knowledge..tandem axle tractor and sever tire conditions in on and off road lots of cutting turns...comments

[kyle4501]

Some operators are "penny wise & pound foolish". I had some work done that required several dumptrucks - the drivers were the owners. One of the discussions concerned the size of the load - one overloaded his truck so he could 'save the wear & tear of extra trips'. Turns out he had lots of tire problems, where as the others seldom had tire failures.

Simply seeing the load on a rig does not tell the whole story. You need to know the axle loading & long term history before you can determine how well something works.


If he is indeed overloading the tires, my guess is that he uses up tire casings faster than the tread & possibly, is falsely attributing the failures to road debris. But, that is only a guess.

[Ed Hackenbruch]

Don't forget that tires come in different load ranges too.

[TomC]

On a 18,000lb front axle, you need to run at least a 315/80R-22.5, or 385/65R-22.5 tire.  The 11R-22.5 simply isn't enough tire, and demonstrates the mentality of some truck drivers (remember, I too was a truck driver).  Good Luck, TomC

[bevans6]

My thought was different - I went to why would a semi need more front tire that normal when the load is on the fifth wheel onto the 8 drive tires?  I wouldn't think that a great percentage of the load transfers to the front axle, does it?  Can't you adjust that anyway, by moving the fifth wheel?  I drive a little car, and I look at semi-tractor tires a lot to see what they are running (mostly to try to find some 24.5", scarce as hens teeth up here) and I can't remember seeing bigger than 11R 22.5's on many semi's.  A load like that, I think it would be on the semi drives, and on the float tires.

How did you know it was an 18K front axle?  How do you tell by looking at them?

Thanks, Brian

[TomC]

Brian- this is a question many ask that are not in the trucking industry.  To go to the max extreme, on a heavy haul 3 axle tractor (for pulling large, heavy equipment) they usually have a 22,000lb front axle and 46,000lb rear axle.  The front can be loaded up to the 20,000lb mark by sliding the fifth wheel (hitch plate) forward to transfer the weight.  Even though 34,000lb is the legal weight limit on rear tandems, heavy haulers use the 46,000lb axles since they have an almost indestructible 18" ring and pinion differential (the same as most buses single rear axle). 
Mostly you can tell it is a 18, 20, or 22,000lb axle just by looking at it since they are visibly much larger.  Also looking at the weight rating on the door helps.  Good Luck, TomC

[bevans6]

Thank you, that is very interesting!  I will look more closely now to try to spot the differences.

Brian

[robertglines1]

I ask the driver he delivers and pickes up frequently ..he is driving a rig for the cat dealer..he said 18000 front axle..the rig is new less than 20,000 miles on it---sure is pretty.. he carries 134,000 lbs regulary..I just ask about tires.Goodyear I think maybe 365 written on side wall but were 11R22.5 size...should have paid more attention to load rating..was amazed at the size 11R

[Sean]

Bob,

You did not post how many axles this 130,000 lbs was sitting on, so it's hard to say whether any of those 11R22.5s was actually overloaded.  Also, as noted, they do come in different load ranges.

That said, almost all tires have an over-rating table for weight vs. speed.  The max load rating for the tire is at the rated speed, but the load can be increased dramatically at lower speeds; manufacturer's even post load ratings for "walking" or "dead slow" speeds.  Similar rules apply to inflation levels.

When I have time I will try to find a link for one of these charts.

So the truck you saw loading up an excavator may in fact be planning to run, say, 45mph tops.  Also, I will point out that some commercial drivers (gasp) are just clueless or unaware of just how much load they are putting on the truck.  In 2007, a similar truck with an excavator on it weighing in at 180,000 lbs drove over a 35,000-lb bridge causing it to collapse.

-Sean
http://OurOdyssey.BlogSpot.com

[robertglines1]

Large cat dealer Wayne supply covers midwest..run truck speed 65 on interstate machine was going 135 mile away.Permit load routed around bridges in cluding on on I-64 that has a 80,000 limit...tandem axle tractor with tri axle trailer..load on tractor has to be at least 60,000 if total weight is 132,000.. I'm sure load rate are declared on tires..I know he had to scale and dot pulled a inspection..no problem.3 1/2 hrs later it was at job site and unloaded..including dot inspection..It seems to be common practice to run 11R on trucks around here..A friend is running over 5,000 trailers with that size..not to mention his tractors..I will continue running 315 ...big dollar differance though...will only be needing to replace 2 in the next several years then all in about 5 years...

[luvrbus]

FWIW guys the last 2 numbers on a 336 or any other Cat excavator is the weight  in tons then they have a operating weight if I remember is around 80,000 lbs on a 336 .
John Deere uses the metric tons in the last 2 numbers on theirs for the weight with a tandem truck and a 3 axle low boy 134,000 is the limit with a permit 118,000 without permit and with a 3 axle low boy it is a hard chore to over load the front axle the truck



good luck

[Sean]

...tandem axle tractor with tri axle trailer..

132,000 lbs/22 tires is just 6,000 per tire.  That's just within the dualed limit for 11R22.5, LR-H tires.  If he had a well-balanced load he could run that at the top speed rating of the tires.

load on tractor has to be at least 60,000 if total weight is 132,000..

That depends where the load is on the trailer.  It's not uncommon to move the load toward the rear to avoid overloading the tractor tandems.  And the fifth wheel can be moved forward as necessary to get as much of the load on the steers as needed.  Ideally with 12 wheels on the trailer and only 10 on the tractor, you'd want exactly 60,000 on the tractor, and you'd want to get st least 12,000 of that on the steers.

..I will continue running 315 ...big dollar differance though...will only be needing to replace 2 in the next several years then all in about 5 years...

You might be able to drop back down to 12R22.5.  That will fit on the same rims as the 315s, is about the same diameter, has a higher load limit than the 11R, but is much cheaper than a 315.

FWIW.

-Sean
http://OurOdyssey.BlogSpot.com

[Sean]

That said, almost all tires have an over-rating table for weight vs. speed.  The max load rating for the tire is at the rated speed, but the load can be increased dramatically at lower speeds; manufacturer's even post load ratings for "walking" or "dead slow" speeds.  Similar rules apply to inflation levels.

When I have time I will try to find a link for one of these charts.
http://OurOdyssey.BlogSpot.com

OK, for anyone who was waiting for this:

I have this chart from the Bridgestone/Firestone Commercial Tire Data Book from a couple years ago.  I just downloaded the 2010 version of the data book, though, and it's no longer in there.  You can download the Data Book here:
http://www.trucktires.com/firestone/us_eng/load/databooks_pdf/F_MediumLightTruckDataBook.pdf


However, I also found this technical article which has a copy of the chart:
http://www.bridgestonetrucktires.com/us_eng/real/magazines/98V3Issue4/v3i4Tech.asp

If you scroll down to the chart, you'll see that for conventional-size tires rated for 65mph, max load can be increased by up to 16% for speeds up to 40mph (with additional air pressure).  Likewise at walking speeds, load can be more than doubled.  (Just noticed there's a typo in this copy; "creep" should read 115%).

I believe this chart actually comes out of the Tire & Rim Association (TRA) Yearbook and applies to all brands (but can only vouch for Bridgestone/Firestone, which is what I run).

-Sean
http://OurOdyssey.BlogSpot.com

[luvrbus]

I seriously doubt the lowboy had 11R/22.5 every 3 or 4 axle lowboy I ever owned had 275/70r-22.5 low profile tires never saw on with 11R's truck tires anyone out there that can tell me why they use low profile for heavy loads Cole's 100 ton+ lowboys use 19.5 on 10 axles ?

[robertglines1]

19.5 on trailer is not uncommon..see that a lot...didn"t pay attention to trailer tires do know they were shorter.I ask if they were the 19.5 and he said no..I was just amazed to see the 11R on tractor..3 axle trailer 12 tires. the 336 is about as large as we can move with counterweight on.On bigger machines we remove crowd and buckett.